fix: a permit on the zero address never reads as ETH (closes #660)

Permit2 has no allowance of ETH, but the swap decoder read a permit's
zero-address token as ETH. Its Allowance token line read ETH. A permit of
1 wei of the zero address before a V4 step of 5 ETH stood as the Amount
figure, which then read 0.000000000000000001 ETH. With that permit to
another spender, there was no Amount line.

Such a permit now never stands as the Amount figure. To another spender,
it no longer removes the Amount line either. Its lines give the amount in
base units and name the zero address, as for a token nothing knows.

Model: opus-5-5

src/shared/uniswap.js

@@ -2031,6 +2031,8 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // before it takes under whatever allowance the router already had, so
         // it may take more. A later permit or batch, or a later step this
         // decoder did not read, may raise what Permit2 lets the router take.
+        // A permit on the zero address never stands as the Amount figure,
+        // because Permit2 has no allowance of ETH.
         // Every other PERMIT2_PERMIT leaves Token In and the Amount line as
         // they read with no permit, and gets lines of its own below. A step
         // that may take from the sender what this decoder did not read leaves
@@ -2047,6 +2049,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             stepCommands.filter((c) => c === "PERMIT2_PERMIT").length === 1 &&
             !stepCommands.includes("PERMIT2_PERMIT_BATCH") &&
             sameAddress(permit.spender, toAddress) &&
+            permit.token !== "0x0000000000000000000000000000000000000000" &&
             !permit.allowedToFail &&
             permit.beforeEveryTake &&
             !stepsUnread.some((step) => step > permit.step);
@@ -2234,17 +2237,19 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // A null token in `spentFromSender`, a step this decoder did not read
         // or a token it does not know, and an allowance to another spender
         // that may be of Token In, leave no Amount figure, which may then be
-        // too low. With no Amount line, each take the total adds up gets
-        // lines of its own, first, so that every amount this decoder read is
-        // shown.
+        // too low. An allowance of the zero address is never one of Token In,
+        // because Permit2 has no allowance of ETH. With no Amount line, each
+        // take the total adds up gets lines of its own, first, so that every
+        // amount this decoder read is shown.
         if (
             present(inputAmount) &&
             spentFromSender.every((s) => present(s.token)) &&
             toAnotherSpender.every(
                 (p) =>
-                    present(p.token) &&
-                    present(inputToken) &&
-                    !sameAddress(p.token, inputToken),
+                    p.token === "0x0000000000000000000000000000000000000000" ||
+                    (present(p.token) &&
+                        present(inputToken) &&
+                        !sameAddress(p.token, inputToken)),
             )
         ) {
             const amount = spentText(inputAmount, inInfo);
@@ -2315,15 +2320,36 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 });
                 continue;
             }
-            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));
+            // Permit2 has no allowance of ETH. An allowance of the zero
+            // address reads as one of a token nothing knows: its amount in
+            // base units, and the zero address as its token.
+            if (p.token === "0x0000000000000000000000000000000000000000") {
+                details.push({
+                    label: "Permit2 allowance",
+                    value:
+                        p.amount >= MAX_UINT160
+                            ? "Unlimited"
+                            : 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,