fix: [#2064] Defensively initialize EventTarget listener maps#2075
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TrevorBurnham wants to merge 1 commit intocapricorn86:masterfrom
Open
fix: [#2064] Defensively initialize EventTarget listener maps#2075TrevorBurnham wants to merge 1 commit intocapricorn86:masterfrom
TrevorBurnham wants to merge 1 commit intocapricorn86:masterfrom
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EventTarget.addEventListener(), removeEventListener(), dispatchEvent(), and destroy() now defensively initialize PropertySymbol.listeners and PropertySymbol.listenerOptions if they are undefined. Class field initializers only run when the constructor executes. If a third-party library creates an object that inherits from EventTarget without calling super() (or attaches listeners before the initializers have run), the internal maps are undefined and every method that accesses them throws a TypeError. The fix adds an ensureListenerMaps() helper that lazily creates the maps on first access, keeping the normal (already-initialized) path as a single falsy check with no allocation. Closes capricorn86#2064
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Fixes #2064
Problem
EventTarget.addEventListener()throws aTypeErrorwhenPropertySymbol.listenersorPropertySymbol.listenerOptionsisundefined:This happens when third-party libraries (e.g. PixiJS) attach event listeners very early in their initialization process, before the class field initializers on
EventTargethave run. Since thelistenersandlistenerOptionsmaps are initialized as class fields, they only exist after the constructor completes. Objects that inherit fromEventTargetwithout callingsuper(), or that interact with the prototype before construction finishes, hitundefined.Fix
Added an
ensureListenerMaps()helper function that lazily initializes both maps if they areundefined. It is called at the entry point of:addEventListener()removeEventListener()#callDispatchEventListeners()(internal, used bydispatchEvent())The
destroy()method also guards againstundefinedwith an early return.On the normal path (maps already initialized), this is a single falsy check with zero allocation.
Test
Added a test that simulates the uninitialized state by constructing an
EventTargetand then forcibly clearing both internal maps toundefined. Verifies thataddEventListener,dispatchEvent, andremoveEventListenerall work without throwing.