Analysis Server slows down when Save performed

[maRci002]

Steps to reproduce

In Android Studio when File | Settings | Languages & Frameworks | Flutter | Format code on save or File | Settings | Tools | Actions on Save | Reformat code is enabled OR WITHOUT THEM and Save action is performed the Analyzer Server is not avaible for the saved file for a long time ~10 sec.

In Visual Studio Code everything working fine.

Example code

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return const Placeholder();
  }
}

Here is a little video both Rename F2 and Context Actions Alt + Enter are working and whenever a Save Action is performed Ctrl + S the Analyzer won't suggest anything for more then 10 seconds and Rename is still not avaliable.

android_studio.mp4

As you can see Bloc's plugin suggestions working fine however I cannot get any suggetsion for a long time from the Analyzer Server.

Sometimes when Format code on save is enabled and I delete some method so some Class definition jumps into it's place then Rename might want to rename some method or it's constructors key paramter <= I think Analyzer Server doesn't get updated file. Edit: I made a seperate issue for this problem: #50968

I can reproduce on both stable and beta channels.

dart --version

Dart SDK version: 2.19.0-444.3.beta (beta) (Wed Jan 4 15:18:31 2023 +0000) on "windows_x64"

flutter --version

Flutter 3.7.0-1.3.pre • channel beta • https://github.com/flutter/flutter.git
Framework • revision 9b4416aaa7 (5 days ago) • 2023-01-04 17:29:34 -0600
Engine • revision 7b8906637f
Tools • Dart 2.19.0 (build 2.19.0-444.3.beta) • DevTools 2.20.0

Android Studio Dolphin | 2021.3.1 Patch 1
Build #AI-213.7172.25.2113.9123335, built on September 30, 2022
Runtime version: 11.0.13+0-b1751.21-8125866 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Windows 10 10.0
GC: G1 Young Generation, G1 Old Generation
Memory: 2048M
Cores: 16
Registry:
    external.system.auto.import.disabled=true
    ide.text.editor.with.preview.show.floating.toolbar=false

Non-Bundled Plugins:
    idea.plugin.protoeditor (213.6461.28)
    com.markskelton.one-dark-theme (5.7.2)
    com.bloc.intellij_generator_plugin (3.4.0)
    Dart (213.7433)
    andrasferenczi.dart-data-plugin (0.2.0)
    io.flutter (71.2.3)

[mraleph]

/cc @jensjoha for visibility

[jensjoha]

Nice.

6de7ea7 is the reason --- a timer delays the analysis for 10 seconds and in the meantime it won't answer.

In particular, when editing the file analysis.updateContent event of type add is sent together with the new content of the file and everything's fine. Then upon saving the file a analysis.updateContent event of type remove is sent which goes here:

sdk/pkg/analysis_server/lib/src/legacy_analysis_server.dart

Lines 765 to 776 in eba2188

	} else if (change is RemoveContentOverlay) {
	_pendingFilesToRemoveOverlay.remove(file)?.cancel();
	_pendingFilesToRemoveOverlay[file] = Timer(
	pendingFilesRemoveOverlayDelay,
	() {
	_pendingFilesToRemoveOverlay.remove(file);
	resourceProvider.removeOverlay(file);
	_changeFileInDrivers(file);
	},
	);
	return;
	} else {

I'll assign this to @scheglov who authored the introduction of this. It seems to have good intentions (from one of the comments in the commit "This helps for analysis server running remotely, with slow remote file systems") but miss the mark in letting everyone have this delay.

[mraleph]

Thanks @jensjoha!

/cc @srawlins for prioritisation. seems like potentially high negative UX impact?

[srawlins]

Yes I imagine this could be the root cause of much of our performance complaints. 6de7ea7 was also the decided culprit in #49107.

[jensjoha]

From #50968 it's probably furthermore the mismatching line-endings between saved and not-saved when the IDE fires requests that make it respond as it does. This means that it's probably only an issue on Windows. If the previous overlay and the new file data has been identical (which it probably is on Mac and Linux) it probably wouldn't be that big of an issue.

[jensjoha]

Oh, depending on how "format on save" is implemented that could possibly introduce a mismatch on non-Windows too. I haven't looked into that though.

[bwilkerson]

@jwren

[scheglov]

https://dart-review.googlesource.com/c/sdk/+/278883

[AlexV525]

Can we CP the fix to 2.19?

[mraleph]

Yes, this most certainly needs to be cherry picked once it bakes a bit.

@srawlins could you make a CP request?

[srawlins]

Can do!

[maRci002]

Thank you Flutter team for the fast fix, I can confirm the prebuilt Dart 2.19.0 which ships via Flutter 3.7.0 has the above changes and works fine.

Before I updated Flutter, I tried one more thing, so that the new lines of the file have unix line separator instead of windows line separator, and everything started to work so 6de7ea7 might be readded however it should work without this workaround. I also tested git autocrlf true but it doesn't change line breaks only after commit.

@jensjoha was right about line endings:

From #50968 it's probably furthermore the mismatching line-endings between saved and not-saved when the IDE fires requests that make it respond as it does. This means that it's probably only an issue on Windows. If the previous overlay and the new file data has been identical (which it probably is on Mac and Linux) it probably wouldn't be that big of an issue.