Javascript Exception: TypeError: Cannot read property 'length' of undefined

[sentry-io[bot]]

Sentry Issue: WORDPRESS-IOS-47HS

Symbolicated Stack Trace

This error is located at:
    in Unknown
    in WithSelect(WithDispatch(f))
    in RCTSafeAreaVi..., stack:
/workdir/gutenberg/packages/editor/src/store/selectors.js:540:<anonymous>
/workdir/gutenberg/packages/data/src/factory.js:52:wrappedSelector
/workdir/gutenberg/packages/editor/src/store/selectors.js:505:isEditedPostSaveable
/workdir/gutenberg/packages/editor/src/store/selectors.native.js:39:<anonymous>
/workdir/gutenberg/packages/data/src/factory.js:52:wrappedSelector
/workdir/gutenberg/packages/data/src/redux-store/index.js:240:boundSelector
/workdir/gutenberg/packages/editor/src/components/autosave-monitor/index.js:110:withSelect$argument_0
/workdir/gutenberg/packages/data/src/components/with-select/index.js:58:mapSelect
/workdir/gutenberg/packages/data/src/components/use-select/index.js:154:registry.__unstableMarkListeningStores$argument_0
/workdir/gutenberg/packages/data/src/registry.js:123:__unstableMarkListeningStores
/workdir/gutenberg/packages/data/src/registry.js:204:<anonymous>
/workdir/gutenberg/packages/data/src/components/use-select/index.js:153:updateValue
/workdir/gutenberg/packages/data/src/components/use-select/index.js:203:<anonymous>
/workdir/gutenberg/packages/data/src/components/use-select/index.js:228:useMappingSelect
/workdir/gutenberg/packages/data/src/components/use-select/index.js:317:useSelect
/workdir/gutenberg/packages/data/src/components/with-select/index.js:59:pure$argument_0
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:3525:renderWithHooks
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:4491:updateFunctionComponent
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:7850:beginWork$1
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:7304:performUnitOfWork
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:7297:workLoopSync
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:7279:renderRootSync
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:6975:performSyncWorkOnRoot
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:2145:flushSyncCallbacks
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:6650:scheduleUpdateOnFiber
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:3767:forceStoreRerender
/workdir/gutenberg/node_modules/react-native/Libraries/Renderer/implementations/ReactNativeRenderer-prod.js:3752:subscribe$argument_0
/workdir/gutenberg/packages/data/src/components/use-select/index.js:89:onStoreChange
/workdir/gutenberg/packages/data/src/components/use-select/index.js:96:onChange
/workdir/gutenberg/packages/data/src/registry.js:247:currentSubscribe$argument_0
/workdir/gutenberg/packages/data/src/redux-store/index.js:351:store.subscribe$argument_0
/workdir/gutenberg/node_modules/redux/lib/redux.js:304:dispatch
/workdir/gutenberg/packages/data/src/redux-store/thunk-middleware.js:7:<anonymous>
/workdir/gutenberg/packages/redux-routine/src/index.js:24:<anonymous>
/workdir/gutenberg/packages/data/src/promise-middleware.js:20:<anonymous>
/workdir/gutenberg/packages/data/src/resolvers-cache-middleware.js:45:<anonymous>
/workdir/gutenberg/packages/data/src/redux-store/index.js:224:Proxy$argument_1.apply
/workdir/gutenberg/packages/core-data/src/actions.js:446:<anonymous>
/workdir/gutenberg/packages/data/src/redux-store/thunk-middleware.js:4:<anonymous>
/workdir/gutenberg/packages/redux-routine/src/index.js:24:<anonymous>
/workdir/gutenberg/packages/data/src/promise-middleware.js:20:<anonymous>
/workdir/gutenberg/packages/data/src/resolvers-cache-middleware.js:45:<anonymous>
/workdir/gutenberg/packages/data/src/redux-store/index.js:204:<anonymous>
/workdir/gutenberg/packages/editor/src/store/actions.js:363:<anonymous>
/workdir/gutenberg/packages/data/src/redux-store/thunk-middleware.js:4:<anonymous>
/workdir/gutenberg/packages/redux-routine/src/index.js:24:<anonymous>
/workdir/gutenberg/packages/data/src/promise-middleware.js:20:<anonymous>
/workdir/gutenberg/packages/data/src/resolvers-cache-middleware.js:45:<anonymous>
/workdir/gutenberg/packages/data/src/redux-store/index.js:204:<anonymous>
/workdir/gutenberg/packages/data/src/components/use-dispatch/use-dispatch-with-map.js:53:<anonymous>
/workdir/gutenberg/node_modules/react-native/Libraries/vendor/emitter/EventEmitter.js:105:emit
/workdir/gutenberg/node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:427:__callFunction
/workdir/gutenberg/node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:113:__guard$argument_0
/workdir/gutenberg/node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:368:__guard
/workdir/gutenberg/node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:112:callFunctionReturnFlushedQueue

Raw stack trace:

``` RCTFatalException: Unhandled JS Exception: TypeError: Cannot read property 'length' of undefined This error is located at: in Unknown in WithSelect(WithDispatch(f)) in RCTSafeAreaView in RCTView in Unknown in Unknown in _ ...: Unhandled JS Exception: TypeError: Cannot read property 'length' of undefined This error is located at: in Unknown in WithSelect(WithDispatch(f)) in RCTSafeAreaVi..., stack: anonymous@1:3864753 s@1:1638058 V@1:3861414 anonymous@1:3858150 s@1:1638058 o@1:1616319 anonymous@1:3938767 anonymous@1:1648165 anonymous@1:1649007 __unstableMarkListeningStores@1:1611211 anonymous@1:1611414 M@1:1648740 anonymous@1:1648648 b@1:1649689 anonymous@1:1649831 anonymous@1:1648096 Or@1:387360 Ol@1:393601 Ma@1:427604 zi@1:414609 Ri@1:414511 Pi@1:414395 ki@1:411895 xt@1:377020 hi@1:409372 nl@1:389264 anonymous@1:389158 c@1:1649285 o@1:1649310 anonymous@1:1610140 anonymous@1:1617138 b@1:1620217 anonymous@1:1639904 anonymous@1:1623257 anonymous@1:1639195 anonymous@1:1639494 apply@1:1616662 anonymous@1:3260023 anonymous@1:1639920 anonymous@1:1623257 anonymous@1:1639195 anonymous@1:1639494 anonymous@1:1616059 anonymous@1:3932520 anonymous@1:1639920 anonymous@1:1623257 anonymous@1:1639195 anonymous@1:1639494 anonymous@1:1616059 anonymous@1:1654436 value@1:167672 value@1:171857 anonymous@1:170357 value@1:171303 value@1:170315 ?, in RCTFatal ?, in -[RCTExceptionsManager reportFatal:stack:exceptionId:extraDataAsJSON:] ?, in -[RCTExceptionsManager reportException:] ?, in -[RCTModuleMethod invokeWithBridge:module:arguments:] ?, in facebook::react::invokeInner ... (14 additional frame(s) were not displayed) ```

[fluiddot]

Based on the breadcrumbs of the Sentry event, I saw that right before the crash the user tapped on editor-undo-button. I wonder if the error is related to the undo/redo logic.

[derekblank]

I wonder if the error is related to the undo/redo logic.

This is plausible, as the stack trace points to the store selectors logic. However, on the line the symbolicated stack trace references, there is no property length:

if ( typeof record.content !== 'function' ) {
    return ! record.content;
}

@fluiddot Could you verify that the stack trace was symbolicated correctly and you produce the same symbolication result? I symbolicated it against iOS and v1.111.2.

Also nothing that there is still only one report of this issue.

[fluiddot]

@fluiddot Could you verify that the stack trace was symbolicated correctly and you produce the same symbolication result? I symbolicated it against iOS and v1.111.2.

@derekblank The symbolization seems correct. The line referenced in the first entry points to access to the length property. You'd need to check the source code in the context of the GB version 1.111.2:

https://github.com/WordPress/gutenberg/blob/rnmobile/1.111.2/packages/editor/src/store/selectors.js#L540

This is the code that seems producing the crash in the selector isEditedPostEmpty:

if ( blocks.length === 0 ) {
    return true;
}

[derekblank]

You'd need to check the source code in the context of the GB version 1.111.2

Yep, makes sense. I was checking trunk. 🤦 Thanks for confirming!