fix: the balance lists and Home cut amounts to four decimals (closes #757)

The balance lists and Home's ETH line rounded with toFixed(4), so 0.99996
ETH read 1.0000 there and 0.9999 on Send. They now cut the stored decimal
string with truncateAmount(), as the history rows do. balanceLine() takes
the stored balance string instead of a parsed number, and escapes the
quantity cell. The screens that state what is authorized keep the floor
of truncateAmountNeverZero().

Model: opus-5-5

README.md

@@ -264,6 +264,8 @@ The shared modules, each in one line:
   messaging, windows and the lock.
 - `buildInfo.js`: the version, license, author, commit and date compiled into
   About.
+- `calldataDecoder.js`: the ERC-20 `approve()` and `transfer()` decoder, which
+  hands other calldata to `uniswap.js`. Popup only.
 - `chainSwitch.js`: the popup's network switch.
 - `chainSwitchFields.js`: the fields a network switch changes.
 - `constants.js`: `DEBUG`, the default endpoints, the ERC-20 ABI and the burn
@@ -1189,8 +1191,8 @@ These helpers write one kind of value on every screen that shows it:
 
 Most screens show token and ETH amounts with four decimal places. History rows
 cut amounts to four decimals and never round up (`truncateAmount()` in
-`src/shared/amountDisplay.js`). The balance lists and Home's ETH balance round
-to four places. The screens that state what is being authorized cut as the
+`src/shared/amountDisplay.js`). The balance lists and Home's ETH balance cut
+them the same way. The screens that state what is being authorized cut as the
 history does, and extend an amount below 0.0001 to its first nonzero digit
 (`truncateAmountNeverZero()`). So a nonzero amount never reads as zero there.
 Those screens are:
@@ -1379,7 +1381,7 @@ approval screens show a red warning.
 ### Transaction decoding
 
 TxApproval and TransactionDetail try to decode calldata into a summary
-(`decodeCalldata()` in `src/popup/views/approval.js`). SuccessTx repeats
+(`decodeCalldata()` in `src/shared/calldataDecoder.js`). SuccessTx repeats
 TxApproval's summary. Decoding is a display aid. When it fails, the raw calldata
 is shown in full. No contract gets any treatment beyond a legible confirmation
 screen.

RULES.md

@@ -108,10 +108,7 @@ contradicts either, the originals govern.
 - [ ] All tool invocations via `make` targets, never directly
 - [ ] `make check` = `make test` + `make lint` + `make fmt-check`
 - [ ] `main` always passes `make check`
-- [ ] Branch per issue, cut from `next`. One PR per issue, based on `next`,
-      squash-merged into `next` on a passed independent review. `main` is
-      reached only by the per-milestone PR from `next`; releases are tagged from
-      `main`. `next` and `main` must stay green; feature branches may be red.
+- [ ] Feature branches for all changes, merge to main when done
 - [ ] No force-push to `main`
 - [ ] Pre-commit hook runs `make check`
 

src/popup/views/addressToken.js

@@ -159,10 +159,10 @@ function renderBalance() {
     const addr =
         state.wallets[state.selectedWallet].addresses[state.selectedAddress];
     const tokenId = state.selectedToken;
-    let amount, price;
+    let balance, price;
     if (tokenId === "ETH") {
         // null when no refresh has read the balance.
-        amount = unknownableAmount(addr.balance);
+        balance = addr.balance;
         price = getPrice("ETH");
     } else {
         const id = tokenId.toLowerCase();
@@ -175,12 +175,13 @@ function renderBalance() {
         // null when the scale is unknown, or when no refresh has read the
         // token's balance: no quantity to show, and none to price.
         // balanceLine() states that rather than printing 0.0000.
-        if (tb) amount = unknownableAmount(tb.balance);
-        else amount = tracked && tracked.balanceNotFetched ? null : 0;
+        if (tb) balance = tb.balance;
+        else balance = tracked && tracked.balanceNotFetched ? null : "0";
         price = getPrice(tokenId);
     }
 
     // USD total for this token only
+    const amount = unknownableAmount(balance);
     const usdVal = price && amount !== null ? amount * price : null;
     const usdStr = formatUsd(usdVal);
     $("address-token-usd-total").innerHTML = escapeHtml(usdStr) || " ";
@@ -188,7 +189,7 @@ function renderBalance() {
     // Single token balance line (no tokenId — not clickable here)
     $("address-token-balance").innerHTML = balanceLine(
         currentSymbol,
-        amount,
+        balance,
         price,
     );
 }

src/popup/views/approval.js

@@ -12,9 +12,13 @@ const {
     formatFee,
     tokenLabel,
     blockscoutOffTokenNoteHtml,
-    tokenSourcesByChainId,
 } = require("./helpers");
-const { state, saveState, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    saveState,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 const {
     networkById,
     networkByChainId,
@@ -26,21 +30,24 @@ const {
     getAddress,
     getBigInt,
     getBytes,
-    Interface,
     MaxUint256,
     toUtf8String,
 } = require("ethers");
 const { getPrice, formatUsd } = require("../../shared/prices");
-const { ERC20_ABI } = require("../../shared/constants");
 const { INVISIBLE_CHARACTERS } = require("../../shared/symbolSpoof");
 const {
     resolveTokenDecimals,
     resolveTokenSymbol,
     unknownDecimalsAmount,
 } = require("../../shared/approvalAmount");
+const {
+    decodeCalldata,
+    tokenAmountText,
+} = require("../../shared/calldataDecoder");
 // Four decimals, with the nonzero floor these screens hold: every amount this
 // view renders — the ERC-20 line, the ETH value, the max fee — and every one
-// it carries forward to the wait/success/error screens goes through it.
+// it carries forward to the wait/success/error screens goes through it. The
+// ERC-20 line gets it from tokenAmountText().
 const {
     truncateAmountNeverZero: formatTxValue,
 } = require("../../shared/amountDisplay");
@@ -54,11 +61,8 @@ const {
     typedDataChainRefusal,
 } = require("../../shared/approvalVerify");
 const txStatus = require("./txStatus");
-const uniswap = require("../../shared/uniswap");
 const { runtimeApi, sendMessage } = require("../../shared/browserApi");
 
-const erc20Iface = new Interface(ERC20_ABI);
-
 // The link opens the explorer of the network with `chainId`, or of the active
 // network when none is given. A chain id that names no network has no
 // explorer, so the address is drawn without a link.
@@ -70,141 +74,6 @@ function approvalAddressHtml(address, chainId) {
     return renderAddressHtml(address, { title, chainId });
 }
 
-// The amount line for a decoded ERC-20 call. With a known scale it is the
-// token quantity; with `decimals` null it is the base-unit integer with the
-// unknown scale stated, because formatting it with an assumed scale is what
-// showed a 5,000-token transfer as `0.0000`. `raw` is what the status screens
-// carry, `display` is what the approval screen shows.
-function tokenAmountText(rawAmount, decimals, symbol) {
-    if (decimals === null) {
-        const unknown = unknownDecimalsAmount(rawAmount);
-        return { raw: unknown, display: unknown };
-    }
-    const formatted = formatTxValue(formatUnits(rawAmount, decimals));
-    return {
-        raw: formatted,
-        display: formatted + (symbol ? " " + symbol : ""),
-    };
-}
-
-// Try to decode calldata sent from `fromAddress` to `toAddress` on the network
-// with chain id `chainId`, using known ABIs.
-// Returns { name, description, details } or null.
-function decodeCalldata(data, toAddress, chainId, fromAddress) {
-    if (!data || data === "0x" || data.length < 10) return null;
-
-    // Where a token's name and scale are looked for, for every decoder below:
-    // what the wallet knows of the tokens on the network with `chainId`, which
-    // need not be the active one. The ERC-20 amount line and the swap's Amount
-    // and Min. received lines resolve the scale the same way, and refuse to
-    // format the same way when it is nowhere.
-    const decimalsSources = tokenSourcesByChainId(chainId);
-
-    // Try ERC-20 (approve / transfer)
-    try {
-        const parsed = erc20Iface.parseTransaction({ data });
-        if (parsed) {
-            const tokenSymbol = resolveTokenSymbol(toAddress, decimalsSources);
-            // null when no source knows this token's scale. It is not
-            // defaulted to 18: an amount formatted with a guessed scale is
-            // the wrong number, and for a token with fewer decimals than the
-            // guess it is the wrong number in the direction that reads as
-            // zero. See tokenAmountText().
-            const tokenDecimals = resolveTokenDecimals(
-                toAddress,
-                decimalsSources,
-            );
-            const contractLabel = tokenSymbol
-                ? tokenSymbol + " (" + toAddress + ")"
-                : toAddress;
-
-            if (parsed.name === "approve") {
-                const spender = parsed.args[0];
-                const rawAmount = parsed.args[1];
-                const maxUint = BigInt(
-                    "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
-                );
-                const isUnlimited = rawAmount === maxUint;
-                // An unbounded allowance needs no scale to describe, so it is
-                // still named rather than refused.
-                const amount = isUnlimited
-                    ? { raw: "Unlimited", display: "Unlimited" }
-                    : tokenAmountText(rawAmount, tokenDecimals, tokenSymbol);
-
-                return {
-                    name: "Token Approval",
-                    description: tokenSymbol
-                        ? "Approve spending of your " + tokenSymbol
-                        : "Approve spending of an ERC-20 token",
-                    details: [
-                        {
-                            label: "Token",
-                            value: contractLabel,
-                            address: toAddress,
-                            isToken: true,
-                        },
-                        {
-                            label: "Spender",
-                            value: spender,
-                            address: spender,
-                        },
-                        {
-                            label: "Amount",
-                            value: amount.display,
-                            rawValue: amount.raw,
-                        },
-                    ],
-                };
-            }
-
-            if (parsed.name === "transfer") {
-                const to = parsed.args[0];
-                const rawAmount = parsed.args[1];
-                const amount = tokenAmountText(
-                    rawAmount,
-                    tokenDecimals,
-                    tokenSymbol,
-                );
-
-                return {
-                    name: "Token Transfer",
-                    description: tokenSymbol
-                        ? "Transfer " + tokenSymbol
-                        : "Transfer ERC-20 token",
-                    details: [
-                        {
-                            label: "Token",
-                            value: contractLabel,
-                            address: toAddress,
-                            isToken: true,
-                        },
-                        { label: "Recipient", value: to, address: to },
-                        {
-                            label: "Amount",
-                            value: amount.display,
-                            rawValue: amount.raw,
-                        },
-                    ],
-                };
-            }
-        }
-    } catch {
-        // Not ERC-20 — fall through
-    }
-
-    // Try Uniswap Universal Router
-    const routerResult = uniswap.decode(
-        data,
-        toAddress,
-        chainId,
-        decimalsSources,
-        fromAddress,
-    );
-    if (routerResult) return routerResult;
-
-    return null;
-}
-
 function showPhishingWarning(elementId, isPhishing) {
     const el = $(elementId);
     if (!el) return;
@@ -1298,7 +1167,6 @@ function init(_ctx) {
 module.exports = {
     init,
     show,
-    decodeCalldata,
     formatTypedDataHtml,
     typedDataRefusal,
 };

src/popup/views/deleteAddress.js

@@ -79,8 +79,8 @@ function recoveryPathText(wallet) {
 // "Holds" means ETH or any ERC-20 the wallet knows about — an address with no
 // ETH and a five-figure stablecoin position must not get the blank line on
 // the one screen whose job is to warn. The sentence names no figure of its
-// own: the rendered lines round to four decimals, so a sentence built from a
-// rounded number would report "0.0000 ETH" for an address holding real money.
+// own: the rendered lines cut to four decimals, so a sentence built from their
+// figure would report "0.0000 ETH" for an address holding real money.
 // The lines below it carry the amounts, in the same format as Home and
 // AddressDetail, followed by the USD total when there is one to give — no
 // total line at all on testnet, before the first price fetch or while no

src/popup/views/helpers.js

@@ -18,6 +18,7 @@
 const { formatEther } = require("ethers");
 const makeBlockie = require("ethereum-blockies-base64");
 const {
+    truncateAmount,
     truncateAmountNeverZero,
     isBelowOneMillionth,
 } = require("../../shared/amountDisplay");
@@ -31,7 +32,12 @@ const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
 const { networkByChainId } = require("../../shared/networks");
 const { formatUsd, getPrice } = require("../../shared/prices");
-const { state, saveState, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    saveState,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 const { displaySymbol } = require("../../shared/symbolDisplay");
 const { isSpoofedSymbol } = require("../../shared/symbolSpoof");
 const { walletHasRecoveryPhrase } = require("../../shared/wallet");
@@ -305,32 +311,6 @@ function nativeCurrency() {
     return currentNetwork().nativeCurrency;
 }
 
-// What the wallet knows of the tokens on the network with this chain id, or
-// on the active network when no chain id is given, as the `sources` that
-// resolveTokenSymbol() and resolveTokenDecimals() take. A contract address
-// names a token on one network only, and every token balance held is the
-// active network's, so another network gets the tokens tracked on it
-// (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
-//
-// The wallets' balances hold what Blockscout reported for each token. So the
-// wallets are returned only while "Use Blockscout" is on.
-function tokenSourcesByChainId(chainId) {
-    const chainIdOrActive = chainId || currentNetwork().chainId;
-    const net = networkByChainId(chainIdOrActive);
-    if (net && net.id === state.networkId) {
-        return {
-            chainId: chainIdOrActive,
-            trackedTokens: state.trackedTokens,
-            wallets: state.useBlockscout ? state.wallets : [],
-        };
-    }
-    return {
-        chainId: chainIdOrActive,
-        trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
-        wallets: [],
-    };
-}
-
 // The line shown under a token while "Use Blockscout" is off. The token gets
 // the line only when the bundled list and the tracked tokens lack its name or
 // decimals. Otherwise this returns "". The token is a contract address on the
@@ -394,13 +374,15 @@ function formatFee(wei, symbol, chainId) {
 // the row that issue #307 was reported against: every screen that lists a
 // holding renders through here.
 //
-// `amount` is null for a holding whose scale nothing knows
+// `balance` is the stored balance, a decimal string. It is null for a holding
+// whose scale nothing knows
 // (https://git.eeqj.de/sneak/AutistMask/issues/349), and for a balance no
 // refresh has read. There is no quantity to print for it and no fiat value to
 // derive from one, and printing 0.0000 for a real holding is the failure this
 // whole rule exists to prevent, so the row says so instead.
-function balanceLine(symbol, amount, price, tokenId) {
-    const qty = amount === null ? "quantity unknown" : amount.toFixed(4);
+function balanceLine(symbol, balance, price, tokenId) {
+    const amount = unknownableAmount(balance);
+    const qty = amount === null ? "quantity unknown" : truncateAmount(balance);
     const usd =
         price && amount !== null
             ? escapeHtml(formatUsd(amount * price)) || " "
@@ -415,7 +397,7 @@ function balanceLine(symbol, amount, price, tokenId) {
         `<div class="flex text-xs${clickClass}"${tokenAttr}>` +
         `<span class="flex justify-between w-[42ch] max-w-full">` +
         `<span>${escapeHtml(displaySymbol(symbol))}</span>` +
-        `<span>${qty}</span>` +
+        `<span>${escapeHtml(qty)}</span>` +
         `</span>` +
         `<span class="text-right text-muted flex-1">${usd}</span>` +
         `</div>`
@@ -441,7 +423,7 @@ function markTrackedTokensNotFetched() {
 function balanceLinesForAddress(addr, trackedTokens, showZero) {
     let html = balanceLine(
         nativeCurrency(),
-        unknownableAmount(addr.balance),
+        addr.balance,
         getPrice("ETH"),
         "ETH",
     );
@@ -459,7 +441,7 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
         if (bal === 0 && !showZero) continue;
         html += balanceLine(
             t.symbol,
-            bal,
+            t.balance,
             getPrice(t.address),
             t.address.toLowerCase(),
         );
@@ -477,7 +459,7 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
             }
             html += balanceLine(
                 t.symbol,
-                t.balanceNotFetched ? null : 0,
+                t.balanceNotFetched ? null : "0",
                 getPrice(t.address),
                 t.address.toLowerCase(),
             );
@@ -488,10 +470,10 @@ 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.
+// under the remove-address warning leaves out too. Deliberately exact — the
+// rendered lines cut 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;
     // A null or absent ETH balance reads as unknown, so the address may hold
@@ -866,7 +848,6 @@ module.exports = {
     keyMaterialName,
     unknownableAmount,
     nativeCurrency,
-    tokenSourcesByChainId,
     blockscoutOffTokenNoteHtml,
     tokenLabel,
     formatFee,

src/popup/views/home.js

@@ -31,6 +31,7 @@ const {
     resetSendValidation,
 } = require("./send");
 const { deriveAddressFromXpub } = require("../../shared/wallet");
+const { truncateAmount } = require("../../shared/amountDisplay");
 const { canRemoveAddress } = require("../../shared/walletDelete");
 const {
     walletDefect,
@@ -81,7 +82,7 @@ function renderTotalValue() {
     if (ethBal === null) {
         el.textContent = "unknown (" + nativeCurrency() + ")";
     } else {
-        const ethStr = ethBal.toFixed(4) + " " + nativeCurrency();
+        const ethStr = truncateAmount(addr.balance) + " " + nativeCurrency();
         const ethUsd = ethPrice
             ? " (" + formatUsd(ethBal * ethPrice) + ")"
             : "";

src/popup/views/send.js

@@ -10,9 +10,13 @@ const {
     renderAddressHtml,
     attachCopyHandlers,
     goBack,
-    tokenSourcesByChainId,
 } = require("./helpers");
-const { state, currentAddress, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    currentAddress,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
 const { resolveTokenDecimals } = require("../../shared/approvalAmount");

src/popup/views/transactionDetail.js

@@ -27,7 +27,7 @@ const { nativeCurrencyByChainId } = require("../../shared/networks");
 const { formatEther, formatUnits } = require("ethers");
 const { log, debugFetch } = require("../../shared/log");
 const { storedSettingIsOn } = require("../../shared/storedSettings");
-const { decodeCalldata } = require("./approval");
+const { decodeCalldata } = require("../../shared/calldataDecoder");
 
 /**
  * Determine a human-readable transaction type string from tx fields.

src/shared/amountDisplay.js

@@ -2,7 +2,7 @@
 // the one exception to it, in one place. Three call sites had grown their own
 // copy of the truncation — the history and balance lists
 // (`src/shared/transactions.js`), the approval screen's ERC-20 amount line
-// (`src/popup/views/approval.js`) and its Uniswap swap detail lines
+// (`src/shared/calldataDecoder.js`) and its Uniswap swap detail lines
 // (`src/shared/uniswap.js`) — and a fix applied to one of them left the other
 // two showing a different number for the same value.
 //

src/shared/calldataDecoder.js

@@ -0,0 +1,155 @@
+// Decode a transaction's calldata into the summary that TxApproval and
+// TransactionDetail show: ERC-20 `approve` and `transfer` calls here, and
+// Uniswap Universal Router calls through uniswap.js. The summary is data; the
+// views turn its addresses into HTML.
+
+const { formatUnits, Interface } = require("ethers");
+const { ERC20_ABI } = require("./constants");
+const { tokenSourcesByChainId } = require("./state");
+const {
+    resolveTokenDecimals,
+    resolveTokenSymbol,
+    unknownDecimalsAmount,
+} = require("./approvalAmount");
+// Four decimals, with the nonzero floor the approval screens hold.
+const { truncateAmountNeverZero } = require("./amountDisplay");
+const uniswap = require("./uniswap");
+
+const erc20Iface = new Interface(ERC20_ABI);
+
+// The amount line for a decoded ERC-20 call. With a known scale it is the
+// token quantity; with `decimals` null it is the base-unit integer with the
+// unknown scale stated, because formatting it with an assumed scale is what
+// showed a 5,000-token transfer as `0.0000`. `raw` is what the status screens
+// carry, `display` is what the approval screen shows.
+function tokenAmountText(rawAmount, decimals, symbol) {
+    if (decimals === null) {
+        const unknown = unknownDecimalsAmount(rawAmount);
+        return { raw: unknown, display: unknown };
+    }
+    const formatted = truncateAmountNeverZero(formatUnits(rawAmount, decimals));
+    return {
+        raw: formatted,
+        display: formatted + (symbol ? " " + symbol : ""),
+    };
+}
+
+// Try to decode calldata sent from `fromAddress` to `toAddress` on the network
+// with chain id `chainId`, using known ABIs.
+// Returns { name, description, details } or null.
+function decodeCalldata(data, toAddress, chainId, fromAddress) {
+    if (!data || data === "0x" || data.length < 10) return null;
+
+    // Where a token's name and scale are looked for, for every decoder below:
+    // what the wallet knows of the tokens on the network with `chainId`, which
+    // need not be the active one. The ERC-20 amount line and the swap's Amount
+    // and Min. received lines resolve the scale the same way, and refuse to
+    // format the same way when it is nowhere.
+    const decimalsSources = tokenSourcesByChainId(chainId);
+
+    // Try ERC-20 (approve / transfer)
+    try {
+        const parsed = erc20Iface.parseTransaction({ data });
+        if (parsed) {
+            const tokenSymbol = resolveTokenSymbol(toAddress, decimalsSources);
+            // null when no source knows this token's scale. It is not
+            // defaulted to 18: an amount formatted with a guessed scale is
+            // the wrong number, and for a token with fewer decimals than the
+            // guess it is the wrong number in the direction that reads as
+            // zero. See tokenAmountText().
+            const tokenDecimals = resolveTokenDecimals(
+                toAddress,
+                decimalsSources,
+            );
+            const contractLabel = tokenSymbol
+                ? tokenSymbol + " (" + toAddress + ")"
+                : toAddress;
+
+            if (parsed.name === "approve") {
+                const spender = parsed.args[0];
+                const rawAmount = parsed.args[1];
+                const maxUint = BigInt(
+                    "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+                );
+                const isUnlimited = rawAmount === maxUint;
+                // An unbounded allowance needs no scale to describe, so it is
+                // still named rather than refused.
+                const amount = isUnlimited
+                    ? { raw: "Unlimited", display: "Unlimited" }
+                    : tokenAmountText(rawAmount, tokenDecimals, tokenSymbol);
+
+                return {
+                    name: "Token Approval",
+                    description: tokenSymbol
+                        ? "Approve spending of your " + tokenSymbol
+                        : "Approve spending of an ERC-20 token",
+                    details: [
+                        {
+                            label: "Token",
+                            value: contractLabel,
+                            address: toAddress,
+                            isToken: true,
+                        },
+                        {
+                            label: "Spender",
+                            value: spender,
+                            address: spender,
+                        },
+                        {
+                            label: "Amount",
+                            value: amount.display,
+                            rawValue: amount.raw,
+                        },
+                    ],
+                };
+            }
+
+            if (parsed.name === "transfer") {
+                const to = parsed.args[0];
+                const rawAmount = parsed.args[1];
+                const amount = tokenAmountText(
+                    rawAmount,
+                    tokenDecimals,
+                    tokenSymbol,
+                );
+
+                return {
+                    name: "Token Transfer",
+                    description: tokenSymbol
+                        ? "Transfer " + tokenSymbol
+                        : "Transfer ERC-20 token",
+                    details: [
+                        {
+                            label: "Token",
+                            value: contractLabel,
+                            address: toAddress,
+                            isToken: true,
+                        },
+                        { label: "Recipient", value: to, address: to },
+                        {
+                            label: "Amount",
+                            value: amount.display,
+                            rawValue: amount.raw,
+                        },
+                    ],
+                };
+            }
+        }
+    } catch {
+        // Not ERC-20 — fall through
+    }
+
+    // Try Uniswap Universal Router
+    const routerResult = uniswap.decode(
+        data,
+        toAddress,
+        chainId,
+        decimalsSources,
+        fromAddress,
+    );
+    if (routerResult) return routerResult;
+
+    return null;
+}
+
+module.exports = { decodeCalldata, tokenAmountText };

src/shared/state.js

@@ -22,7 +22,7 @@
 // same thing in the editor is fast feedback in front of the build, not the
 // guarantee.
 
-const { networkById } = require("./networks");
+const { networkById, networkByChainId } = require("./networks");
 const { copyChainSwitchFields } = require("./chainSwitchFields");
 const {
     DEFAULT_STATE,
@@ -125,6 +125,32 @@ function currentNetwork() {
     return networkById(state.networkId);
 }
 
+// What the wallet knows of the tokens on the network with this chain id, or
+// on the active network when no chain id is given, as the `sources` that
+// resolveTokenSymbol() and resolveTokenDecimals() take. A contract address
+// names a token on one network only, and every token balance held is the
+// active network's, so another network gets the tokens tracked on it
+// (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
+//
+// The wallets' balances hold what Blockscout reported for each token. So the
+// wallets are returned only while "Use Blockscout" is on.
+function tokenSourcesByChainId(chainId) {
+    const chainIdOrActive = chainId || currentNetwork().chainId;
+    const net = networkByChainId(chainIdOrActive);
+    if (net && net.id === state.networkId) {
+        return {
+            chainId: chainIdOrActive,
+            trackedTokens: state.trackedTokens,
+            wallets: state.useBlockscout ? state.wallets : [],
+        };
+    }
+    return {
+        chainId: chainIdOrActive,
+        trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
+        wallets: [],
+    };
+}
+
 // `baseline` holds the persisted fields as this page held them when its last
 // loadState() finished, or when its last successful saveState() began.
 // takeStoredNetwork(), takeStoredTrackedTokens() and
@@ -820,5 +846,6 @@ module.exports = {
     loadState,
     currentAddress,
     currentNetwork,
+    tokenSourcesByChainId,
     StateNotLoadedError,
 };

tests/approvalAmount.test.js

@@ -23,7 +23,7 @@ const {
     resolveTokenDecimals,
     unknownDecimalsAmount,
 } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const iface = new Interface(ERC20_ABI);
 

tests/approvalDisplayFloor.test.js

@@ -13,7 +13,7 @@
 // asserted on `rawValue` alongside the displayed line.
 //
 // Both amount paths of that screen are covered: the ERC-20 line decoded by
-// `src/popup/views/approval.js`, and the swap's `Amount` and `Min. received`
+// `src/shared/calldataDecoder.js`, and the swap's `Amount` and `Min. received`
 // lines decoded by `src/shared/uniswap.js`.
 
 globalThis.chrome = {
@@ -23,12 +23,8 @@ globalThis.chrome = {
 const { AbiCoder, Interface } = require("ethers");
 const { ERC20_ABI } = require("../src/shared/constants");
 const { state } = require("../src/shared/state");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const uniswap = require("../src/shared/uniswap");
-const {
-    truncateAmount,
-    truncateAmountNeverZero,
-} = require("../src/shared/amountDisplay");
 
 const iface = new Interface(ERC20_ABI);
 
@@ -183,15 +179,4 @@ describe("the four-decimal rule is otherwise unchanged", () => {
     test("a genuine zero still renders as zero", () => {
         expect(amount(transferData(0n), DAI).rawValue).toBe("0.0000");
     });
-
-    // The three truncators now share one module. The floor is a policy of the
-    // approval and confirmation screens only: the history and balance lists
-    // keep plain truncation, because the transaction detail view is the
-    // authoritative record and already shows exact precision.
-    test("the list rule stays unfloored", () => {
-        expect(truncateAmount("0.000000000000000001")).toBe("0.0000");
-        expect(truncateAmountNeverZero("0.000000000000000001")).toBe(
-            "0.000000000000000001",
-        );
-    });
 });

tests/balanceLineEscaping.test.js

@@ -41,13 +41,13 @@ describe("balanceLine", () => {
         // this payload before its id attribute, so an assertion about the
         // rest of the payload would pass on the cap and say nothing about
         // the escape.
-        const html = balanceLine(HOSTILE_SYMBOL, 1, null, null);
+        const html = balanceLine(HOSTILE_SYMBOL, "1", null, null);
         expect(html).not.toContain("<iframe");
         expect(html).toContain("&lt;iframe");
     });
 
     test("caps the symbol before rendering it", () => {
-        const html = balanceLine("A".repeat(4096), 1, null, null);
+        const html = balanceLine("A".repeat(4096), "1", null, null);
         expect(html).toContain("A".repeat(MAX_SYMBOL_LENGTH - 1) + "…");
         expect(html).not.toContain("A".repeat(MAX_SYMBOL_LENGTH + 1));
     });
@@ -55,13 +55,13 @@ describe("balanceLine", () => {
     // The token id lands inside data-token="...", so a quote in it is a
     // way out of the attribute and into a new one.
     test("keeps a quote-bearing token id inside its attribute", () => {
-        const html = balanceLine("TKN", 1, null, '" onclick="alert(1)');
+        const html = balanceLine("TKN", "1", null, '" onclick="alert(1)');
         expect(html).not.toContain('onclick="');
         expect(html).toContain('data-token="&quot; onclick=&quot;alert(1)"');
     });
 
     test("renders an ordinary holding unchanged", () => {
-        const html = balanceLine("USDC", 1.5, null, "0xabc");
+        const html = balanceLine("USDC", "1.5", null, "0xabc");
         expect(html).toContain("<span>USDC</span>");
         expect(html).toContain("<span>1.5000</span>");
         expect(html).toContain('data-token="0xabc"');
@@ -69,7 +69,7 @@ describe("balanceLine", () => {
 
     // formatUsd() writes a value under a cent as "< $0.01".
     test("escapes the USD value along with the symbol", () => {
-        const html = balanceLine("USDC", 0.001, 1, null);
+        const html = balanceLine("USDC", "0.001", 1, null);
         expect(html).toContain("&lt; $0.01");
         expect(html).not.toContain("< $0.01");
     });

tests/balanceTruncation.test.js

@@ -0,0 +1,77 @@
+// The balance lists and Home's ETH line show a balance as the history rows do
+// (README.md, Amounts): cut to four decimal places, never rounded up
+// (https://git.eeqj.de/sneak/AutistMask/issues/757).
+//
+// Driven through the real popup over a stored profile on Ethereum Mainnet.
+
+const {
+    ADDRESS,
+    bootPopup,
+    cleanupPopup,
+    unversionedValidProfile,
+} = require("./support/popupBoot");
+const { balanceLine } = require("../src/popup/views/helpers");
+
+const USDC = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
+
+afterEach(() => {
+    cleanupPopup();
+});
+
+// The quantity cell of a balance row.
+function quantity(row) {
+    return row.match(/<span>([^<]*)<\/span><\/span>/)[1];
+}
+
+// The popup on Home over one address holding `eth` ETH and `usdc` USDC.
+function bootHolding(eth, usdc) {
+    const profile = unversionedValidProfile({
+        trackedTokens: [{ address: USDC, symbol: "USDC", decimals: 6 }],
+    });
+    profile.wallets[0].addresses[0] = {
+        address: ADDRESS,
+        balance: eth,
+        tokenBalances: [
+            { address: USDC, symbol: "USDC", decimals: 6, balance: usdc },
+        ],
+    };
+    return bootPopup(profile);
+}
+
+// The balance row for `token` in Home's wallet list.
+function homeRow(page, token) {
+    return page
+        .node("wallet-list")
+        .innerHTML.split("<div ")
+        .find((row) => row.includes('data-token="' + token + '"'));
+}
+
+describe("balanceLine", () => {
+    test("cuts 0.99996 to 0.9999, never rounding it up to 1.0000", () => {
+        expect(quantity(balanceLine("ETH", "0.99996", null, "ETH"))).toBe(
+            "0.9999",
+        );
+    });
+
+    test("cuts 0.00004 to 0.0000", () => {
+        expect(quantity(balanceLine("USDC", "0.00004", null, USDC))).toBe(
+            "0.0000",
+        );
+    });
+});
+
+describe("Home", () => {
+    test("the ETH line and the balance list read 0.99996 ETH as 0.9999", async () => {
+        const page = await bootHolding("0.99996", "0.00004");
+
+        expect(page.visibleViews()).toEqual(["main"]);
+        expect(page.text("total-value")).toBe("0.9999 ETH");
+        expect(quantity(homeRow(page, "ETH"))).toBe("0.9999");
+    });
+
+    test("the balance list reads 0.00004 USDC as 0.0000", async () => {
+        const page = await bootHolding("0.99996", "0.00004");
+
+        expect(quantity(homeRow(page, USDC.toLowerCase()))).toBe("0.0000");
+    });
+});

tests/deleteAddress.test.js

@@ -4,8 +4,8 @@
 // the copy is the substance and is tested as such. Two things it must not
 // get wrong: what it takes to get the address back — the app refuses both
 // obvious routes — and what counts as holding something, which is any
-// ERC-20 as well as ETH, at any size, including a balance that rounds to
-// zero at the four decimals the balance lines render. The DOM behaviour
+// ERC-20 as well as ETH, at any size, including a balance below the four
+// decimals the balance lines render. The DOM behaviour
 // around them is driven against the real popup by tests/e2e/run.js.
 
 // helpers.js pulls in state.js, which reads chrome.storage.local at load.

tests/e2e/run.js

@@ -829,12 +829,11 @@ test("a common-token quick-pick fills in the contract address (#150)", async (en
     await visible(env.page, "#view-address");
 });
 
-// The native amount as the transaction list writes it (four decimals) and
-// as the detail screen writes it (full precision). Both are rendered here
-// from the fixture rather than read off the screen, so the assertions
-// compare against the wei the stub served.
-const NATIVE_ROW_TEXT =
-    parseFloat(formatEther(STUB_NATIVE_VALUE_WEI)).toFixed(4) + " ETH";
+// The native amount as the transaction list writes it (cut to four decimals,
+// quantity() below) and as the detail screen writes it (full precision). Both
+// are rendered here from the fixture rather than read off the screen, so the
+// assertions compare against the wei the stub served.
+const NATIVE_ROW_TEXT = quantity(STUB_NATIVE_VALUE_WEI) + " ETH";
 const NATIVE_DETAIL_TEXT = formatEther(STUB_NATIVE_VALUE_WEI) + " ETH";
 
 test("the native ETH transaction detail still renders (#151)", async (env) => {
@@ -2724,10 +2723,11 @@ async function goToConfirm(page, send) {
     await assertAddressesFit(page, "the confirmation screen");
 }
 
-// A balance as the main view renders it: balanceLinesForAddress() writes
-// every quantity with four decimal places.
+// An amount in wei as the main view's balance lines and the transaction list
+// write it: cut to four decimal places, never rounded, as feeEth() does.
 function quantity(wei) {
-    return parseFloat(formatEther(wei)).toFixed(4);
+    const [whole, frac = ""] = formatEther(wei).split(".");
+    return whole + "." + (frac + "0000").slice(0, 4);
 }
 
 // Wait on the main view until a changed balance fixture has been picked up.

tests/fabricatedDecimals.test.js

@@ -47,7 +47,7 @@ const { fetchTokenBalances } = require("../src/shared/balances");
 const { debugFetch } = require("../src/shared/log");
 const { state } = require("../src/shared/state");
 const { unknownDecimalsAmount } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const { TOKEN_BY_ADDRESS } = require("../src/shared/tokenList");
 
 const HOLDER = "0x" + "a".repeat(40);

tests/resolveTokenSymbol.test.js

@@ -22,7 +22,7 @@ const { Interface } = require("ethers");
 const { ERC20_ABI } = require("../src/shared/constants");
 const { state } = require("../src/shared/state");
 const { resolveTokenSymbol } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const iface = new Interface(ERC20_ABI);
 

tests/transactions.test.js

@@ -1361,6 +1361,31 @@ describe("fetchRecentTransactions merge and dedup", () => {
         expect(txs[0].holders).toBe(3500000);
     });
 
+    // README.md, Amounts: a history row cuts to four decimals, with no floor.
+    test("a token transfer below 0.0001 reads 0.0000", async () => {
+        respondWith(
+            [],
+            [
+                {
+                    transaction_hash: "0x" + "4".repeat(64),
+                    block_number: 21000040,
+                    timestamp: TS,
+                    from: { hash: ORDINARY_PEER },
+                    to: { hash: VICTIM },
+                    total: { value: "40", decimals: "6" },
+                    token: {
+                        symbol: "USDC",
+                        address_hash: USDC_CONTRACT,
+                        holders_count: "3500000",
+                    },
+                },
+            ],
+        );
+
+        const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT, "0x1");
+        expect(txs[0].value).toBe("0.0000");
+    });
+
     test("two transfers of the same token in one transaction collapse to one entry", async () => {
         const hash = "0x" + "3".repeat(64);
         const leg = (value) => ({

tests/uniswapRouterAddress.test.js

@@ -47,7 +47,7 @@ globalThis.chrome = {
 const { state } = require("../src/shared/state");
 const { fetchRecentTransactions } = require("../src/shared/transactions");
 const approval = require("../src/popup/views/approval");
-const { decodeCalldata } = approval;
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const transactionDetail = require("../src/popup/views/transactionDetail");
 
 const MAINNET = "0x1";

tests/uniswapUnknownDecimals.test.js

@@ -18,7 +18,7 @@ globalThis.chrome = {
 const { AbiCoder, Interface } = require("ethers");
 const { state } = require("../src/shared/state");
 const { unknownDecimalsAmount } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const ROUTER = "0x66a9893cc07d91d95644aedd05d03f95e1dba8af";
 const RECIPIENT = "0xC0FfEE0000000000000000000000000000c0fFEe";

tests/unknownScaleDisplay.test.js

@@ -96,7 +96,7 @@ afterEach(() => {
 describe("balanceLine", () => {
     test("an unknown quantity and a zero one render differently", () => {
         const unknown = balanceLine("NOVEL", null, null, NOVEL);
-        const zero = balanceLine("NOVEL", 0, null, NOVEL);
+        const zero = balanceLine("NOVEL", "0", null, NOVEL);
         expect(unknown).not.toBe(zero);
         expect(quantities(unknown)).toEqual(["NOVEL", "quantity unknown"]);
         expect(quantities(zero)).toEqual(["NOVEL", "0.0000"]);
@@ -105,7 +105,7 @@ describe("balanceLine", () => {
     test("an unknown quantity produces no fiat figure, a zero one does", () => {
         prices[NOVEL] = 3;
         const unknown = balanceLine("NOVEL", null, 3, NOVEL);
-        const zero = balanceLine("NOVEL", 0, 3, NOVEL);
+        const zero = balanceLine("NOVEL", "0", 3, NOVEL);
         // A price times an unknown quantity is not $0.00: that is the same
         // claim of "nothing here" the quantity cell just refused to make.
         expect(unknown).toContain(