[Autocomplete] "A component is changing the controlled value state to be uncontrolled" error

[p-himik]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

If the list of Autocomplete options is changed when some other than first value is highlighted, pressing Enter will result in the error in the title.

Material-UI: A component is changing the controlled value state of Autocomplete to be uncontrolled.
Elements should not switch from uncontrolled to controlled (or vice versa).
Decide between using a controlled or uncontrolled Autocomplete element for the lifetime of the component.
The nature of the state is determined during the first render, it's considered controlled if the value is not `undefined`.
More info: https://fb.me/react-controlled-components 
    in Autocomplete (created by WithStyles(ForwardRef(Autocomplete)))
    in WithStyles(ForwardRef(Autocomplete)) (at demo.js:44)
    in BrokenAutocomplete (at index.js:6)

Expected Behavior 🤔

There should be no error - you should be able to select any option just fine.

Steps to Reproduce 🕹

1. Go to https://codesandbox.io/s/material-demo-kw16l
2. Put text cursor in the Autocomplete input field that should read "abcf"
3. Delete the character "f". Now the pop-up should display all options
4. Type "f" once again. Now the pop-up should display only the "abcf" option
5. Hit Enter. The input should disappear completely and the console should have the above error

After some debugging, it seems that the root cause is that the selected item index is not recomputed on options change.
Take a look at this dependency list of the relevant effect: https://github.com/mui-org/material-ui/blob/9bd4277ecd660ebe2fd4cb08960f58e98ddb6d43/packages/material-ui-lab/src/useAutocomplete/useAutocomplete.js#L457-L464
As you can see, it only cares about whether there are any options at all and not about the number of options.

Context 🔦

I'm trying to implement a simple autocomplete that loads its options via network.

Your Environment 🌎

Tech	Version
Material-UI	v4.11.0 / v5.0.0-alpha5
Material-UI lab	v4.0.0-alpha56 / v5.0.0-alpha5
React	v16.3.1

[oliviertassinari]

@p-himik This one is tough, it's an issue with the syncHighlightedIndex logic. When the error happens (returning undefined value in onChange), the highlight is on the 3rd option, but there is only 1 displayed because of the fetch in a useEffect.

I don't know what would be the best solution in this case:

1. Force options to be memorized, we can include it in the effect logic, I'm not sure about the implications.
2. Add an API to resync the highlight, similar to resetAfterIndex of https://react-window.now.sh/#/api/VariableSizeList.
3. We add a new effect to guarantees we stay in the possible boundaries.
4. Else?

On a side note, this makes me think of facebook/react#17070, mentioning undefined in the error would help.

[p-himik]

(2) seems very counter-intuitive. Autocomplete is already complicated enough so that it's almost impossible to use it correctly without studying the API documentation and the examples.

(1) was my immediate thought, because it just seems logical. And I don't know about the implications as well. But right now it seems that it's worth pursuing it simply because it's logical. (3) is in the same camp, I'd say it's just implementation details as long as they achieve the same goal and don't change the API.

mentioning undefined in the error would help.

Right, my bad - I've added the error message to the OP.

[oliviertassinari]

@p-himik Cool, do you want to keep exploring the scope of the problem? :)

[p-himik]

To be honest, not really - I'm trying to do my best at avoiding going outside of ClojureScript. Especially when it comes to unfamiliar and complicated components with long history.

[oliviertassinari]

The problem is very close to #22170, we are discussing the solutions possible in https://github.com/mui-org/material-ui/issues/22170#issuecomment-691825640

[oliviertassinari]

Since https://github.com/mui-org/material-ui/issues/22170#issuecomment-691901855 we have a proposal that should, in theory, work. It's up for grab.

[oliviertassinari]

The reproduction is now working correctly on the latest version (v5.0.0-alpha.12): https://codesandbox.io/s/material-demo-forked-t5j4w?file=/demo.js. I don't know when the issue was solved.