fix: a swap split across steps the user pays for shows every amount it spends (closes #625)

The Amount line gave only the first swap step's amount. It now gives the
total the steps take of Token In: the amount of the step that sets the
input side plus each later take of it by a step the user pays. A V4
step, the first included, takes what its SETTLEs paid by the user state.
A take of another token, one after an amount that is not a quantity, or
one of unknown amount gets lines of its own. A step that may take what
the decoder did not read gets one line saying so and leaves no figure.
A PERMIT2_PERMIT names Token In; its amount stands only in the plain
shape of Uniswap's own routes.

Also closes #628.

Model: opus-5-5

README.md

@@ -1235,7 +1235,9 @@ only when no earlier step set it. It finds each side by three rules:
    is their sum; in any other case the step gives no `Amount`. The decoder reads
    no amount from an exact-out action, and an open delta is not a stated amount.
    Its `Min. received` is found the same way, from the `amountOutMin` of the
-   actions that buy the output currency.
+   actions that buy the output currency. When the user pays the step any of the
+   input currency, its `Amount` is what the user pays instead (see Transaction
+   Decoding).
 3. If any swap action in the step could not be read, only `SETTLE`,
    `SETTLE_ALL`, `TAKE` and `TAKE_ALL` name its sides, and the step gives no
    `Amount` or `Min. received`. A side they did not name is unknown, and the
@@ -3136,42 +3138,46 @@ Currently supported:
   token or amount. A V4 step with a swap action sets the input side when no
   earlier step set it, even when it names neither (see Display Consistency).
   That step counts its own amount, whoever pays it: a V2 exact-out step its
-  `amountInMax`, and a V4 swap step the `amountIn` of the swap action that
-  spends its input currency. Each later V2 or V3 exact-in or V2 exact-out step
-  whose `payerIsUser` is true takes its amount, found in the same way, from the
-  user's wallet. So does every V4 step but the one that sets the input side,
-  with a swap action or without: it takes what its `SETTLE`s paid by the user
-  (`payerIsUser` true) and its `SETTLE_ALL`s pay, for each token on its own. A
-  `SETTLE` of any amount but `OPEN_DELTA` pays that amount, and a `SETTLE` of
-  `OPEN_DELTA` or a `SETTLE_ALL` pays what the step owes, as above. A later step
-  paid from the router spends what the router holds and takes nothing, and so
-  does a V2 exact-in whose `amountIn` is `ALREADY_PAID`. A later take of
-  `Token In` is 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
-  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 and
-  there is no `Amount` line, that step gets them too whenever another take's
+  `amountInMax`, and a V4 step what it takes of its input token from the user's
+  wallet, as below, or, when the user pays it none of that token, the `amountIn`
+  of the swap action that spends it. Each later V2 or V3 exact-in or V2
+  exact-out step whose `payerIsUser` is true takes its amount, found in the same
+  way, from the user's wallet. Every V4 step, with a swap action or without,
+  takes from the user's wallet what its `SETTLE`s paid by the user
+  (`payerIsUser` true) and its `SETTLE_ALL`s pay, for each token on its own;
+  what the step that sets the input side takes of any other token counts as a
+  later step's take. A `SETTLE` of any amount but `OPEN_DELTA` pays that amount,
+  and a `SETTLE` of `OPEN_DELTA` or a `SETTLE_ALL` pays what the step owes, as
+  above. So a V4 step that swaps 400 USDT, with a `SETTLE` of 5,000 USDT paid by
+  the user and the rest taken to another address, reads `5000.0000 USDT`. A
+  later step paid from the router spends what the router holds and takes
+  nothing, and so does a V2 exact-in whose `amountIn` is `ALREADY_PAID`. A later
+  take of `Token In` is 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 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
+  and there is no `Amount` line, that step gets them too whenever another take's
   lines give a figure, so that figure cannot read as all that leaves. 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
@@ -3179,13 +3185,13 @@ Currently supported:
   `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, other
-  than the one that sets the input side, whose input or one of whose `SETTLE`s
-  or `SETTLE_ALL`s it cannot read, which the router still runs; a V2 or V3
-  exact-in or V2 exact-out step or a `PERMIT2_TRANSFER_FROM` whose input it
-  cannot read; every `PERMIT2_TRANSFER_FROM_BATCH`; every `V3_SWAP_EXACT_OUT`,
-  which the decoder does not read, wherever it stands; every `EXECUTE_SUB_PLAN`,
-  wherever it stands; and every step it fails on. Each such step gives one
+  take from the user's wallet what the decoder did not read: a V4 step whose
+  input or one of whose `SETTLE`s or `SETTLE_ALL`s it cannot read, which the
+  router still runs; a V2 or V3 exact-in or V2 exact-out step or a
+  `PERMIT2_TRANSFER_FROM` whose input it cannot read; every
+  `PERMIT2_TRANSFER_FROM_BATCH`; every `V3_SWAP_EXACT_OUT`, which the decoder
+  does not read, wherever it stands; every `EXECUTE_SUB_PLAN`, wherever it
+  stands; and every step it fails on. Each such step gives one
   `Moved from the sender` line among those, reading
   `Unknown (could not be decoded)`. That line, or any line for a token the
   decoder does not know, leaves no `Amount` line, whose figure might be too low,

src/shared/uniswap.js

@@ -903,7 +903,8 @@ function totalAmount(amounts) {
 // input side from it only when no earlier step set it. A side it sets that
 // these rules leave unknown is set unknown, with no figure. A step with no
 // swap action sets only the sides SETTLE, SETTLE_ALL, TAKE and TAKE_ALL
-// name.
+// name. When the user pays the step any of Token In (`paidByUser` below),
+// decode() takes that, not the Amount of rule 2, as the step's amount.
 //
 // `takes` is every TAKE, TAKE_ALL and TAKE_PORTION, as the currency it takes
 // and its recipient as written, MSG_SENDER for a TAKE_ALL. TAKE_PORTION takes
@@ -1220,9 +1221,10 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             outputEstablished = true;
         };
 
-        // What each step but the one that sets the input side takes from the
-        // sender, as { token, amount }, in step order. After the loop each
-        // joins the Amount line or gets lines of its own (see permitStands).
+        // What the steps take from the sender beyond the amount of the step
+        // that sets the input side, as { token, amount }, in step order.
+        // After the loop each joins the Amount line or gets lines of its own
+        // (see permitStands).
         const userPaid = [];
         // A swap step the user pays for (`payerIsUser` true) takes `amount`
         // of `token` from the sender. A V2 exact-in of ALREADY_PAID takes
@@ -1231,14 +1233,14 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (amount !== ALREADY_PAID) userPaid.push({ token, amount });
         };
         // A step may take from the sender what this decoder did not read: a
-        // V4 step, other than the one that sets the input side, whose input
-        // or one of whose SETTLEs or SETTLE_ALLs it cannot read; a V2 or V3
-        // exact-in or V2 exact-out step or PERMIT2_TRANSFER_FROM whose input
-        // it cannot read; a PERMIT2_TRANSFER_FROM_BATCH; a V3_SWAP_EXACT_OUT;
-        // an EXECUTE_SUB_PLAN; and a step it fails on. It is recorded with a
-        // null token and amount: one line says so, there is no Amount line,
-        // whose figure may then be too low, and the amount of a permit after
-        // it does not stand (see permitStands).
+        // V4 step whose input or one of whose SETTLEs or SETTLE_ALLs it
+        // cannot read; a V2 or V3 exact-in or V2 exact-out step or
+        // PERMIT2_TRANSFER_FROM whose input it cannot read; a
+        // PERMIT2_TRANSFER_FROM_BATCH; a V3_SWAP_EXACT_OUT; an
+        // EXECUTE_SUB_PLAN; and a step it fails on. It is recorded with a null
+        // token and amount: one line says so, there is no Amount line, whose
+        // figure may then be too low, and the amount of a permit after it
+        // does not stand (see permitStands).
         const spentUnread = () => {
             userPaid.push({ token: null, amount: null });
         };
@@ -1677,6 +1679,14 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         swapUndecoded = true;
                         commandNames[i] += " (could not be decoded)";
                     }
+                    // The step's amount, if it sets the input side: what the
+                    // user pays it of its input currency (see
+                    // decodeV4Swap()), or, when the user pays none of it,
+                    // what its swap actions spend of it, whoever pays that.
+                    const paidIn = v4?.paidByUser.find(
+                        (p) => p.currency === v4.tokenIn,
+                    );
+                    const amountIn = paidIn ? paidIn.amount : v4?.amountIn;
                     if (v4 && v4.hasSwapAction) {
                         // A step with a swap action always sets the output
                         // side, as the last swap step wins, and sets the
@@ -1688,7 +1698,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         // token, likewise never sits beside an earlier step's
                         // other half.
                         if (!inputEstablished) {
-                            setInput(v4.tokenIn, v4.amountIn);
+                            setInput(v4.tokenIn, amountIn);
                         }
                         outputToken = v4.tokenOut;
                         minOutput = v4.amountOutMin;
@@ -1698,26 +1708,26 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         // SETTLE, SETTLE_ALL, TAKE or TAKE_ALL names:
                         // setInputOnce() and setOutput() leave alone a side
                         // whose two halves are both unstated.
-                        setInputOnce(v4.tokenIn, v4.amountIn);
+                        setInputOnce(v4.tokenIn, amountIn);
                         setOutput(v4.tokenOut, v4.amountOutMin);
                     }
-                    // Every V4 step but the one that sets the input side,
-                    // with a swap action or without, takes from the sender
-                    // what the user pays it (an amount an unread action may
-                    // change is null). One whose input, or one of whose
-                    // SETTLEs or SETTLE_ALLs, this decoder could not read may
-                    // take anything: the router still runs it.
+                    // Every V4 step, with a swap action or without, takes
+                    // from the sender what the user pays it (an amount an
+                    // unread action may change is null), less what the step
+                    // that sets the input side counts as its amount. One
+                    // whose input, or one of whose SETTLEs or SETTLE_ALLs,
+                    // this decoder could not read may take anything: the
+                    // router still runs it.
                     const setInputHere = inputEstablished && !inputSetBefore;
-                    if (!setInputHere) {
-                        if (v4) {
-                            for (const p of v4.paidByUser) {
-                                addUserPaid(p.currency, p.amount);
-                            }
-                        }
-                        if (!v4 || v4.settleUnread) {
-                            spentUnread();
+                    if (v4) {
+                        for (const p of v4.paidByUser) {
+                            if (setInputHere && p === paidIn) continue;
+                            addUserPaid(p.currency, p.amount);
                         }
                     }
+                    if (!v4 || v4.settleUnread) {
+                        spentUnread();
+                    }
                 } else if (command === "UNWRAP_WETH") {
                     hasUnwrapWeth = true;
                     const u = decodeUnwrapWeth(inputs[i]);

tests/uniswap.test.js

@@ -1590,6 +1590,61 @@ describe("uniswap decoder", () => {
             },
         );
 
+        // https://git.eeqj.de/sneak/AutistMask/issues/628 — the V4 step that
+        // sets the input side takes what its SETTLE paid by the user states,
+        // not what its swap spends. Each of these read 400.0000 USDT before;
+        // on next the first two read 400.0000 USDT and 1.0000 USDT.
+        const V4_SETTLE_5000 = encodeV4Swap(
+            new Uint8Array([
+                V4_SETTLE_ID,
+                V4_SWAP_EXACT_IN_SINGLE_ID,
+                V4_TAKE_ID,
+                V4_TAKE_ALL_ID,
+            ]),
+            [
+                settle(USDT_ADDR, 5000000000n, true),
+                USDT_FOR_USDC_400,
+                take(USDT_ADDR, OTHER_ADDR, 0n), // the rest
+                encodeV4TakeAll(USDC_ADDR, 0n),
+            ],
+        );
+        test.each([
+            {
+                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],
+            },
+            {
+                kind: "a PERMIT2_PERMIT of 1 USDT that the router may let fail, then that V4 step,",
+                commands: [0x8a, 0x10],
+                inputs: [
+                    encodePermit2(USDT_ADDR, 1000000n, ROUTER_ADDR),
+                    V4_SETTLE_5000,
+                ],
+            },
+            // The unread SWEEP keeps the permit's amount from standing.
+            {
+                kind: "a PERMIT2_PERMIT of 5,000 USDT to the router, that V4 step, then a SWEEP that cannot be read,",
+                commands: [0x0a, 0x10, 0x04],
+                inputs: [
+                    encodePermit2(USDT_ADDR, 5000000000n, ROUTER_ADDR),
+                    V4_SETTLE_5000,
+                    dirtyWord(
+                        coder.encode(
+                            ["address", "address", "uint256"],
+                            [USDC_ADDR, USER_ADDR, 0n],
+                        ),
+                        1,
+                    ),
+                ],
+            },
+        ])("$kind shows the 5,000 USDT", ({ commands, inputs }) => {
+            const result = decodeSteps(commands, inputs);
+            expect(linesBetweenTokens(result)).toEqual([
+                ["Amount", "5000.0000 USDT"],
+            ]);
+        });
+
         // A step that may take from the sender what the decoder did not read
         // leaves no Amount figure, which may be too low, and one line says so.
         const UNREAD_SWAP = V4_SWAP_ACTION_SHAPES[0].newer;
@@ -1644,6 +1699,24 @@ describe("uniswap decoder", () => {
         });
 
         test.each([
+            {
+                kind: "a V4 step swapping 400 USDT whose SETTLE by the user cannot be read",
+                commands: [0x10],
+                inputs: [
+                    encodeV4Swap(
+                        new Uint8Array([
+                            V4_SWAP_EXACT_IN_SINGLE_ID,
+                            V4_SETTLE_ID,
+                            V4_TAKE_ALL_ID,
+                        ]),
+                        [
+                            USDT_FOR_USDC_400,
+                            dirtyWord(settle(USDT_ADDR, USDT_400, true), 0),
+                            encodeV4TakeAll(USDC_ADDR, 0n),
+                        ],
+                    ),
+                ],
+            },
             {
                 kind: "a V3 step of 600 USDT, then a V4 step whose input cannot be read",
                 commands: [0x00, 0x10],
@@ -2042,8 +2115,10 @@ describe("uniswap decoder", () => {
                 first: V4_EXACT_OUT_600,
                 lines: [...UNKNOWN_USDT, ...UP_TO_400_USDT],
             },
+            // Settled by the user, the step's amount would be what that
+            // SETTLE pays, which the decoder cannot state here.
             {
-                kind: "a V4 exact-in step of the open delta",
+                kind: "a V4 exact-in step of the open delta, settled from the router",
                 commands: [0x10, 0x09],
                 first: encodeV4Swap(
                     new Uint8Array([
@@ -2053,7 +2128,7 @@ describe("uniswap decoder", () => {
                     ]),
                     [
                         encodeV4ExactInSingle(USDT_ADDR, USDC_ADDR, 0n, 1n),
-                        encodeV4Settle(USDT_ADDR),
+                        settle(USDT_ADDR, 0n, false),
                         encodeV4TakeAll(USDC_ADDR, 0n),
                     ],
                 ),
@@ -2283,7 +2358,9 @@ describe("uniswap decoder", () => {
     // (v4-periphery ActionConstants.OPEN_DELTA = 0, applied by V4Router's
     // _swapExactInputSingle / _swapExactInput). It is not a quantity, and
     // printing "0.0000 WETH" for it would state the exact inverse of what the
-    // step does. Against c9ebac8 the Amount line was omitted entirely.
+    // step does. Against c9ebac8 the Amount line was omitted entirely. The
+    // SETTLE is paid from the router: one paid by the user would make the
+    // step's amount what that SETTLE pays.
     test("a V4 open-delta amountIn is named, not printed as zero", () => {
         const data = buildExecute(
             "0x10",
@@ -2295,7 +2372,10 @@ describe("uniswap decoder", () => {
                         V4_TAKE_ID,
                     ]),
                     [
-                        encodeV4Settle(WETH_ADDR),
+                        coder.encode(
+                            ["address", "uint256", "bool"],
+                            [WETH_ADDR, 0n, false],
+                        ),
                         encodeV4ExactInSingle(
                             WETH_ADDR,
                             USDC_ADDR,