Fix IntelliJ IDEA project open hang by removing FlutterProjectOpenProcessor

[0ttik]

Description

The custom FlutterProjectOpenProcessor silently fails to open Flutter projects that lack a .idea directory in IntelliJ IDEA (Community and Ultimate). When getDelegateImportProvider() finds no other processor that can claim the project, openProjectAsync() returns null — a silent failure with no error logged. Since this processor is registered with order="first", no other processor gets a chance to try.

This is the IntelliJ IDEA equivalent of PR #8710, which fixed the same class of issue for Android Studio by removing FlutterStudioProjectOpenProcessor.

Changes

• Removed FlutterProjectOpenProcessor.kt entirely
• Removed its <projectOpenProcessor> registration from plugin.xml
• Added module-type-fixing logic to FlutterInitializer (the existing IntelliJ IDEA startup activity) — sets Flutter module type and enables Dart SDK for unconfigured modules
• Added changelog entry

This lets the platform's default project opener handle opening, then FlutterInitializer configures Flutter-specific settings after the project is loaded — the same pattern used in the Android Studio fix.

Reproduction

flutter create test_app && rm -rf test_app/.idea

Then open test_app via File > Open in IntelliJ IDEA — previously nothing happened, now the project opens correctly.

Testing

Tested with:

• IntelliJ IDEA CE 2025.2
• Android Studio 2025.2.3.9 (sandboxed via ./gradlew runIde)
• Flutter 3.8.1 / Dart 3.8.1
• macOS

Verified:

• Opening a Flutter project without .idea directory works in IntelliJ IDEA
• Opening a Flutter project with existing .idea directory still works
• No regressions in Android Studio (sandboxed runIde)
• IDE logs show FlutterInitializer running correctly, no errors

Fixes #8845
Related: #8661, #8710

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[gemini-code-assist]

Code Review

This pull request addresses a hang in IntelliJ IDEA when opening Flutter projects that lack a .idea directory. The fix involves removing the FlutterProjectOpenProcessor, which was the source of the issue, and relocating its module configuration logic to FlutterInitializer. This is a clean architectural improvement that resolves the hang by letting the platform's default project opener handle the initial project loading, with Flutter-specific setup occurring as a post-startup activity. The changes are correct and consistent with a similar fix previously made for Android Studio.

_{Note: Security Review did not run due to the size of the PR.}

[helin24]

Thanks for the fix! I appreciate the detailed log of verification testing.

I think this needs a rebase on main but in the meantime I will assign to Phil to review / merge if he approves.

[pq]

If you could make that wee changelog entry, that'd be great. Otherwise, I started our verification workflows and assuming they run green, this LGTM!

[0ttik]

@pq, I think I've made the change to the changelog and also rebased the branch onto main, so everything should be ready to merge now, thanks.

[pq]

Thank you, @0ttik!