[Codegen] feat: handle negative values in enums

[okwasniewski]

Summary:

This PR adds support for negative values in enums.

Currently when we try to use an enum with negative value:

enum MyEnum {
  ZERO = 0,
  POSITIVE = 1,
  NEGATIVE = -1,
}

export interface Spec extends TurboModule {
  useArg(arg: MyEnum): void;
}

export default TurboModuleRegistry.get<Spec>('Foo');

It will fail:

Enum values can not be mixed. They all must be either blank, number, or string values.

This is because negative values are parsed as UnaryExpressions which have - operator in front and value as argument.

With the new approach codegen properly generates enums with negative values.

Changelog:

[GENERAL] [ADDED] - Support negative values in enums

Test Plan:

I've added tests to see if everything is working properly

[elicwhite]

Ah, yep, this is definitely something that needs to be supported.

You'll need to add support for this to Flow too.

Please add an example that exercises this code path to the parser fixture file here: https://github.com/facebook/react-native/blob/main/packages/react-native-codegen/src/parsers/typescript/modules/__test_fixtures__/fixtures.js

You'll also need to modify the same fixture in the same way for Flow here: https://github.com/facebook/react-native/blob/main/packages/react-native-codegen/src/parsers/flow/modules/__test_fixtures__/fixtures.js

the fixtures should stay in sync between Flow and TypeScript.

Also, since unary types aren't just negative, can you add a case to the failure fixture file in the same directory for something to exercise the failure case, like

enum Foo {
  BAD = !4
}

[elicwhite]

Can you leave a comment explaining this case, because it's very very strange to see undefined as a case in a switch. It's almost worth pulling it out into its own if statement above the switch.

[okwasniewski]

Fixed, I've extracted this to a separate if statement above the switch

[okwasniewski]

@elicwhite Thanks for your review! I applied your suggestions and added test cases for both Flow and Typescript.

Looks like Flow handles this case without any changes. Let me know if I should fix anything else

[elicwhite]

Thanks for making the changes!

I think this is the last thing before I will import.

[facebook-github-bot]

@elicwhite has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@elicwhite merged this pull request in 177bf4d.

[react-native-bot]

This pull request was successfully merged by @okwasniewski in 177bf4d

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