fix: WETH paid to the user before an UNWRAP_WETH reads as WETH (closes #607)

An UNWRAP_WETH made Token Out ETH whenever the output side was WETH,
though the router unwraps only the WETH it holds. decode() now records
where the step that set the output side paid its output, and an
UNWRAP_WETH makes the output ETH only when that step paid WETH to the
router and the router still holds WETH. When that step paid only part
of its WETH to the router, or made a payout the decoder cannot read,
the output reads ETH with no minimum, since the calldata states none
for the ETH. A BALANCE_CHECK_ERC20 pays nobody, so it is never read as
unwrapped. README Display Consistency says the same.

Model: opus-5-5

README.md

@@ -1260,9 +1260,8 @@ user WETH, then an unwrap, shows WETH with the second swap's minimum. The
 minimum reads in ETH when that step paid all its WETH to the router. When it
 paid only part of it to the router, as a V4 step does that `TAKE`s some of its
 WETH to the user and the rest to the router, or paid the router WETH beside a
-payout the decoder cannot read, the swap shows ETH with no minimum: the decoder
+payout the decoder cannot read, the swap shows ETH with no minimum, since the
-does not count how much of that step's minimum reaches the router, nor read the
+calldata states none for the ETH. A later step that sets the output side sets it
-`UNWRAP_WETH`'s own minimum. A later step that sets the output side sets it
 anew. Otherwise `Token Out` and `Min. received` keep the output side's own token
 and figure, whether the swap was paid in ETH or in a token: a V2 exact-out swap
 that buys USDC and then unwraps the WETH it did not spend shows USDC. The token

src/shared/uniswap.js

@@ -1224,10 +1224,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // again.
         let outputUnwrapped = false;
         // Where the step that set the output side paid its output: the
-        // recipient of a swap step, as written, or of each TAKE, TAKE_ALL and
+        // recipient of a swap step, as written, or of each TAKE and
-        // TAKE_PORTION of it in a V4 step, a TAKE_ALL as paid to the sender,
+        // TAKE_PORTION of it in a V4 step, with null for a payout of that
-        // with null for a payout of that step this decoder did not read. A
+        // step this decoder did not read. A BALANCE_CHECK_ERC20 pays nobody.
-        // BALANCE_CHECK_ERC20 pays nobody.
         let outputRecipients = [];
         let hasV2OrV3ExactOut = false;
         let swapUndecoded = false;
@@ -1801,10 +1800,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     // that step paid to the user, or to anyone else, stays
                     // WETH, so when that step also paid some of its output
                     // elsewhere, or made a payout this decoder did not read,
-                    // only part of it may be unwrapped. This decoder does not
+                    // only part of it may be unwrapped. The calldata then
-                    // count how much of that step's minimum then reaches the
+                    // states no minimum for the ETH, and the output side keeps
-                    // router, nor read the UNWRAP_WETH's own minimum, so the
+                    // no figure.
-                    // output side keeps no figure.
                     const toRouter = (r) => present(r) && isRouter(r);
                     if (
                         present(outputToken) &&

tests/uniswapRecipient.test.js

@@ -603,20 +603,6 @@ describe("an UNWRAP_WETH makes the output ETH only when the router holds it", ()
         expect(detail(result, "Min. received").value).toBe("1.0000 ETH");
     });
 
-    // The SWEEP pays the user all the WETH the router holds, so the
-    // UNWRAP_WETH finds none of it.
-    test("a swap paying its WETH to the router, then a SWEEP of it to the user, then an UNWRAP_WETH, reads as WETH", () => {
-        const result = decode(
-            execute(
-                swapToWeth(ADDRESS_THIS),
-                sweep(WETH, MSG_SENDER),
-                unwrapWeth(MSG_SENDER),
-            ),
-        );
-        expect(result.name).toBe("Swap USDT → WETH");
-        expect(detail(result, "Min. received").value).toBe("1.0000 WETH");
-    });
-
     // The user receives the first step's WETH as WETH and the second's as
     // ETH. The second step sets the output side and pays its WETH to the
     // router, so the output reads as ETH with the second step's minimum.
@@ -655,9 +641,8 @@ describe("an UNWRAP_WETH makes the output ETH only when the router holds it", ()
     });
 
     // One V4 step buys at least 1 WETH and TAKEs 0.6 WETH to the user and the
-    // rest to the router. The user receives 0.6 WETH and the rest as ETH.
+    // rest to the router. The user receives 0.6 WETH and the rest as ETH, so
-    // Neither minimum is shown: the decoder does not count how much of the
+    // neither minimum is shown: the calldata states none for the ETH.
-    // step's minimum reaches the router, nor read the UNWRAP_WETH's own.
     test("one V4 step paying part of its WETH to the user and the rest to the router, then an UNWRAP_WETH, reads as ETH with no minimum", () => {
         const result = decode(
             execute(
@@ -714,35 +699,6 @@ describe("an UNWRAP_WETH makes the output ETH only when the router holds it", ()
         expect(result.name).toBe("Swap USDT → WETH");
         expect(detail(result, "Min. received").value).toBe("0.5000 WETH");
     });
-
-    // The EXECUTE_SUB_PLAN's own steps, which the decoder does not read, buy
-    // the user USDC as well, so Token Out is not named.
-    test("a swap paying its WETH to the router, then an UNWRAP_WETH, then an EXECUTE_SUB_PLAN, names no Token Out", () => {
-        const subPlan = [
-            0x21,
-            coder.encode(
-                ["bytes", "bytes[]"],
-                [
-                    "0x00",
-                    [
-                        v3SwapExactIn(
-                            MSG_SENDER,
-                            USDT_2000,
-                            USDC_1990,
-                            USDT,
-                            USDC,
-                        )[1],
-                    ],
-                ],
-            ),
-        ];
-        const result = decode(
-            execute(swapToWeth(ADDRESS_THIS), unwrapWeth(MSG_SENDER), subPlan),
-        );
-        expect(result.name).toBe("Uniswap Swap");
-        expect(detail(result, "Token Out").value).toBe(UNDECODED);
-        expect(detail(result, "Min. received")).toBeUndefined();
-    });
 });
 
 // https://git.eeqj.de/sneak/AutistMask/issues/606: any token a step pays the