fix: a chain switch gives trackedTokens its own copy of the network's list (closes #719)

After a switch, `trackedTokens` and that network's list in
`networkTrackedTokens` were one array. So a page's next add or removal also
changed `networkTrackedTokens`, and the save wrote that page's older copy over
the stored one. Another page's add on the previous network was lost, and its
removal was undone.

`applyChainSwitchFields()` now copies the incoming network's list. An add or
removal on the active network changes only `trackedTokens`.

Model: opus-5-5

src/shared/chainSwitchFields.js

@@ -42,11 +42,15 @@ function applyChainSwitchFields(s, newNetworkId) {
     // Tracked tokens are kept per network the same way, because a contract
     // address names a token on one network only. s.trackedTokens stays the
     // active network's list, so nothing that reads it changes: the outgoing
-    // list is put away under its network, and the incoming network's list, or
-    // an empty one, takes its place.
+    // list is put away under its network, and a copy of the incoming network's
+    // list, or an empty list, takes its place.
+    //
+    // It is a copy because a save writes a changed s.networkTrackedTokens whole,
+    // over any list another page stored. An add or removal on the active network
+    // must change only s.trackedTokens.
     if (!s.networkTrackedTokens) s.networkTrackedTokens = {};
     s.networkTrackedTokens[s.networkId] = s.trackedTokens;
-    s.trackedTokens = s.networkTrackedTokens[net.id] || [];
+    s.trackedTokens = structuredClone(s.networkTrackedTokens[net.id] || []);
 
     s.networkId = net.id;
     s.rpcUrl = remembered.rpcUrl || net.defaultRpcUrl;

tests/trackedTokensPerNetwork.test.js

@@ -466,6 +466,56 @@ test("a token another page removed on Ethereum Mainnet stays removed when this p
     expect(stored.trackedTokens).toEqual([]);
 });
 
+// This page switches to Sepolia, where TST is tracked. Another popup page has
+// not taken that switch, and its save tracks DAI on Ethereum Mainnet. This page
+// then adds a token on Sepolia. Its save changes only `trackedTokens`, so DAI
+// stays on Ethereum Mainnet's list.
+test("a token another page added on Ethereum Mainnet stays when this page adds a token on Sepolia", async () => {
+    const boot = await bootOnAddToken("mainnet", {
+        networkTrackedTokens: { sepolia: [SEPOLIA_TOKEN] },
+    });
+    expect(boot.pageErrors).toEqual([]);
+    await gearSwitchBack(boot);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkTrackedTokens: {
+            mainnet: [MAINNET_TOKEN],
+            sepolia: [SEPOLIA_TOKEN],
+        },
+    });
+
+    const added = await addNewToken(boot);
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkTrackedTokens.mainnet).toEqual([MAINNET_TOKEN]);
+    expect(stored.networkTrackedTokens.sepolia).toEqual([SEPOLIA_TOKEN]);
+    expect(stored.trackedTokens).toEqual([SEPOLIA_TOKEN, added]);
+});
+
+// This page tracks DAI on Ethereum Mainnet and switches to Sepolia, where TST is
+// tracked. Another popup page has not taken that switch, and its save removes
+// DAI from Ethereum Mainnet's list. This page then adds a token on Sepolia. Its
+// save changes only `trackedTokens`, so DAI does not come back.
+test("a token another page removed on Ethereum Mainnet stays removed when this page adds a token on Sepolia", async () => {
+    const boot = await bootOnAddToken("mainnet", {
+        trackedTokens: [MAINNET_TOKEN],
+        networkTrackedTokens: { sepolia: [SEPOLIA_TOKEN] },
+    });
+    expect(boot.pageErrors).toEqual([]);
+    await gearSwitchBack(boot);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkTrackedTokens: { mainnet: [], sepolia: [SEPOLIA_TOKEN] },
+    });
+
+    const added = await addNewToken(boot);
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkTrackedTokens.mainnet).toEqual([]);
+    expect(stored.networkTrackedTokens.sepolia).toEqual([SEPOLIA_TOKEN]);
+    expect(stored.trackedTokens).toEqual([SEPOLIA_TOKEN, added]);
+});
+
 // Another popup page records a fraud contract on Ethereum Mainnet after this
 // page's last save. The switch to Sepolia drops that fraud contract, as the
 // switch drops this page's own.