fix: a Permit2 transfer of the zero address never reads as ETH (closes #685)

A PERMIT2_TRANSFER_FROM of the zero address read Token moved: ETH, with an ETH figure, though Permit2 moves no ETH. Such a move now names the zero address as its token on Token moved and Token moved into the router, and gives its amount in base units on Moved from the sender and Paid to. The zero-address check from the permit lines is now one function, permit2TokenInfo(), shared by the move lines. A V4 step of ETH that states no amount still gets its own lines beside such a move, so no line about ETH leaving is dropped. Model: opus-5-5
2026-10-27 07:53:05 +01:00
parent 5615b08760
commit fc6cffcaba
3 changed files with 120 additions and 49 deletions
@@ -3440,6 +3440,82 @@ describe("uniswap decoder", () => {
            });
        });

+        // https://git.eeqj.de/sneak/AutistMask/issues/685 — Permit2 moves no
+        // ETH, so a PERMIT2_TRANSFER_FROM of the zero address reads as a move
+        // of a token nothing knows. On next at ec6b6b5 its lines read ETH,
+        // with an ETH figure.
+        describe("a PERMIT2_TRANSFER_FROM of the zero address", () => {
+            const MOVED_AMOUNT =
+                "1000000000000000000 base units (decimals unknown)";
+
+            test("to another address names the address", () => {
+                const result = decodeSteps(
+                    [0x00, 0x02],
+                    [V3_600, transfer(ZERO_ADDR, OTHER_ADDR, ONE_WETH)],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ["Moved from the sender", MOVED_AMOUNT],
+                    ["Token moved", ZERO_ADDR],
+                    ["Moved to", OTHER_ADDR],
+                ]);
+                expect(detail(result, "Token moved").address).toBe(ZERO_ADDR);
+            });
+
+            test("into the router names the address", () => {
+                const result = decodeSteps(
+                    [0x02, 0x00],
+                    [transfer(ZERO_ADDR, ROUTER_ADDR, ONE_WETH), V3_600],
+                );
+                expect(detail(result, "Paid to").value).toBe(
+                    "The router, " +
+                        MOVED_AMOUNT +
+                        " from the sender (later steps may not spend all of it)",
+                );
+                expect(detail(result, "Token moved into the router")).toEqual({
+                    label: "Token moved into the router",
+                    value: ZERO_ADDR,
+                    address: ZERO_ADDR,
+                    isToken: true,
+                });
+            });
+
+            // The V4 step's SETTLE names the user as payer and states no
+            // amount. The step's lines say that the ETH amount is not known.
+            test("after a V4 exact-out step of ETH, also shows that the ETH amount is not known", () => {
+                const v4EthExactOut = encodeV4Swap(
+                    new Uint8Array([
+                        V4_SWAP_EXACT_OUT_SINGLE_ID,
+                        V4_SETTLE_ID,
+                        V4_TAKE_ALL_ID,
+                    ]),
+                    [
+                        encodeV4ExactOutSingle(
+                            ZERO_ADDR,
+                            USDC_ADDR,
+                            590000000n,
+                            ONE_WETH,
+                        ),
+                        encodeV4Settle(ZERO_ADDR),
+                        encodeV4TakeAll(USDC_ADDR, 0n),
+                    ],
+                );
+                const result = decodeSteps(
+                    [0x10, 0x02],
+                    [v4EthExactOut, transfer(ZERO_ADDR, OTHER_ADDR, ONE_WETH)],
+                );
+                expect(detail(result, "Token In").value).toBe("ETH (native)");
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Moved from the sender", UNDECODED],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                    ["Moved from the sender", MOVED_AMOUNT],
+                    ["Token moved", ZERO_ADDR],
+                    ["Moved to", OTHER_ADDR],
+                ]);
+            });
+        });
+
        // https://git.eeqj.de/sneak/AutistMask/issues/682 — V4 pays a SETTLE
        // of ETH from the router's own ETH, whichever payer the SETTLE names,
        // and the router holds the transaction's value. On next at 36b2002 a