Simplify helper dependencies

[JLHwung]

Q	A
Fixed Issues?	Fixes #15765
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

In this PR we simplify the helper dependencies by replacing imports from @babel/types, @babel/template and @babel/traverse to a peer dependent @babel/core. It probably also fixes #15765 but we will need confirmation once the proposed changes are published.

Possible story on #15765:

Given node_modules layouts as followed. Here dotted link means the start point has declared dependency on the end point, and solid link means the start point has a folder named the end point.

graph TD;
    A[node_modules]-->B["@babel/traverse@7.16"];
    A-->C["@babel/types@7.16"];
    A-->F["@babel/core@7.16"];
    F -.-> C
    F -.-> B
    A-->ECH["ember-composable-helpers@5"]
    ECH-.->D
    ECH-.-> F
    A-->D["ember-cli-babel@7"];
    D-.-> F
    D-.-> I
    D-->E[node_modules];
    E-->G["@babel/traverse@7.22.8"];
    E-->H["@babel/types@7.22"];
    E-->I["@babel/preset-env@7.22"]
    I -.-> BTC
    E-->BTC["@babel/plugin-transform-classes@7.22"]
    BTC-.->BRS
    E-->BRS["@babel/helper-replace-supers@7.22"]
    BRS-.-> G
    G -.-> H

The helper-replace-supers calls traverse.visitors.merge from @babel/traverse to merge the environment visitor with a visitor hooking on the Scopeable alias .

babel/packages/babel-helper-replace-supers/src/index.ts

Lines 80 to 93 in 30ff3ac

	const unshadowSuperBindingVisitor = traverse.visitors.merge<{
	refName: string;
	}>([
	environmentVisitor,
	{
	Scopable(path, { refName }) {
	// https://github.com/Zzzen/babel/pull/1#pullrequestreview-564833183
	const binding = path.scope.getOwnBinding(refName);
	if (binding && binding.identifier.name === refName) {
	path.scope.rename(refName);
	}
	},
	},
	]);

After #15702 is merged in @babel/traverse@7.22.8, visitors.merge will explode the alias into node types. Here Scopeable is expanded to ClassAccessorProperty and other AST nodes according to the latest @babel/types definition. At this time the visitor is not executed.

Now when the visitor is eventually invoked by ember-cli-babel, the root @babel/traverse is backed by an older version of @babel/types, which does not recognize ClassAccessorProperty and therefore an error is thrown.

So in this PR we replace all traverse usage with peer dependencies of @babel/core. It should at least alleviate the situation of duplicated libraries.

For end users, the best solution is still to deduplicate @babel/types instances in node_modules: It is more memory efficient and less prone to compatibility issues like this.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/54843/

[liuxingbaoyu]

CI errors seem to be related?

[JLHwung]

Yes, CI error is related, I will investigate tomorrow.
CI is green again, 🤟

[nicolo-ribaudo]

When I tried to this in the past, I had problems with ESM and cycles.

i.e. if you have these files:

// @babel/core
export { x } from "@babel/helper-1";
export { y } from "@babel/helper-2";

// @babel/helper-1
import { y } from "@babel/core";
export let x = 1 + x;

// @babel/helper-2
export let y = 2;

it fails because y is in TDZ when evaluating @babel/helper-1, even if @babel/helper-2 is a transitive dependency of @babel/helper-1. I talked about this problem with some TC39 delegates that worked on the original ESM design, but it's very unlikely that the evaluation order will ever be changed.

[nicolo-ribaudo]

Note: I'm also exploring a fix that doesn't rely on the shape of the dependencies tree.

[nicolo-ribaudo]

Releasing this, hoping to fix the regression.