fix: Home's list drops the previous network's rows after a network switch (closes #718)

A network switch left the previous network's rows or failure message in Home's
list until the new network's answer landed. Home now replaces them with
"Loading..." when it first draws on a new network. A redraw on the same network
keeps its rows.

Home, AddressDetail and AddressToken compared the page's network before reading
storage. A switch made in Settings could change the page during that read, and
the answer was still drawn. They now compare after the read, for an answer and
for a failure.

Model: opus-5-5

tests/historyAfterNetworkSwitch.test.js

@@ -1,6 +1,8 @@
 // Home, AddressDetail and AddressToken drop a transaction history answer that
 // lands after a network switch. A dropped answer draws no rows and saves no
-// fraud contracts (https://git.eeqj.de/sneak/AutistMask/issues/657).
+// fraud contracts (https://git.eeqj.de/sneak/AutistMask/issues/657). Home's list
+// shows nothing of the previous network once it is drawn after a switch
+// (https://git.eeqj.de/sneak/AutistMask/issues/718).
 //
 // Most tests hold the history request open, switch the network or what the
 // screen shows, and then let the answer land. The views run against a minimal
@@ -154,6 +156,21 @@ function holdLock() {
     };
 }
 
+// Every read of storage waits until the returned function is called. Each read
+// then answers with what storage holds at that moment, the oldest read first.
+function holdReads() {
+    const read = storage.local.get;
+    const waiting = [];
+    storage.local.get = (key) =>
+        new Promise((resolve) => {
+            waiting.push(() => resolve(read(key)));
+        });
+    return () => {
+        storage.local.get = read;
+        for (const answer of waiting) answer();
+    };
+}
+
 function makeElement(id) {
     const el = {
         id,
@@ -409,6 +426,91 @@ describe.each([HOME, ADDRESS_DETAIL, ADDRESS_TOKEN])("$name", (screen) => {
         expect(drawn).toContain("tx-row");
         expect(node(screen.listId).innerHTML).toBe(drawn);
     });
+
+    // The user picks Sepolia in Settings, and the switch reads storage. The
+    // answer lands during that read, so the screen's own read of storage still
+    // finds Ethereum Mainnet. The switch changes the page before the screen's
+    // read ends. The answer is the transfer of ETH alone, so nothing is saved,
+    // and only a check after the screen's read can drop the answer.
+    test("an answer that lands during the first read of a switch made in Settings adds nothing", async () => {
+        const land = holdHistory(history().slice(0, 1));
+        screen.open();
+        await settle();
+        const before = node(screen.listId).innerHTML;
+        const answerReads = holdReads();
+        const switching = onChainSwitch("sepolia");
+        await settle();
+        land();
+        await settle();
+        answerReads();
+        await switching;
+        await settle();
+
+        expectNothingAdded(screen, before);
+    });
+
+    test("a request that fails during the first read of a switch made in Settings shows no message", async () => {
+        const fail = holdFailure();
+        screen.open();
+        await settle();
+        const before = node(screen.listId).innerHTML;
+        const answerReads = holdReads();
+        const switching = onChainSwitch("sepolia");
+        await settle();
+        fail();
+        await settle();
+        answerReads();
+        await switching;
+        await settle();
+
+        expect(node(screen.listId).innerHTML).toBe(before);
+    });
+});
+
+describe("Home's list", () => {
+    test.each([
+        { what: "rows", hold: holdHistory, shown: "tx-row" },
+        {
+            what: "failure message",
+            hold: holdFailure,
+            shown: "Failed to load transactions.",
+        },
+    ])(
+        "shows the previous network's $what neither before nor after the new network's answer lands",
+        async ({ hold, shown }) => {
+            const answer = hold();
+            HOME.open();
+            answer();
+            await settle();
+            expect(node(HOME.listId).innerHTML).toContain(shown);
+
+            await onChainSwitch("sepolia");
+            const land = holdHistory([]);
+            HOME.open();
+            await settle();
+            expect(node(HOME.listId).innerHTML).toContain("Loading...");
+
+            land();
+            await settle();
+            expect(node(HOME.listId).innerHTML).toContain(
+                "No transactions found.",
+            );
+        },
+    );
+
+    // Each balance refresh draws Home again, so the rows must not blink.
+    test("keeps its rows while a redraw on the same network waits for the answer", async () => {
+        fetchRecentTransactions.mockImplementationOnce(async () => history());
+        HOME.open();
+        await settle();
+        const drawn = node(HOME.listId).innerHTML;
+        holdHistory();
+        HOME.open();
+        await settle();
+
+        expect(drawn).toContain("tx-row");
+        expect(node(HOME.listId).innerHTML).toBe(drawn);
+    });
 });
 
 describe.each([ADDRESS_DETAIL, ADDRESS_TOKEN])("$name", (screen) => {

tests/popupFollowsNetworkSwitch.test.js

@@ -137,6 +137,60 @@ test.each([
     expect(page.text("total-value")).toBe("0.0000 SepoliaETH");
 });
 
+// A request on Ethereum Mainnet fails, so Home's list holds the failure message.
+// The list shows it neither before nor after Sepolia's answer lands.
+test.each([
+    {
+        how: "saved by the background",
+        switchToSepolia: (page) => backgroundSwitch(page, "sepolia"),
+    },
+    {
+        how: "made in Settings",
+        switchToSepolia: async (page) => {
+            await page.click("btn-settings");
+            const select = page.node("settings-network");
+            select.value = "sepolia";
+            for (const fn of select.listeners.change) await fn();
+            await page.settle();
+            await page.click("btn-settings-back");
+        },
+    },
+])(
+    "Home's list drops the previous network's message after a switch $how",
+    async ({ switchToSepolia }) => {
+        const page = await bootPopup(
+            unversionedValidProfile({ useBlockscout: true }),
+        );
+        const {
+            fetchRecentTransactions,
+        } = require("../src/shared/transactions");
+        fetchRecentTransactions.mockRejectedValueOnce(
+            new Error("Blockscout is down"),
+        );
+        await page.tick();
+        expect(page.node("home-tx-list").innerHTML).toContain(
+            "Failed to load transactions.",
+        );
+
+        let land;
+        fetchRecentTransactions.mockImplementationOnce(
+            () =>
+                new Promise((resolve) => {
+                    land = () => resolve([]);
+                }),
+        );
+        await switchToSepolia(page);
+        expect(page.visibleViews()).toEqual(["main"]);
+        expect(page.node("home-tx-list").innerHTML).toContain("Loading...");
+
+        land();
+        await page.settle();
+        expect(page.node("home-tx-list").innerHTML).toContain(
+            "No transactions found.",
+        );
+    },
+);
+
 // The report of the switch's own save names the network the page already has.
 test("a switch in Settings is not taken a second time when its save is reported", async () => {
     const page = await bootOnAddress();