Bug on Dropdown.componentWillUnmount()

[MeXaaR]

Simple bug on every component dependants on Dropdown (FormSelect, Select, etc...)
it happens since the last update

Error: Cannot read property '_bound' of undefined
TypeError: Cannot read property '_bound' of undefined
    at EventStack._unlisten (modules.js:47055)
    at EventStack.unsub (modules.js:47083)
    at Dropdown.componentWillUnmount (modules.js:48677)
    at modules.js:20397
    at measureLifeCyclePerf (modules.js:20064)
    at ReactCompositeComponentWrapper.unmountComponent (modules.js:20396)
    at Object.unmountComponent (modules.js:13040)
    at ReactCompositeComponentWrapper.unmountComponent (modules.js:20406)
    at Object.unmountComponent (modules.js:13040)

anybody has the same issue ?

[levithomason]

I have not, but this may be related to #2117. It is being released now as 0.74.2. Let's see if it fixes it.

[levithomason]

@MeXaaR please try the latest release, 0.74.2, and let us know if you're still seeing this bug.

[MeXaaR]

Thanks guys, it work fine now

Great fix

[ewiechowicz]

@levithomason I'm still seeing this on 0.74.2 and 0.75.1. Please see the trace below:

Error: Cannot read property '_bound' of undefined
TypeError: Cannot read property '_bound' of undefined
    at EventTarget._unlisten (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:91254:18)
    at EventTarget.unsub (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:91282:11)
    at EventStack.unsub (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:91125:19)
    at Dropdown.componentWillUnmount (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:99245:23)
    at http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:39978:25
    at measureLifeCyclePerf (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:39645:12)
    at ReactCompositeComponentWrapper.unmountComponent (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:39977:11)
    at Object.unmountComponent (http://localhost:3000/packages/modules.js?hash=0051c69b4aad0f180713cf5acfcf13ef81b7be36:32715:22)
    at Object.obj.(anonymous function) [as unmountComponent] (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/backend.js:8598:20)

As a workaround I disabled componentWillMount:

import {
  Dropdown as BaseDropdown,
} from 'semantic-ui-react';

class Dropdown extends BaseDropdown {
  componentWillUnmount() {
    // don't call the buggy code
    // See datails at https://github.com/Semantic-Org/Semantic-UI-React/issues/2120
  }
}

[layershifter]

Please fill our issue template, we need the reproduction case and its example on the codesandbox. We will reopen the issue once we will have it.

[mhagmajer]

+1

@layershifter can you work out the issue from the stack trace she provided? Seems like undefined reference kind of thing...

[layershifter]

@mhagmajer Make codepen on sandbox and describe how we can reproduce it.

[mhagmajer]

@layershifter Despite my best effort, I wasn't able to isolate a clean example of this issue. However, I was able to pin down the bug in code:

Semantic-UI-React/src/lib/eventStack/EventTarget.js

Line 46 in 40e2368

this.target.removeEventListener(name, handler)

The line above causes error if handler is undefined (probably introduced in #1733). I propose to check if handler is defined before attempting to remove it.

[levithomason]

What browser is this happening in? I'm unable to reproduce the issue. We also have passing tests that remove handlers multiple times. This covers removing undefined handlers.

can you work out the issue from the stack trace she provided? Seems like undefined reference kind of thing...

Not in this case, the error occurs in removeEventListener which is a browser function, not our code. The thing is, this browser method also handles undefined handlers without throwing:

Without a reproduction case, we cannot tell why this is happening. The proposed PR will only prevent the above workflows, removing an undefined handler. However, as I've shown, this is not the problem.

Please submit a reproduction and we can help.