fix: defer UserInteractionInstrumentation enable() past field init to fix _eventNames TypeError #SUPERLOG

[superlog-app]

Summary

Every user click on the production web app was throwing TypeError: this._eventNames is undefined inside the Zone.js runTask patch, generating 207+ noisy browser.exception spans in ~46 seconds. The global window.error handler added in #414 surfaced this pre-existing silent failure.

Root Cause

UserInteractionInstrumentation@0.59.0 has a class field initialization ordering bug when bundled by Vite/esbuild. InstrumentationBase.constructor calls this.enable() inside super(), before the derived class's own field initializers run. Vite transforms _eventNames; (class field, no initializer) into an explicit I(this,"_eventNames") statement placed after super() but before the constructor body assignment this._eventNames = new Set(['click']).

Confirmed in the production bundle (index-CS7X72oT.js:15:79301):

// Inside sN (UserInteractionInstrumentation) constructor:
super(eN,sS,i);          // ← enable() fires here, patches Zone.js with plugin=this
// …
I(this,"_eventNames");   // ← _eventNames = undefined  ← WRONG STATE
this._eventNames=new Set(…);  // ← set correctly, but too late for async Zone tasks

When Zone.js tasks fire asynchronously (React dynamic-import Promise callbacks, click events) between those two lines, _allowEventName calls this._eventNames.has(eventName) and throws. The error propagates to window.onerror, the new handler captures it as a browser.exception span.

Fix

Pass { enabled: false } to the constructor so enable() is not called during super(). Call enable() explicitly after the constructor returns, at which point _eventNames = new Set(['click']) is guaranteed. Zone.js is then patched with the correct state.

registerInstrumentations calls c.getConfig().enabled || c.enable() — since enabled: false, it would call enable() again, but _isEnabled is already true from our explicit call, so it returns immediately with no double-patching.

Impact

Stops 207+ false-positive browser.exception spans per session on the / route. Click-to-fetch trace correlation continues to work correctly after this fix.

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Fixes incident f47626e5-9d9d-4ef7-aed5-cdc22414fce1 (chalky-lynx).

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Summary by cubic

Defer enabling of UserInteractionInstrumentation until after its fields are initialized to prevent _eventNames TypeError. This stops noisy browser.exception spans and keeps click instrumentation working.

• Bug Fixes
  • Instantiate UserInteractionInstrumentation with { enabled: false } and call .enable() after construction, avoiding InstrumentationBase calling enable() in super().
  • Ensures _eventNames is set before Zone.js patches run, fixing the Vite/esbuild class field order issue and removing 200+ exception spans per session.

^{Written for commit ad67b66. Summary will update on new commits.}

[superlog-app]

Observability review

All clear — no observability concerns found.

Keep shipping