fix(web): closing a file tab no longer overwrites newer changes

apps/web/src/components/files/fileSaveCoordinator.test.ts

@@ -73,6 +73,117 @@ describe("FileSaveCoordinator", () => {
     expect(onPendingChange.mock.calls.at(-1)).toEqual([false]);
   });
 
+  it("does not rewrite already saved contents when the editor closes", async () => {
+    vi.useFakeTimers();
+    const persist = vi
+      .fn<(contents: string) => Promise<AtomCommandResult<void, never>>>()
+      .mockResolvedValue(AsyncResult.success(undefined));
+    const coordinator = new FileSaveCoordinator({
+      debounceMs: 500,
+      persist,
+      onPendingChange: vi.fn(),
+      onConfirmed: vi.fn(),
+    });
+
+    coordinator.change("edited");
+    await vi.advanceTimersByTimeAsync(500);
+    expect(persist).toHaveBeenCalledOnce();
+
+    coordinator.dispose();
+    await vi.runAllTimersAsync();
+    expect(persist).toHaveBeenCalledOnce();
+  });
+
+  it("saves an edit made inside the debounce window when the editor closes", async () => {
+    vi.useFakeTimers();
+    const persist = vi
+      .fn<(contents: string) => Promise<AtomCommandResult<void, never>>>()
+      .mockResolvedValue(AsyncResult.success(undefined));
+    const coordinator = new FileSaveCoordinator({
+      debounceMs: 500,
+      persist,
+      onPendingChange: vi.fn(),
+      onConfirmed: vi.fn(),
+    });
+
+    coordinator.change("unsaved");
+    coordinator.dispose();
+    await vi.runAllTimersAsync();
+    expect(persist).toHaveBeenCalledOnce();
+    expect(persist).toHaveBeenCalledWith("unsaved");
+  });
+
+  it("flushes an edit made while a write was in flight when the editor closes", async () => {
+    vi.useFakeTimers();
+    const inFlight = deferred();
+    const persist = vi
+      .fn<(contents: string) => Promise<AtomCommandResult<void, never>>>()
+      .mockReturnValueOnce(inFlight.promise)
+      .mockResolvedValue(AsyncResult.success(undefined));
+    const coordinator = new FileSaveCoordinator({
+      debounceMs: 500,
+      persist,
+      onPendingChange: vi.fn(),
+      onConfirmed: vi.fn(),
+    });
+
+    coordinator.change("first");
+    await vi.advanceTimersByTimeAsync(500);
+    coordinator.change("latest");
+    coordinator.dispose();
+    inFlight.resolve(AsyncResult.success(undefined));
+    await vi.runAllTimersAsync();
+
+    expect(persist).toHaveBeenCalledTimes(2);
+    expect(persist).toHaveBeenLastCalledWith("latest");
+  });
+
+  it("does not rewrite a write that lands while the editor closes", async () => {
+    vi.useFakeTimers();
+    const inFlight = deferred();
+    const persist = vi
+      .fn<(contents: string) => Promise<AtomCommandResult<void, never>>>()
+      .mockReturnValueOnce(inFlight.promise)
+      .mockResolvedValue(AsyncResult.success(undefined));
+    const coordinator = new FileSaveCoordinator({
+      debounceMs: 500,
+      persist,
+      onPendingChange: vi.fn(),
+      onConfirmed: vi.fn(),
+    });
+
+    coordinator.change("only");
+    await vi.advanceTimersByTimeAsync(500);
+    coordinator.dispose();
+    inFlight.resolve(AsyncResult.success(undefined));
+    await vi.runAllTimersAsync();
+
+    expect(persist).toHaveBeenCalledOnce();
+  });
+
+  it("retries a failed write when the editor closes", async () => {
+    vi.useFakeTimers();
+    const persist = vi
+      .fn()
+      .mockResolvedValueOnce(AsyncResult.failure(Cause.fail(new Error("write failed"))))
+      .mockResolvedValue(AsyncResult.success(undefined));
+    const coordinator = new FileSaveCoordinator({
+      debounceMs: 500,
+      persist,
+      onPendingChange: vi.fn(),
+      onConfirmed: vi.fn(),
+    });
+
+    coordinator.change("latest");
+    await vi.advanceTimersByTimeAsync(500);
+    expect(persist).toHaveBeenCalledOnce();
+
+    coordinator.dispose();
+    await vi.runAllTimersAsync();
+    expect(persist).toHaveBeenCalledTimes(2);
+    expect(persist).toHaveBeenLastCalledWith("latest");
+  });
+
   it("leaves the file pending when the latest write fails", async () => {
     vi.useFakeTimers();
     const onPendingChange = vi.fn();

apps/web/src/components/files/fileSaveCoordinator.ts

@@ -11,6 +11,9 @@ export class FileSaveCoordinator<A = unknown, E = unknown> {
   private timer: ReturnType<typeof setTimeout> | null = null;
   private latestContents = "";
   private latestRevision = 0;
+  // Revision of the last edit confirmed on disk, so `dispose` can tell an
+  // unsaved edit from one the debounce already wrote and only flush the former.
+  private persistedRevision = 0;
   private lastChangeAt = 0;
   private saving = false;
   private disposed = false;
@@ -28,7 +31,7 @@ export class FileSaveCoordinator<A = unknown, E = unknown> {
   dispose(): void {
     this.disposed = true;
     this.clearTimer();
-    if (this.latestRevision > 0) void this.persistLatest();
+    if (this.latestRevision > this.persistedRevision) void this.persistLatest();
   }
 
   private schedule(delay: number): void {
@@ -54,6 +57,7 @@ export class FileSaveCoordinator<A = unknown, E = unknown> {
     const result = await this.options.persist(contents);
     const succeeded = result._tag === "Success";
     if (succeeded) {
+      this.persistedRevision = revision;
       this.options.onConfirmed(contents);
     }