fix: a V4 swap action not in the deployed shape is shown as not decoded (closes #358)

The four V4 swap actions are read only as the parameter structs deployed
on mainnet and Sepolia. ethers decoded the newer v4-periphery structs,
which add minHopPriceX36, as the deployed ones without an error, and the
newer multi-hop exact-in struct showed the offset of its hop-price array
as the swap amount. A decode now counts only when encoding it again gives
back the same bytes. When a swap action fails that, the Steps line lists
its step as "V4 Swap (could not be decoded)", so the screen no longer
looks complete without it. The README records the pinned shape.

Model: opus-5-5

README.md

@@ -2071,9 +2071,7 @@ view would leave a wallet one click from deletion.
   artifact can be compared with it field for field. A nonce the site supplies is
   ignored: the nonce is always the account's next nonce from the node, so a site
   cannot replace one of the user's pending transactions or leave this one stuck
-  behind a gap. A gas limit the site supplies, as `gas` or `gasLimit`, is used
-  in place of the node's estimate; a request giving both with different values
-  is refused. A request that cannot be populated — unreachable node, reverting
+  behind a gap. A request that cannot be populated — unreachable node, reverting
   gas estimate — opens no window and is failed back to the site. Only one
   transaction approval exists at a time: populating fixes the nonce, so a second
   `eth_sendTransaction` arriving while one is unanswered is refused with
@@ -2680,7 +2678,11 @@ Currently supported:
   or recipient, and amount.
 - **Uniswap Universal Router**: `execute()` calls — shows swap direction (e.g.
   "Swap USDT → ETH"), token addresses, amounts, execution steps, and deadline.
-  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks.
+  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks. A V4 swap
+  action is read only in the parameter shape deployed on mainnet and Sepolia,
+  not in the newer one on `v4-periphery` `main`, which adds a `minHopPriceX36`
+  field. An action in any other shape is not read, and its step is listed as
+  `V4 Swap (could not be decoded)`.
 
 ### Non-Goals Forever
 

src/shared/approvalTx.js

@@ -31,7 +31,6 @@ const {
     VoidSigner,
     accessListify,
     getAddress,
-    getBigInt,
     getBytes,
     hexlify,
     toQuantity,
@@ -48,11 +47,10 @@ const {
 // minutes long, which is not a wait anyone will sit through.
 const POPULATE_TIMEOUT_MS = 20000;
 
-// The request fields taken from the page, plus `gas`, which requestFrom()
-// takes as the gas limit. Anything else is dropped rather than passed to
-// ethers: the object is page-controlled, and a future ethers that learns to
-// carry a new transaction field must not start picking one up out of it
-// without this module knowing.
+// The request fields taken from the page. Anything else is dropped rather than
+// passed to ethers: the object is page-controlled, and a future ethers that
+// learns to carry a new transaction field must not start picking one up out of
+// it without this module knowing.
 //
 // The nonce is not taken from the page; it is always the account's next nonce
 // from the network. A page that chose it could replace one of the user's
@@ -86,16 +84,6 @@ function present(v) {
     return v !== null && v !== undefined && v !== "";
 }
 
-// Whether two quantities from the page are the same number. One that is not a
-// number matches nothing.
-function sameQuantity(a, b) {
-    try {
-        return getBigInt(a) === getBigInt(b);
-    } catch {
-        return false;
-    }
-}
-
 // These strings reach the user through the requesting page, so they are full
 // sentences even when the tail of one came from ethers or from the node.
 function sentence(text) {
@@ -123,20 +111,6 @@ function requestFrom(txParams, from) {
     for (const key of REQUEST_FIELDS) {
         if (present(txParams[key])) request[key] = txParams[key];
     }
-    // JSON-RPC calls the gas limit `gas`, and that is the name sites send.
-    // ethers only reads `gasLimit`: left as `gas` it would be dropped and an
-    // estimate signed in its place.
-    if (present(txParams.gas)) {
-        if (
-            present(request.gasLimit) &&
-            !sameQuantity(request.gasLimit, txParams.gas)
-        ) {
-            throw fail(
-                "The site asked for two different gas limits for this transaction.",
-            );
-        }
-        request.gasLimit = txParams.gas;
-    }
     if (
         present(request.type) &&
         !ALLOWED_TX_TYPES.includes(Number(request.type))

src/shared/uniswap.js

@@ -295,6 +295,24 @@ function v4ExactInAmount(raw) {
     return raw === 0n ? OPEN_DELTA : raw;
 }
 
+// The V4 swap actions are read only in the parameter structs V4Router has
+// deployed on mainnet and Sepolia. v4-periphery `main` has since added a
+// `minHopPriceX36` field to all four (`src/interfaces/IV4Router.sol`), and
+// reading a shape nobody has deployed would be guessing. ethers alone would
+// read the newer structs anyway: it takes whatever word sits where a
+// deployed field would be, ignores bytes left over, and holds back an error
+// in a field until that field is used. The newer multi-hop exact-in struct
+// then yields the offset of its hop-price array as `amountIn`. So a decode
+// counts only when encoding the result again gives back the same bytes;
+// otherwise this throws, and decodeV4Swap() marks the step as not decoded.
+function decodeExactly(types, data) {
+    const decoded = coder.decode(types, data);
+    if (coder.encode(types, decoded) !== data) {
+        throw new Error("Not in the deployed V4 parameter shape.");
+    }
+    return decoded;
+}
+
 // Decode V4_SWAP (command 0x10) input bytes.
 // The input is ABI-encoded as (bytes actions, bytes[] params).
 // We extract token addresses from SETTLE (input) and TAKE (output) sub-actions,
@@ -309,6 +327,10 @@ function decodeV4Swap(input) {
         let takeToken = null;
         let amountIn = null;
         let amountOutMin = null;
+        // Set when a swap action's parameters are not in the deployed shape
+        // (see decodeExactly()), so nothing was read from that action. SETTLE
+        // and TAKE may still name both currencies.
+        let swapUndecoded = false;
 
         for (let i = 0; i < actions.length; i++) {
             const actionId = actions[i];
@@ -337,7 +359,7 @@ function decodeV4Swap(input) {
                         //   tuple(address,uint24,int24,address,bytes)[] path,
                         //   uint128 amountIn, uint128 amountOutMin)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -355,13 +377,13 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through — SETTLE/TAKE will provide tokens
+                            swapUndecoded = true;
                         }
                     } else {
                         // ExactInputSingleParams: (tuple(address,address,uint24,int24,address) poolKey,
                         //   bool zeroForOne, uint128 amountIn, uint128 amountOutMin, bytes hookData)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -384,7 +406,7 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 } else if (
@@ -393,7 +415,7 @@ function decodeV4Swap(input) {
                 ) {
                     if (actionId === V4_SWAP_EXACT_OUT) {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -405,11 +427,11 @@ function decodeV4Swap(input) {
                                 settleToken = path[path.length - 1][0];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     } else {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -426,7 +448,7 @@ function decodeV4Swap(input) {
                                     ? poolKey[1]
                                     : poolKey[0];
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 }
@@ -440,6 +462,7 @@ function decodeV4Swap(input) {
             tokenOut: takeToken,
             amountIn,
             amountOutMin,
+            swapUndecoded,
         };
     } catch {
         return null;
@@ -568,6 +591,11 @@ function decode(data, toAddress, sources) {
                 if (cmdId === 0x10) {
                     const v4 = decodeV4Swap(inputs[i]);
                     if (v4) {
+                        // Without this, a swap action that went unread would
+                        // look like one that had nothing to show.
+                        if (v4.swapUndecoded) {
+                            commandNames[i] += " (could not be decoded)";
+                        }
                         setInputOnce(v4.tokenIn, v4.amountIn);
                         // Always update output: last swap step wins. A step
                         // that carries the Min. received figure but decoded no

tests/approvalTx.test.js

@@ -9,7 +9,7 @@
 // requesting page or the RPC node can say turns it into an approval that
 // should never have been raised.
 
-const { Network, Transaction, Wallet, toQuantity } = require("ethers");
+const { Network, Wallet } = require("ethers");
 const {
     prepareApprovalTx,
     serializeApprovedTx,
@@ -138,43 +138,6 @@ describe("prepareApprovalTx", () => {
         expect(approved.maxFeePerGas).toBe("0x12a05f200");
     });
 
-    // `gas` is the JSON-RPC name for the gas limit and the one sites send.
-    // The node would estimate 21000; the site's 200000 is what is shown and
-    // what is signed.
-    test("uses the gas limit a site sends as gas", async () => {
-        const approved = await prepareApprovalTx(
-            providerWith(),
-            signer.address,
-            { ...TX_PARAMS, gas: "0x30d40" },
-        );
-        expect(approved.gasLimit).toBe("0x30d40");
-        const signed = Transaction.from(
-            await signer.signTransaction({ ...approved }),
-        );
-        expect(signed.gasLimit).toBe(200000n);
-    });
-
-    test("accepts gas and gasLimit that name the same number", async () => {
-        const approved = await prepareApprovalTx(
-            providerWith(),
-            signer.address,
-            { ...TX_PARAMS, gas: "0x30d40", gasLimit: 200000 },
-        );
-        expect(approved.gasLimit).toBe("0x30d40");
-    });
-
-    test("refuses gas and gasLimit that disagree", async () => {
-        await expect(
-            prepareApprovalTx(providerWith(), signer.address, {
-                ...TX_PARAMS,
-                gas: "0x30d40",
-                gasLimit: "0x5208",
-            }),
-        ).rejects.toThrow(
-            "The site asked for two different gas limits for this transaction.",
-        );
-    });
-
     test("carries an access list the request asked for", async () => {
         const approved = await prepareApprovalTx(
             providerWith(),
@@ -249,15 +212,6 @@ describe("prepareApprovalTx", () => {
         ).rejects.toThrow(/gas limit no network this wallet supports/);
     });
 
-    test("refuses a gas limit the site sent above the ceiling", async () => {
-        await expect(
-            prepareApprovalTx(providerWith(), signer.address, {
-                ...TX_PARAMS,
-                gas: toQuantity(MAX_GAS_LIMIT + 1n),
-            }),
-        ).rejects.toThrow(/gas limit no network this wallet supports/);
-    });
-
     // The combined bound at population: a gas limit and a fee that are each
     // under their own ceiling but multiply to thousands of ETH is refused
     // before the approval window opens, so the user is never shown a

tests/uniswap.test.js

@@ -163,6 +163,110 @@ function encodeV4ExactInSingle(currency0, currency1, amountIn, amountOutMin) {
     );
 }
 
+// Each V4 swap action's parameters in two shapes: the struct V4Router has
+// deployed on mainnet and Sepolia, and the one v4-periphery `main` has since
+// moved to, which adds a `minHopPriceX36` field. Each swaps WETH for USDC.
+const POOL_KEY = "tuple(address,address,uint24,int24,address)";
+const PATH_KEY = "tuple(address,uint24,int24,address,bytes)";
+const WETH_USDC_POOL = [WETH_ADDR, USDC_ADDR, 100, 1, ZERO_ADDR];
+const ONE_WETH = 1000000000000000000n;
+const V4_SWAP_ACTION_SHAPES = [
+    {
+        action: "SWAP_EXACT_IN_SINGLE",
+        id: 0x06,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_IN",
+        id: 0x07,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT_SINGLE",
+        id: 0x08,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT",
+        id: 0x09,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+    },
+];
+
+// Helper: execute() with one V4_SWAP step holding the swap action, then
+// SETTLE of WETH and TAKE of USDC.
+function v4SwapCalldata(actionId, swapParams) {
+    return buildExecute(
+        "0x10",
+        [
+            encodeV4Swap(new Uint8Array([actionId, V4_SETTLE_ID, V4_TAKE_ID]), [
+                swapParams,
+                encodeV4Settle(WETH_ADDR),
+                encodeV4Take(USDC_ADDR),
+            ]),
+        ],
+        9999999999n,
+    );
+}
+
 function detail(result, label) {
     return result.details.find((d) => d.label === label);
 }
@@ -203,11 +307,45 @@ describe("uniswap decoder", () => {
             result.details.find((d) => d.label === "Min. received").value,
         ).toBe("0.0002 ETH");
 
+        // Real mainnet calldata is in the deployed shape, so its V4 step is
+        // not said to be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
-        expect(steps.value).toContain("Permit2 Permit");
-        expect(steps.value).toContain("V4 Swap");
+        expect(steps.value).toBe("Permit2 Permit → V4 Swap");
     });
 
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the deployed shape is read",
+        ({ id, deployed }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, deployed),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Steps").value).toBe("V4 Swap");
+        },
+    );
+
+    // https://git.eeqj.de/sneak/AutistMask/issues/358 — before it, all four
+    // newer structs decoded as the deployed ones without an error, and the
+    // newer SWAP_EXACT_IN showed the offset of its hop-price array as Amount
+    // ("0.0000000000000004 WETH") and its amountIn as Min. received.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer periphery shape is shown as not decoded",
+        ({ id, newer }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, newer),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Amount")).toBeUndefined();
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            // SETTLE and TAKE keep their own shape and still name both sides.
+            expect(detail(result, "Token In").address).toBe(WETH_ADDR);
+            expect(detail(result, "Token Out").address).toBe(USDC_ADDR);
+        },
+    );
+
     test("decodes V2_SWAP_EXACT_IN with known tokens", () => {
         const data = buildExecute(
             "0x08", // V2_SWAP_EXACT_IN
@@ -548,9 +686,11 @@ describe("uniswap decoder", () => {
         const result = uniswap.decode(data, ROUTER_ADDR);
         expect(result).not.toBeNull();
 
+        // The V4 swap action's parameters are empty, so that step is said to
+        // be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
         expect(steps.value).toBe(
-            "Permit2 Permit \u2192 V4 Swap \u2192 Unwrap WETH",
+            "Permit2 Permit \u2192 V4 Swap (could not be decoded) \u2192 Unwrap WETH",
         );
     });