fix(js): support private methods and static blocks in babel preset (#36218)

## Current Behavior

The `@nx/js/babel` preset loads
`@babel/plugin-transform-class-properties` on its own. That plugin runs
babel's shared class-features transform, which hard-errors on `#private`
methods and `static {}` blocks unless their companion transforms are
also loaded. When babel-jest transforms an ESM-only dependency that uses
this syntax (un-ignored through `transformIgnorePatterns`, the
documented way to consume ESM-only packages), the transform fails:

```
SyntaxError: Class private methods are not enabled. Please add `@babel/plugin-transform-private-methods` to your configuration.
```

## Expected Behavior

The preset transforms private methods, `#private in obj` checks, and
static blocks instead of erroring. It now loads the companion
class-features transforms next to `class-properties`: `private-methods`
and `private-property-in-object` with the same `loose` setting (babel
requires `loose` to match across the three), plus `class-static-block`.
This clears the whole family of "not enabled" hard-errors, not just
private methods. A regression test covering the affected syntax is
added.

## Related Issue(s)

Fixes #36205

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Author: leosvelperez

packages/js/babel.spec.ts

@@ -0,0 +1,36 @@
+import { transformSync } from '@babel/core';
+
+describe('@nx/js/babel preset', () => {
+  // Regression for https://github.com/nrwl/nx/issues/36205: the class-properties
+  // plugin shares @babel/helper-create-class-features-plugin, which hard-errors on
+  // private methods and static blocks unless their transforms are also loaded. This
+  // surfaces when an ESM-only dep using that syntax is transformed via a
+  // transformIgnorePatterns exception.
+  it('does not error on private methods, static blocks, or "#private in obj" checks', () => {
+    const code = [
+      'class Container {',
+      '  static registry = new Map<string, boolean>();',
+      '  static {',
+      "    Container.registry.set('init', true);",
+      '  }',
+      '  #buildAutobindOptions(autobind: boolean, defaultScope: string) {',
+      '    return autobind ? { scope: defaultScope } : undefined;',
+      '  }',
+      '  has() {',
+      '    return #buildAutobindOptions in this;',
+      '  }',
+      '}',
+    ].join('\n');
+
+    const result = transformSync(code, {
+      babelrc: false,
+      configFile: false,
+      filename: 'container.ts',
+      presets: [require.resolve('./babel')],
+    });
+
+    expect(result?.code).toBeTruthy();
+    // Private members are transformed away rather than left to error.
+    expect(result?.code).not.toContain('#buildAutobindOptions');
+  });
+});

packages/js/babel.ts

@@ -70,6 +70,17 @@ module.exports = function (api: any, options: NxWebBabelPresetOptions = {}) {
       options.decorators ?? { legacy: true },
     ],
     [require.resolve('@babel/plugin-transform-class-properties'), { loose }],
+    // class-properties runs babel's shared class-features plugin, which hard-errors
+    // on private methods and static blocks unless their transforms are loaded too.
+    // This bites when an ESM-only dep using that syntax is transformed (un-ignored
+    // via transformIgnorePatterns). private-property-in-object completes babel's
+    // loose-consistency trio so `loose` stays uniform across the class-features transforms.
+    [require.resolve('@babel/plugin-transform-private-methods'), { loose }],
+    [
+      require.resolve('@babel/plugin-transform-private-property-in-object'),
+      { loose },
+    ],
+    require.resolve('@babel/plugin-transform-class-static-block'),
   ].filter(Boolean);
 
   return {

packages/js/package.json

@@ -123,6 +123,9 @@
     "@babel/core": "catalog:",
     "@babel/plugin-proposal-decorators": "^7.22.7",
     "@babel/plugin-transform-class-properties": "^7.22.5",
+    "@babel/plugin-transform-class-static-block": "^7.22.5",
+    "@babel/plugin-transform-private-methods": "^7.22.5",
+    "@babel/plugin-transform-private-property-in-object": "^7.22.5",
     "@babel/plugin-transform-runtime": "^7.23.2",
     "@babel/preset-env": "^7.23.2",
     "@babel/preset-typescript": "^7.22.5",