PropTypes.array and PropTypes.arrayOf handling with null

[alexandesigner]

• 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 😯

When filtering an item that does not exist in the list (options), it is returning null and the .filter method is broken

Expected Behavior 🤔

The ideal would be to check if there are options and if it is an array if it is not going to return an empty array.

Steps to Reproduce 🕹

if you want to reproduce it directly, just go to https://carhoo.com.br/comprar and look for an item when filling out automatic or simple reproduction ... See https://codesandbox.io/s/tender-breeze-gj3zr

Your Environment 🌎

Tech	Version
Material-UI	v4.9.2
React	v16.10.2
Browser	Chrome

[oliviertassinari]

Please provide a full reproduction test case. This would help a lot 👷 .
A live example would be perfect. This codesandbox.io template may be a good starting point. Thank you!

[alexandesigner]

@oliviertassinari Thanks for the feedback, I'll try to create this reproduction in the codesandbox, however, I provide the link to my production application where the error is occurring.

[alexandesigner]

The problem is when the list return is null in my suggestion and the agent just does this little check, maybe I can handle the side of my application however, it would be nice if we could avoid this behavior.

See https://codesandbox.io/s/tender-breeze-gj3zr

[oliviertassinari]

@alexandesigner Thanks. I could reproduce the same issue with react-select: https://codesandbox.io/s/react-codesandboxer-example-y2rwr

However, I'm surprised they are no prop-types warnings. null is compatible with PropTypes.array and PropTypes.arrayOf. I see two good options:

1. We patch prop-types to report a warning.
2. We accept null. I have looked at the codebase, we have very few cases like this one (3 exactly).
   Autocomplete.options, TreeView.expanded, TablePagination.rowsPerPageOptions,

In any case, the tradeoff is close to #17480. I think that I would be in favor of not crashing here (2.) nor in #17480. A crash forces the developer to solve the issue immediately, while he might prefer to work solve another issue first, and later come back to the warning.

cc @mui-org/core

[eps1lon]

prop-types handling of is required is not ideal but the way the eco-system is set up. With TypeScript you'd already wouldn't pass the type checker. I'd stick with the current behavior to not cause too much confusion. Leveraging default assignments with undefined is a lot easier than having custom default handlers for nullish values.

[oliviertassinari]

@eps1lon So we give the same answer than #17480 (we close + waiting for upvotes)?

[eps1lon]

Yeah. Since this is the lab I would honestly reconsider making it optional. It doesn't make sense to not set it anyway. If the list is empty (because you're loading) your can default to an empty array.

Makes the type-checker, prop-types and the implementation happy.

Unless there is an actual use case for <Autocomplete /> that never receives options.

[oliviertassinari]

@alexandesigner What about we make the options required?