fix(v3): guard dispatchWailsEvent against race condition on reload by ddmoney420 · Pull Request #4925 · wailsapp/wails

ddmoney420 · 2026-01-29T09:16:10Z

Summary

Guards window._wails.dispatchWailsEvent calls against race conditions during page reload.

Problem

When the page is reloaded, the WindowLoadFinished event can fire before the JavaScript runtime has mounted dispatchWailsEvent on window._wails. This causes:

TypeError: window._wails.dispatchWailsEvent is not a function

This is a classic race condition between:

Path A: Native WebKit firing WindowLoadFinished event immediately
Path B: JavaScript runtime modules loading and initializing

Solution

Added a guard to check if window._wails and dispatchWailsEvent exist before calling:

msg := fmt.Sprintf("if(window._wails&&window._wails.dispatchWailsEvent){window._wails.dispatchWailsEvent(%s);}", event.ToJSON())

If the runtime isn't ready, the event is silently skipped (correct behavior since there's no handler).

Test plan

Run wails3 dev on a fresh project
Right-click and click "Reload" on the frontend window
Verify no error appears in console

Fixes #4872

🤖 Generated with Claude Code

Summary by CodeRabbit

Bug Fixes
- Prevented errors occurring during page reloads when the runtime isn't fully initialized, improving stability when events fire before the runtime is ready.
- Reduced race-condition impact on event dispatch to make reloads more reliable and less likely to trigger transient failures.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

When the page is reloaded, the WindowLoadFinished event can fire before the JavaScript runtime has mounted dispatchWailsEvent on window._wails. This causes a TypeError: window._wails.dispatchWailsEvent is not a function. This fix adds a guard to check if window._wails and dispatchWailsEvent exist before attempting to call the function. If the runtime isn't ready, the event is silently skipped (which is correct since there's no handler). Fixes wailsapp#4872 Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

coderabbitai · 2026-01-29T09:16:42Z

Caution

Review failed

The pull request is closed.

Walkthrough

Guards the runtime call to window._wails.dispatchWailsEvent by checking that window._wails and window._wails.dispatchWailsEvent exist before invoking, preventing errors when events fire before the Wails runtime is mounted (e.g., during page reload).

Changes

Cohort / File(s)	Summary
Race Condition Guard `v3/pkg/application/webview_window.go`	Wraps the JavaScript invocation of `window._wails.dispatchWailsEvent` with a runtime existence check and adds comments explaining the reload-time race condition. (+4/-1 lines)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

Bug, Documentation, v3-alpha, runtime, size:XS

Poem

🐇 I hopped to the window, ears full of cheer,
Events came too early and caused a small fear.
Now I peek before calling, I wait and I see—
If _wails is ready, then let the events be! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding a runtime guard to dispatchWailsEvent to fix a race condition on reload.
Description check	✅ Passed	The description includes a clear summary, problem statement, solution, and test plan. However, the description checklist items are not checked off.
Linked Issues check	✅ Passed	The PR directly addresses issue `#4872` by implementing the runtime guard to prevent TypeError when WindowLoadFinished fires before JavaScript runtime initialization.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the race condition in issue `#4872`; no unrelated or out-of-scope modifications are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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leaanthony · 2026-02-01T09:57:01Z

Thanks 🙏 Please could you add an entry to the changelog located at v3/UNRELEASED_CHANGELOG.md? Thanks!

Fix race condition causing TypeError during page reload. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sonarqubecloud · 2026-02-02T09:00:21Z

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

Fix race condition causing TypeError during page reload. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

…ailsapp#4925) * fix(v3): guard dispatchWailsEvent against race condition on reload When the page is reloaded, the WindowLoadFinished event can fire before the JavaScript runtime has mounted dispatchWailsEvent on window._wails. This causes a TypeError: window._wails.dispatchWailsEvent is not a function. This fix adds a guard to check if window._wails and dispatchWailsEvent exist before attempting to call the function. If the runtime isn't ready, the event is silently skipped (which is correct since there's no handler). Fixes wailsapp#4872 Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * docs: Add changelog entry for wailsapp#4872 --------- Co-authored-by: ddmoney420 <ddmoney420@users.noreply.github.com> Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com> Co-authored-by: Lea Anthony <lea.anthony@gmail.com>

leaanthony added a commit that referenced this pull request Feb 2, 2026

docs: Add changelog entry for #4925

8b99993

Fix race condition causing TypeError during page reload. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs: Add changelog entry for wailsapp#4872

e786689

leaanthony approved these changes Feb 2, 2026

View reviewed changes

Merge branch 'v3-alpha' into fix/4872-dispatch-event-race

445f7ca

leaanthony merged commit 5d0dd30 into wailsapp:v3-alpha Feb 2, 2026
8 of 11 checks passed

coderabbitai Bot mentioned this pull request Feb 3, 2026

fix(runtime): file drop not working with @wailsio/runtime npm module #4953

Merged

coderabbitai Bot mentioned this pull request Apr 15, 2026

Fixes #5016 - Fix deadlock in EventIPCTransport.DispatchWailsEvent holding RLock during InvokeSync #5107

Merged

15 tasks

Grantmartin2002 pushed a commit to Grantmartin2002/wails that referenced this pull request Apr 29, 2026

docs: Add changelog entry for wailsapp#4925

5a4d101

Fix race condition causing TypeError during page reload. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

coderabbitai Bot mentioned this pull request Jun 11, 2026

fix(v3/runtime): make @wailsio/runtime importable without a DOM #5571

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fix(v3): guard dispatchWailsEvent against race condition on reload#4925

fix(v3): guard dispatchWailsEvent against race condition on reload#4925
leaanthony merged 3 commits into
wailsapp:v3-alphafrom
ddmoney420:fix/4872-dispatch-event-race

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ddmoney420 commented Jan 29, 2026 •

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