fix: show balances and fees below 0.000001 ETH as nonzero on the send screens (closes #343)

The stored ETH balance and the send-confirm screen's fee were each cut to six
decimal places, so a value below 0.000001 read as 0.0. The ETH balance is now
stored exactly, and the send and send-confirm screens' balances, reserve and
insufficient-balance messages go through truncateAmountNeverZero(). Both the
send-confirm and approval screens render the fee through formatFee(), which
prices the exact fee in USD, so the same fee reads the same on both. Token
balances keep their six-decimal value: it also leaves dust off the balance
list, and keeps the string within the 18 decimals the balance check reads.

Model: opus-5-5

README.md

@@ -882,9 +882,12 @@ On those screens, when the truncated string would contain no digit from 1 to 9
 and the value does, the amount is extended to its first significant digit
 instead: `0.000000000000000001 DAI`, not `0.0000 DAI`. The test is on the whole
 truncated string, integer part included, so `1.00005` still shows as `1.0000` —
-the exception only fires where the entire displayed figure would read as zero. A
+the exception only fires where the entire displayed figure would read as zero.
-genuine zero still renders `0.0000`, and truncation stays truncation: `0.99999`
+Truncation stays truncation: `0.99999` shows as `0.9999`, never rounded up. The
-shows as `0.9999`, never rounded up.
+rule still renders a genuine zero as `0.0000`. Two lines of a swap say a zero in
+words instead: `Min. received` reads `None (no minimum guaranteed)` for a zero
+minimum, and `Amount` reads `All available (V4 open delta)` when the amount it
+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
@@ -893,13 +896,16 @@ 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`), so a fee reads the same there as on the
+(`src/popup/views/confirmTx.js`). Both screens render a network fee through
-approval screen. For this the ETH balance is stored exactly. A token balance is
+`formatFee()` in `src/popup/views/helpers.js`, which prices the exact fee in USD
-stored to six decimal places, and a holding below 0.000001 is not listed at all.
+rather than its truncated figure, so the same fee reads the same on both, USD
-The history and balance lists (`src/shared/transactions.js`) use the unfloored
+value included. The ETH balance is stored exactly, so a balance below the floor
-one: the transaction detail view is the authoritative record and already shows
+reaches these screens as it is. A token balance is stored to six decimal places,
-exact precision. The 4-decimal rule is unchanged everywhere else, including for
+and a holding below 0.000001 is not listed at all. The history and balance lists
-amounts at or above the floor on the approval screens.
+(`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
@@ -942,6 +948,41 @@ and compare against. Reading the stored field directly instead answers `null`
 for a bundled or tracked token the explorer merely omitted, which is not a
 refusal the wallet has any reason to make.
 
+**Decoded amount lines on the transaction approval screen:** the `Amount` line
+of a decoded ERC-20 call, and the `Amount` and `Min. received` lines of a
+decoded swap (see TxApproval below), do not always read as a number. They can
+read:
+
+- A formatted quantity, e.g. `17.1900 USDT`, when the token's scale is known:
+  truncated to four decimals, with the floor and the zero cases described above.
+- `<amount> base units (decimals unknown)` when the scale is unknown: the
+  base-unit integer, rather than a figure at a guessed scale (see Unknown token
+  scale above).
+- `Unlimited`: on the ERC-20 `Amount` line, an `approve` of the `uint256`
+  maximum, an unbounded allowance. On the swap's `Amount` line, any amount at or
+  above the `uint160` maximum, whichever step set the line: a `PERMIT2_PERMIT`
+  amount at that maximum, which is an unbounded permit, or a V2 or V3 exact-in
+  or `WRAP_ETH` amount that large, which is not an allowance. The router's
+  whole-balance value, `CONTRACT_BALANCE` (`2^255`), is one such amount.
+- `All available (V4 open delta)`: the swap's `Amount` line, when the amount it
+  shows is a V4 exact-in `amountIn` of zero. V4 reads that zero as "use the
+  whole open delta", so the calldata states no quantity. The line shows the
+  amount of one step that names an input token or amount: the last
+  `PERMIT2_PERMIT` step if there is one, otherwise the first V2 or V3 exact-in,
+  `WRAP_ETH` or V4 swap step, a V4 swap step giving the `amountIn` of its first
+  readable exact-in action.
+- `None (no minimum guaranteed)`: the swap's `Min. received` line, when the
+  minimum it shows is zero, whether a V2, V3 or V4 swap's minimum or a
+  `BALANCE_CHECK_ERC20` step's `minBalance`. Before
+  [#359](https://git.eeqj.de/sneak/AutistMask/issues/359), a zero `minBalance`
+  read `0.0000` when the token's scale was known.
+
+The swap's `Token In` and `Token Out` lines name a currency, not an amount; each
+reads `Unknown (not named in the calldata)` when the decoder found no token for
+that side. The token permission warning on the signature screen has its own
+amount wording, including `Unknown`; the SignApproval section below describes
+it.
+
 #### Partial USD totals
 
 Prices are fetched for the top 25 tokens only, so an address can hold assets the

TODO.md

@@ -53,10 +53,12 @@ but the review is broader than any of them.
   stored exactly, and 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, so the same fee reads the same on both screens.
+  approval screen already used. The confirmation and approval screens both
-  Token balances are still stored to six decimal places: that cut is also what
+  render the fee through `formatFee()` in `src/popup/views/helpers.js`, which
-  leaves a holding below 0.000001 off the balance list, and keeps the stored
+  prices the exact fee in USD, so the same fee reads the same on both, USD value
-  string within the 18 decimals the balance check reads.
+  included. Token balances are still stored to six decimal places: that cut is
+  also what leaves a holding below 0.000001 off the balance list, and keeps the
+  stored string within the 18 decimals the balance check reads.
 - 2026-10-03: The typed-data signing screen warns for a token permission, and
   names the primary type ethers signs
   ([#400](https://git.eeqj.de/sneak/AutistMask/issues/400)). A Permit or Permit2
@@ -185,6 +187,20 @@ but the review is broader than any of them.
   standalone storage entry, never part of the versioned `autistmask` profile, so
   the state schema is untouched and no existing profile is affected.
 
+- 2026-09-21: `README.md` no longer says a genuine zero always renders `0.0000`
+  ([#369](https://git.eeqj.de/sneak/AutistMask/issues/369)). The amount rule
+  still renders one as `0.0000`, but two swap lines say a zero in words instead:
+  `Min. received` reads `None (no minimum guaranteed)` for a zero minimum, and
+  `Amount` reads `All available (V4 open delta)` when the amount it shows is a
+  V4 exact-in `amountIn` of zero. A new list says what the decoded ERC-20 and
+  swap amount lines on the transaction approval screen can read: a formatted
+  quantity, base units with decimals unknown, `Unlimited`,
+  `All available (V4 open delta)` and `None (no minimum guaranteed)`, which a
+  zero `minBalance` on a `BALANCE_CHECK_ERC20` step now reads instead of
+  `0.0000` at a known scale. The README also names
+  `Unknown (not named in the calldata)` on the swap's token lines, and points to
+  SignApproval for the token permission warning's own wording. Docs only.
+
 - 2026-08-30: An address no longer wraps, or is shortened to fit, in any of the
   common views ([#380](https://git.eeqj.de/sneak/AutistMask/issues/380)). The
   wallet list was the reported case: the address shared one row with the

src/popup/views/approval.js

@@ -8,6 +8,7 @@ const {
     renderAddressHtml,
     attachCopyHandlers,
     onViewLeave,
+    formatFee,
 } = require("./helpers");
 const { state, saveState } = require("../../shared/state");
 const { networkByChainId } = require("../../shared/networks");
@@ -207,7 +208,7 @@ 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, ethPrice) {
+function showTxFee(approvedTx) {
     const network = networkByChainId(approvedTx.chainId);
     $("approve-tx-network").textContent = network
         ? network.name
@@ -215,12 +216,9 @@ function showTxFee(approvedTx, ethPrice) {
 
     const gasLimit = BigInt(approvedTx.gasLimit);
     const feePerGas = BigInt(approvedTx.maxFeePerGas || approvedTx.gasPrice);
-    const maxFeeEth = formatTxValue(formatEther(gasLimit * feePerGas));
+    // Through formatFee(), as the confirmation screen's fee is, so the same
-    const usdStr = formatUsd(
+    // fee reads the same on both.
-        ethPrice ? parseFloat(maxFeeEth) * ethPrice : null,
+    $("approve-tx-fee").textContent = formatFee(gasLimit * feePerGas);
-    );
-    $("approve-tx-fee").textContent =
-        maxFeeEth + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
 
     let detail =
         gasLimit.toString() +
@@ -332,7 +330,7 @@ function showTxApproval(details) {
     $("approve-tx-value").textContent =
         ethValueFormatted + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
 
-    showTxFee(approvedTx, ethPrice);
+    showTxFee(approvedTx);
 
     // Decode calldata (reuse decoded from above)
     const decodedEl = $("approve-tx-decoded");

src/popup/views/confirmTx.js

@@ -15,6 +15,7 @@ const {
     attachCopyHandlers,
     goBack,
     onViewLeave,
+    formatFee,
 } = require("./helpers");
 const { state } = require("../../shared/state");
 const { getSignerForAddress } = require("../../shared/wallet");
@@ -31,8 +32,8 @@ const {
     transferAmountUnits,
 } = require("../../shared/transferAmount");
 const { assertWithinCeilings } = require("../../shared/approvalVerify");
-// Every balance and fee this screen shows goes through it, as the approval
+// The balance lines, the fee reserve and the insufficient-balance messages go
-// screen's do, so the same value reads the same on both.
+// through it, as the approval screen's amounts do.
 const { truncateAmountNeverZero } = require("../../shared/amountDisplay");
 const {
     CODES,
@@ -360,17 +361,10 @@ async function estimateGas(txInfo) {
         // flight; a stale fee must not reach the screen or the balance check.
         if (pendingTx !== txInfo) return;
 
-        const ethPrice = getPrice("ETH");
+        // The fee lines go through formatFee(), as the approval screen's
-        const usd = (wei) =>
+        // does, so the same fee reads the same on both.
-            ethPrice ? parseFloat(formatEther(wei)) * ethPrice : null;
-
         if (estimateWei !== null && estimateWei < gasCostWei) {
-            $("confirm-fee-amount").textContent = valueWithUsd(
+            $("confirm-fee-amount").textContent = "~" + formatFee(estimateWei);
-                "~" +
-                    truncateAmountNeverZero(formatEther(estimateWei)) +
-                    " ETH",
-                usd(estimateWei),
-            );
             $("confirm-fee-reserve").textContent =
                 "up to " +
                 truncateAmountNeverZero(formatEther(gasCostWei)) +
@@ -380,10 +374,7 @@ async function estimateGas(txInfo) {
             // 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 = valueWithUsd(
+            $("confirm-fee-amount").textContent = formatFee(gasCostWei);
-                truncateAmountNeverZero(formatEther(gasCostWei)) + " ETH",
-                usd(gasCostWei),
-            );
             setVisible("confirm-fee-reserve", false);
         }
         feeStatus = FEE_KNOWN;

src/popup/views/helpers.js

@@ -12,6 +12,8 @@
 // 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 } = require("../../shared/amountDisplay");
 const { DEBUG } = require("../../shared/constants");
 const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
@@ -243,6 +245,19 @@ 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, so it never understates what the fee costs.
+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,
@@ -610,6 +625,7 @@ module.exports = {
     balanceLinesForAddress,
     addressHoldsFunds,
     unknownableAmount,
+    formatFee,
     addressColor,
     addressDotHtml,
     escapeHtml,

tests/e2e/run.js

@@ -1505,11 +1505,10 @@ async function backToAddress(page) {
 
 // Drive the popup to the confirmation screen for one send.
 //
-// It waits for the send screen to be showing `balance` before filling
+// It waits for the send screen to be showing `balance`, the fixture's balance
-// anything in. That figure is the exact number the spend gate compares
+// as that screen displays it, before filling anything in. Waiting for it —
-// against, so waiting for it — rather than for a refresh to have probably
+// rather than for a refresh to have probably landed — is what keeps every
-// landed — is what keeps every assertion below deterministic after a
+// assertion below deterministic after a fixture change.
-// fixture change.
 async function goToConfirm(page, { token, balance, amount }) {
     await backToAddress(page);
     await page.click("#btn-send");

tests/sendDisplayFloor.test.js

@@ -139,6 +139,7 @@ global.navigator = { clipboard: { writeText() {} } };
 
 const { refreshBalances } = require("../src/shared/balances");
 const { state } = require("../src/shared/state");
+const { prices, clearPrices } = 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");
@@ -256,18 +257,28 @@ describe("a fee below 0.000001 ETH never renders as zero", () => {
 
 // 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.
+// 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([
-        ["below the floor", 1n],
+        // 21000 gas at 1 wei.
-        ["with more than four decimals", 58823529411n],
+        ["below the floor", 1n, "0.00000000000002 ETH (< $0.01)"],
-    ])("%s", async (_label, feePerGas) => {
+        // 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 confirmEthSend("0.1");
-        const onConfirm = text("confirm-fee-amount");
+        expect(text("confirm-fee-amount")).toBe(expected);
         await approveTxWithFeePerGas(feePerGas);
-        expect(text("approve-tx-fee")).toBe(onConfirm);
+        expect(text("approve-tx-fee")).toBe(expected);
-        expect(onConfirm).toMatch(/[1-9]/);
     });
 });