[image_picker_ios] infinite await in picking methods when native picker is closed quickly

[raju-muliyashiya]

fixes Issue #134715

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List which issues are fixed by this PR. You must list at least one issue.

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• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
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• I [linked to at least one issue that this PR fixes] in the description above.
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• I updated/added any relevant documentation (doc comments with ///).
• I added updated tests to check the change I am making, or I have commented below to indicate which [test exemption] this PR falls under[^1].
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request addresses an issue where picking methods could await indefinitely if the native picker was closed quickly. The fix introduces a FLTImagePickerRemoveObserverView, a clever solution that uses the view lifecycle to detect when the picker is dismissed, covering edge cases not handled by standard delegate methods. A new isProcessingSelection flag prevents this new mechanism from interfering with normal selection flows. The changes are accompanied by a comprehensive set of new tests to validate the fix and prevent regressions. My review includes a few suggestions to improve documentation, code style, and one of the new tests for better robustness and maintainability.

[gemini-code-assist]

The documentation for FLTImagePickerRemoveCallback and FLTImagePickerRemoveObserverView could be improved for clarity and grammar. Clear documentation is important for long-term maintainability.

/**
 * A callback that is invoked when the picker view controller is removed from the window.
 */
typedef void (^FLTImagePickerRemoveCallback)(void);

/**
 * A view that uses `didMoveToWindow` to observe when it has been removed from a window.
 *
 * This is added to the picker's view hierarchy to detect when the picker has been dismissed
 * in cases where the standard delegate methods are not called (e.g., a quick interactive
 * dismissal).
 */

[gemini-code-assist]

There's a minor style issue here: a missing space before the opening brace {. Adhering to a consistent code style improves readability.

- (instancetype)initWithRemoveCallback:(FLTImagePickerRemoveCallback)callback {

[gemini-code-assist]

There are a couple of minor style issues here (missing spaces) that deviate from the project's coding style. Consistent formatting improves code readability.

  FLTImagePickerRemoveObserverView *removeObserverView =
      [[FLTImagePickerRemoveObserverView alloc] initWithRemoveCallback:^{
        __strong typeof(weakSelf) strongSelf = weakSelf;
        // Add a small delay to ensure delegate methods have a chance to run first
        // This prevents the observer from firing during normal selection flow
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
          if (strongSelf && strongSelf.callContext == context && !strongSelf.isProcessingSelection) {

[gemini-code-assist]

This test manually creates a removeCallback that duplicates the implementation logic from bindRemoveObserver:. This makes the test brittle; if the implementation changes, this test would need to be updated manually and might not fail correctly. It also doesn't test the new FLTImagePickerRemoveObserverView class and its didMoveToWindow trigger.

A better approach would be to write this as an integration test that calls one of the pick... methods to set up the real observer, and then simulates the dismissal to trigger it. This would provide more robust testing of the actual code path.

- (void)testUIImagePickerImmediateCloseReturnsEmptyArray {
  FLTImagePickerPlugin *plugin = [[FLTImagePickerPlugin alloc] init];
  UIImagePickerController *controller = [[UIImagePickerController alloc] init];
  [plugin setImagePickerControllerOverrides:@[ controller ]];

  // Mock camera access to avoid permission dialogs and device-specific logic.
  id mockUIImagePicker = OCMClassMock([UIImagePickerController class]);
  OCMStub(ClassMethod([mockUIImagePicker isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]))
      .andReturn(YES);
  OCMStub(ClassMethod([mockUIImagePicker isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceRear]))
      .andReturn(YES);
  id mockAVCaptureDevice = OCMClassMock([AVCaptureDevice class]);
  OCMStub([mockAVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo])
      .andReturn(AVAuthorizationStatusAuthorized);

  XCTestExpectation *resultExpectation = [self expectationWithDescription:@"result"];

  FLTSourceSpecification *source = [FLTSourceSpecification makeWithType:FLTSourceTypeCamera
                                                                 camera:FLTSourceCameraRear];
  [plugin pickImageWithSource:source
                      maxSize:[[FLTMaxSize alloc] init]
                      quality:nil
                 fullMetadata:NO
                   completion:^(NSString *_Nullable result, FlutterError *_Nullable error) {
                     XCTAssertNil(result);
                     XCTAssertNil(error);
                     [resultExpectation fulfill];
                   }];

  // The `pickImage` call will attach the observer. Now, simulate dismissal.
  // This needs to happen on the next run loop to ensure the observer is attached.
  dispatch_async(dispatch_get_main_queue(), ^{
    UIWindow *testWindow = [[UIWindow alloc] init];
    [testWindow addSubview:controller.view];
    [controller.view removeFromSuperview];
  });

  [self waitForExpectationsWithTimeout:1.0 handler:nil];
}