fix: Settings never shows "Saved." for a URL the input no longer shows (closes #695)

The RPC and Blockscout "Save" buttons in Settings now store nothing when the input no longer shows the URL that was checked. When another page changes the network, "Use Blockscout" or "Check recipients on Etherscan", this page draws Settings again, and a redraw during the check puts this page's URL back in the input. Before this change, the typed URL was then stored and "Saved." appeared. A save refused because the input changed shows "The URL was not saved because it was changed during the check." A user's own edit during the check refuses the save too.

Model: opus-5-5

README.md

@@ -2279,6 +2279,9 @@ view would leave a wallet one click from deletion.
           no user data and is made whether or not "Use Blockscout" is ticked.
     - If the network changes before either "Save" stores its URL, the URL is not
       saved and a flash message says so
+    - Either "Save" stores its URL only if the input still shows that URL when
+      the endpoint answers. Otherwise a flash message says that the URL was not
+      saved
     - Etherscan:
         - "Check recipients on Etherscan" checkbox, unticked until the user
           ticks it

src/popup/views/settings.js

@@ -339,17 +339,31 @@ function showNewSettings() {
 // Another page may have stored a different URL since then. So `url` is set in
 // the stored record too. "Saved." then means that the stored record holds
 // `url`.
-async function saveEndpoint(field, url, networkId) {
+//
+// `input` is the id of the input that the user typed `url` in. When another
+// page changes the network, "Use Blockscout" or "Check recipients on
+// Etherscan", this page draws Settings again. A redraw during the endpoint
+// check puts the URL from `state` back in the input. So if the input no longer
+// shows `url`, nothing is saved. The flash message then says that the URL was
+// changed during the check. The save compares the input and sets `url` in
+// `state` in one step. So a redraw after the comparison shows `url`.
+async function saveEndpoint(field, input, url, networkId) {
     let refused = false;
+    let inputChanged = false;
     await saveState((stored) => {
         refused =
             state.networkId !== networkId || stored.networkId !== networkId;
-        if (refused) return false;
+        inputChanged = $(input).value.trim() !== url;
+        if (refused || inputChanged) return false;
         state[field] = url;
         stored[field] = url;
     });
     if (refused) {
         showFlash("The URL was not saved because the network changed.");
+    } else if (inputChanged) {
+        showFlash(
+            "The URL was not saved because it was changed during the check.",
+        );
     } else {
         showFlash("Saved.");
     }
@@ -401,7 +415,7 @@ function init(_ctx) {
             showFlash("Could not reach endpoint.");
             return;
         }
-        await saveEndpoint("rpcUrl", url, net.id);
+        await saveEndpoint("rpcUrl", "settings-rpc", url, net.id);
     });
 
     $("btn-save-blockscout").addEventListener("click", async () => {
@@ -425,7 +439,7 @@ function init(_ctx) {
             showFlash("Could not reach endpoint.");
             return;
         }
-        await saveEndpoint("blockscoutUrl", url, net.id);
+        await saveEndpoint("blockscoutUrl", "settings-blockscout", url, net.id);
     });
 
     // Each change is made inside the save, holding the lock. So

tests/settingsEndpointSave.test.js

@@ -47,3 +47,123 @@ test.each([
         expect(page.text("flash-msg")).toBe("Saved.");
     },
 );
+
+// The user types a URL in Settings and taps "Save". While the check waits for
+// the endpoint's answer, another page turns "Use Blockscout" on. This page
+// follows that change and draws Settings again, with the stored URL in the
+// input. The check then passes. The typed URL is not stored. The flash message
+// says that the URL was changed during the check
+// (https://git.eeqj.de/sneak/AutistMask/issues/695).
+test.each([
+    { button: "btn-save-rpc", input: "settings-rpc", field: "rpcUrl" },
+    {
+        button: "btn-save-blockscout",
+        input: "settings-blockscout",
+        field: "blockscoutUrl",
+    },
+])(
+    "$button stores nothing when Settings is drawn again during the check",
+    async ({ button, input, field }) => {
+        const page = await bootPopup(unversionedValidProfile());
+        await page.click("btn-settings");
+        const storedUrl = page.value(input);
+        let answer;
+        globalThis.fetch.mockReturnValue(
+            new Promise((resolve) => {
+                answer = resolve;
+            }),
+        );
+
+        page.node(input).value = "https://typed.example.invalid";
+        const saving = page.node(button).listeners.click.map((fn) => fn());
+        await page.settle();
+        // The browser announces this write to this page.
+        await page.storage.local.set({
+            autistmask: {
+                ...page.storage.read("autistmask"),
+                useBlockscout: true,
+            },
+        });
+        await page.settle();
+        expect(page.node("settings-use-blockscout").checked).toBe(true);
+        // This answer passes both endpoint checks on Ethereum Mainnet.
+        answer({
+            ok: true,
+            json: async () => ({ result: NETWORKS.mainnet.chainId }),
+        });
+        await Promise.all(saving);
+        await page.settle();
+
+        expect(page.storage.read("autistmask")[field]).toBe(storedUrl);
+        expect(page.value(input)).toBe(storedUrl);
+        expect(page.text("flash-msg")).toBe(
+            "The URL was not saved because it was changed during the check.",
+        );
+    },
+);
+
+// As above, but another write holds the lock. So this page's follow of the
+// change to "Use Blockscout" waits for the lock. The endpoint answers while the
+// input still shows the typed URL. The save then asks for the lock, after the
+// follow did. So the follow draws Settings again before the save compares the
+// input.
+test.each([
+    { button: "btn-save-rpc", input: "settings-rpc", field: "rpcUrl" },
+    {
+        button: "btn-save-blockscout",
+        input: "settings-blockscout",
+        field: "blockscoutUrl",
+    },
+])(
+    "$button stores nothing when Settings is drawn again while the save waits for the lock",
+    async ({ button, input, field }) => {
+        const page = await bootPopup(unversionedValidProfile());
+        await page.click("btn-settings");
+        const storedUrl = page.value(input);
+        let answer;
+        globalThis.fetch.mockReturnValue(
+            new Promise((resolve) => {
+                answer = resolve;
+            }),
+        );
+        const typedUrl = "https://typed.example.invalid";
+
+        page.node(input).value = typedUrl;
+        const saving = page.node(button).listeners.click.map((fn) => fn());
+        await page.settle();
+        let releaseLock;
+        const lockHeld = navigator.locks.request(
+            "autistmask",
+            () =>
+                new Promise((resolve) => {
+                    releaseLock = resolve;
+                }),
+        );
+        // The browser announces this write to this page.
+        await page.storage.local.set({
+            autistmask: {
+                ...page.storage.read("autistmask"),
+                useBlockscout: true,
+            },
+        });
+        await page.settle();
+        // This answer passes both endpoint checks on Ethereum Mainnet.
+        answer({
+            ok: true,
+            json: async () => ({ result: NETWORKS.mainnet.chainId }),
+        });
+        await page.settle();
+        expect(page.value(input)).toBe(typedUrl);
+        releaseLock();
+        await lockHeld;
+        await Promise.all(saving);
+        await page.settle();
+
+        expect(page.node("settings-use-blockscout").checked).toBe(true);
+        expect(page.storage.read("autistmask")[field]).toBe(storedUrl);
+        expect(page.value(input)).toBe(storedUrl);
+        expect(page.text("flash-msg")).toBe(
+            "The URL was not saved because it was changed during the check.",
+        );
+    },
+);