Feature request: expose CustomWebpackSchema options to indexTransform #2419

It would be useful if the custom index HTML transform received the active CustomWebpackSchema options in addition to target and indexHtml.

Currently, the transform is called as follows:

return transform(target, indexHtml);

I propose changing it to:

return transform(target, indexHtml, options);

Current behavior

An indexTransform can access:

The Angular builder target
The generated index HTML

However, it cannot directly access the normalized options passed to the custom webpack builder.

Proposed behavior

Update the transform invocation in indexHtmlTransformFactory:

export const indexHtmlTransformFactory: (
  options: CustomWebpackSchema,
  context: BuilderContext
) => IndexHtmlTransform = (options, { workspaceRoot, target, logger }) => {
  if (!options.indexTransform) return null;

  const transformPath = path.join(
    getSystemPath(normalize(workspaceRoot)),
    options.indexTransform
  );
  const tsConfig = path.join(
    getSystemPath(normalize(workspaceRoot)),
    options.tsConfig
  );

  return async (indexHtml: string) => {
    const transform = await loadModule<IndexHtmlTransformWithOptions>(
      transformPath,
      tsConfig,
      logger
    );

    return transform(target, indexHtml, options);
  };
};

Use case

My index transform needs to generate different HTML depending on the active custom webpack builder options.

Backward compatibility

This change should be backward-compatible at runtime because existing transforms can continue accepting only two arguments:

The additional argument will simply be ignored by existing JavaScript functions.

Making the third TypeScript parameter optional would also help preserve compatibility for existing typed transforms.

I would like to request this enhancement specifically for the release/v22 branch