Optimize transform-async-to-generator output

[magic-akari]

• remove wrapper if the function length is zero.
• remove wrapper if the assumptions.ignoreFunctionLength is true.

Q	A
Fixed Issues?	Fixes #14121
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

[nicolo-ribaudo]

I know that you didn't write this code but you just moved it from a few lines below, however it's an example of "overusing reduce" and we can probably simplify it since we are touching these lines anyway:

Suggested change

	const params = node.params.reduce(
	(acc, param) => {
	acc.done = acc.done || isAssignmentPattern(param) || isRestElement(param);
	if (!acc.done) {
	acc.params.push(path.scope.generateUidIdentifier("x"));
	}
	return acc;
	},
	{
	params: [],
	done: false,
	},
	).params;
	const params = [];
	for (const param of node.params) {
	if (isAssignmentPattern(param) || isRestElement(param)) break;
	params.push(path.scope.generateUidIdentifier("x"));
	}

[nicolo-ribaudo]

All these functions would have length: 0 anyway: to test the behavior of ignoreFunctionLength, we shuold use functions with .length >= 1.

[magic-akari]

Thanks.
I was writing on the first case and accidentally mixed it up.
I will update this test case.

[nicolo-ribaudo]

There is one more case that we should test:

export default async function (x) {}

The function should still be wrapped, because it is a function declaration and it needs to be hoisted.

Why?

Otherwise this code doesn't work, when a.js is the entrypoint:

// a.js

import x from "./b.js";

x.then(console.log);

export default async function () { return 1 }

// b.js

import f from "./a.js";
export default f();

[magic-akari]

Done. test added.

[nicolo-ribaudo]

Probably we can do it by adding || isFunctionDeclaration(retFunction) here.

[magic-akari]

We don't need to change it.
default export use a different template builder.

The wrapper is in another function.
You can check the test case.

[nicolo-ribaudo]

Oh awesome, thanks for the test!