Fix t.arrowFunctionExpression and t.functionExpression builders by adding all fields

[deificx]

Q	A
Fixed Issues?	Fixes #12319
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link	N/A
Any Dependency Changes?	No
License	MIT

This fix adds the additional fields to the builder arrays for the definitions.
However, this does feel like a workaround, I also found this bug to apply to assignmentPattern, and there are probably more.
It looks like defineType in utils.js makes sure to add both builder and visitor fields to a node while the builder function in builder.js only checks the builder values.

Somewhat unrelated, but I can't figure out how to add types to function parameters.
t.tsParameterProperty looks like the wrong type to me, it looks like something you'd add to a class (ie: readonly property = "value").
The closest thing I can find for this is t.tsPropertySignature, but that looks like some thing for an interface (ie: key: type; note the trailing ;).

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[deificx]

I force pushed as I was branching from master, rebased from main and now I've broken a bunch of tests. So adding these properties to builder in definition is probably not the correct solution.

[deificx]

To answer my side note I guess t.identifier could be used, as that has a typeAnnotation, but t.identifier() only accepts 1 argument. And when trying to manually build it generator doesn't seem to do anything with it.

const g = require("@babel/generator").default;

console.log(
  g({
    name: "foo",
    optional: true,
    type: "Identifier",
    typeAnnotation: {
      type: "TSTypeAnnotation",
      typeAnnotation: {
        type: "TSStringKeyword",
      },
    },
  }).code
); // foo

I would expect something like foo?: string

[nicolo-ribaudo]

@deificx As you may have noticed, we don't provide builder parameters for types in JS nodes. We only support parameters for JavaScript syntax and for JavaScript proposal.
If we started adding params for type annotations, we would have to somehow support both TS and Flow features at the same time.

The recommended way of achieving what you need is this:

Object.assign(t.arrowFunctionExpression(params, body, async), {
  returnType: yourReturnTypeNode,
});

Object.assign(t.identifier("foo"), {
  typeAnnotation: t.tsTypeAnnotation(t.tsStringKeyword())
});

[deificx]

...we don't provide builder parameters for types in JS nodes.

It looks like you used to, ie. identifier:

typeAnnotation: TypeAnnotation | TSTypeAnnotation | Noop (default: null)

Or is TypeAnnotation not the same as a FlowType?

Adding a more complete example here, mostly for my understanding, identifier with type annotation must be used in parameters for it to print the type annotation, because by itself it would only print the identifier:

const g = require("@babel/generator").default;
const t = require("@babel/types");

console.log(
  g({
    ...t.arrowFunctionExpression(
      [
        {
          ...t.identifier("foo"),
          typeAnnotation: t.tsTypeAnnotation(t.tsStringKeyword()),
        },
        {
          ...t.identifier("bar"),
          typeAnnotation: t.tsTypeAnnotation(t.tsBooleanKeyword()),
        },
      ],
      t.stringLiteral("")
    ),
    returnType: t.tsTypeAnnotation(t.tsStringKeyword()),
  }).code
); // (foo: string, bar: boolean): string => ""

[nicolo-ribaudo]

The recommended way is what is shown in #12334 (comment).

Thanks for opening the PR anyway, it's always good to check if old team decisions are still valid 🙏

Btw, you might also be interested in #9545.