fix(preview): keep slim snapshots honest and fail closed

Pointer-cursor div/td controls were never selected. An empty <main>
fell back to body text, leaking sidebar chrome. A failed capturePage
plus an empty CDP screenshot became a 0x0 image.

Snapshots now select those controls, keep empty main text empty, and
surface a typed capture failure. Tests cover the slim default, include
ax, wait scope, and the failed-screenshot path.

Author: gbarros-dev

apps/desktop/src/preview/Manager.test.ts

@@ -87,6 +87,14 @@ vi.mock("electron", () => ({
   },
   nativeImage: {
     createFromPath,
+    createFromBuffer: (buffer: Buffer) => ({
+      getSize: () => ({ width: buffer.length > 0 ? 1 : 0, height: buffer.length > 0 ? 1 : 0 }),
+      toPNG: () => buffer,
+      resize: () => ({
+        getSize: () => ({ width: 1, height: 1 }),
+        toPNG: () => buffer,
+      }),
+    }),
   },
   shell: {
     showItemInFolder,
@@ -168,6 +176,7 @@ const makeTestPreviewWebContents = (
     getURL: () => "https://example.com",
     getTitle: () => "Example",
     isLoading: () => false,
+    isDevToolsOpened: () => false,
     getZoomFactor: () => 1,
     setZoomFactor: vi.fn(),
     on: vi.fn(),
@@ -2840,3 +2849,134 @@ describe("Preview automation diagnostics", () => {
     expect("locator" in error).toBe(false);
   });
 });
+
+describe("Preview automation snapshots", () => {
+  const pageValue = {
+    url: "https://example.com",
+    title: "Example",
+    loading: false,
+    visibleText: "Dashboard",
+    interactiveElements: [],
+  };
+
+  const snapshotImage = {
+    getSize: () => ({ width: 100, height: 80 }),
+    toPNG: () => Buffer.from("png"),
+    resize: () => ({
+      getSize: () => ({ width: 100, height: 80 }),
+      toPNG: () => Buffer.from("png"),
+    }),
+  };
+
+  effectIt.effect("omits ax, console, and network unless include asks", () =>
+    withManager((manager) =>
+      Effect.gen(function* () {
+        const sendCommand = vi.fn(async (method: string) => {
+          if (method === "Runtime.evaluate") {
+            return { result: { value: pageValue } };
+          }
+          if (method === "Accessibility.getFullAXTree") {
+            return { nodes: [{ role: "main" }] };
+          }
+          return undefined;
+        });
+        fromId.mockReturnValue({
+          ...makeTestPreviewWebContents(vi.fn(async () => snapshotImage)),
+          debugger: {
+            isAttached: () => false,
+            attach: vi.fn(),
+            sendCommand,
+            on: vi.fn(),
+            off: vi.fn(),
+          },
+        } as never);
+
+        yield* manager.createTab("tab_snapshot");
+        yield* manager.registerWebview("tab_snapshot", 42);
+        const slim = yield* manager.automationSnapshot("tab_snapshot");
+        expect(slim.accessibilityTree).toBeUndefined();
+        expect(slim.consoleEntries).toEqual([]);
+        expect(slim.networkEntries).toEqual([]);
+        const slimMethods = sendCommand.mock.calls.map(([method]) => method);
+        expect(slimMethods).not.toContain("Accessibility.getFullAXTree");
+
+        sendCommand.mockClear();
+        const withAx = yield* manager.automationSnapshot("tab_snapshot", ["ax"]);
+        expect(withAx.accessibilityTree).toEqual({ nodes: [{ role: "main" }] });
+        expect(sendCommand.mock.calls.map(([method]) => method)).toContain(
+          "Accessibility.getFullAXTree",
+        );
+      }),
+    ),
+  );
+
+  effectIt.effect("fails the snapshot when capturePage and CDP screenshot both miss", () =>
+    withManager((manager) =>
+      Effect.gen(function* () {
+        const sendCommand = vi.fn(async (method: string) => {
+          if (method === "Runtime.evaluate") {
+            return { result: { value: pageValue } };
+          }
+          if (method === "Page.captureScreenshot") {
+            return {};
+          }
+          return undefined;
+        });
+        fromId.mockReturnValue({
+          ...makeTestPreviewWebContents(
+            vi.fn(async () => {
+              throw new Error("capturePage failed");
+            }),
+          ),
+          debugger: {
+            isAttached: () => false,
+            attach: vi.fn(),
+            sendCommand,
+            on: vi.fn(),
+            off: vi.fn(),
+          },
+        } as never);
+
+        yield* manager.createTab("tab_snapshot_fail");
+        yield* manager.registerWebview("tab_snapshot_fail", 42);
+        const exit = yield* Effect.exit(manager.automationSnapshot("tab_snapshot_fail"));
+        expect(Exit.isFailure(exit)).toBe(true);
+        if (Exit.isSuccess(exit)) return;
+        expect(Option.getOrThrow(Cause.findErrorOption(exit.cause))).toMatchObject({
+          _tag: "PreviewOperationError",
+          operation: "automationSnapshot.capturePage",
+        });
+      }),
+    ),
+  );
+
+  effectIt.effect("defaults waitFor text search to the main landmark", () =>
+    withManager((manager) =>
+      Effect.gen(function* () {
+        const expressions: string[] = [];
+        const sendCommand = vi.fn(async (method: string, params?: Record<string, unknown>) => {
+          if (method === "Runtime.evaluate") {
+            expressions.push(String(params?.expression ?? ""));
+            return { result: { value: { matched: true } } };
+          }
+          return undefined;
+        });
+        fromId.mockReturnValue({
+          ...makeTestPreviewWebContents(vi.fn(async () => snapshotImage)),
+          debugger: {
+            isAttached: () => false,
+            attach: vi.fn(),
+            sendCommand,
+            on: vi.fn(),
+            off: vi.fn(),
+          },
+        } as never);
+
+        yield* manager.createTab("tab_wait");
+        yield* manager.registerWebview("tab_wait", 42);
+        yield* manager.automationWaitFor("tab_wait", { text: "Dashboard" });
+        expect(expressions.some((expression) => expression.includes('"main"'))).toBe(true);
+      }),
+    ),
+  );
+});

apps/desktop/src/preview/Manager.ts

@@ -2921,7 +2921,7 @@ const makeNativeOperations = Effect.fn("PreviewManager.makeOperations")(function
           };
           const seen = new Set();
           const elements = Array.from(document.querySelectorAll(
-            "a[href],button,input,textarea,select,[role],[tabindex],[role=row],tr,[role=gridcell]"
+            "a[href],button,input,textarea,select,[role],[tabindex],[role=row],tr,[role=gridcell],div,td"
           )).filter((element) => {
             if (!visible(element) || !clickable(element) || seen.has(element)) return false;
             seen.add(element);
@@ -2945,7 +2945,7 @@ const makeNativeOperations = Effect.fn("PreviewManager.makeOperations")(function
             url: location.href,
             title: document.title,
             loading: document.readyState !== "complete",
-            visibleText: ((main && main.innerText) || document.body?.innerText || "").slice(0, ${MAX_VISIBLE_TEXT_LENGTH}),
+            visibleText: (main ? main.innerText : document.body?.innerText || "").slice(0, ${MAX_VISIBLE_TEXT_LENGTH}),
             interactiveElements: elements
           };
         })()`,
@@ -2964,18 +2964,16 @@ const makeNativeOperations = Effect.fn("PreviewManager.makeOperations")(function
         },
         () => wc.capturePage(),
       ).pipe(
-        Effect.catch(() =>
+        Effect.catch((captureFailure) =>
           send("Page.captureScreenshot", { format: "png" }).pipe(
-            Effect.map((result) => {
-              const data =
-                result !== null &&
-                typeof result === "object" &&
-                "data" in result &&
-                typeof result.data === "string"
-                  ? result.data
-                  : "";
-              return nativeImage.createFromBuffer(Buffer.from(data, "base64"));
-            }),
+            Effect.flatMap((result) =>
+              result !== null &&
+              typeof result === "object" &&
+              "data" in result &&
+              typeof result.data === "string"
+                ? Effect.succeed(nativeImage.createFromBuffer(Buffer.from(result.data, "base64")))
+                : Effect.fail(captureFailure),
+            ),
           ),
         ),
       );