fix: only a permit whose amount is the Amount figure names Token In (closes #370)

A PERMIT2_PERMIT named Token In whether or not its amount stood as the
Amount figure, so the approval screen could show a permit's token, or an
allowance, where the swap's own input belonged. A permit whose spender
was not the router, or that the router may let fail, had no line naming
its spender.

Now only a permit whose amount stands names Token In. Every other
permit, before the swap steps or after them, leaves Token In and Amount
as they read with no permit and gets three lines of its own: Permit2
allowance, Allowance token and Allowance spender. README Transaction
Decoding, its unknown token scale passage and the TxApproval element
list match.

Model: opus-5-5

README.md

@@ -1129,13 +1129,15 @@ scale is not an approximation but a different number — 1,000 units of a
 6-decimal token formatted at 18 decimals reads `0.000000001` — on the screen
 whose only job is to state what is being authorized. Both amount paths of that
 screen take this rule: the ERC-20 `transfer`/`approve` line
-(`src/popup/views/approval.js`) and the swap's `Amount` and `Min. received`
-lines (`src/shared/uniswap.js`). The token permission warning on the signature
-screen takes the same rule for its amounts. An unbounded allowance or permit
-needs no scale to describe and is still shown as `Unlimited`. A source's answer
-counts only if it is a whole number from 0 to 80: `decimals()` returns a
-`uint8`, but `formatUnits()` cannot format more than 80 decimal places, so a
-token that reports 81 to 255 is shown as one whose scale nothing knows.
+(`src/popup/views/approval.js`) and the swap's `Amount`, `Min. received`,
+`Moved from the sender` and `Permit2 allowance` lines and the `Paid to` line of
+a move into the router (`src/shared/uniswap.js`). The token permission warning
+on the signature screen takes the same rule for its amounts. An unbounded
+allowance or permit needs no scale to describe and is still shown as
+`Unlimited`. A source's answer counts only if it is a whole number from 0 to 80:
+`decimals()` returns a `uint8`, but `formatUnits()` cannot format more than 80
+decimal places, so a token that reports 81 to 255 is shown as one whose scale
+nothing knows.
 
 The rule holds only if nothing invents a scale UPSTREAM of it. Those three
 sources are read as authoritative, so a value written into one of them cannot be
@@ -2425,10 +2427,11 @@ view would leave a wallet one click from deletion.
       transaction"
     - Decoded action (if calldata is recognized): action name, token details,
       amounts, what each swap step spends that the `Amount` line does not give,
-      what each `PERMIT2_TRANSFER_FROM` moves and where to, steps, deadline, and
-      unless a swap pays only the From address, a `Paid to` line for each other
-      address it pays, or saying that a token stays in the router or who it pays
-      is unknown (see Transaction Decoding)
+      what each `PERMIT2_TRANSFER_FROM` moves and where to, what each
+      `PERMIT2_PERMIT` whose amount is not the `Amount` figure lets its spender
+      take, steps, deadline, and unless a swap pays only the From address, a
+      `Paid to` line for each other address it pays, or saying that a token
+      stays in the router or who it pays is unknown (see Transaction Decoding)
     - From: color dot + full address + etherscan link
     - Contract: color dot + full address + etherscan link, token symbol label if
       known; for a contract creation, the same sentence as on WaitTx
@@ -3217,40 +3220,42 @@ Currently supported:
   added to the total while both are quantities: a V3 exact-in of 600 USDT and a
   V2 exact-in of 400 USDT, both paid by the user, read `1000.0000 USDT`. When
   the decoder does not know a take's amount, the total is not known and there is
-  no `Amount` line. `Token In` is the token of the last `PERMIT2_PERMIT` the
-  decoder reads, when there is one. Its amount, `Unlimited` included, stands as
-  the `Amount` figure in place of the total only in the plain shape of Uniswap's
-  own routes: it is the only `PERMIT2_PERMIT`, its spender is the router, the
-  router may not let it fail, no step before it takes its token or a token the
-  decoder does not know, and the decoder reads every step after it in full.
-  Permit2 then lets the router take no more of the token than that amount, so
-  the permit covers every take of it. A step the decoder does not read in full
-  may raise what Permit2 lets the router take, as a `PERMIT2_PERMIT_BATCH` can:
-  a command the decoder does not read (listed at the end of this section), a
-  step whose input it cannot read, in whole or in part, and a step it fails on.
-  In any other case the line gives the total, as with no permit. When the step
-  that sets the input side spends a token other than the permit's, or one the
-  decoder does not know, its amount gets lines of its own, unless it states no
-  amount and the user pays it none of its input token, and the total has no
-  figure to start from: unless the permit's amount stands there is no `Amount`
-  line, and each take of the permit's token gets lines of its own. Each take the
-  total does not count gives three lines after the `Amount` line (after
-  `Token In` when there is none): one of a token other than `Token In`; one of
-  `Token In` after an amount that is not a quantity (a V4 open delta,
-  `ALREADY_PAID`, which keep their wording on the `Amount` line, or no stated
-  amount, as of a V4 exact-out step); and one whose amount the decoder does not
-  know. When the step that sets the input side states no amount, the user pays
-  it some of its input token, and there is no `Amount` line, that step gets them
-  too whenever another take's lines give a figure, or a `PERMIT2_TRANSFER_FROM`
-  of its token gives one, on the lines below or, into the router, on its
-  `Paid to` line, so that figure cannot read as all that leaves. When it states
-  no amount and the user pays it none of its input token, as when the router
-  pays it, that step takes none of that token from the user's wallet and never
-  gets them, with a permit or without. They come in step order, the step that
-  sets the input side first when it has them: `Moved from the sender`, its
-  amount, worded as the `Amount` line words one, or
-  `Unknown (could not be decoded)` when the decoder does not know it;
-  `Token moved`, giving the token's address as the `Token In` line does; and
+  no `Amount` line. A `PERMIT2_PERMIT` names `Token In` only when its amount,
+  `Unlimited` included, stands as the `Amount` figure in place of the total,
+  which it does only in the plain shape of Uniswap's own routes: it comes before
+  the step that sets the input side, it is the only `PERMIT2_PERMIT` in the
+  transaction, its spender is the router, the router may not let it fail, no
+  step before it takes its token or a token the decoder does not know, and the
+  decoder reads every step after it in full. Permit2 then lets the router take
+  no more of the token than that amount, so the permit covers every take of it.
+  A step the decoder does not read in full may raise what Permit2 lets the
+  router take, as a `PERMIT2_PERMIT_BATCH` can: a command the decoder does not
+  read (listed at the end of this section), a step whose input it cannot read,
+  in whole or in part, and a step it fails on. Every other `PERMIT2_PERMIT`,
+  before the step that sets the input side or after it, leaves `Token In` and
+  the `Amount` line as they read with no permit: a permit of 5,000 DAI to
+  another address and then a V3 exact-in of 600 USDT read `Swap USDT → USDC`
+  with `Amount 600.0000 USDT`, and so do that exact-in and then a permit of
+  5,000 DAI to the router. When a permit's amount stands and the step that sets
+  the input side spends a token other than the permit's, or one the decoder does
+  not know, that step's amount gets lines of its own, unless it states no amount
+  and the user pays it none of its input token. Each take the total does not
+  count gives three lines after the `Amount` line (after `Token In` when there
+  is none): one of a token other than `Token In`; one of `Token In` after an
+  amount that is not a quantity (a V4 open delta, `ALREADY_PAID`, which keep
+  their wording on the `Amount` line, or no stated amount, as of a V4 exact-out
+  step); and one whose amount the decoder does not know. When the step that sets
+  the input side states no amount, the user pays it some of its input token, and
+  there is no `Amount` line, that step gets them too whenever another take's
+  lines give a figure, or a `PERMIT2_TRANSFER_FROM` of its token gives one, on
+  the lines below or, into the router, on its `Paid to` line, so that figure
+  cannot read as all that leaves. When it states no amount and the user pays it
+  none of its input token, as when the router pays it, that step takes none of
+  that token from the user's wallet and never gets them, with a permit or
+  without. They come in step order, the step that sets the input side first when
+  it has them: `Moved from the sender`, its amount, worded as the `Amount` line
+  words one, or `Unknown (could not be decoded)` when the decoder does not know
+  it; `Token moved`, giving the token's address as the `Token In` line does; and
   `Moved to`, which reads `The swap step that spends it`. A token the decoder
   does not know gives the `Moved from the sender` line alone. A step may also
   take from the user's wallet what the decoder did not read: a V4 step whose
@@ -3271,11 +3276,19 @@ Currently supported:
   on every router but `UniversalRouterV1`, and otherwise gives the address. A
   move into the router needs none of them, because its `Paid to` line and
   `Token moved into the router` line already give the amount, the token and
-  where it goes, and so its amount is shown once. These lines change neither the
-  `Paid to` lines nor the minimum's label. A step goes unread when its recipient
-  does not decode as an address, when it is a V3 swap step whose path is shorter
-  than one token address or has bytes after its last hop, or when it is a
-  command the decoder does not read: every command other than `PERMIT2_PERMIT`,
+  where it goes, and so its amount is shown once. Every `PERMIT2_PERMIT` whose
+  amount does not stand as the `Amount` figure, before the step that sets the
+  input side or after it, gives three lines, in step order, after those for each
+  `PERMIT2_TRANSFER_FROM`: `Permit2 allowance`, its amount, for example
+  `5000.0000 DAI`, or `Unlimited` for Permit2's maximum; `Allowance token`,
+  giving the token's address as the `Token In` line does; and
+  `Allowance spender`, the address it lets take the token. Only a permit whose
+  amount stands gives none: the `Amount` line gives its amount, `Token In` its
+  token, and its spender is the router. These lines change neither the `Paid to`
+  lines nor the minimum's label. A step goes unread when its recipient does not
+  decode as an address, when it is a V3 swap step whose path is shorter than one
+  token address or has bytes after its last hop, or when it is a command the
+  decoder does not read: every command other than `PERMIT2_PERMIT`,
   `PERMIT2_TRANSFER_FROM`, `V2_SWAP_EXACT_IN`, `V2_SWAP_EXACT_OUT`,
   `V3_SWAP_EXACT_IN`, `V3_SWAP_EXACT_OUT`, `V4_SWAP`, `SWEEP`, `TRANSFER`,
   `PAY_PORTION`, `PAY_PORTION_FULL_PRECISION`, `ACROSS_V4_DEPOSIT_V3`,

src/shared/uniswap.js

@@ -494,8 +494,9 @@ function amountText(raw, info) {
     };
 }
 
-// The line giving a moved token under `label`, in the shape of the Token In
-// line, so the screens show it as they show that one. ETH has no address.
+// The line giving a moved token, or the token of a permit, under `label`, in
+// the shape of the Token In line, so the screens show it as they show that
+// one. ETH has no address.
 function tokenMovedLine(label, token, sources) {
     const info = tokenInfo(token, sources);
     if (!present(info.address)) {
@@ -1208,9 +1209,14 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // its input currency (see decodeV4Swap()). Only a V4 step can set the
         // input side with no amount, the one case in which this is read.
         let inputPaidByUser = false;
-        // The last PERMIT2_PERMIT this decoder read, or null (see
-        // permitStands after the loop).
+        // The last PERMIT2_PERMIT this decoder read before a step set the
+        // input side, or null (see permitStands after the loop).
         let permit = null;
+        // Every PERMIT2_PERMIT this decoder read, before a step set the input
+        // side or after, in step order, as { token, amount, spender, step }.
+        // Each whose amount is not the Amount figure gets lines of its own
+        // (see after the PERMIT2_TRANSFER_FROM lines).
+        const permits = [];
         // The index of each step this decoder did not read in full: a
         // command it does not read, a step whose input it cannot read, in
         // whole or in part, and one it fails on (see permitStands).
@@ -1268,8 +1274,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // when no earlier hop set it. A half the establishing hop did not
         // state stays null and the line says so, rather than being filled in
         // from a different hop. A PERMIT2_PERMIT sets no side here: after the
-        // loop, the last one read names Token In, and the Amount line is
-        // formed there, in one place (see permitStands).
+        // loop, one whose amount stands as the Amount figure names Token In,
+        // and the Amount line is formed there, in one place (see
+        // permitStands).
         const setInput = (token, amount) => {
             inputToken = present(token) ? token : null;
             inputAmount = present(amount) ? amount : null;
@@ -1465,24 +1472,33 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 } else if (command === "PERMIT2_PERMIT") {
                     const p = decodePermit2(inputs[i]);
                     if (p) {
+                        permits.push({ ...p, step: i });
+                        keepsRouterWeth = true;
+                    } else {
+                        stepsUnread.push(i);
+                    }
+                    // Only a permit whose amount stands as the Amount figure
+                    // names Token In (see permitStands). Every other permit,
+                    // before the step that sets the input side or after it,
+                    // leaves Token In and Amount as they read with no permit
+                    // and gets lines of its own. One after a step set the input
+                    // side never stands, so only one before it is kept here.
+                    if (p && !inputEstablished) {
                         // Whether a step before it took its token, or may
-                        // have: the step that set the input side or one in
-                        // `userPaid`, when its token is the permit's or not
-                        // known.
+                        // have: one in `userPaid`, when its token is the
+                        // permit's or not known. No step has set the input
+                        // side yet.
                         const mayBeItsToken = (token) =>
                             !present(token) || sameAddress(token, p.token);
-                        const tookBefore =
-                            (inputEstablished && mayBeItsToken(inputToken)) ||
-                            userPaid.some((t) => mayBeItsToken(t.token));
+                        const tookBefore = userPaid.some((t) =>
+                            mayBeItsToken(t.token),
+                        );
                         permit = {
                             ...p,
                             step: i,
                             allowedToFail,
                             beforeEveryTake: !tookBefore,
                         };
-                        keepsRouterWeth = true;
-                    } else {
-                        stepsUnread.push(i);
                     }
                 } else if (command === "PERMIT2_TRANSFER_FROM") {
                     const p = decodePermit2TransferFrom(inputs[i]);
@@ -1939,18 +1955,21 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // lines of its own. One whose amount is not known also leaves the
         // total unknown, with no figure.
         //
-        // The last PERMIT2_PERMIT read names Token In. Its amount stands as
-        // the Amount figure in place of the total only in the plain shape of
-        // Uniswap's own routes: it is the only PERMIT2_PERMIT, its spender is
-        // the router, the router may not let it fail, no step before it took
-        // its token or one not known, and this decoder read every step after
-        // it in full (see stepsUnread). Permit2 then lets the router take no
-        // more of the token than that amount, so the permit covers every take
-        // of it. A later step this decoder did not read may raise what Permit2
-        // lets the router take, as a PERMIT2_PERMIT_BATCH can. A step that
-        // may take from the sender what this decoder did not read leaves no
-        // figure, permit or not (see spentUnread()), and an EXECUTE_SUB_PLAN
-        // step leaves both sides unknown (below).
+        // A PERMIT2_PERMIT names Token In only when its amount stands as the
+        // Amount figure in place of the total, which it does only in the
+        // plain shape of Uniswap's own routes: it comes before the step that
+        // set the input side, it is the only PERMIT2_PERMIT in the
+        // transaction, its spender is the router, the router may not let it
+        // fail, no step before it took its token or one not known, and this
+        // decoder read every step after it in full (see stepsUnread). Permit2
+        // then lets the router take no more of the token than that amount, so
+        // the permit covers every take of it. A later step this decoder did
+        // not read may raise what Permit2 lets the router take, as a
+        // PERMIT2_PERMIT_BATCH can. Every other PERMIT2_PERMIT leaves Token In
+        // and the Amount line as they read with no permit, and gets lines of
+        // its own below. A step that may take from the sender what this decoder
+        // did not read leaves no figure, permit or not (see spentUnread()),
+        // and an EXECUTE_SUB_PLAN step leaves both sides unknown (below).
         const stepCommands = Array.from(
             commandsBytes,
             (b) => commands[b & commandTypeMask],
@@ -1977,17 +1996,17 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // The take of the step that set the input side, when the total
         // starts from it and it stated no amount (see below), or null.
         let firstTakeUnstated = null;
-        if (permit === null || sameAddress(inputToken, permit.token)) {
+        if (!permitStands || sameAddress(inputToken, permit.token)) {
             total = inputAmount;
             if (hasFirstTake && !present(inputAmount)) {
                 firstTakeUnstated = { token: inputToken, amount: null };
             }
         } else if (hasFirstTake) {
             // The step that set the input side spent a token other than the
-            // permit's, or one not known, so the total starts with no figure.
+            // permit's, or one not known, so its amount gets lines of its own.
             spentFromSender.push({ token: inputToken, amount: inputAmount });
         }
-        if (permit !== null) inputToken = permit.token;
+        if (permitStands) inputToken = permit.token;
         for (const t of userPaid) {
             const ofTokenIn = sameAddress(t.token, inputToken);
             if (ofTokenIn && permitStands) continue;
@@ -2181,6 +2200,32 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             );
         }
 
+        // What each PERMIT2_PERMIT lets its spender take: its amount, its
+        // token and the spender, an address on a line of its own. Permit2's
+        // maximum is unbounded. Only a permit whose amount stands as the
+        // Amount figure (see permitStands) gets none: that line already gives
+        // its amount and Token In its token, and its spender is the router.
+        // Every other permit, one after the step that set the input side
+        // included, gets these lines, so nothing it lets anyone take goes
+        // unstated.
+        for (const p of permits) {
+            if (permitStands && p.step === permit.step) continue;
+            details.push({
+                label: "Permit2 allowance",
+                value:
+                    p.amount >= MAX_UINT160
+                        ? "Unlimited"
+                        : amountText(p.amount, tokenInfo(p.token, sources))
+                              .display,
+            });
+            details.push(tokenMovedLine("Allowance token", p.token, sources));
+            details.push({
+                label: "Allowance spender",
+                value: p.spender,
+                address: p.spender,
+            });
+        }
+
         // Keyed on the address, not the symbol: a token absent from the
         // bundled list has no symbol, and gating the line on one dropped it
         // entirely, leaving a Min. received figure with nothing saying what is

tests/uniswap.test.js

@@ -1,4 +1,4 @@
-const { AbiCoder, Interface, solidityPacked } = require("ethers");
+const { AbiCoder, Interface, getAddress, solidityPacked } = require("ethers");
 const uniswap = require("../src/shared/uniswap");
 
 // A Universal Router on Ethereum Mainnet, chain id 0x1: UniversalRouterV2,
@@ -1406,6 +1406,14 @@ describe("uniswap decoder", () => {
             return lines.slice(from + 1, to);
         }
 
+        // The lines of a PERMIT2_PERMIT whose amount does not stand as the
+        // Amount figure, of `amount` of `token` for `spender`.
+        const permitLines = (amount, token, symbol, spender) => [
+            ["Permit2 allowance", amount],
+            ["Allowance token", symbol + " (" + token + ")"],
+            ["Allowance spender", getAddress(spender)],
+        ];
+
         // execute() of these command bytes and inputs, decoded as sent by
         // the user.
         function decodeSteps(commands, inputs) {
@@ -1711,6 +1719,7 @@ describe("uniswap decoder", () => {
                 kind: "a V4 step swapping 400 USDT with a SETTLE of 5,000 USDT by the user, the rest taken to another address,",
                 commands: [0x10],
                 inputs: [V4_SETTLE_5000],
+                permit: [],
             },
             {
                 kind: "a PERMIT2_PERMIT of 1 USDT that the router may let fail, then that V4 step,",
@@ -1719,6 +1728,12 @@ describe("uniswap decoder", () => {
                     encodePermit2(USDT_ADDR, 1000000n, ROUTER_ADDR),
                     V4_SETTLE_5000,
                 ],
+                permit: permitLines(
+                    "1.0000 USDT",
+                    USDT_ADDR,
+                    "USDT",
+                    ROUTER_ADDR,
+                ),
             },
             // The unread SWEEP keeps the permit's amount from standing.
             {
@@ -1735,11 +1750,18 @@ describe("uniswap decoder", () => {
                         1,
                     ),
                 ],
+                permit: permitLines(
+                    "5000.0000 USDT",
+                    USDT_ADDR,
+                    "USDT",
+                    ROUTER_ADDR,
+                ),
             },
-        ])("$kind shows the 5,000 USDT", ({ commands, inputs }) => {
+        ])("$kind shows the 5,000 USDT", ({ commands, inputs, permit }) => {
             const result = decodeSteps(commands, inputs);
             expect(linesBetweenTokens(result)).toEqual([
                 ["Amount", "5000.0000 USDT"],
+                ...permit,
             ]);
         });
 
@@ -2023,19 +2045,24 @@ describe("uniswap decoder", () => {
         });
 
         // Out of that shape the permit caps nothing the Amount line can rely
-        // on, so the line gives the total the steps take, as with no permit.
+        // on, so the line gives the total the steps take, as with no permit,
+        // and each permit gets lines of its own.
         const ONE_USDT_PERMIT = (spender) =>
             encodePermit2(USDT_ADDR, 1000000n, spender);
+        const ONE_USDT_LINES = (spender) =>
+            permitLines("1.0000 USDT", USDT_ADDR, "USDT", spender);
         test.each([
             {
                 kind: "to another spender",
                 commands: [0x0a],
                 permits: [ONE_USDT_PERMIT(OTHER_ADDR)],
+                lines: ONE_USDT_LINES(OTHER_ADDR),
             },
             {
                 kind: "that the router lets fail",
                 commands: [0x8a],
                 permits: [ONE_USDT_PERMIT(ROUTER_ADDR)],
+                lines: ONE_USDT_LINES(ROUTER_ADDR),
             },
             {
                 kind: "followed by a second one",
@@ -2044,10 +2071,14 @@ describe("uniswap decoder", () => {
                     ONE_USDT_PERMIT(ROUTER_ADDR),
                     ONE_USDT_PERMIT(ROUTER_ADDR),
                 ],
+                lines: [
+                    ...ONE_USDT_LINES(ROUTER_ADDR),
+                    ...ONE_USDT_LINES(ROUTER_ADDR),
+                ],
             },
         ])(
             "a split after a PERMIT2_PERMIT $kind shows the total the steps take",
-            ({ commands, permits }) => {
+            ({ commands, permits, lines }) => {
                 const result = decodeSteps(
                     [...commands, 0x00, 0x08],
                     [
@@ -2061,10 +2092,20 @@ describe("uniswap decoder", () => {
                 );
                 expect(linesBetweenTokens(result)).toEqual([
                     ["Amount", "1000.0000 USDT"],
+                    ...lines,
                 ]);
             },
         );
 
+        // The lines of a PERMIT2_PERMIT of 600 USDT to the router whose
+        // amount does not stand.
+        const USDT_600_LINES = permitLines(
+            "600.0000 USDT",
+            USDT_ADDR,
+            "USDT",
+            ROUTER_ADDR,
+        );
+
         // A PERMIT2_PERMIT_BATCH, which this decoder does not read, may raise
         // what the router may take of the permit's token again.
         test("a split after a PERMIT2_PERMIT and a PERMIT2_PERMIT_BATCH shows the total the steps take", () => {
@@ -2096,6 +2137,7 @@ describe("uniswap decoder", () => {
             );
             expect(linesBetweenTokens(result)).toEqual([
                 ["Amount", "10000.0000 USDT"],
+                ...USDT_600_LINES,
             ]);
         });
 
@@ -2141,6 +2183,7 @@ describe("uniswap decoder", () => {
                 );
                 expect(linesBetweenTokens(result)).toEqual([
                     ["Amount", "10000.0000 USDT"],
+                    ...USDT_600_LINES,
                 ]);
             },
         );
@@ -2168,8 +2211,9 @@ describe("uniswap decoder", () => {
         ];
         // What a V3_SWAP_EXACT_OUT takes, at most its amountInMax, counts
         // as a V2_SWAP_EXACT_OUT's does, and the Amount line is a maximum.
-        // The permit of 10,000 USDT stands; the one of 600 USDT does not,
-        // because the step before it took its token.
+        // The permit of 10,000 USDT stands. The one of 600 USDT comes after
+        // the step that set the input side, so it does not stand and gets
+        // lines of its own.
         test.each([
             {
                 kind: "a V3 exact-in of 600 USDT, then a V3_SWAP_EXACT_OUT of at most 400 USDT",
@@ -2201,17 +2245,183 @@ describe("uniswap decoder", () => {
                     V3_600,
                 ],
                 amount: "Up to 10000.0000 USDT",
+                permit: USDT_600_LINES,
             },
         ])(
             "$kind, all paid by the user, shows the total as a maximum",
-            ({ commands, inputs, amount }) => {
+            ({ commands, inputs, amount, permit = [] }) => {
                 const result = decodeSteps(commands, inputs);
                 expect(linesBetweenTokens(result)).toEqual([
                     ["Amount", amount],
+                    ...permit,
                 ]);
             },
         );
 
+        // https://git.eeqj.de/sneak/AutistMask/issues/370 — a PERMIT2_PERMIT
+        // after the step that set the input side named Token In in place of
+        // that step's token, and its amount could stand as the Amount figure.
+        // Only a permit whose amount stands as the Amount figure names Token
+        // In now. Every other, before the swap steps or after them, leaves
+        // Token In and Amount as they read with no permit and gets lines of
+        // its own.
+        describe("a PERMIT2_PERMIT whose amount does not stand as the Amount figure", () => {
+            const DAI_5000 = 5000000000000000000000n;
+            const USDT_5000 = 5000000000n;
+            const MAX_UINT160 = 2n ** 160n - 1n;
+
+            test.each([
+                {
+                    kind: "a V3 exact-in of 600 USDT, then a PERMIT2_PERMIT of 5,000 DAI to the router,",
+                    commands: [0x00, 0x0a],
+                    inputs: [
+                        V3_600,
+                        encodePermit2(DAI_ADDR, DAI_5000, ROUTER_ADDR),
+                    ],
+                    lines: permitLines(
+                        "5000.0000 DAI",
+                        DAI_ADDR,
+                        "DAI",
+                        ROUTER_ADDR,
+                    ),
+                },
+                {
+                    kind: "a V3 exact-in of 600 USDT, then a PERMIT2_PERMIT of unlimited DAI to another spender,",
+                    commands: [0x00, 0x0a],
+                    inputs: [
+                        V3_600,
+                        encodePermit2(DAI_ADDR, MAX_UINT160, OTHER_ADDR),
+                    ],
+                    lines: permitLines(
+                        "Unlimited",
+                        DAI_ADDR,
+                        "DAI",
+                        OTHER_ADDR,
+                    ),
+                },
+                {
+                    kind: "a V3 exact-in of 600 USDT, then a PERMIT2_PERMIT of 600 USDT, the swap's own token, to the router,",
+                    commands: [0x00, 0x0a],
+                    inputs: [
+                        V3_600,
+                        encodePermit2(USDT_ADDR, USDT_600, ROUTER_ADDR),
+                    ],
+                    lines: USDT_600_LINES,
+                },
+                {
+                    kind: "a PERMIT2_PERMIT of 5,000 USDT to another spender, then a V3 exact-in of 600 USDT,",
+                    commands: [0x0a, 0x00],
+                    inputs: [
+                        encodePermit2(USDT_ADDR, USDT_5000, OTHER_ADDR),
+                        V3_600,
+                    ],
+                    lines: permitLines(
+                        "5000.0000 USDT",
+                        USDT_ADDR,
+                        "USDT",
+                        OTHER_ADDR,
+                    ),
+                },
+                {
+                    kind: "a PERMIT2_PERMIT of 5,000 USDT to the router that the router may let fail, then a V3 exact-in of 600 USDT,",
+                    commands: [0x8a, 0x00],
+                    inputs: [
+                        encodePermit2(USDT_ADDR, USDT_5000, ROUTER_ADDR),
+                        V3_600,
+                    ],
+                    lines: permitLines(
+                        "5000.0000 USDT",
+                        USDT_ADDR,
+                        "USDT",
+                        ROUTER_ADDR,
+                    ),
+                },
+                {
+                    kind: "a PERMIT2_PERMIT of 5,000 DAI to another spender, then a V3 exact-in of 600 USDT,",
+                    commands: [0x0a, 0x00],
+                    inputs: [
+                        encodePermit2(DAI_ADDR, DAI_5000, OTHER_ADDR),
+                        V3_600,
+                    ],
+                    lines: permitLines(
+                        "5000.0000 DAI",
+                        DAI_ADDR,
+                        "DAI",
+                        OTHER_ADDR,
+                    ),
+                },
+                {
+                    kind: "a PERMIT2_PERMIT of 5,000 DAI to the router, a V3 exact-in of 600 USDT, then a PERMIT2_PERMIT of 600 USDT to the router,",
+                    commands: [0x0a, 0x00, 0x0a],
+                    inputs: [
+                        encodePermit2(DAI_ADDR, DAI_5000, ROUTER_ADDR),
+                        V3_600,
+                        encodePermit2(USDT_ADDR, USDT_600, ROUTER_ADDR),
+                    ],
+                    lines: [
+                        ...permitLines(
+                            "5000.0000 DAI",
+                            DAI_ADDR,
+                            "DAI",
+                            ROUTER_ADDR,
+                        ),
+                        ...USDT_600_LINES,
+                    ],
+                },
+            ])(
+                "$kind shows the swap's 600 USDT and each permit's own lines",
+                ({ commands, inputs, lines }) => {
+                    const result = decodeSteps(commands, inputs);
+                    expect(result.name).toBe("Swap USDT → USDC");
+                    expect(
+                        detail(result, "Token In").address.toLowerCase(),
+                    ).toBe(USDT_ADDR.toLowerCase());
+                    expect(linesBetweenTokens(result)).toEqual([
+                        ["Amount", "600.0000 USDT"],
+                        ...lines,
+                    ]);
+                    expect(detail(result, "Amount").rawValue).toBe("600.0000");
+                },
+            );
+
+            // With two permits neither amount stands, so the Amount line
+            // gives the total the steps take of USDT, the 400 DAI the last
+            // step takes gets lines of its own, and so does each permit.
+            test("a PERMIT2_PERMIT of USDT, a V3 exact-in of 600 USDT, a PERMIT2_PERMIT of DAI and a V2 exact-in of 400 DAI shows both tokens' amounts and each permit's own lines", () => {
+                const result = decodeSteps(
+                    [0x0a, 0x00, 0x0a, 0x08],
+                    [
+                        encodePermit2(USDT_ADDR, USDT_5000, ROUTER_ADDR),
+                        V3_600,
+                        encodePermit2(DAI_ADDR, DAI_400, ROUTER_ADDR),
+                        encodeV2SwapExactIn(USER_ADDR, DAI_400, 390000000n, [
+                            DAI_ADDR,
+                            USDC_ADDR,
+                        ]),
+                    ],
+                );
+                expect(result.name).toBe("Swap USDT → USDC");
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ["Moved from the sender", "400.0000 DAI"],
+                    ["Token moved", "DAI (" + DAI_ADDR + ")"],
+                    ["Moved to", "The swap step that spends it"],
+                    ...permitLines(
+                        "5000.0000 USDT",
+                        USDT_ADDR,
+                        "USDT",
+                        ROUTER_ADDR,
+                    ),
+                    ...permitLines(
+                        "400.0000 DAI",
+                        DAI_ADDR,
+                        "DAI",
+                        ROUTER_ADDR,
+                    ),
+                ]);
+            });
+        });
+
         // A V3_SWAP_EXACT_OUT whose path is shorter than one token cannot be
         // read. It may pay any address and take from the sender, so it
         // leaves no Amount figure.
@@ -2257,7 +2467,7 @@ describe("uniswap decoder", () => {
         // A V3 exact-out of 1,500 USDC for at most 0.5 WETH spends WETH, not
         // SPK. After it, a PERMIT2_PERMIT of 1 WETH and a V3 exact-in of 0.5
         // WETH: the permit's amount does not stand, because the step before
-        // it also takes WETH.
+        // it also takes WETH, so the permit gets lines of its own.
         test("a V3_SWAP_EXACT_OUT whose path has bytes after its last hop, then a PERMIT2_PERMIT and a V3 exact-in, shows no Amount figure", () => {
             const path = pathEndingIn([USDC_ADDR, WETH_ADDR], SPK_ADDR);
             const result = decodeSteps(
@@ -2273,6 +2483,7 @@ describe("uniswap decoder", () => {
             );
             expect(linesBetweenTokens(result)).toEqual([
                 ["Moved from the sender", UNDECODED],
+                ...permitLines("1.0000 WETH", WETH_ADDR, "WETH", ROUTER_ADDR),
             ]);
             expect(detail(result, "Paid to").value).toBe(UNDECODED);
         });
@@ -2443,7 +2654,11 @@ describe("uniswap decoder", () => {
                     V4_EXACT_OUT_600,
                     V2_EXACT_OUT_400,
                 ],
-                lines: [...UNKNOWN_USDT, ...UP_TO_400_USDT],
+                lines: [
+                    ...UNKNOWN_USDT,
+                    ...UP_TO_400_USDT,
+                    ...ONE_USDT_LINES(OTHER_ADDR),
+                ],
             },
             {
                 kind: "a V4 step whose swap action cannot be read, with a SETTLE of WETH by the user, then a V2 exact-out of at most 400 USDT",

tests/uniswapRecipient.test.js

@@ -2809,7 +2809,7 @@ describe("the allow-revert flag", () => {
             mark: " (allowed to fail)",
         },
     ])(
-        "on $router, a PERMIT2_PERMIT with the flag is listed as 'Permit2 Permit$mark', and the swap reads as without the flag",
+        "on $router, a PERMIT2_PERMIT with the flag is listed as 'Permit2 Permit$mark', and the swap's lines read as without the flag",
         ({ address, mark }) => {
             const steps = [
                 permit2Permit(USDT, USDT_2000),
@@ -2824,9 +2824,30 @@ describe("the allow-revert flag", () => {
             expect(detail(withFlag, "Steps").value).toBe(
                 "Permit2 Permit" + mark + " → V3 Swap (Exact In)",
             );
-            const withoutSteps = (r) =>
-                r.details.filter((d) => d.label !== "Steps");
-            expect(withoutSteps(withFlag)).toEqual(withoutSteps(plain));
+            // The permit names the router at ROUTER as its spender, so its
+            // amount stands as the Amount figure only there, and only without
+            // the flag. With the flag it stands on no router and gets lines
+            // of its own, and the swap step names Token In: the same token,
+            // its address in lowercase.
+            const permitLines = [
+                "Permit2 allowance",
+                "Allowance token",
+                "Allowance spender",
+            ];
+            const swapLines = (r) =>
+                r.details.filter(
+                    (d) =>
+                        !["Steps", "Token In", ...permitLines].includes(
+                            d.label,
+                        ),
+                );
+            expect(swapLines(withFlag)).toEqual(swapLines(plain));
+            expect(detail(withFlag, "Token In").address.toLowerCase()).toBe(
+                detail(plain, "Token In").address.toLowerCase(),
+            );
+            expect(
+                labels(withFlag).filter((l) => permitLines.includes(l)),
+            ).toEqual(permitLines);
             expect(detail(withFlag, "Min. received").value).toBe("1.0000 WETH");
         },
     );