fix: keep the flash line to its one line at any message length (closes #252)

The flash line reserves one line, so a message that wrapped pushed the
screen below it down. #flash-msg no longer wraps: text too long for it is
cut with an ellipsis, and showFlash() puts the whole message in its title.
Every message is also reworded to at most 50 characters so none is cut,
and the add-token screens flash a fixed line for any error other than the
two lookup messages, logging the detail.

A new end-to-end test writes a message several lines long into the line
and fails if the line or the screen below it moves.

Model: opus-5-5

README.md

@@ -892,21 +892,12 @@ shows is a V4 exact-in `amountIn` of zero.
 The rule and its exception live in `src/shared/amountDisplay.js` as
 `truncateAmount()` and `truncateAmountNeverZero()`. Everything the approval and
 confirmation screens display goes through the floored one — the ERC-20 amount,
-the ETH value and max fee (`src/popup/views/approval.js`), the swap's `Amount`
-and `Min. received` lines (`src/shared/uniswap.js`), the Send screen's
-`Current balance` (`src/popup/views/send.js`), and the balance and network fee
-on the confirmation screen for the wallet's own send
-(`src/popup/views/confirmTx.js`). Both screens render a network fee through
-`formatFee()` in `src/popup/views/helpers.js`, which prices the exact fee in USD
-rather than its truncated figure, so the same fee reads the same on both, USD
-value included. Balances are stored exactly (`src/shared/balances.js`), whatever
-decimals a token declares, so a balance below the floor reaches these screens as
-it is. The history list (`src/shared/transactions.js`) uses the unfloored one:
-the transaction detail view is the authoritative record and already shows exact
-precision. The balance lists use neither: they round to four places with
-`toFixed(4)` (`balanceLine()` in `src/popup/views/helpers.js`). The 4-decimal
-rule is unchanged everywhere else, including for amounts at or above the floor
-on the approval screens.
+the ETH value and max fee (`src/popup/views/approval.js`), and the swap's
+`Amount` and `Min. received` lines (`src/shared/uniswap.js`). The history and
+balance lists (`src/shared/transactions.js`) use the unfloored one: the
+transaction detail view is the authoritative record and already shows exact
+precision. The 4-decimal rule is unchanged everywhere else, including for
+amounts at or above the floor on the approval screens.
 
 The floor applies only where the token's scale is known. Where it is not, the
 approval screen states base units instead of a quantity — see Unknown token
@@ -1064,13 +1055,8 @@ list from any other contract address is always dropped, and so is any token
 claiming a symbol that belongs to the native asset and therefore has no
 legitimate contract at all (`"ETH"`). That filter is unconditional — the "Hide
 tokens with fewer than 1,000 holders" setting governs the transaction history
-and the send-screen token selector, not this list. `fetchTokenBalances()` stores
-every nonzero holding of a token it admits, however small, but a holding below
-0.000001 is left out of the balance lists, the send-screen token selector, the
-address total and the remove-address warning (`isBelowOneMillionth()` in
-`src/shared/amountDisplay.js`). The Send and confirmation screens show it when
-its token is the one being sent. Tracked tokens with a zero balance are listed
-as well while "Show tracked tokens with zero balance" is on.
+and the send-screen token selector, not this list. Tracked tokens with a zero
+balance are listed as well while "Show tracked tokens with zero balance" is on.
 
 #### Stored state and its version
 

TODO.md

@@ -45,23 +45,25 @@ but the review is broader than any of them.
 
 # Completed Steps
 
-- 2026-10-04: The Send and confirmation screens no longer show an ETH balance, a
-  token balance or a network fee below 0.000001 as zero
-  ([#343](https://git.eeqj.de/sneak/AutistMask/issues/343)). The stored balances
-  (`src/shared/balances.js`) and the confirmation screen's fee were each cut to
-  six decimal places by a rule of their own, and a token holding cut to zero was
-  dropped. Balances are now stored exactly, whatever decimals a token declares,
-  and every nonzero token holding is kept; the balance check reads a token
-  balance to its first 18 places, the most an amount can have. The balance
-  lists, the send-screen token selector, the address total and the
-  remove-address warning leave out a holding below 0.000001 themselves, as
-  before. The Send screen's `Current balance`, and the confirmation screen's
-  balance, fee, reserve and insufficient-balance messages, go through
-  `truncateAmountNeverZero()` in `src/shared/amountDisplay.js`, the helper the
-  approval screen already used. The confirmation and approval screens both
-  render the fee through `formatFee()` in `src/popup/views/helpers.js`, which
-  prices the exact fee in USD, so the same fee reads the same on both, USD value
-  included.
+- 2026-10-04: The flash line keeps to the one line it reserves at any message
+  length ([#252](https://git.eeqj.de/sneak/AutistMask/issues/252)). A message
+  that wrapped pushed the whole screen below it down. `#flash-msg` no longer
+  wraps: text too long for the line is cut with an ellipsis, and `showFlash()`
+  puts the whole message in the line's title. Every message is also reworded to
+  at most 50 characters so none is cut; none carries a wallet name or text from
+  a server, and the add-token screens flash a fixed line for any error other
+  than a contract that is not a token. A new test in `tests/e2e/run.js` puts a
+  message several lines long on the line and fails if the line or the screen
+  below it moves. The two approval-screen error boxes are left to
+  [#297](https://git.eeqj.de/sneak/AutistMask/issues/297).
+
+- 2026-10-04: A method the wallet does not implement is refused with EIP-1193
+  code `4200` ([#279](https://git.eeqj.de/sneak/AutistMask/issues/279)). The
+  background's `Unsupported method: <method>` error carried no code, so a site
+  probing for an optional method could not tell "not implemented" from "the call
+  failed". The message is unchanged; the background's other errors with no code
+  are untouched.
+
 - 2026-10-04: Settings lists the sites connected without "Remember", and
   removing a site there disconnects it
   ([#406](https://git.eeqj.de/sneak/AutistMask/issues/406)). Such a connection

src/background/index.js

@@ -932,7 +932,9 @@ async function handleRpc(method, params, origin) {
         }
     }
 
-    return { error: { message: "Unsupported method: " + method } };
+    // EIP-1193 4200 lets a site tell "this wallet does not implement that"
+    // from "that call failed", and fall back.
+    return { error: { code: 4200, message: "Unsupported method: " + method } };
 }
 
 // The body of eth_sendTransaction, from the connection check through to the

src/content/inpage.js

@@ -31,11 +31,12 @@
     // an error instead of accepting the refusal.
     //
     // Whatever code arrived is passed through verbatim rather than being
-    // matched against a list: the extension emits 4001, 4100 and 4902 today,
-    // and a code this file has never heard of is still the truth about what
-    // happened. An error reported with no code at all stays a plain Error —
-    // a ProviderRpcError whose `code` is undefined would advertise a
-    // conformance it does not have. `message` is untouched in every case.
+    // matched against a list: the extension emits codes such as 4001, 4100,
+    // 4200 and 4902, and a code this file has never heard of is still the
+    // truth about what happened. An error reported with no code at all stays
+    // a plain Error — a ProviderRpcError whose `code` is undefined would
+    // advertise a conformance it does not have. `message` is untouched in
+    // every case.
     function toPageError(error) {
         const message = (error && error.message) || "Request failed";
         if (error && error.code !== undefined && error.code !== null) {

src/popup/dustThreshold.js

@@ -19,13 +19,9 @@
 // that the user did not type — the same silent substitution the visible
 // rejection message exists to end.
 
-// Must render on ONE line of #flash-msg, whose reserved height
-// (min-h-[1.25rem]) is exactly one line at text-xs. A string long enough to
-// wrap to two lines pushes the settings view down, which the No Layout Shift
-// policy forbids. Do not lengthen this without re-running the layout test in
-// tests/e2e/run.js, which measures the flash line and goes red on a shift.
-const DUST_THRESHOLD_MESSAGE =
-    "Please enter a whole number of gwei, zero or greater.";
+// Must render on ONE line of #flash-msg; see showFlash() in
+// src/popup/views/helpers.js for how long that is.
+const DUST_THRESHOLD_MESSAGE = "Enter a whole number of gwei, zero or greater.";
 
 // Returns the threshold in gwei, or null if the input is not one.
 function parseDustThresholdGwei(raw) {

src/popup/index.html

@@ -33,7 +33,7 @@
             <!-- ============ FLASH MESSAGE AREA ============ -->
             <div
                 id="flash-msg"
-                class="text-xs text-muted min-h-[1.25rem] mb-1"
+                class="text-xs text-muted min-h-[1.25rem] mb-1 truncate"
             ></div>
 
             <!-- ============ WELCOME / FIRST USE ============ -->

src/popup/views/addToken.js

@@ -28,9 +28,7 @@ function init(ctx) {
     $("btn-add-token-confirm").addEventListener("click", async () => {
         const contractAddr = $("add-token-address").value.trim();
         if (!contractAddr || !contractAddr.startsWith("0x")) {
-            showFlash(
-                "Please enter a valid contract address starting with 0x.",
-            );
+            showFlash("Enter a valid contract address starting with 0x.");
             return;
         }
         const already = state.trackedTokens.find(
@@ -71,8 +69,15 @@ function init(ctx) {
             require("./addressDetail").show();
         } catch (e) {
             const detail = e.shortMessage || e.message || String(e);
-            log.errorf("Token lookup failed for", contractAddr, detail);
-            showFlash(detail);
+            log.errorf("Adding token failed for", contractAddr, detail);
+            // lookupTokenInfo() rejects a contract with a one-line message
+            // starting "Not a valid ERC-20 token". Any other error, such as a
+            // failed save, can be far longer, so it is only logged.
+            showFlash(
+                detail.startsWith("Not a valid ERC-20 token")
+                    ? detail
+                    : "Could not add the token.",
+            );
             infoEl.textContent = "";
             infoEl.style.visibility = "hidden";
         }

src/popup/views/addWallet.js

@@ -142,15 +142,13 @@ function validatePassword() {
 async function importMnemonic(ctx) {
     const mnemonic = $("wallet-mnemonic").value.trim();
     if (!mnemonic) {
-        showFlash("Enter a recovery phrase or press the die to generate one.");
+        showFlash("Enter a recovery phrase, or press the die.");
         return;
     }
     const words = mnemonic.split(/\s+/);
     if (words.length !== 12 && words.length !== 24) {
         showFlash(
-            "Recovery phrase must be 12 or 24 words. You entered " +
-                words.length +
-                ".",
+            "Recovery phrase must be 12 or 24 words, not " + words.length + ".",
         );
         return;
     }
@@ -163,14 +161,12 @@ async function importMnemonic(ctx) {
     const { xpub, firstAddress } = hdWalletFromMnemonic(mnemonic);
     const xpubDup = findWalletByXpub(xpub);
     if (xpubDup) {
-        showFlash(
-            "This recovery phrase is already added (" + xpubDup.name + ").",
-        );
+        showFlash("This recovery phrase is already added.");
         return;
     }
     const addrDup = findWalletByAddress(firstAddress);
     if (addrDup) {
-        showFlash("Address already exists in wallet (" + addrDup.name + ").");
+        showFlash("Address already exists in a wallet.");
         return;
     }
     const encrypted = await encryptWithPassword(mnemonic, pw);
@@ -229,9 +225,7 @@ async function importPrivateKey(ctx) {
     if (!pw) return;
     const duplicate = findWalletByAddress(addr);
     if (duplicate) {
-        showFlash(
-            "This address already exists in wallet (" + duplicate.name + ").",
-        );
+        showFlash("This address already exists in a wallet.");
         return;
     }
     const encrypted = await encryptWithPassword(key, pw);
@@ -258,36 +252,29 @@ async function importXprvKey(ctx) {
         return;
     }
     if (!isValidXprv(xprv)) {
-        showFlash(
-            "That extended private key is not valid. Please check it and try again.",
-        );
+        showFlash("That extended private key is not valid.");
         return;
     }
     if (!isMasterExtendedKey(xprv)) {
-        showFlash(
-            "That is an account-level or child key, which cannot be imported. " +
-                "Please paste the master extended private key for the wallet.",
-        );
+        showFlash("Please paste the master key, not a child key.");
         return;
     }
     let result;
     try {
         result = hdWalletFromXprv(xprv);
     } catch {
-        showFlash(
-            "That extended private key is not valid. Please check it and try again.",
-        );
+        showFlash("That extended private key is not valid.");
         return;
     }
     const { xpub, firstAddress } = result;
     const xpubDup = findWalletByXpub(xpub);
     if (xpubDup) {
-        showFlash("This key is already added (" + xpubDup.name + ").");
+        showFlash("This key is already added.");
         return;
     }
     const addrDup = findWalletByAddress(firstAddress);
     if (addrDup) {
-        showFlash("Address already exists in wallet (" + addrDup.name + ").");
+        showFlash("Address already exists in a wallet.");
         return;
     }
     const pw = validatePassword();

src/popup/views/approval.js

@@ -8,7 +8,6 @@ const {
     renderAddressHtml,
     attachCopyHandlers,
     onViewLeave,
-    formatFee,
 } = require("./helpers");
 const { state, saveState } = require("../../shared/state");
 const { networkByChainId } = require("../../shared/networks");
@@ -208,7 +207,7 @@ function showPhishingWarning(elementId, isPhishing) {
 // and the nonce. The background compares every one of them against the signed
 // artifact, so every one of them has to be on the screen — a number that is
 // verified but never displayed is verified against nothing the user agreed to.
-function showTxFee(approvedTx) {
+function showTxFee(approvedTx, ethPrice) {
     const network = networkByChainId(approvedTx.chainId);
     $("approve-tx-network").textContent = network
         ? network.name
@@ -216,9 +215,12 @@ function showTxFee(approvedTx) {
 
     const gasLimit = BigInt(approvedTx.gasLimit);
     const feePerGas = BigInt(approvedTx.maxFeePerGas || approvedTx.gasPrice);
-    // Through formatFee(), as the confirmation screen's fee is, so the same
-    // fee reads the same on both.
-    $("approve-tx-fee").textContent = formatFee(gasLimit * feePerGas);
+    const maxFeeEth = formatTxValue(formatEther(gasLimit * feePerGas));
+    const usdStr = formatUsd(
+        ethPrice ? parseFloat(maxFeeEth) * ethPrice : null,
+    );
+    $("approve-tx-fee").textContent =
+        maxFeeEth + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
 
     let detail =
         gasLimit.toString() +
@@ -330,7 +332,7 @@ function showTxApproval(details) {
     $("approve-tx-value").textContent =
         ethValueFormatted + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
 
-    showTxFee(approvedTx);
+    showTxFee(approvedTx, ethPrice);
 
     // Decode calldata (reuse decoded from above)
     const decodedEl = $("approve-tx-decoded");

src/popup/views/confirmTx.js

@@ -15,7 +15,6 @@ const {
     attachCopyHandlers,
     goBack,
     onViewLeave,
-    formatFee,
 } = require("./helpers");
 const { state } = require("../../shared/state");
 const { getSignerForAddress } = require("../../shared/wallet");
@@ -32,9 +31,6 @@ const {
     transferAmountUnits,
 } = require("../../shared/transferAmount");
 const { assertWithinCeilings } = require("../../shared/approvalVerify");
-// The balance lines, the fee reserve and the insufficient-balance messages go
-// through it, as the approval screen's amounts do.
-const { truncateAmountNeverZero } = require("../../shared/amountDisplay");
 const {
     CODES,
     FEE_PENDING,
@@ -154,17 +150,11 @@ function show(txInfo) {
         $("confirm-balance").textContent =
             bal == null
                 ? "unknown (" + symbol + ")"
-                : valueWithUsd(
-                      truncateAmountNeverZero(bal) + " " + symbol,
-                      balUsd,
-                  );
+                : valueWithUsd(bal + " " + symbol, balUsd);
     } else {
         const bal = txInfo.balance || "0";
         const balUsd = ethPrice ? parseFloat(bal) * ethPrice : null;
-        $("confirm-balance").textContent = valueWithUsd(
-            truncateAmountNeverZero(bal) + " ETH",
-            balUsd,
-        );
+        $("confirm-balance").textContent = valueWithUsd(bal + " ETH", balUsd);
     }
 
     // Check for warnings (synchronous local checks)
@@ -259,7 +249,7 @@ function renderValidation(txInfo) {
                 : "Insufficient " +
                       symbol +
                       " balance. You have " +
-                      truncateAmountNeverZero(txInfo.tokenBalance) +
+                      txInfo.tokenBalance +
                       " " +
                       symbol +
                       " but are trying to send " +
@@ -272,7 +262,7 @@ function renderValidation(txInfo) {
     if (codes.includes(CODES.INSUFFICIENT_ETH)) {
         messages.push(
             "Insufficient balance. You have " +
-                truncateAmountNeverZero(txInfo.balance || "0") +
+                txInfo.balance +
                 " ETH but are trying to send " +
                 txInfo.amount +
                 " ETH.",
@@ -315,6 +305,14 @@ function setVisible(id, visible) {
     $(id).style.visibility = visible ? "visible" : "hidden";
 }
 
+// A fee in wei as an ETH string, truncated to 6 decimal places.
+function formatFeeEth(wei) {
+    const parts = formatEther(wei).split(".");
+    const dec =
+        parts.length > 1 ? parts[1].slice(0, 6).replace(/0+$/, "") || "0" : "0";
+    return parts[0] + "." + dec + " ETH";
+}
+
 async function estimateGas(txInfo) {
     try {
         const provider = getProvider(state.rpcUrl, state.networkId);
@@ -361,20 +359,26 @@ async function estimateGas(txInfo) {
         // flight; a stale fee must not reach the screen or the balance check.
         if (pendingTx !== txInfo) return;
 
-        // The fee line goes through formatFee(), as the approval screen's
-        // does, so the same fee reads the same on both.
+        const ethPrice = getPrice("ETH");
+        const usd = (wei) =>
+            ethPrice ? parseFloat(formatEther(wei)) * ethPrice : null;
+
         if (estimateWei !== null && estimateWei < gasCostWei) {
-            $("confirm-fee-amount").textContent = "~" + formatFee(estimateWei);
+            $("confirm-fee-amount").textContent = valueWithUsd(
+                "~" + formatFeeEth(estimateWei),
+                usd(estimateWei),
+            );
             $("confirm-fee-reserve").textContent =
-                "up to " +
-                truncateAmountNeverZero(formatEther(gasCostWei)) +
-                " ETH reserved";
+                "up to " + formatFeeEth(gasCostWei) + " reserved";
             setVisible("confirm-fee-reserve", true);
         } else {
             // No spread to report: either there is no estimate, or the node
             // quotes a gas price at or above maxFeePerGas, so the expected
             // cost is not below the reserve. Show the reserve alone.
-            $("confirm-fee-amount").textContent = formatFee(gasCostWei);
+            $("confirm-fee-amount").textContent = valueWithUsd(
+                formatFeeEth(gasCostWei),
+                usd(gasCostWei),
+            );
             setVisible("confirm-fee-reserve", false);
         }
         feeStatus = FEE_KNOWN;

src/popup/views/deleteAddress.js

@@ -87,8 +87,7 @@ function recoveryPathText(wallet) {
 // AddressDetail, followed by the USD total when there is one to give — no
 // total line at all on testnet or before the first price fetch, and no figure
 // when every holding here is one with no price, since "$0.00" directly under
-// "This address holds a balance." is a contradiction. A token holding below
-// 0.000001 does not count, as the lines below leave it out.
+// "This address holds a balance." is a contradiction.
 function balanceWarningHtml(addr) {
     if (!addressHoldsFunds(addr)) return " ";
     const line = formatAddressTotal(getAddressValue(addr));

src/popup/views/helpers.js

@@ -12,11 +12,6 @@
 // escapeHtml lives in src/shared/html.js, where the escape and the
 // reasoning behind it are; it is re-exported below so views keep importing
 // it from here.
-const { formatEther } = require("ethers");
-const {
-    truncateAmountNeverZero,
-    isBelowOneMillionth,
-} = require("../../shared/amountDisplay");
 const { DEBUG } = require("../../shared/constants");
 const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
@@ -228,15 +223,19 @@ function clearFlash() {
         flashTimer = null;
     }
     $("flash-msg").textContent = "";
+    $("flash-msg").title = "";
 }
 
+// The flash line reserves exactly one line, and a message that wrapped would
+// push the screen below it down (README, No Layout Shift). So #flash-msg never
+// wraps: text too long for the line is cut with an ellipsis, and the whole
+// message is also put in the line's title. Write messages to fit, at most 50
+// characters, so none is cut.
 function showFlash(msg, duration = 2000) {
     clearFlash();
     $("flash-msg").textContent = msg;
-    flashTimer = setTimeout(() => {
-        $("flash-msg").textContent = "";
-        flashTimer = null;
-    }, duration);
+    $("flash-msg").title = msg;
+    flashTimer = setTimeout(clearFlash, duration);
 }
 
 // A stored token balance as a number, or null when there is no number in it.
@@ -248,19 +247,6 @@ function unknownableAmount(balance) {
     return Number.isFinite(n) ? n : null;
 }
 
-// A network fee in wei as the confirmation and approval screens both show it:
-// the ETH figure through truncateAmountNeverZero(), then its USD value when the
-// ETH price is known. The USD value is of the exact fee, not of the truncated
-// figure.
-function formatFee(wei) {
-    const eth = formatEther(wei);
-    const ethPrice = getPrice("ETH");
-    const usd = ethPrice ? formatUsd(parseFloat(eth) * ethPrice) : "";
-    return (
-        truncateAmountNeverZero(eth) + " ETH" + (usd ? " (" + usd + ")" : "")
-    );
-}
-
 // One row of the balance list: symbol, quantity, fiat value.
 //
 // `symbol` is the ERC-20's own symbol() as the block explorer reported it,
@@ -306,9 +292,6 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
     );
     const seen = new Set();
     for (const t of addr.tokenBalances || []) {
-        // A holding below 0.000001 is not listed, tracked or not. A tracked
-        // token then gets the zero row below while showZero is on.
-        if (isBelowOneMillionth(t.balance)) continue;
         // A null balance is a holding of an unstatable amount, not a holding
         // of zero, so the show-zero setting has no say over it: hiding it
         // would be asserting the zero nobody established. Anything that does
@@ -339,16 +322,14 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
 }
 
 // Whether an address holds anything at all: ETH or any ERC-20 the wallet
-// knows about, except a token holding below 0.000001, which the balance list
-// under the remove-address warning leaves out too. Deliberately unrounded —
-// the rendered lines round to four decimals, so a dust balance displays as
-// 0.0000 while still being real money at a real address. Callers that warn
-// about holdings must ask this, not the rendered figure.
+// knows about. Deliberately unrounded — the rendered lines round to four
+// decimals, so a dust balance displays as 0.0000 while still being real
+// money at a real address. Callers that warn about holdings must ask this,
+// not the rendered figure.
 function addressHoldsFunds(addr) {
     if (!addr) return false;
     if (parseFloat(addr.balance || "0") > 0) return true;
     for (const t of addr.tokenBalances || []) {
-        if (isBelowOneMillionth(t.balance)) continue;
         // A null balance is a holding whose amount could not be stated —
         // balances.js drops a row of zero base units before the scale is
         // consulted, so a row that survived with no quantity is holding
@@ -633,7 +614,6 @@ module.exports = {
     balanceLinesForAddress,
     addressHoldsFunds,
     unknownableAmount,
-    formatFee,
     addressColor,
     addressDotHtml,
     escapeHtml,

src/popup/views/send.js

@@ -16,10 +16,6 @@ const { resolveTokenDecimals } = require("../../shared/approvalAmount");
 const { resolveSymbol } = require("../../shared/tokenList");
 const { isLowHolderCount } = require("../../shared/holders");
 const { isSpoofedSymbol } = require("../../shared/symbolSpoof");
-const {
-    truncateAmountNeverZero,
-    isBelowOneMillionth,
-} = require("../../shared/amountDisplay");
 const { getAddress } = require("ethers");
 
 const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
@@ -67,13 +63,13 @@ function validateToAddress(value) {
             if (checksummed !== v) {
                 return {
                     valid: false,
-                    error: "Address checksum is invalid. Please double-check the address.",
+                    error: "Address checksum is invalid. Check the address.",
                 };
             }
         } catch {
             return {
                 valid: false,
-                error: "Address checksum is invalid. Please double-check the address.",
+                error: "Address checksum is invalid. Check the address.",
             };
         }
     }
@@ -129,10 +125,6 @@ function renderSendTokenSelect(addr) {
         (state.fraudContracts || []).map((a) => a.toLowerCase()),
     );
     for (const t of addr.tokenBalances || []) {
-        // A holding below 0.000001 is left out, as the balance lists leave it
-        // out. Its token's own screen can still send it: there
-        // state.selectedToken picks the token, not this list.
-        if (isBelowOneMillionth(t.balance)) continue;
         if (isSpoofedSymbol(t.symbol, t.address)) continue;
         if (fraudSet.has(t.address.toLowerCase())) continue;
         // An unknown holder count does not withhold a token the user holds:
@@ -158,9 +150,7 @@ function updateSendBalance() {
     const token = state.selectedToken || $("send-token").value;
     if (token === "ETH") {
         $("send-balance").textContent =
-            "Current balance: " +
-            truncateAmountNeverZero(addr.balance || "0") +
-            " ETH";
+            "Current balance: " + (addr.balance || "0") + " ETH";
     } else {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === token.toLowerCase(),
@@ -177,10 +167,7 @@ function updateSendBalance() {
         $("send-balance").textContent =
             bal == null
                 ? "Current balance: unknown (" + symbol + ")"
-                : "Current balance: " +
-                  truncateAmountNeverZero(bal) +
-                  " " +
-                  symbol;
+                : "Current balance: " + bal + " " + symbol;
     }
 }
 
@@ -224,7 +211,7 @@ function init(_ctx) {
                 const provider = getProvider(state.rpcUrl, state.networkId);
                 const resolved = await provider.resolveName(to);
                 if (!resolved) {
-                    showFlash("Could not resolve " + to);
+                    showFlash("That ENS name has no address.");
                     return;
                 }
                 resolvedTo = resolved;

src/popup/views/settings.js

@@ -264,18 +264,12 @@ function init(ctx) {
             const json = await resp.json();
             if (json.error) {
                 log.errorf("RPC validation error:", json.error);
-                showFlash("Endpoint returned error: " + json.error.message);
+                showFlash("Endpoint returned an error.");
                 return;
             }
             const net = currentNetwork();
             if (json.result !== net.chainId) {
-                showFlash(
-                    "Wrong network (expected " +
-                        net.name +
-                        ", got chain " +
-                        json.result +
-                        ").",
-                );
+                showFlash("Wrong network: expected " + net.name + ".");
                 return;
             }
         } catch (e) {

src/popup/views/settingsAddToken.js

@@ -115,9 +115,7 @@ function init(_ctx) {
     $("btn-settings-addtoken-manual").addEventListener("click", async () => {
         const addr = $("settings-addtoken-address").value.trim();
         if (!addr || !addr.startsWith("0x")) {
-            showFlash(
-                "Please enter a valid contract address starting with 0x.",
-            );
+            showFlash("Enter a valid contract address starting with 0x.");
             return;
         }
         if (isTracked(addr)) {
@@ -155,8 +153,15 @@ function init(_ctx) {
             ctx.doRefreshAndRender();
         } catch (e) {
             const detail = e.shortMessage || e.message || String(e);
-            log.errorf("Token lookup failed for", addr, detail);
-            showFlash(detail);
+            log.errorf("Adding token failed for", addr, detail);
+            // lookupTokenInfo() rejects a contract with a one-line message
+            // starting "Not a valid ERC-20 token". Any other error, such as a
+            // failed save, can be far longer, so it is only logged.
+            showFlash(
+                detail.startsWith("Not a valid ERC-20 token")
+                    ? detail
+                    : "Could not add the token.",
+            );
             infoEl.textContent = "";
             infoEl.style.visibility = "hidden";
         }

src/shared/amountDisplay.js

@@ -6,10 +6,10 @@
 // (`src/shared/uniswap.js`) — and a fix applied to one of them left the other
 // two showing a different number for the same value.
 //
-// The two truncation functions below are the two policies, not two
-// implementations of one: summary lists truncate, and the screens that state
-// what is being authorized truncate with a floor. Keeping them adjacent is the
-// point, so a change to the rule cannot reach one screen and miss another.
+// The two functions below are the two policies, not two implementations of
+// one: summary lists truncate, and the screens that state what is being
+// authorized truncate with a floor. Keeping them adjacent is the point, so a
+// change to the rule cannot reach one screen and miss another.
 
 // Truncate to exactly four decimal places. Truncation, never rounding: an
 // amount must never be displayed as larger than it is, so 0.99999 stays
@@ -43,18 +43,4 @@ function truncateAmountNeverZero(val) {
     return parts[0] + "." + parts[1].slice(0, sig + 1);
 }
 
-// Whether a stored token balance is a holding below 0.000001. The balance
-// lists, the send-screen token selector, the address total and the
-// remove-address warning leave such a holding out; the Send and confirmation
-// screens show it when its token is the one being sent. Exact, because
-// src/shared/balances.js stores plain decimal digits: below 0.000001 the
-// balance reads "0.000000" and then more digits.
-function isBelowOneMillionth(balance) {
-    return typeof balance === "string" && balance.startsWith("0.000000");
-}
-
-module.exports = {
-    truncateAmount,
-    truncateAmountNeverZero,
-    isBelowOneMillionth,
-};
+module.exports = { truncateAmount, truncateAmountNeverZero };

src/shared/balances.js

@@ -52,16 +52,19 @@ function requireNetworkId(networkId) {
     return net;
 }
 
-// A token balance as an exact decimal string, never cut: a cut stores a small
-// nonzero holding as zero. fetchTokenBalances() stores every nonzero holding of
-// a token it admits, however small; the screens that leave out one below
-// 0.000001 decide that themselves, through isBelowOneMillionth() in
-// src/shared/amountDisplay.js.
+function formatBalance(wei) {
+    const eth = formatEther(wei);
+    const parts = eth.split(".");
+    if (parts.length === 1) return eth + ".0";
+    const dec = parts[1].slice(0, 6).replace(/0+$/, "") || "0";
+    return parts[0] + "." + dec;
+}
+
 function formatTokenBalance(raw, decimals) {
     const val = formatUnits(raw, decimals);
     const parts = val.split(".");
     if (parts.length === 1) return val + ".0";
-    const dec = parts[1].replace(/0+$/, "") || "0";
+    const dec = parts[1].slice(0, 6).replace(/0+$/, "") || "0";
     return parts[0] + "." + dec;
 }
 
@@ -146,7 +149,11 @@ async function fetchTokenBalances(address, blockscoutUrl, trackedTokens) {
             const scale = known !== null ? known : decimals;
             // null is a holding of an amount that cannot be stated, which is
             // not the same as a holding of zero, and must never render as one.
+            // With a scale, the display filter proper applies: a balance that
+            // rounds to zero at six places is dust and is not listed. Without
+            // one there is no such judgement to make, and the row is kept.
             const bal = scale === null ? null : formatTokenBalance(raw, scale);
+            if (bal === "0.0") continue;
             // null means the explorer reported no count, which is not the
             // same as a count of zero.  This gate is not the low-holder
             // display filter: it has no user-facing off switch and governs
@@ -214,9 +221,7 @@ async function refreshBalances(
                 provider
                     .getBalance(addr.address)
                     .then((bal) => {
-                        // Exact, never cut: a cut here stores a small nonzero
-                        // balance as zero.
-                        addr.balance = formatEther(bal);
+                        addr.balance = formatBalance(bal);
                         log.debugf("ETH balance", addr.address, addr.balance);
                     })
                     .catch((e) => {

src/shared/prices.js

@@ -1,7 +1,6 @@
 // Price fetching with 5-minute cache, USD formatting, value aggregation.
 
 const { getTopTokenPrices } = require("./tokenList");
-const { isBelowOneMillionth } = require("./amountDisplay");
 
 const PRICE_CACHE_TTL = 300000; // 5 minutes
 
@@ -79,9 +78,6 @@ function getAddressValue(addr) {
     let usd = parseFloat(addr.balance || "0") * prices.ETH;
     let partial = false;
     for (const token of addr.tokenBalances || []) {
-        // A holding below 0.000001 is left out, as the balance lists leave it
-        // out, so the total never counts a holding the list does not show.
-        if (isBelowOneMillionth(token.balance)) continue;
         // A null balance is a holding whose scale nothing knows, so it has no
         // quantity to price — but it is still a holding, and a total that
         // silently omits it would read as complete. That is exactly what

src/shared/txValidation.js

@@ -139,15 +139,7 @@ function validateTransfer({
     const feeFp = known ? feeWei : null;
 
     if (isErc20) {
-        // A token can declare more than 18 decimals, and its balance is
-        // stored with all of them. Only the first 18 places (SCALE_DECIMALS)
-        // are read: an amount with more was refused above, so the places
-        // after them cannot decide whether the amount fits.
-        const tokenText =
-            typeof tokenBalance === "string"
-                ? tokenBalance.replace(/(\.\d{18})\d+$/, "$1")
-                : tokenBalance;
-        const tokenFp = toFixedPoint(tokenText) ?? 0n;
+        const tokenFp = toFixedPoint(tokenBalance) ?? 0n;
         if (amountFp > tokenFp) codes.push(CODES.INSUFFICIENT_TOKEN);
         if (feeFp !== null && feeFp > ethFp) {
             codes.push(CODES.INSUFFICIENT_ETH_FOR_FEE);

src/shared/walletDefects.js

@@ -41,12 +41,10 @@ const DEFECTS = {
                 "changed or removed, and this wallet stays until you delete " +
                 "it yourself.",
         ],
-        // One sentence for the places that have room for one: the flash on a
-        // blocked Send, the inline error on the approval screens.
-        shortMessage:
-            "This wallet cannot sign, because it was imported from an " +
-            "extended private key that is not a master key. The wallet list " +
-            "explains what happened.",
+        // One line, for the flash on a blocked Send and the inline error on
+        // the approval screens. It must fit on the flash line; see showFlash()
+        // in src/popup/views/helpers.js.
+        shortMessage: "This wallet cannot sign. See the wallet list.",
     },
 };
 

tests/dustThreshold.test.js

@@ -99,12 +99,13 @@ describe("the flash line the message is shown in", () => {
     // length, including one that wrapped to two lines and pushed the
     // settings view down 12px.
     //
-    // The assertion that actually measures — empty line vs. the message,
-    // real Chromium, documented 360x600 popup — is
-    // "a rejected dust threshold shifts no layout (#233)" in
-    // tests/e2e/run.js, run by make test-e2e. It is not in make check
-    // because REPO_POLICIES.md caps make test at 20 seconds and a browser
-    // suite does not fit; run it before changing the wording.
+    // The line cuts a message too long for it with an ellipsis (see
+    // showFlash() in src/popup/views/helpers.js). The assertions that
+    // measure that, in a real browser at the documented 360x600 popup, are
+    // "a rejected dust threshold shifts no layout (#233)" and "an over-long
+    // flash message keeps to one line (#252)" in tests/e2e/run.js, run by
+    // make test-e2e. They are not in make check because REPO_POLICIES.md
+    // caps make test at 20 seconds and a browser suite does not fit.
     test("reserves its height in the markup", () => {
         const flashLine = POPUP_HTML.match(
             /<div\s+id="flash-msg"\s+class="([^"]*)"/,

tests/e2e/run.js

@@ -1320,17 +1320,13 @@ async function waitForFilledFlashLine(page) {
 }
 
 // README, No Layout Shift: the rejection message goes into #flash-msg,
-// whose min-h-[1.25rem] reserves exactly ONE line at text-xs. Reserving
-// the space is not enough on its own — a message too long for one line
-// wraps and pushes everything below it down anyway, which is what the
-// first version of this change shipped: 75 characters, 32px, the settings
-// view and the threshold field 12px lower than with an empty line.
-//
-// So this measures rather than inspects markup. It is the only assertion
-// in the repo that can see the wording grow: the unit suite runs on the
-// node environment with no layout engine, where every height is zero (see
-// the note in tests/dustThreshold.test.js). Lengthen
-// DUST_THRESHOLD_MESSAGE past one line and this test goes red.
+// whose min-h-[1.25rem] reserves exactly ONE line at text-xs, and which
+// cuts a message too long for that line with an ellipsis rather than wrap
+// it. This shows the real message and measures that nothing moves; the
+// test after it does the same with a message several lines long. Both
+// measure rather than inspect markup: the unit suite runs on the node
+// environment with no layout engine, where every height is zero (see the
+// note in tests/dustThreshold.test.js).
 test("a rejected dust threshold shifts no layout (#233)", async (env) => {
     const page = await openPopup(env.ctx, env.popupUrl);
     try {
@@ -1377,11 +1373,11 @@ test("a rejected dust threshold shifts no layout (#233)", async (env) => {
         );
         assert(
             after.flashHeight === before.flashHeight,
-            "the message does not fit the reserved line: " +
+            "the message does not keep to the reserved line: " +
                 before.flashHeight +
                 "px empty vs " +
                 after.flashHeight +
-                "px with the message. Shorten DUST_THRESHOLD_MESSAGE",
+                "px with the message",
         );
         assert(
             after.settingsTop === before.settingsTop,
@@ -1400,6 +1396,59 @@ test("a rejected dust threshold shifts no layout (#233)", async (env) => {
     }
 });
 
+// ------------------------------------------------ the flash line (#252)
+
+// #flash-msg never wraps: a message too long for its one line is cut with an
+// ellipsis (see showFlash() in src/popup/views/helpers.js). This puts a
+// message several lines long into it and measures that the line and the
+// screen below it stay where they were.
+test("an over-long flash message keeps to one line (#252)", async (env) => {
+    const page = await openPopup(env.ctx, env.popupUrl);
+    try {
+        await page.setViewportSize(POPUP_VIEWPORT);
+        await openSettings(page);
+
+        const before = await page.evaluate(measureFlashLine);
+        const overflows = await page.evaluate(() => {
+            const line = document.getElementById("flash-msg");
+            line.textContent =
+                "This message is far too long for one line. ".repeat(5);
+            return line.scrollWidth > line.clientWidth;
+        });
+        const after = await page.evaluate(measureFlashLine);
+
+        assert(
+            after.flashHeight === before.flashHeight,
+            "the flash line is " +
+                before.flashHeight +
+                "px before and " +
+                after.flashHeight +
+                "px with an over-long message, so it wraps",
+        );
+        assert(
+            after.settingsTop === before.settingsTop,
+            "the settings view moved " +
+                (after.settingsTop - before.settingsTop) +
+                "px when the message appeared",
+        );
+        assert(
+            after.fieldTop === before.fieldTop,
+            "the dust threshold field moved " +
+                (after.fieldTop - before.fieldTop) +
+                "px when the message appeared",
+        );
+        // Checked last: a line that wraps does not run past its right edge,
+        // so this only shows the message really was cut once nothing moved.
+        assert(
+            overflows,
+            "the message fits on the line, so it proves nothing: " +
+                JSON.stringify(after.text),
+        );
+    } finally {
+        await page.close();
+    }
+});
+
 // --------------------------------------------- confirmation screen (#238)
 //
 // The screen that decides what gets signed. The arithmetic underneath it
@@ -1414,10 +1463,9 @@ test("a rejected dust threshold shifts no layout (#233)", async (env) => {
 // on opposite sides of the reserve while sitting on the same side of the
 // estimate.
 
-// The balance the funded fixture serves, as the Send and confirmation screens
-// show it, and the amounts sent against it.
+// The balance the funded fixture serves, and the amounts sent against it.
 const FUNDED_ETH_WEI = 10n ** 18n;
-const FUNDED_ETH_TEXT = "1.0000";
+const FUNDED_ETH_TEXT = "1.0";
 const COMFORTABLE_AMOUNT = "0.1";
 const OVER_BALANCE_AMOUNT = "2.0";
 
@@ -1431,7 +1479,7 @@ const GAP_AMOUNT = formatEther(FUNDED_ETH_WEI - FEE_ESTIMATE_WEI);
 // fee test: it covers the expected cost to the wei and falls short of the
 // reserve, so the same swap flips this assertion too — through a different
 // balance and a different message than the ETH path uses.
-const TOKEN_BALANCE_TEXT = "1.5000";
+const TOKEN_BALANCE_TEXT = "1.5";
 const TOKEN_AMOUNT = "0.25";
 const OVER_TOKEN_AMOUNT = "9.0";
 const FEE_ONLY_ETH_WEI = FEE_ESTIMATE_WEI;
@@ -1440,15 +1488,16 @@ function toHexWei(wei) {
     return "0x" + wei.toString(16);
 }
 
-// A fee in wei as the confirmation screen writes it: truncated to four decimal
-// places (README.md, Display Consistency). Deliberately a second
-// implementation rather than an import of src/shared/amountDisplay.js:
-// asserting against an independent rendering is stronger than asserting a
-// function equals itself. The fixture's fees are above 0.0001 ETH, so the
-// nonzero floor never applies here.
+// A fee in wei as the confirmation screen writes it. Deliberately a second
+// implementation of formatFeeEth() from src/popup/views/confirmTx.js rather
+// than an import of it: that module pulls in the whole popup and cannot be
+// required outside a browser, and asserting against an independent rendering
+// is stronger than asserting a function equals itself.
 function feeEth(wei) {
-    const [whole, frac = ""] = formatEther(wei).split(".");
-    return whole + "." + (frac + "0000").slice(0, 4) + " ETH";
+    const parts = formatEther(wei).split(".");
+    const dec =
+        parts.length > 1 ? parts[1].slice(0, 6).replace(/0+$/, "") || "0" : "0";
+    return parts[0] + "." + dec + " ETH";
 }
 
 // What the confirmation screen is showing right now, read out of the DOM in
@@ -1505,10 +1554,11 @@ async function backToAddress(page) {
 
 // Drive the popup to the confirmation screen for one send.
 //
-// It waits for the send screen to be showing `balance`, the fixture's balance
-// as that screen displays it, before filling anything in. Waiting for it —
-// rather than for a refresh to have probably landed — is what keeps every
-// assertion below deterministic after a fixture change.
+// It waits for the send screen to be showing `balance` before filling
+// anything in. That figure is the exact number the spend gate compares
+// against, so waiting for it — rather than for a refresh to have probably
+// landed — is what keeps every assertion below deterministic after a
+// fixture change.
 async function goToConfirm(page, { token, balance, amount }) {
     await backToAddress(page);
     await page.click("#btn-send");

tests/flashLine.test.js

@@ -0,0 +1,130 @@
+// The flash line (#252). #flash-msg reserves one line and cuts a message too
+// long for it with an ellipsis; that is measured in a real browser by
+// tests/e2e/run.js. Here: showFlash() keeps the whole message readable in the
+// line's title, and the two add-token screens flash a fixed line, not the text
+// of whatever error adding the token threw.
+
+const ADDRESS = "0x1111111111111111111111111111111111111111";
+
+let elements;
+
+function fakeElement() {
+    return {
+        value: "",
+        textContent: "",
+        title: "",
+        style: {},
+        listeners: {},
+        addEventListener(event, handler) {
+            this.listeners[event] = handler;
+        },
+    };
+}
+
+// Stands in for document.getElementById(): one fake element per id.
+function element(id) {
+    return (elements[id] ||= fakeElement());
+}
+
+beforeEach(() => {
+    jest.resetModules();
+    elements = {};
+    globalThis.document = { getElementById: element };
+    // state.js reads chrome.storage.local at load.
+    globalThis.chrome = {
+        storage: { local: { get: async () => ({}), set: async () => {} } },
+    };
+});
+
+afterEach(() => {
+    jest.dontMock("../src/popup/views/helpers");
+    jest.dontMock("../src/shared/state");
+    jest.dontMock("../src/shared/balances");
+    jest.restoreAllMocks();
+    jest.useRealTimers();
+    delete globalThis.document;
+    delete globalThis.chrome;
+});
+
+test("showFlash() puts the whole message in the title, and clears both", () => {
+    jest.useFakeTimers();
+    const { showFlash } = require("../src/popup/views/helpers");
+
+    showFlash("Saved.");
+    expect(element("flash-msg").textContent).toBe("Saved.");
+    expect(element("flash-msg").title).toBe("Saved.");
+
+    jest.advanceTimersByTime(2000);
+    expect(element("flash-msg").textContent).toBe("");
+    expect(element("flash-msg").title).toBe("");
+});
+
+describe.each([
+    ["addToken", "add-token-address", "btn-add-token-confirm"],
+    [
+        "settingsAddToken",
+        "settings-addtoken-address",
+        "btn-settings-addtoken-manual",
+    ],
+])("adding a token on %s", (view, field, button) => {
+    let flashes;
+    let errors;
+
+    // Clicks the screen's add button with lookupTokenInfo() and saveState()
+    // replaced by the given functions.
+    async function add(lookupTokenInfo, saveState) {
+        flashes = [];
+        errors = jest.spyOn(console, "error").mockImplementation(() => {});
+        jest.spyOn(console, "log").mockImplementation(() => {});
+        jest.doMock("../src/shared/balances", () => ({ lookupTokenInfo }));
+        jest.doMock("../src/shared/state", () => ({
+            state: { trackedTokens: [] },
+            saveState,
+        }));
+        jest.doMock("../src/popup/views/helpers", () => ({
+            $: element,
+            showView: () => {},
+            showFlash: (msg) => flashes.push(msg),
+            escapeHtml: (s) => s,
+            goBack: () => {},
+        }));
+
+        require("../src/popup/views/" + view).init({
+            doRefreshAndRender: () => {},
+        });
+        element(field).value = ADDRESS;
+        await element(button).listeners.click();
+    }
+
+    test("a failed save flashes a fixed line and logs the error", async () => {
+        const detail = "A sentence about the stored record. ".repeat(4);
+
+        await add(
+            async () => ({ symbol: "TKN", decimals: 18, name: "Token" }),
+            async () => {
+                throw new Error(detail);
+            },
+        );
+
+        expect(flashes).toEqual(["Could not add the token."]);
+        expect(errors).toHaveBeenCalledWith(
+            "[AutistMask]",
+            "Adding token failed for",
+            ADDRESS,
+            detail,
+        );
+    });
+
+    test("a contract that is not a token flashes the lookup message", async () => {
+        const detail = "Not a valid ERC-20 token (symbol() failed).";
+
+        await add(
+            async () => {
+                throw new Error(detail);
+            },
+            async () => {},
+        );
+
+        expect(flashes).toEqual([detail]);
+    });
+});

tests/inpageErrors.test.js

@@ -49,11 +49,12 @@ class StubCustomEvent extends StubEvent {
     }
 }
 
-// Every code the background emits on the RPC path today, read out of
-// src/background/index.js. The provider must not know this list — it passes
-// through whatever arrived — but the cases below are the real ones.
+// Examples of codes the background emits on the RPC path, read out of
+// src/background/index.js. The provider must not know any list of codes — it
+// passes through whatever arrived — but the cases below are real ones.
 const REJECTED = 4001; // user rejected the request
 const UNAUTHORIZED = 4100; // site not connected / wrong address
+const UNSUPPORTED_METHOD = 4200; // a method the wallet does not implement
 const UNRECOGNIZED_CHAIN = 4902; // switch/add to an unsupported chain
 
 // A stub window with the four things inpage.js touches: message listeners,
@@ -115,6 +116,41 @@ async function rejectionFrom(start, response) {
     return outcome.error;
 }
 
+// The reply the real background worker (src/background/index.js) sends for
+// `method`, loaded against just enough of the extension API to receive one
+// RPC message. Same shape as tests/coldWorkerChainId.test.js.
+function backgroundReply(method) {
+    jest.resetModules();
+    jest.doMock("../src/shared/alarms", () => ({
+        BALANCE_REFRESH_ALARM: "balance",
+        BALANCE_REFRESH_PERIOD_MINUTES: 1,
+        ensureRecurringAlarms: async () => {},
+        registerAlarmHandlers: () => {},
+    }));
+
+    let messageListener = null;
+    global.chrome = {
+        runtime: {
+            onMessage: {
+                addListener: (fn) => {
+                    messageListener = fn;
+                },
+            },
+            onConnect: { addListener: () => {} },
+        },
+    };
+
+    require("../src/background/index");
+
+    return new Promise((resolve) => {
+        messageListener(
+            { type: "AUTISTMASK_RPC", method, params: [] },
+            { origin: "https://dapp.example" },
+            resolve,
+        );
+    });
+}
+
 describe("an EIP-1193 code reaches the page", () => {
     test("a user rejection arrives as code 4001", async () => {
         const err = await rejectionFrom(
@@ -164,8 +200,9 @@ describe("an EIP-1193 code reaches the page", () => {
         expect(err.message).toBe(message);
     });
 
-    // The provider is not allowed to know the list above: a code added to the
-    // background later must reach the page without this file being edited.
+    // The provider is not allowed to know the codes above: any other code,
+    // including one added to the background later, must reach the page
+    // without inpage.js being edited.
     test("a code the provider has never heard of is passed through", async () => {
         const err = await rejectionFrom(
             (p) => p.request({ method: "eth_accounts" }),
@@ -203,6 +240,26 @@ describe("an EIP-1193 code reaches the page", () => {
     });
 });
 
+// The reply here is the background's own, not one written in this file: it
+// used to carry no code for a method the wallet does not implement
+// (https://git.eeqj.de/sneak/AutistMask/issues/279), so a site probing for an
+// optional method could not tell "not implemented" from "the call failed".
+describe("a method the wallet does not implement", () => {
+    afterEach(() => {
+        delete global.chrome;
+    });
+
+    test("reaches the page as code 4200", async () => {
+        const method = "wallet_noSuchMethod";
+        const err = await rejectionFrom(
+            (p) => p.request({ method }),
+            await backgroundReply(method),
+        );
+        expect(err.code).toBe(UNSUPPORTED_METHOD);
+        expect(err.message).toBe("Unsupported method: " + method);
+    });
+});
+
 describe("the message is untouched", () => {
     test("a coded error keeps the message byte for byte", async () => {
         const message =

tests/sendDisplayFloor.test.js

@@ -1,452 +0,0 @@
-// The balance and fee lines of the Send and confirmation screens, and the fee
-// line they must share with the approval screen.
-//
-// An ETH balance, a token balance or a fee below 0.000001 rendered as zero on
-// these screens (https://git.eeqj.de/sneak/AutistMask/issues/343): the stored
-// balances and the fee were each cut to six decimal places, a rule of their
-// own, and a token holding cut to zero was dropped, while the approval screen
-// showed the same fee through src/shared/amountDisplay.js with the nonzero
-// floor. The balances are now stored exactly, every nonzero token holding
-// kept, and the screens show them and the fee through that helper.
-//
-// Driven through the real refreshBalances(), Send screen, confirmation screen
-// and approval screen, with only the node, the explorer and the DOM stubbed: a
-// balance written onto state by hand would skip the place the cut happened.
-
-"use strict";
-
-// What the stub node answers. Each test sets what it needs.
-const mockNode = {
-    balanceWei: 0n,
-    feeData: { maxFeePerGas: 1n, gasPrice: 1n },
-};
-
-// The token rows the stub explorer reports for the address.
-const mockExplorer = { items: [] };
-
-jest.mock("ethers", () => {
-    const actual = jest.requireActual("ethers");
-    class StubProvider {
-        async getBalance() {
-            return mockNode.balanceWei;
-        }
-        async lookupAddress() {
-            return null;
-        }
-        async getFeeData() {
-            return mockNode.feeData;
-        }
-        async estimateGas() {
-            return 21000n;
-        }
-        async getCode() {
-            return "0x";
-        }
-        async getTransactionCount() {
-            return 1;
-        }
-    }
-    return {
-        ...actual,
-        JsonRpcProvider: StubProvider,
-        Network: { from: () => ({}) },
-    };
-});
-
-jest.mock("../src/shared/log", () => ({
-    log: {
-        debugf: () => {},
-        infof: () => {},
-        warnf: () => {},
-        errorf: () => {},
-    },
-    // The explorer's token list, which refreshBalances() also fetches.
-    debugFetch: jest.fn(async () => ({
-        ok: true,
-        status: 200,
-        json: async () => mockExplorer.items,
-    })),
-    setRuntimeDebug: () => {},
-    isDebug: () => false,
-}));
-
-// The confirmation screen's Etherscan label lookup is the only fetch() these
-// screens make; it fails, as it does offline.
-global.fetch = jest.fn(() => {
-    throw new Error("tests must not perform network requests");
-});
-
-// The approval the background hands the approval screen. Set per test.
-let approvalDetails = null;
-
-const { makeStorageStub } = require("./support/storageStub");
-global.chrome = {
-    storage: makeStorageStub(),
-    runtime: {
-        connect: () => ({
-            postMessage() {},
-            disconnect() {},
-            onDisconnect: { addListener() {} },
-        }),
-        sendMessage(message, callback) {
-            callback(
-                message.type === "AUTISTMASK_GET_APPROVAL"
-                    ? approvalDetails
-                    : undefined,
-            );
-        },
-    },
-};
-
-// A stub DOM: every id resolves to a recording element.
-const elements = new Map();
-
-function makeEl(id) {
-    const handlers = new Map();
-    return {
-        id,
-        textContent: "",
-        innerHTML: "",
-        value: "",
-        disabled: false,
-        style: {},
-        dataset: {},
-        classList: {
-            add() {},
-            remove() {},
-            toggle() {},
-            contains: () => false,
-        },
-        handlers,
-        children: [],
-        addEventListener(name, fn) {
-            handlers.set(name, fn);
-        },
-        appendChild(child) {
-            this.children.push(child);
-            return child;
-        },
-        querySelectorAll: () => [],
-        querySelector: () => null,
-        remove() {},
-        focus() {},
-    };
-}
-
-global.document = {
-    getElementById(id) {
-        if (!elements.has(id)) elements.set(id, makeEl(id));
-        return elements.get(id);
-    },
-    createElement: (tag) => makeEl(tag),
-    body: { prepend() {}, appendChild() {} },
-    addEventListener() {},
-};
-global.navigator = { clipboard: { writeText() {} } };
-
-const { refreshBalances } = require("../src/shared/balances");
-const { state } = require("../src/shared/state");
-const {
-    prices,
-    clearPrices,
-    formatAddressTotal,
-    getAddressValue,
-} = require("../src/shared/prices");
-const send = require("../src/popup/views/send");
-const confirmTx = require("../src/popup/views/confirmTx");
-const approval = require("../src/popup/views/approval");
-const {
-    addressHoldsFunds,
-    balanceLinesForAddress,
-} = require("../src/popup/views/helpers");
-
-const HOLDER = "0x" + "a".repeat(40);
-const RECIPIENT = "0xC0FfEE0000000000000000000000000000c0fFEe";
-
-// 0.0000005 ETH, or 0.0000005 of an 18-decimal token.
-const HALF_MICRO_ETH = 500000000000n;
-
-// A token the bundled list does not know.
-const TOKEN = "0x" + "d".repeat(40);
-
-// The explorer's row for TOKEN, holding `value` base units. With only five
-// holders, it is listed only when the user tracks the token.
-function tokenRow(value, token = {}) {
-    return {
-        value: String(value),
-        token: {
-            type: "ERC-20",
-            address_hash: TOKEN,
-            symbol: "TOK",
-            name: "Token",
-            decimals: "18",
-            holders_count: "5",
-            ...token,
-        },
-    };
-}
-
-function text(id) {
-    return global.document.getElementById(id).textContent;
-}
-
-function errors() {
-    return global.document.getElementById("confirm-errors").innerHTML;
-}
-
-// The ETH balance the node reports and the token rows the explorer reports,
-// fetched and stored exactly where the popup stores them.
-async function refreshWith(balanceWei, tokenItems = []) {
-    mockNode.balanceWei = balanceWei;
-    mockExplorer.items = tokenItems;
-    state.wallets = [{ name: "Wallet 1", addresses: [{ address: HOLDER }] }];
-    state.selectedWallet = 0;
-    state.selectedAddress = 0;
-    await refreshBalances(
-        state.wallets,
-        "https://rpc.example.invalid",
-        "https://blockscout.example/api/v2",
-        state.trackedTokens,
-        "mainnet",
-    );
-}
-
-// Press Review on the Send screen for a send of `token` ("ETH" or a token
-// address), and show the confirmation screen it leads to with its fee estimate
-// settled.
-async function confirmSend(amount, token = "ETH") {
-    let txInfo = null;
-    send.init({ showConfirmTx: (info) => (txInfo = info) });
-    state.selectedToken = token;
-    global.document.getElementById("send-to").value = RECIPIENT;
-    global.document.getElementById("send-amount").value = amount;
-    await global.document
-        .getElementById("btn-send-review")
-        .handlers.get("click")();
-    confirmTx.show(txInfo);
-    for (let i = 0; i < 10; i++) await new Promise((r) => setTimeout(r, 0));
-}
-
-// The approval screen for a dApp transaction of 21000 gas, the gas the stub
-// node estimates for the send above.
-async function approveTxWithFeePerGas(maxFeePerGas) {
-    approvalDetails = {
-        type: "tx",
-        hostname: "dapp.example",
-        approvedFrom: HOLDER,
-        approvedTx: {
-            to: RECIPIENT,
-            value: "0",
-            data: "0x",
-            chainId: "0x1",
-            gasLimit: "21000",
-            maxFeePerGas: String(maxFeePerGas),
-            nonce: 0,
-        },
-    };
-    await approval.show("1");
-}
-
-beforeEach(() => {
-    elements.clear();
-    state.selectedToken = null;
-    state.trackedTokens = [];
-    state.fraudContracts = [];
-    state.currentView = null;
-    mockNode.feeData = { maxFeePerGas: 1n, gasPrice: 1n };
-});
-
-describe("an ETH balance below 0.000001 never renders as zero", () => {
-    test("on the Send screen", async () => {
-        await refreshWith(HALF_MICRO_ETH);
-        state.selectedToken = "ETH";
-        send.updateSendBalance();
-        expect(text("send-balance")).toBe("Current balance: 0.0000005 ETH");
-    });
-
-    test("on the confirmation screen", async () => {
-        await refreshWith(HALF_MICRO_ETH);
-        await confirmSend("0.0000001");
-        expect(text("confirm-balance")).toBe("0.0000005 ETH");
-    });
-
-    test("while a balance above the floor keeps four decimals", async () => {
-        await refreshWith(1234567890000000000n);
-        await confirmSend("0.1");
-        expect(text("confirm-balance")).toBe("1.2345 ETH");
-    });
-});
-
-// A token the user tracks stays on the balance list when the explorer's row is
-// dropped, so a holding of it below 0.000001 reached these screens as zero, and
-// the send was checked against zero.
-describe("a tracked token holding below 0.000001 never renders as zero", () => {
-    beforeEach(() => {
-        state.trackedTokens = [
-            { address: TOKEN, symbol: "TOK", name: "Token", decimals: 18 },
-        ];
-    });
-
-    test("on the Send screen", async () => {
-        await refreshWith(10n ** 18n, [tokenRow(HALF_MICRO_ETH)]);
-        state.selectedToken = TOKEN;
-        send.updateSendBalance();
-        expect(text("send-balance")).toBe("Current balance: 0.0000005 TOK");
-    });
-
-    test("on the confirmation screen, which checks the send against it", async () => {
-        await refreshWith(10n ** 18n, [tokenRow(HALF_MICRO_ETH)]);
-        await confirmSend("0.0000005", TOKEN);
-        expect(text("confirm-balance")).toBe("0.0000005 TOK");
-        expect(errors()).toBe("");
-        await confirmSend("0.0000006", TOKEN);
-        expect(errors()).toContain(
-            "You have 0.0000005 TOK but are trying to send 0.0000006 TOK.",
-        );
-    });
-
-    // The stored balance keeps all 24 places, and the balance check reads the
-    // first 18 of them rather than refusing it as no balance at all.
-    test("with more than 18 decimals, the send is checked against 18 of them", async () => {
-        state.trackedTokens[0].decimals = 24;
-        // 1.5 plus one base unit.
-        const value = 15n * 10n ** 23n + 1n;
-        await refreshWith(10n ** 18n, [tokenRow(value, { decimals: "24" })]);
-        await confirmSend("1.5", TOKEN);
-        expect(text("confirm-balance")).toBe("1.5000 TOK");
-        expect(errors()).toBe("");
-    });
-
-    test("with more than 18 decimals and a holding below 10^-18", async () => {
-        state.trackedTokens[0].decimals = 24;
-        // One base unit, 0.000000000000000000000001 TOK.
-        await refreshWith(10n ** 18n, [tokenRow(1n, { decimals: "24" })]);
-        state.selectedToken = TOKEN;
-        send.updateSendBalance();
-        expect(text("send-balance")).toBe(
-            "Current balance: 0.000000000000000000000001 TOK",
-        );
-        await confirmSend("0.000000000000000001", TOKEN);
-        expect(text("confirm-balance")).toBe("0.000000000000000000000001 TOK");
-        expect(errors()).toContain(
-            "You have 0.000000000000000000000001 TOK but are trying to send" +
-                " 0.000000000000000001 TOK.",
-        );
-    });
-});
-
-// A token the user does not track, with enough holders to be admitted. The
-// balance fetch dropped a holding of it below 0.000001, but the token stays
-// selected while its own screen is open: after sending 2 of a 2.0000003
-// holding, the user is back on that screen, and Send read the missing row as
-// zero.
-describe("an untracked token holding below 0.000001 never renders as zero", () => {
-    const row = () => tokenRow(HALF_MICRO_ETH, { holders_count: "50000" });
-
-    test("on the Send screen", async () => {
-        await refreshWith(10n ** 18n, [row()]);
-        state.selectedToken = TOKEN;
-        send.updateSendBalance();
-        expect(text("send-balance")).toBe("Current balance: 0.0000005 TOK");
-    });
-
-    test("on the confirmation screen, which checks the send against it", async () => {
-        await refreshWith(10n ** 18n, [row()]);
-        await confirmSend("0.0000005", TOKEN);
-        expect(text("confirm-balance")).toBe("0.0000005 TOK");
-        expect(errors()).toBe("");
-        await confirmSend("0.0000006", TOKEN);
-        expect(errors()).toContain(
-            "You have 0.0000005 TOK but are trying to send 0.0000006 TOK.",
-        );
-    });
-});
-
-// The fetch keeps every holding, so the screens that showed only what it kept
-// leave out a holding below 0.000001 themselves, and look as they did.
-describe("a token holding below 0.000001 is still not listed", () => {
-    afterEach(() => {
-        clearPrices();
-    });
-
-    test("for a token the user does not track", async () => {
-        prices.ETH = 3000;
-        await refreshWith(0n, [
-            tokenRow(HALF_MICRO_ETH, { holders_count: "50000" }),
-        ]);
-        const addr = state.wallets[0].addresses[0];
-        expect(balanceLinesForAddress(addr, [], true)).not.toContain(TOKEN);
-        expect(balanceLinesForAddress(addr, [], false)).not.toContain(TOKEN);
-        send.renderSendTokenSelect(addr);
-        const options = global.document.getElementById("send-token").children;
-        expect(options.map((o) => o.value)).toEqual([]);
-        // Not an unpriced token in the total, and not funds on the
-        // remove-address warning.
-        expect(formatAddressTotal(getAddressValue(addr))).toBe("Total: $0.00");
-        expect(addressHoldsFunds(addr)).toBe(false);
-    });
-
-    // As a tracked token holding nothing: listed only while zero balances are
-    // shown.
-    test("for a tracked token, unless zero balances are shown", async () => {
-        state.trackedTokens = [
-            { address: TOKEN, symbol: "TOK", name: "Token", decimals: 18 },
-        ];
-        await refreshWith(0n, [tokenRow(HALF_MICRO_ETH)]);
-        const addr = state.wallets[0].addresses[0];
-        expect(
-            balanceLinesForAddress(addr, state.trackedTokens, false),
-        ).not.toContain(TOKEN);
-        expect(
-            balanceLinesForAddress(addr, state.trackedTokens, true),
-        ).toContain(`data-token="${TOKEN}"`);
-    });
-});
-
-describe("a fee below 0.000001 ETH never renders as zero", () => {
-    test("when the estimate and the reserve are the same", async () => {
-        await refreshWith(10n ** 18n);
-        await confirmSend("0.1");
-        // 21000 gas at 1 wei is 0.000000000000021 ETH, shown to its first
-        // significant digit.
-        expect(text("confirm-fee-amount")).toBe("0.00000000000002 ETH");
-    });
-
-    test("when they differ, on both lines", async () => {
-        mockNode.feeData = { maxFeePerGas: 2n, gasPrice: 1n };
-        await refreshWith(10n ** 18n);
-        await confirmSend("0.1");
-        expect(text("confirm-fee-amount")).toBe("~0.00000000000002 ETH");
-        expect(text("confirm-fee-reserve")).toBe(
-            "up to 0.00000000000004 ETH reserved",
-        );
-    });
-});
-
-// The confirmation screen shows the reserve alone when the node quotes no
-// cheaper estimate, and that reserve is the same gas limit times maximum fee
-// per gas that the approval screen calls the max fee. An ETH price is set, as
-// it is on mainnet, so the USD value has to match too.
-describe("the same fee reads the same on the confirmation and approval screens", () => {
-    beforeEach(() => {
-        prices.ETH = 3000;
-    });
-    afterEach(() => {
-        clearPrices();
-    });
-
-    test.each([
-        // 21000 gas at 1 wei.
-        ["below the floor", 1n, "0.00000000000002 ETH (< $0.01)"],
-        // 0.001235294117631 ETH, which is $3.71. Pricing the truncated
-        // 0.0012 instead would read $3.60.
-        ["with more than four decimals", 58823529411n, "0.0012 ETH ($3.71)"],
-    ])("%s", async (_label, feePerGas, expected) => {
-        mockNode.feeData = { maxFeePerGas: feePerGas, gasPrice: feePerGas };
-        await refreshWith(10n ** 18n);
-        await confirmSend("0.1");
-        expect(text("confirm-fee-amount")).toBe(expected);
-        await approveTxWithFeePerGas(feePerGas);
-        expect(text("approve-tx-fee")).toBe(expected);
-    });
-});

tests/unknownScaleSend.test.js

@@ -389,7 +389,7 @@ describe("a scale the explorer's own rows disagree about", () => {
         expect(txInfo.tokenBalance).toBe("5.0");
         confirmTx.show(txInfo);
         await settle();
-        expect(text("confirm-balance")).toBe("5.0000 NOVEL");
+        expect(text("confirm-balance")).toBe("5.0 NOVEL");
         expect(errors()).toBe("");
         expect(sendDisabled()).toBe(false);
     });
@@ -431,7 +431,7 @@ describe("the confirmation screen tells an unknown balance from a zero one", ()
         const zero = await render("0.0");
         expect(unknown.balance).not.toBe(zero.balance);
         expect(unknown.balance).toBe("unknown (NOVEL)");
-        expect(zero.balance).toBe("0.0000 NOVEL");
+        expect(zero.balance).toBe("0.0 NOVEL");
     });
 
     // Both hit INSUFFICIENT_TOKEN — an unknown balance is treated as nothing to
@@ -443,7 +443,7 @@ describe("the confirmation screen tells an unknown balance from a zero one", ()
         expect(unknown.errors).not.toBe(zero.errors);
         expect(unknown.errors).toContain("This token's balance is unknown");
         expect(unknown.errors).not.toContain("You have");
-        expect(zero.errors).toContain("You have 0.0000 NOVEL");
+        expect(zero.errors).toContain("You have 0.0 NOVEL");
         expect(zero.errors).not.toContain("balance is unknown");
     });
 });