Devtools benchmarks fail with dart2wasm on highest optimization level

@kenzieschmoll

The devtools benchmarks run with the newest version of flutter causes dart2wasm to emit code that results in a typecasting failure, but only at the highest optimization levels.

Steps to Reproduce:

Check out @kenzieschmoll 's branch here: Upgrade to latest flutter flutter/devtools#8306
Change to the packages/devtools_app directory
Run the following script: dart ./benchmark/devtools_benchmarks_test.dart

Results:
Tests output the following exception:

  Caught browser-side error: Type '(minified:Class2107) => minified:Class4570<void>' is not a subtype of type '(Object) => minified:Class4570<void>' in type cast
      at _TypeError._throwAsCheckError (http://localhost:9999/main.dart.wasm:wasm-function[1117]:0x1aa4a2)
      at _RouterState.restoreState closure at file:///home/runner/work/devtools/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:623:72 (http://localhost:9999/main.dart.wasm:wasm-function[33056]:0x4ade86)
      at closure wrapper at file:///home/runner/work/devtools/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:623:72 trampoline (http://localhost:9999/main.dart.wasm:wasm-function[33060]:0x4adeb4)
      at _RouterState._processParsedRouteInformation closure at file:///home/runner/work/devtools/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 inner (http://localhost:9999/main.dart.wasm:wasm-function[32757]:0x4a80cf)
      at _RouterState._processParsedRouteInformation closure at file:///home/runner/work/devtools/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 (http://localhost:9999/main.dart.wasm:wasm-function[32754]:0x4a7fce)
      at closure wrapper at file:///home/runner/work/devtools/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 trampoline (http://localhost:9999/main.dart.wasm:wasm-function[32756]:0x4a7ff8)
      at _rootRunUnary (http://localhost:9999/main.dart.wasm:wasm-function[1550]:0x1bfa56)
      at _CustomZone.runUnary (http://localhost:9999/main.dart.wasm:wasm-function[33328]:0x4b5988)

This only appears to occur at the full optimization level. Changing the web benchmarking code to compile at -O1, -O1 or -O2 does not emit this error. Unfortunately, it's difficult to tell what exactly is being cast due to the minified types.

Summary: Dart2wasm emits incorrect code when compiling Devtools benchmarks at the highest optimization level, causing a type casting error during runtime. The issue only occurs at -O3 and not at lower optimization levels.

I can confirm that this is happening iff --omit-implicit-type-checks is enabled.

The error being thrown looks like this:

Caught browser-side error:
   Type
       '(DevToolsRouteConfiguration) => Future<void>' is not a subtype of type
       '(Object) => Future<void>'
   in type cast

The code looks like this:

  @override
  void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
    registerForRestoration(_routeInformation, 'route');
    if (_routeInformation.value != null) {
      assert(widget.routeInformationParser != null);
      _processRouteInformation(_routeInformation.value!, () => widget.routerDelegate.setRestoredRoutePath);
    } else if (widget.routeInformationProvider != null) {
      _processRouteInformation(widget.routeInformationProvider!.value, () => widget.routerDelegate.setInitialRoutePath);
                                                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    }
  }

The inner closure returns a function. That function is a tear-off of RouterDelegate<T>.setInitialRoutePath.

The widget.routerDelegate is a DevToolsRouterDelegate:

class DevToolsRouterDelegate extends RouterDelegate<DevToolsRouteConfiguration> ... {
  ...
}
abstract class RouterDelegate<T> extends Listenable {
  Future<void> setInitialRoutePath(T configuration) { ...  }
  ...
}

=> So at runtime this widget.routerDelegate.setInitialRoutePath will be (DevToolsRouteConfiguration) -> Future<void>

So the closure we give to _processRouteInformations 2nd argument is () -> ((DevToolsRouteConfiguration) -> Future<void>).

That function looks like this:

class _RouterState<T> 
  void _processRouteInformation(RouteInformation information, ValueGetter<_RouteSetter<T>> delegateRouteSetter) {
    ....
  }
}
typedef ValueGetter<T> = T Function();
typedef _RouteSetter<T> = Future<void> Function(T);

=> We seemingly have T == Object
=> We expect ValueGetter<_RouteSetter<T>>
=> We expect ValueGetter<_RouteSetter<Object>>
=> We expect ValueGetter<Future<void> Function(Object)>
=> We expect Future<void> Function(Object) Function()

So we're trying to assign () -> ((DevToolsRouteConfiguration) -> Future<void> where () -> ((Object) -> Future<void>) is expected.

Not quite clear yet why this happens precisely iff --omit-implicit-checks is enabled.

Turns out that because the tear-off is of a method with covariant parameters the parameter of the closure should be Object. Though in --omit-implicit-checks it was rather DevToolsRouteConfiguration.

=> cl/384285

[dart2wasm] Fix bug in --omit-implicit-checks

I am still seeing this issue even with the attempted fix (which was first included in Dart 3.6.0-235.0.dev - see commit).

Flutter 3.26.0-1.0.pre.76 • channel [user-branch] • unknown source
Framework • revision 9108b6d0cf (9 hours ago) • 2024-09-11 05:11:17 -0400
Engine • revision 0a14c519ea
Tools • Dart 3.6.0 (build 3.6.0-238.0.dev) • DevTools 2.39.0

Repro steps:

patch Add wasm opt-in setting flutter/devtools#8270
run devtools_tool serve --wasm --no-strip-wasm

Exception:

Type '(minified:Class2376) => minified:Class4651<void>' is not a subtype of type '(Object) => minified:Class4651<void>' in type cast
main.dart.mjs:69     at _TypeError._throwAsCheckError (http://127.0.0.1:9103/main.dart.wasm:wasm-function[1106]:0x1b3fb0)
    at _RouterState.restoreState closure at file:///Users/kenzieschmoll/develop/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:623:72 (http://127.0.0.1:9103/main.dart.wasm:wasm-function[13887]:0x2e9b21)
    at closure wrapper at file:///Users/kenzieschmoll/develop/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:623:72 trampoline (http://127.0.0.1:9103/main.dart.wasm:wasm-function[13891]:0x2e9b4c)
    at _RouterState._processParsedRouteInformation closure at file:///Users/kenzieschmoll/develop/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 inner (http://127.0.0.1:9103/main.dart.wasm:wasm-function[13880]:0x2e96b5)
    at _RouterState._processParsedRouteInformation closure at file:///Users/kenzieschmoll/develop/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 (http://127.0.0.1:9103/main.dart.wasm:wasm-function[13877]:0x2e95b7)
    at closure wrapper at file:///Users/kenzieschmoll/develop/devtools/tool/flutter-sdk/packages/flutter/lib/src/widgets/router.dart:759:12 trampoline (http://127.0.0.1:9103/main.dart.wasm:wasm-function[13879]:0x2e95df)
    at _rootRunUnary (http://127.0.0.1:9103/main.dart.wasm:wasm-function[1539]:0x1c99ac)
    at _CustomZone.runUnary (http://127.0.0.1:9103/main.dart.wasm:wasm-function[34744]:0x4e3593)

@kenzieschmoll

From my testing it seems very clear that this error occurs with

<flutter> % git reset --hard '2fb154f8203cbb021003b9cd9bf7661e8de6d473^'

<devtools> % flutter clean
<devtools> % flutter packages get
<devtools> % dart ./benchmark/devtools_benchmarks_test.dart     
...                                                                                                                
[CHROME]: DevTools listening on ws://127.0.0.1:10000/devtools/browser/b1b2aed3-5ed5-4a49-b43d-73066f493a73                    
                                                                                                                              
Connecting to DevTools: ws://localhost:10000/devtools/page/A61FEE23E814B2964DA720C9D59E2B6A                                   
                                                                                                                                                                                                                                                             
Connected to Chrome tab:  (http://localhost:9999/)                                                                                                                                                                                                           
                                                                                                                                                                                                                                                             
Launching benchmark "devtools_navigateThroughOfflineScreens"                                                                                                                                                                                                 
                                                                                                                              
Unrecognized URL path: /api/ping                                                                                              
02:23 +0 -1: Can run web benchmarks with WASM [E]                                                                             
                                                                                                                              
  Caught browser-side error: Type '(minified:Class2110) => minified:Class4558<void>' is not a subtype of type '(Object) => minified:Class4558<void>' in type cast
      at _TypeError._throwAsCheckError (http://localhost:9999/main.dart.wasm:wasm-function[1108]:0x1ad1c3)

but no longer with

<flutter> % git reset --hard '2fb154f8203cbb021003b9cd9bf7661e8de6d473'

<devtools> % flutter clean
<devtools> % flutter packages get
<devtools> % dart ./benchmark/devtools_benchmarks_test.dart 
...    
[CHROME]: DevTools listening on ws://127.0.0.1:10000/devtools/browser/4f1a5882-91fa-45df-9493-c4d9a526bb9b                    
                                                                                                                                                                                                                                                             
Connecting to DevTools: ws://localhost:10000/devtools/page/9AE8F6F0F0FC7A39DC8771612ADF4D24                                   
                                                                                                                                                                                                                                                             
Connected to Chrome tab:  (http://localhost:9999/)                                                                                                                                                                                                           
                                                                                                                                                                                                                                                             
Launching benchmark "devtools_navigateThroughOfflineScreens"                                                                                                                                                                                                 
                                                                                                                                                                                                                                                             
Unrecognized URL path: /api/ping                                                                                              
[APP] TEST STATUS: Warming up.                                                                                                
                                                               
[APP] TEST STATUS: Warm-up finished.                                                                                          
                                                                                                                                                                                                                                                             
[APP] TEST STATUS: Navigate through offline DevTools tabs                                                                     
                                                                                                                                                                                                                                                             
[APP] TEST STATUS: switching to home screen (icon null, iconAsset: icons/app_bar/devtools.png)                                
                                                                                                                              
[APP] TEST STATUS: switching to performance screen (icon null, iconAsset: icons/app_bar/performance.png)                      
                                                                                                                              
[APP] TEST STATUS: switching to cpu-profiler screen (icon null, iconAsset: icons/app_bar/cpu_profiler.png)                    
                                                                                                                              
[APP] TEST STATUS: switching to memory screen (icon null, iconAsset: icons/app_bar/memory.png)                                                                                                                                                               
                                                                                                                                                                                                                                                             
[APP] TEST STATUS: switching to app-size screen (icon null, iconAsset: icons/app_bar/app_size.png)                                                                                                                                                           
                                                                                                                                                                                                                                                             
[APP] TEST STATUS: switching to deep-links screen (icon null, iconAsset: icons/app_bar/deep_links.png)

@kenzieschmoll Are you sure you're on the right flutter/flutter commits? Have you run flutter clean & flutter packages get afterwords?

When you run devtools_tool serve --wasm --no-strip-wasm, do you see the error? I ran flutter clean and flutter packages get and I still see the error when I build and serve DevTools with wasm.

Flutter 3.26.0-1.0.pre.76 • channel [user-branch] • unknown source
Framework • revision 9108b6d0cf (10 hours ago) • 2024-09-11 05:11:17 -0400
Engine • revision 0a14c519ea
Tools • Dart 3.6.0 (build 3.6.0-238.0.dev) • DevTools 2.39.0

You no longer need to patch any code locally, just pull the latest from the Devtools master branch and run the serve command above. When Devtools loads in the browser, be sure to do a hard refresh (just clicking in the URL and hitting enter) to ensure that the browser is not caching an old version of DevTools.

You no longer need to patch any code locally, just pull the latest from the Devtools master branch and run the serve command above. When Devtools loads in the browser, be sure to do a hard refresh (just clicking in the URL and hitting enter) to ensure that the browser is not caching an old version of DevTools.

I still used the original instructions to reproduce (and cannot reproduce anymore after the rolled fix).

Will try with new instructions from #56664 (comment) and report back.

When you run devtools_tool serve --wasm --no-strip-wasm, do you see the error? I ran flutter clean and flutter packages get and I still see the error when I build and serve DevTools with wasm.

So the instructions would be

% git clone https://github.com/flutter/devtools; cd devtools
devtools % cd tool; dart pub get; cd ..
...
devtools % export LOCAL_DART_SDK=<path-to-real-dart-lang/sdk-gclient-checkout>
devtools % tool/bin/devtools_tool serve --wasm --no-strip-wasm
...

If I follow these instructions it seems to only serve dart2js (i.e. main.dart.js)

Are you on the tip of flutter/devtools master and the tip of the Dart SDK? there was a commit to each that landed this morning that you would need.

One potential difference between running devtools serve --wasm --no-strip-wasm and running the benchmark tests is that the former builds DevTools in release mode by default, and web_benchmarks builds Devtools in profile mode.

Are you on the tip of flutter/devtools master and the tip of the Dart SDK? there was a commit to each that landed this morning that you would need.

Yes.

If I follow these instructions it seems to only serve dart2js (i.e. main.dart.js)

After debugging the JS a bit it turns out the packages/devtools_app/web/flutter_bootstrap.js's shouldUseSkwasm() returns false

async function shouldUseSkwasm() {
  const searchParams = new URLSearchParams(window.location.search);
  const wasmEnabledFromQueryParameter = searchParams.get(wasmQueryParameterKey) === 'true';
  const wasmEnabledFromDevToolsPreference = await getDevToolsWasmPreference();
  return wasmEnabledFromQueryParameter === true || wasmEnabledFromDevToolsPreference === true;
}

Though I can manually serve via

<devtools>/packages/devtools_app/build/web % dhttpd  '--headers=Cross-Origin-Embedder-Policy=credentialless;Cross-Origin-Opener-Policy=same-origin'

and put ?wasm=true in the http://localhost:8080?wasm=true URL. Then it uses the main.dart.wasm and it works just fine (e.g. cpu profiler).

=> I see no sign in the console of the bug mentioned here.

The error this issue is about makes entirely sense given the bug I've found and fixed - I would be very surprised if another bug manifests in the same way.

=> Without clear, detailed instructions on how to reproduce this with newest flutter master there's nothing I can do.

@kenzieschmoll

@kenzieschmoll Do you still experience this issue and have reproduction instructions? Or is the issue fixed for you as well (as I would expect)?

I tried to reproduce this morning and could not, so it appears this issue is fixed. Thanks!

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Devtools benchmarks fail with dart2wasm on highest optimization level #56664

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Devtools benchmarks fail with dart2wasm on highest optimization level #56664

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dart-github-bot commented on Sep 6, 2024

mkustermann commented on Sep 9, 2024

mkustermann commented on Sep 9, 2024

kenzieschmoll commented on Sep 11, 2024

mkustermann commented on Sep 11, 2024

kenzieschmoll commented on Sep 11, 2024

mkustermann commented on Sep 11, 2024

mkustermann commented on Sep 11, 2024

kenzieschmoll commented on Sep 11, 2024

kenzieschmoll commented on Sep 11, 2024

mkustermann commented on Sep 12, 2024

mkustermann commented on Sep 20, 2024

kenzieschmoll commented on Sep 26, 2024

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