[Web] Release picked file data for Web

[tddang-linagora]

Issue

There's a memory leak happening with web version

Reproducible code

See here

import 'package:file_picker/file_picker.dart';
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: FirstScreen(),
    );
  }
}

class FirstScreen extends StatelessWidget {
  const FirstScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: TextButton(
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => const SecondScreen()),
            );
          },
          child: Text('Go to second screen'),
        ),
      ),
    );
  }
}

class SecondScreen extends StatefulWidget {
  const SecondScreen({super.key});

  @override
  State<SecondScreen> createState() => _SecondScreenState();
}

class _SecondScreenState extends State<SecondScreen> {
  String _name = '';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("Picked file's name: $_name"),
            TextButton(
              onPressed: () async {
                final picked = await FilePicker.platform.pickFiles(
                  type: FileType.image,
                  withData: true,
                );
                if (mounted && picked != null) {
                  setState(() {
                    _name = picked.files.firstOrNull?.name ?? '';
                  });
                }
              },
              child: Text('Pick image'),
            ),
            TextButton(
              onPressed: () {
                Navigator.pop(context);
              },
              child: Text('Go back'),
            ),
          ],
        ),
      ),
    );
  }
}

Steps to reproduce

1. Run flutter run -d chrome --profile
2. Open Chrome dev tools, Memory tab, trigger garbage collector then snapshot main heap
3. Navigate to second screen by clicking on Go to second screen button
4. Pick a heavy file. In the above code, I chose to pick image because I already have a heavy image (16.3mb)
5. Go back to the previous screen either by clicking on Go back or any conventional ways for web
6. Trigger garbage collector then snapshot main heap again. Compare two snapshots.

Expected behavior

The file's data will be deallocated from memory

Actual behavior

The file's data is still on memory

Resolved demo

Before

After

[amrgetment]

as my PR for WASM support got merged you need to update clear children, check the file changes here
https://github.com/miguelpruivo/flutter_file_picker/pull/1481/files

[tddang-linagora]

as my PR for WASM support got merged you need to update clear children, check the file changes here https://github.com/miguelpruivo/flutter_file_picker/pull/1481/files

Right. Thank you.

[navaronbracke]

@tddang-linagora Could you fix the merge conflict for the version & changelog? We released a new version, which removes references to the v1 Android embedding, but that means your version needs to be incremented to 8.0.5.

[tddang-linagora]

@tddang-linagora Could you fix the merge conflict for the version & changelog? We released a new version, which removes references to the v1 Android embedding, but that means your version needs to be incremented to 8.0.5.

Done, thank you.

[navaronbracke]

@tddang-linagora Hmm, it seems the clear() method is not defined for the Element class (of which _target is an instance). I think you can just remove that line? You iterate manually using firstChild anyway.

As for the Windows deprecation warnings, I think you can just replace them with their replacements, as noted in the deprecation message. I think we picked up a new version of win32 along the way.

   info - lib/src/windows/file_picker_windows.dart:97:18 - 'COINIT_APARTMENTTHREADED' is deprecated and shouldn't be used. Use COINIT.COINIT_APARTMENTTHREADED instead. Try replacing the use of the deprecated member with the replacement. - deprecated_member_use
   info - lib/src/windows/file_picker_windows.dart:97:45 - 'COINIT_DISABLE_OLE1DDE' is deprecated and shouldn't be used. Use COINIT.COINIT_DISABLE_OLE1DDE instead. Try replacing the use of the deprecated member with the replacement. - deprecated_member_use
   info - lib/src/windows/file_picker_windows.dart:137:36 - 'ERROR_CANCELLED' is deprecated and shouldn't be used. Use WIN32_ERROR.ERROR_CANCELLED instead. Try replacing the use of the deprecated member with the replacement. - deprecated_member_use

[tddang-linagora]

Hmm, it seems the clear() method is not defined for the Element class (of which _target is an instance). I think you can just remove that line? You iterate manually using firstChild anyway.

Yep, my bad sorry. Fixed.

As for the Windows deprecation warnings, I think you can just replace them with their replacements, as noted in the deprecation message.

Also done.

[navaronbracke]

@tddang-linagora Looks like you'll need to run dart format on lib/src/windows/file_picker_windows.dart.
It think that first change in the Windows implementation is now over the 80 character threshold for formatting.

Adding a comma like this should fix it.

    int hr = CoInitializeEx(
        nullptr, COINIT.COINIT_APARTMENTTHREADED | COINIT.COINIT_DISABLE_OLE1DDE,);

then the formatter will probably format it like:

    int hr = CoInitializeEx(
        nullptr,
        COINIT.COINIT_APARTMENTTHREADED | COINIT.COINIT_DISABLE_OLE1DDE,
     );

[tddang-linagora]

Yep sorry I turned off my formatters