feat: Don't require defaultProps for function components

[bradenmacdonald]

I think react/require-default-props is an annoying rule in TSX files, as often it's perfectly fine to have undefined as the default value of a prop, and TypeScript already forces you to handle it accordingly in your component implementation.

But eslint currently wants us to add a default value for no reason. See example below, where eslint complains that three of the props lack defaults, even though 2 have a default and the third makes sense to have no default.

In this example, we don't need onToggleChildren to have a default value of an empty function, because TypeScript will make sure we call it as onToggleChildren?.(path); to handle the case where it's undefined. Or the author may choose to add a default, but in any case there's no errors nor incorrect code resulting from a missing default, so I don't believe the eslint rule is providing any value at all.

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[adamstankiewicz]

Definitely in favor of disabling/modifying this rule, especially as we adopt more TypeScript stuff. Though, I do wonder if it's worth disabling the rule for both .jsx and .tsx, given defaultProps for functions are technically deprecated and are expected to be removed in React 19. Non-TypeScript files could also probably incrementally start migrating to ES6 default function parameters today as well.

If we were to disable the rule across all .jsx and .tsx files now, would this config be moved under the rules property instead of overrides?

---

[suggestion] Also, I wonder if it'd be worth considering whether to modify the rule versus disabling it altogether. For example, I imagine we might still want linting on missing defaultProps for any class components that might still exist (where ES6 default function params aren't applicable?). Similarly, there is a rule option (i.e., functions) for changing the expected strategy for defaulting props; by default, it is defaultProps but could be changed to defaultArguments instead (see docs). Changing the functions option to defaultArguments seems like it might be preferable versus disabling the rule altogether? 🤔

[bradenmacdonald]

I'd love to just disable the rule altogether.

As for changing to defaultArguments, that's fine with me but I think it would cause way too many warnings/errors with existing code which is written using defaultProps (unless that's what you want, to force a big migration).

I'd still prefer to disable it altogether in TypeScript files, because I often write code like this (real example), which I think is perfectly fine:

const SearchUI: React.FC<{ courseId?: string, closeSearchModal?: () => void }> = (props) => {
  ...

and yet with defaultArguments on, eslint wants me to write it much more verbosely as:

const SearchUI: React.FC<{ courseId?: string, closeSearchModal?: () => void }> = ({
  courseId = undefined,
  closeSearchModal = undefined,
}) => {
  ...

[bradenmacdonald]

@adamstankiewicz Would you like me to update this to just disable the rule altogether? (for JSX and TSX)

[bradenmacdonald]

@adamstankiewicz I updated this to not required defaultProps for function components in general, and added a comment explaining why it's deprecated.

I'd love to change the rule to also require defaultArguments but I'm not sure how to roll that out without requiring major changes of existing code, so I think this is the best incremental improvement.

Could you please take a look and approve if it's good with you?

[adamstankiewicz]

@bradenmacdonald I will take a look later this evening!

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