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 structs deployed on mainnet
and Sepolia. ethers read the newer v4-periphery structs, which add
minHopPriceX36, as the deployed ones, 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.
A swap action that fails that marks its step "V4 Swap (could not be
decoded)", and a side its SETTLE or TAKE did not name reads "Unknown
(could not be decoded)". The wait and error screens no longer show the
ETH value as the amount of a swap whose amount was not read, unless the
swap is paid in native ETH.

Model: opus-5-5

tests/swapStatusAmount.test.js

@@ -0,0 +1,342 @@
+// The amount the wait and error screens show for a swap whose amount the
+// decoder did not read (https://git.eeqj.de/sneak/AutistMask/issues/358).
+//
+// A V4 swap action not in the deployed shape is not read, and a V4 exact-out
+// action is read for its currencies only, so the approval screen has no
+// Amount line for either. The wait and error screens then showed the
+// transaction's ETH value as the amount, in the swap's input token when the
+// calldata named one ("0.0000 WETH" for a swap of 1 WETH) and in ETH when it
+// did not ("0.0000 ETH"). They now say the amount could not be decoded. A swap
+// paid in native ETH still shows the transaction's ETH value there: that value
+// is the ETH the swap pays.
+//
+// Driven through the real approval screen, password and Confirm included,
+// against a minimal DOM stub in the shape tests/approvalNonce.test.js uses.
+// The vault is mocked so that no password has to be hashed.
+
+jest.mock("../src/shared/vault", () => ({
+    decryptWithPassword: jest.fn(),
+}));
+
+// The wait screen polls for a receipt, which is there once mockReceipt is set.
+let mockReceipt = null;
+jest.mock("../src/shared/balances", () => ({
+    getProvider: () => ({ getTransactionReceipt: async () => mockReceipt }),
+    refreshBalances: () => {},
+}));
+
+globalThis.chrome = {
+    storage: { local: { get: async () => ({}), set: async () => {} } },
+};
+
+const { AbiCoder, Interface } = require("ethers");
+const { state } = require("../src/shared/state");
+const { decryptWithPassword } = require("../src/shared/vault");
+const approval = require("../src/popup/views/approval");
+const txStatus = require("../src/popup/views/txStatus");
+
+// A well-known test phrase, and its first address.
+const PHRASE = "test test test test test test test test test test test junk";
+const FROM = "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266";
+const TX_HASH = "0x" + "4".repeat(64);
+
+const ROUTER = "0x66a9893cc07d91d95644aedd05d03f95e1dba8af";
+const ZERO = "0x0000000000000000000000000000000000000000";
+// Both in the bundled list: WETH at 18 decimals, USDC at 6.
+const WETH = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2";
+const USDC = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
+const ONE_WETH = 1000000000000000000n;
+
+const coder = AbiCoder.defaultAbiCoder();
+const routerIface = new Interface([
+    "function execute(bytes commands, bytes[] inputs, uint256 deadline)",
+]);
+
+// V4 action ids and their parameters, each swapping WETH for USDC.
+const POOL_KEY = "tuple(address,address,uint24,int24,address)";
+const WETH_USDC_POOL = [WETH, USDC, 100, 1, ZERO];
+const SWAP_EXACT_IN_SINGLE = 0x06;
+const SWAP_EXACT_OUT_SINGLE = 0x08;
+const SETTLE = 0x0b;
+const SETTLE_ALL = 0x0c;
+const TAKE = 0x0e;
+const TAKE_ALL = 0x0f;
+
+// The struct V4Router has deployed on mainnet and Sepolia.
+const exactInSingle = coder.encode(
+    [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+    [[WETH_USDC_POOL, true, ONE_WETH, 990000n, "0x"]],
+);
+// The one v4-periphery `main` has moved to, with a `minHopPriceX36` field.
+const newerExactInSingle = coder.encode(
+    [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+    [[WETH_USDC_POOL, true, ONE_WETH, 990000n, 0n, "0x"]],
+);
+// Deployed shape: buys 990000 base units of USDC for at most 1 WETH.
+const exactOutSingle = coder.encode(
+    [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+    [[WETH_USDC_POOL, true, 990000n, ONE_WETH, "0x"]],
+);
+const settleWeth = coder.encode(
+    ["address", "uint256", "bool"],
+    [WETH, 0n, true],
+);
+const takeUsdc = coder.encode(
+    ["address", "address", "uint256"],
+    [USDC, FROM, 0n],
+);
+const settleAllWeth = coder.encode(["address", "uint256"], [WETH, ONE_WETH]);
+const takeAllUsdc = coder.encode(["address", "uint256"], [USDC, 990000n]);
+
+// The same swaps paid in native ETH, which V4 names as the zero address.
+const ETH_USDC_POOL = [ZERO, USDC, 500, 10, ZERO];
+const ONE_ETH = 1000000000000000000n;
+const ethExactOutSingle = coder.encode(
+    [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+    [[ETH_USDC_POOL, true, 990000n, ONE_ETH, "0x"]],
+);
+const newerEthExactInSingle = coder.encode(
+    [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+    [[ETH_USDC_POOL, true, ONE_ETH, 990000n, 0n, "0x"]],
+);
+// The router pays it from the ETH the transaction sends.
+const settleEth = coder.encode(
+    ["address", "uint256", "bool"],
+    [ZERO, 0n, false],
+);
+
+// execute() with one V4_SWAP step of these actions, given as [id, params].
+function v4SwapData(actions) {
+    const input = coder.encode(
+        ["bytes", "bytes[]"],
+        [new Uint8Array(actions.map((a) => a[0])), actions.map((a) => a[1])],
+    );
+    return routerIface.encodeFunctionData("execute", [
+        "0x10",
+        [input],
+        9999999999n,
+    ]);
+}
+
+function makeElement(id) {
+    const classes = new Set();
+    const el = {
+        id,
+        textContent: "",
+        value: "",
+        innerHTML: "",
+        disabled: false,
+        style: {},
+        dataset: {},
+        listeners: {},
+        classList: {
+            add: (...names) => names.forEach((n) => classes.add(n)),
+            remove: (...names) => names.forEach((n) => classes.delete(n)),
+            contains: (n) => classes.has(n),
+            toggle: (n, force) => {
+                const on = force === undefined ? !classes.has(n) : force;
+                if (on) classes.add(n);
+                else classes.delete(n);
+                return on;
+            },
+        },
+        addEventListener: (name, fn) => {
+            el.listeners[name] = el.listeners[name] || [];
+            el.listeners[name].push(fn);
+        },
+        querySelectorAll: () => [],
+        appendChild: () => {},
+    };
+    // Views reach for .parentElement to hide whole sections.
+    Object.defineProperty(el, "parentElement", {
+        get: () => node(id + "-parent"),
+    });
+    return el;
+}
+
+function makeDocument() {
+    const els = new Map();
+    return {
+        getElementById(id) {
+            // The debug banner is created on demand by helpers.js; absent
+            // is the state a non-debug, non-testnet popup is in.
+            if (id === "debug-banner") return null;
+            if (!els.has(id)) els.set(id, makeElement(id));
+            return els.get(id);
+        },
+        createElement: () => makeElement("created"),
+        body: { prepend: () => {} },
+    };
+}
+
+function node(id) {
+    return globalThis.document.getElementById(id);
+}
+
+function click(id) {
+    return Promise.all((node(id).listeners.click || []).map((fn) => fn()));
+}
+
+// Open the approval screen for this calldata, sent to the router with `value`
+// wei (no ETH unless given), and confirm it. The background answers the signed
+// transaction with `response`.
+async function approveSwap(data, response, value = 0n) {
+    globalThis.document = makeDocument();
+    globalThis.window = { location: { search: "" }, close: () => {} };
+    globalThis.chrome.runtime = {
+        connect: () => ({ postMessage: () => {} }),
+        sendMessage: (msg, reply) => {
+            if (!reply) return;
+            if (msg.type !== "AUTISTMASK_GET_APPROVAL") return reply(response);
+            reply({
+                type: "tx",
+                origin: "https://dapp.example",
+                isPhishingDomain: false,
+                approvedFrom: FROM,
+                approvedTx: {
+                    type: 2,
+                    from: FROM,
+                    chainId: "0x1",
+                    nonce: "0x7",
+                    gasLimit: "0x30d40",
+                    maxPriorityFeePerGas: "0x3b9aca00",
+                    maxFeePerGas: "0x77359400",
+                    to: ROUTER,
+                    value: "0x" + value.toString(16),
+                    data,
+                    accessList: [],
+                },
+            });
+        },
+    };
+    state.activeAddress = FROM;
+    state.trackedTokens = [];
+    state.wallets = [
+        {
+            type: "hd",
+            name: "Wallet 1",
+            xpub: "xpub-wallet-1",
+            encryptedSecret: "encrypted-secret-1",
+            nextIndex: 1,
+            addresses: [
+                { address: FROM, index: 0, balance: "0", tokenBalances: [] },
+            ],
+        },
+    ];
+    txStatus.init({ doRefreshAndRender: () => {} });
+    approval.init({});
+    await approval.show(1);
+    decryptWithPassword.mockResolvedValue(PHRASE);
+    node("approve-tx-password").value = "any password";
+    await click("btn-approve-tx");
+}
+
+afterEach(() => {
+    txStatus.endWait();
+    mockReceipt = null;
+});
+
+describe.each([
+    [
+        "a swap action in the deployed shape",
+        [
+            [SWAP_EXACT_IN_SINGLE, exactInSingle],
+            [SETTLE, settleWeth],
+            [TAKE, takeUsdc],
+        ],
+        "1.0000 WETH",
+    ],
+    [
+        "a swap action in the newer shape, with SETTLE naming WETH",
+        [
+            [SWAP_EXACT_IN_SINGLE, newerExactInSingle],
+            [SETTLE, settleWeth],
+            [TAKE, takeUsdc],
+        ],
+        "Unknown (could not be decoded)",
+    ],
+    [
+        "a swap action in the newer shape, with SETTLE_ALL and TAKE_ALL",
+        [
+            [SWAP_EXACT_IN_SINGLE, newerExactInSingle],
+            [SETTLE_ALL, settleAllWeth],
+            [TAKE_ALL, takeAllUsdc],
+        ],
+        "Unknown (could not be decoded)",
+    ],
+    [
+        "an exact-out swap action, which is read for its currencies only",
+        [
+            [SWAP_EXACT_OUT_SINGLE, exactOutSingle],
+            [SETTLE, settleWeth],
+            [TAKE, takeUsdc],
+        ],
+        "Unknown (could not be decoded)",
+    ],
+])("%s", (_name, actions, expected) => {
+    test("the wait screen's amount", async () => {
+        await approveSwap(v4SwapData(actions), { txHash: TX_HASH });
+        expect(node("wait-tx-summary").textContent).toBe(expected);
+    });
+
+    test("the error screen's amount", async () => {
+        await approveSwap(v4SwapData(actions), {
+            error: "The transaction could not be sent.",
+            retryable: false,
+        });
+        expect(node("error-tx-summary").textContent).toBe(expected);
+    });
+
+    // The success screen shows the approval screen's decoded lines in place
+    // of the amount, so the ETH value is not on it either.
+    test("the success screen has no amount line of its own", async () => {
+        await approveSwap(v4SwapData(actions), { txHash: TX_HASH });
+        mockReceipt = { blockNumber: 1 };
+        // A later popup resumes the wait, and the receipt is there.
+        txStatus.restoreWait();
+        for (let i = 0; i < 10; i++) {
+            await new Promise((r) => setTimeout(r, 0));
+        }
+        const summary = node("success-tx-summary").parentElement;
+        expect(summary.classList.contains("hidden")).toBe(true);
+        expect(node("success-tx-decoded").innerHTML).not.toContain("0.0000");
+    });
+});
+
+// A swap paid in native ETH has a Token In of "ETH (native)" and no Amount
+// line, and sends 1 ETH.
+describe.each([
+    [
+        "an exact-out swap action paid in ETH, in the deployed shape",
+        [
+            [SWAP_EXACT_OUT_SINGLE, ethExactOutSingle],
+            [SETTLE, settleEth],
+            [TAKE, takeUsdc],
+        ],
+    ],
+    [
+        "a swap action in the newer shape paid in ETH, with SETTLE naming ETH",
+        [
+            [SWAP_EXACT_IN_SINGLE, newerEthExactInSingle],
+            [SETTLE, settleEth],
+            [TAKE, takeUsdc],
+        ],
+    ],
+])("%s", (_name, actions) => {
+    test("the wait screen shows the ETH the transaction sends", async () => {
+        await approveSwap(v4SwapData(actions), { txHash: TX_HASH }, ONE_ETH);
+        expect(node("wait-tx-summary").textContent).toBe("1.0000 ETH");
+    });
+
+    test("the error screen shows the ETH the transaction sends", async () => {
+        await approveSwap(
+            v4SwapData(actions),
+            {
+                error: "The transaction could not be sent.",
+                retryable: false,
+            },
+            ONE_ETH,
+        );
+        expect(node("error-tx-summary").textContent).toBe("1.0000 ETH");
+    });
+});

tests/uniswap.test.js

@@ -163,6 +163,122 @@ 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,
+    );
+}
+
+// V4 SETTLE_ALL (currency, maxAmount) and TAKE_ALL (currency, minAmount). The
+// decoder reads neither, so in a V4_SWAP of a swap action and these, only the
+// swap action names the currencies.
+const V4_SETTLE_ALL_ID = 0x0c;
+const V4_TAKE_ALL_ID = 0x0f;
+function encodeV4SettleAll(currency, maxAmount) {
+    return coder.encode(["address", "uint256"], [currency, maxAmount]);
+}
+function encodeV4TakeAll(currency, minAmount) {
+    return coder.encode(["address", "uint256"], [currency, minAmount]);
+}
+
 function detail(result, label) {
     return result.details.find((d) => d.label === label);
 }
@@ -203,9 +319,157 @@ 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);
+        },
+    );
+
+    // Only the unread swap action names the currencies here. The token lines
+    // must not say the calldata did not name them.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer shape, then SETTLE_ALL and TAKE_ALL, says both tokens could not be decoded",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                "0x10",
+                [
+                    encodeV4Swap(
+                        new Uint8Array([id, V4_SETTLE_ALL_ID, V4_TAKE_ALL_ID]),
+                        [
+                            newer,
+                            encodeV4SettleAll(WETH_ADDR, ONE_WETH),
+                            encodeV4TakeAll(USDC_ADDR, 990000n),
+                        ],
+                    ),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            expect(detail(result, "Token In").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Token Out").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+        },
+    );
+
+    // The user receives the V4 step's USDC, which only its unread swap
+    // action names. The V3 step's WETH and its Min. received figure were
+    // shown instead.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V3 step, then a V4 $action in the newer shape and TAKE_ALL, does not show the V3 step's output",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                solidityPacked(["uint8", "uint8"], [0x00, 0x10]),
+                [
+                    encodeV3SwapExactIn(USER_ADDR, 2000000n, ONE_WETH, [
+                        USDT_ADDR,
+                        WETH_ADDR,
+                    ]),
+                    encodeV4Swap(new Uint8Array([id, V4_TAKE_ALL_ID]), [
+                        newer,
+                        encodeV4TakeAll(USDC_ADDR, 990000n),
+                    ]),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(result.name).toBe("Uniswap Swap");
+            expect(detail(result, "Amount").value).toBe("2.0000 USDT");
+            expect(detail(result, "Token Out").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Min. received")).toBeUndefined();
+        },
+    );
+
+    // The user pays the V4 step's WETH, which only its unread swap action
+    // names. The V3 step's USDC and its amount were shown instead.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer shape and SETTLE_ALL, then a V3 step, does not show the V3 step's input",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                solidityPacked(["uint8", "uint8"], [0x10, 0x00]),
+                [
+                    encodeV4Swap(new Uint8Array([id, V4_SETTLE_ALL_ID]), [
+                        newer,
+                        encodeV4SettleAll(WETH_ADDR, ONE_WETH),
+                    ]),
+                    encodeV3SwapExactIn(
+                        USER_ADDR,
+                        990000n,
+                        980000000000000000n,
+                        [USDC_ADDR, DAI_ADDR],
+                    ),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(result.name).toBe("Uniswap Swap");
+            expect(detail(result, "Token In").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Amount")).toBeUndefined();
+            expect(detail(result, "Min. received").value).toBe("0.9800 DAI");
+        },
+    );
+
+    // UNWRAP_WETH makes Token Out ETH when no step set the output side. An
+    // unread swap action's step did set it, to undetermined.
+    test("an UNWRAP_WETH after an unread V4 swap action does not make Token Out ETH", () => {
+        const { id, newer } = V4_SWAP_ACTION_SHAPES[0];
+        const data = buildExecute(
+            solidityPacked(["uint8", "uint8"], [0x10, 0x0c]),
+            [
+                encodeV4Swap(new Uint8Array([id, V4_TAKE_ALL_ID]), [
+                    newer,
+                    encodeV4TakeAll(USDC_ADDR, 990000n),
+                ]),
+                encodeWrapEth(USER_ADDR, 0n), // UNWRAP_WETH, same encoding
+            ],
+            9999999999n,
+        );
+        const result = uniswap.decode(data, ROUTER_ADDR);
+        expect(detail(result, "Token Out").value).toBe(
+            "Unknown (could not be decoded)",
+        );
     });
 
     test("decodes V2_SWAP_EXACT_IN with known tokens", () => {
@@ -548,9 +812,11 @@ 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",
         );
     });
 

tests/uniswapUndeterminedTokenIn.test.js

@@ -97,7 +97,11 @@ describe("an execute() whose input currency never decoded", () => {
         ]);
 
     test("says the input token is unknown instead of naming ETH", () => {
-        expect(detail(data(), "Token In").value).toBe(REFUSAL);
+        // The swap action that would name it could not be read, so the line
+        // says that rather than REFUSAL's "not named in the calldata".
+        expect(detail(data(), "Token In").value).toBe(
+            "Unknown (could not be decoded)",
+        );
     });
 
     test("keeps a Token In line, so the screen never omits what is paid", () => {