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

Permit2 moves no ETH, but the swap decoder read the zero address in a
PERMIT2_TRANSFER_FROM as ETH, with an ETH figure. Such a move now names
the zero address as its token and gives its amount in base units. The
token is named on `Token moved` and `Token moved into the router`, and
the amount is on `Moved from the sender` and `Paid to`.

The zero-address check the permit lines already made is now one function,
permit2TokenInfo(), which the move lines share. tokenMovedLine() takes
the token's info instead of its address.

A V4 step of ETH that states no amount still gets its own lines beside
such a move. A test covers that case.

Model: opus-5-5

README.md

@@ -3566,10 +3566,14 @@ Currently supported:
   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
   `Token moved into the router` line already give the amount, the token and
-  where it goes, and so its amount is shown once. Every `PERMIT2_PERMIT` whose
+  where it goes, and so its amount is shown once. For a move of the zero
-  amount does not stand as the `Amount` figure, before the step that sets the
+  address, `Moved from the sender` gives the amount in base units and
-  input side or after it, gives three lines, in step order, after those for each
+  `Token moved` gives the zero address. For such a move into the router, the
-  `PERMIT2_TRANSFER_FROM`: `Permit2 allowance`, its amount, for example
+  `Paid to` line gives the amount in base units and
+  `Token moved into the router` gives the zero address. Every `PERMIT2_PERMIT`
+  whose amount does not stand as the `Amount` figure, before the step that sets
+  the input side or after it, gives three lines, in step order, after those for
+  each `PERMIT2_TRANSFER_FROM`: `Permit2 allowance`, its amount, for example
   `5000.0000 DAI`, or `Unlimited` for Permit2's maximum; `Allowance token`,
   giving the token's address as the `Token In` line does; and
   `Allowance spender`, the address it lets take the token. Only a permit whose

src/shared/uniswap.js

@@ -479,6 +479,17 @@ function tokenInfo(address, sources) {
     };
 }
 
+// The token of a Permit2 allowance or of a PERMIT2_TRANSFER_FROM, in the
+// shape tokenInfo() gives. Permit2 has no allowance of ETH and moves no ETH.
+// The zero address there reads as a token nothing knows: its amount in base
+// units, and the zero address as its token.
+function permit2TokenInfo(address, sources) {
+    if (address === "0x0000000000000000000000000000000000000000") {
+        return { symbol: null, decimals: null, address };
+    }
+    return tokenInfo(address, sources);
+}
+
 // A swap amount line. With a scale it is the token quantity; with none it is
 // the base-unit integer with the unknown scale stated, the same refusal the
 // ERC-20 amount line makes, so the screen has one way of saying it. `display`
@@ -497,16 +508,18 @@ function amountText(raw, info) {
 
 // The line giving a moved token, or the token of a permit, under `label`, in
 // the shape of the Token In line, so the screens show it as they show that
-// one. ETH has no address.
+// one. `info` is what tokenInfo() or permit2TokenInfo() gives for the token.
-function tokenMovedLine(label, token, sources) {
+// ETH has no address.
-    const info = tokenInfo(token, sources);
+function tokenMovedLine(label, info) {
     if (!present(info.address)) {
         return { label, value: info.symbol };
     }
     return {
         label,
-        value: info.symbol ? info.symbol + " (" + token + ")" : token,
+        value: info.symbol
-        address: token,
+            ? info.symbol + " (" + info.address + ")"
+            : info.address,
+        address: info.address,
         isToken: true,
     };
 }
@@ -2329,7 +2342,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     : UNDECODED_CURRENCY,
             });
             if (present(s.token)) {
-                details.push(tokenMovedLine("Token moved", s.token, sources));
+                details.push(
+                    tokenMovedLine("Token moved", tokenInfo(s.token, sources)),
+                );
                 details.push({
                     label: "Moved to",
                     value: "The swap step that spends it",
@@ -2340,12 +2355,12 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // What each PERMIT2_TRANSFER_FROM moves: its amount, its token and
         // where it goes, an address on a line of its own.
         for (const m of movedFromSender) {
+            const info = permit2TokenInfo(m.token, sources);
             details.push({
                 label: "Moved from the sender",
-                value: amountText(m.amount, tokenInfo(m.token, sources))
+                value: amountText(m.amount, info).display,
-                    .display,
             });
-            details.push(tokenMovedLine("Token moved", m.token, sources));
+            details.push(tokenMovedLine("Token moved", info));
             details.push(
                 present(m.to)
                     ? { label: "Moved to", value: m.to }
@@ -2375,36 +2390,15 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 });
                 continue;
             }
-            // Permit2 has no allowance of ETH. An allowance of the zero
+            const info = permit2TokenInfo(p.token, sources);
-            // address reads as one of a token nothing knows: its amount in
+            details.push({
-            // base units, and the zero address as its token.
+                label: "Permit2 allowance",
-            if (p.token === "0x0000000000000000000000000000000000000000") {
+                value:
-                details.push({
+                    p.amount >= MAX_UINT160
-                    label: "Permit2 allowance",
+                        ? "Unlimited"
-                    value:
+                        : amountText(p.amount, info).display,
-                        p.amount >= MAX_UINT160
+            });
-                            ? "Unlimited"
+            details.push(tokenMovedLine("Allowance token", info));
-                            : unknownDecimalsAmount(p.amount),
-                });
-                details.push({
-                    label: "Allowance token",
-                    value: p.token,
-                    address: p.token,
-                    isToken: true,
-                });
-            } else {
-                details.push({
-                    label: "Permit2 allowance",
-                    value:
-                        p.amount >= MAX_UINT160
-                            ? "Unlimited"
-                            : amountText(p.amount, tokenInfo(p.token, sources))
-                                  .display,
-                });
-                details.push(
-                    tokenMovedLine("Allowance token", p.token, sources),
-                );
-            }
             details.push({
                 label: "Allowance spender",
                 value: p.spender,
@@ -2462,7 +2456,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             paidTo.push({ label: "Paid to", value: PAID_TO_BRIDGE });
         }
         for (const m of movedIntoRouter) {
-            const info = tokenInfo(m.token, sources);
+            const info = permit2TokenInfo(m.token, sources);
             paidTo.push({
                 label: "Paid to",
                 value:
@@ -2470,9 +2464,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     amountText(m.amount, info).display +
                     " from the sender (later steps may not spend all of it)",
             });
-            paidTo.push(
+            paidTo.push(tokenMovedLine("Token moved into the router", info));
-                tokenMovedLine("Token moved into the router", m.token, sources),
-            );
         }
         if (outputHeld) {
             paidTo.push({ label: "Paid to", value: STAYS_IN_ROUTER });
@@ -2489,8 +2481,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             paidTo.push(
                 tokenMovedLine(
                     "Token moved into the router",
-                    getAddress(token),
+                    tokenInfo(getAddress(token), sources),
-                    sources,
                 ),
             );
         }

tests/uniswap.test.js

@@ -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