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

The swap's Amount line took 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 what each later step the user pays takes of it.
A take of another token, one after an amount that is not a quantity, or
one the decoder cannot tell, gets lines of its own; an unread take, a
V3_SWAP_EXACT_OUT's included, leaves no figure wherever it stands. A V4
step counts every SETTLE paid by the user and every SETTLE_ALL. A
PERMIT2_PERMIT names Token In, and its amount stands only in the plain
shape of Uniswap's own routes, with every later step read.

Model: opus-5-5

README.md

@@ -3170,29 +3170,26 @@ Currently supported:
   `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
-  `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, 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; 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,
-  and such a step before a `PERMIT2_PERMIT` keeps the permit's amount from
-  standing. Then each `PERMIT2_TRANSFER_FROM` but one into the router, in step
-  order, gives three lines: `Moved from the sender`, the amount it moves, for
-  example `1000000.0000 USDT`; `Token moved`, giving the token's address as the
-  `Token In` line does; and `Moved to`, which reads
+  does not know. 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,
+  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; 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, and such a step before a `PERMIT2_PERMIT` keeps the permit's
+  amount from standing. Then each `PERMIT2_TRANSFER_FROM` but one into the
+  router, in step order, gives three lines: `Moved from the sender`, the amount
+  it moves, for example `1000000.0000 USDT`; `Token moved`, giving the token's
+  address as the `Token In` line does; and `Moved to`, which reads
   `The V2 pair the next swap spends` for a hop and `The sender` for `address(1)`
   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

src/shared/uniswap.js

@@ -1795,14 +1795,8 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // (see spentUnread()), or a token it does not know.
         const spentFromSender = [];
         let total = null;
-        // 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)) {
             total = inputAmount;
-            if (inputEstablished && !present(inputAmount)) {
-                firstTakeUnstated = { token: inputToken, amount: null };
-            }
         } else if (inputEstablished) {
             // 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.
@@ -1824,17 +1818,6 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (ofTokenIn && !present(t.amount)) total = null;
         }
         inputAmount = permitStands ? permit.amount : total;
-        // With no Amount figure, a later take's own figure could read as all
-        // that leaves, so the step that set the input side, when it stated
-        // no amount, then gets lines of its own too, first, saying its amount
-        // is not known.
-        if (
-            !present(inputAmount) &&
-            firstTakeUnstated !== null &&
-            spentFromSender.some((s) => present(s.amount))
-        ) {
-            spentFromSender.unshift(firstTakeUnstated);
-        }
 
         // The commands of an EXECUTE_SUB_PLAN step may spend the user's tokens
         // or pay the user, before or after any other step, and a permit among

tests/uniswap.test.js

@@ -1942,9 +1942,7 @@ describe("uniswap decoder", () => {
 
         // A later step's amount that cannot be added to the Amount line,
         // because the amount of the step that set the input side is not a
-        // quantity, gets lines of its own. When that step stated no amount,
-        // it gets lines of its own too, saying so, so the 400 USDT cannot
-        // read as all that leaves.
+        // quantity, gets lines of its own.
         const V2_EXACT_OUT_400 = encodeV2SwapExactOut(
             USER_ADDR,
             390000000n,
@@ -1956,37 +1954,28 @@ describe("uniswap decoder", () => {
             ["Token moved", "USDT (" + USDT_ADDR + ")"],
             ["Moved to", "The swap step that spends it"],
         ];
-        const UNKNOWN_USDT = [
-            ["Moved from the sender", UNDECODED],
-            ["Token moved", "USDT (" + USDT_ADDR + ")"],
-            ["Moved to", "The swap step that spends it"],
-        ];
-        // A V4 exact-out step of at most 600 USDT for 1 WETH, in the shape
-        // of Uniswap's own routes: a SETTLE of OPEN_DELTA by the user pays
-        // what the swap spends.
-        const V4_EXACT_OUT_600 = encodeV4Swap(
-            new Uint8Array([
-                V4_SWAP_EXACT_OUT_SINGLE_ID,
-                V4_SETTLE_ID,
-                V4_TAKE_ALL_ID,
-            ]),
-            [
-                encodeV4ExactOutSingle(
-                    USDT_ADDR,
-                    WETH_ADDR,
-                    ONE_WETH,
-                    USDT_600,
-                ),
-                encodeV4Settle(USDT_ADDR),
-                encodeV4TakeAll(WETH_ADDR, 0n),
-            ],
-        );
         test.each([
             {
                 kind: "a V4 exact-out step with a SETTLE of OPEN_DELTA by the user",
                 commands: [0x10, 0x09],
-                first: V4_EXACT_OUT_600,
-                lines: [...UNKNOWN_USDT, ...UP_TO_400_USDT],
+                first: encodeV4Swap(
+                    new Uint8Array([
+                        V4_SWAP_EXACT_OUT_SINGLE_ID,
+                        V4_SETTLE_ID,
+                        V4_TAKE_ALL_ID,
+                    ]),
+                    [
+                        encodeV4ExactOutSingle(
+                            USDT_ADDR,
+                            WETH_ADDR,
+                            ONE_WETH,
+                            USDT_600,
+                        ),
+                        encodeV4Settle(USDT_ADDR),
+                        encodeV4TakeAll(WETH_ADDR, 0n),
+                    ],
+                ),
+                lines: UP_TO_400_USDT,
             },
             {
                 kind: "a V4 exact-in step of the open delta",
@@ -2031,59 +2020,6 @@ describe("uniswap decoder", () => {
             },
         );
 
-        // The V4 exact-out route above the other way round, where the later
-        // take's unknown amount leaves no figure at all, and other ways the
-        // step that sets the input side states no amount.
-        test.each([
-            {
-                kind: "a V2 exact-out of at most 400 USDT, then a V4 exact-out step of at most 600 USDT",
-                commands: [0x09, 0x10],
-                inputs: [V2_EXACT_OUT_400, V4_EXACT_OUT_600],
-                lines: UNKNOWN_USDT,
-            },
-            {
-                kind: "a PERMIT2_PERMIT of 1 USDT to another spender, a V4 exact-out step of at most 600 USDT, then a V2 exact-out of at most 400 USDT",
-                commands: [0x0a, 0x10, 0x09],
-                inputs: [
-                    encodePermit2(USDT_ADDR, 1000000n, OTHER_ADDR),
-                    V4_EXACT_OUT_600,
-                    V2_EXACT_OUT_400,
-                ],
-                lines: [...UNKNOWN_USDT, ...UP_TO_400_USDT],
-            },
-            {
-                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",
-                commands: [0x10, 0x09],
-                inputs: [
-                    encodeV4Swap(
-                        new Uint8Array([
-                            V4_SWAP_EXACT_IN_SINGLE_ID,
-                            V4_SETTLE_ID,
-                            V4_TAKE_ALL_ID,
-                        ]),
-                        [
-                            UNREAD_SWAP,
-                            encodeV4Settle(WETH_ADDR),
-                            encodeV4TakeAll(USDC_ADDR, 0n),
-                        ],
-                    ),
-                    V2_EXACT_OUT_400,
-                ],
-                lines: [
-                    ["Moved from the sender", UNDECODED],
-                    ["Token moved", "WETH (" + WETH_ADDR + ")"],
-                    ["Moved to", "The swap step that spends it"],
-                    ...UP_TO_400_USDT,
-                ],
-            },
-        ])(
-            "$kind, all paid by the user, shows that an amount is not known",
-            ({ commands, inputs, lines }) => {
-                const result = decodeSteps(commands, inputs);
-                expect(linesBetweenTokens(result)).toEqual(lines);
-            },
-        );
-
         // A V2 exact-out step makes every amount the swap steps spend a maximum,
         // the total included.
         test("a split with a V2 exact-out step the user pays for shows the total as a maximum", () => {