After Transformer called with a Bundle, not a Source file

[LucasSloan]

TypeScript Version: 2.9.0-rc

Search Terms: bundle transformer

Code

import * as ts from 'typescript';
import * as path from 'path';

const {cachedLibPath, cachedLib} = (() => {
  const host = ts.createCompilerHost({});
  const fn = host.getDefaultLibFileName({});
  const p = ts.getDefaultLibFilePath({});
  return {
    // Normalize path to fix mixed/wrong directory separators on Windows.
    cachedLibPath: path.normalize(p),
    cachedLib: host.getSourceFile(fn, ts.ScriptTarget.Latest),
  };
})();

const reproTransformer: (context: ts.TransformationContext) => ts.Transformer<ts.SourceFile> =
  (context: ts.TransformationContext): ts.Transformer<ts.SourceFile> => {
    return (sf: ts.SourceFile): ts.SourceFile => {
      console.error(ts.SyntaxKind[sf.kind]);
      return sf;
    }
  }

function createSourceCachingHost(
  sources: Map<string, string>, options: ts.CompilerOptions): ts.CompilerHost {
const host = ts.createCompilerHost({});

host.getSourceFile = (fileName: string, languageVersion: ts.ScriptTarget,
                      onError?: (msg: string) => void): ts.SourceFile|undefined => {
  // Normalize path to fix wrong directory separators on Windows which
  // would break the equality check.
  fileName = path.normalize(fileName);
  if (fileName === cachedLibPath) return cachedLib;
  if (path.isAbsolute(fileName)) fileName = path.relative(process.cwd(), fileName);
  const contents = sources.get(fileName);
  if (contents !== undefined) {
    return ts.createSourceFile(fileName, contents, ts.ScriptTarget.Latest, true);
  }
  throw new Error(
      'unexpected file read of ' + fileName + ' not in ' + Array.from(sources.keys()));
};
const originalFileExists = host.fileExists;
host.fileExists = (fileName: string): boolean => {
  if (path.isAbsolute(fileName)) fileName = path.relative(process.cwd(), fileName);
  if (sources.has(fileName)) {
    return true;
  }
  // Typescript occasionally needs to look on disk for files we don't pass into
  // the program as a source (eg to resolve a module that's in node_modules),
  // but only .ts files explicitly passed in should be findable
  if (/\.ts$/.test(fileName)) {
    return false;
  }
  return originalFileExists.call(host, fileName);
};

return host;
}


function emit(sources: Map<string, string>, options: ts.CompilerOptions) {
  const fileNames = Array.from(sources.keys());
  const tsHost = createSourceCachingHost(sources, options);
  const program = ts.createProgram(fileNames, options, tsHost);

  const tsTransformers: ts.CustomTransformers = {
    after: [reproTransformer],
  }

  program.emit(undefined, undefined, undefined, undefined, tsTransformers);
}

const one_source_file = new Map([['a.ts', 'const x = 1']]);
const two_source_files = new Map([['a.ts', 'const x = 1'], ['b.ts', 'const y = ""']]);

emit(one_source_file, {});
emit(two_source_files, {outFile: 'c.js'});

Expected behavior:
reproTransformer is a scheduled as an after transformer, and the type for ts.CustomTransformers says that it will only ever be called with a SourceFile, so the two emit calls should print out:
SourceFile
SourceFile
SourceFile
Actual behavior:
SourceFile
Bundle

I tested without the outFile flag, and I got the expected behavior, so the issue is to do with the outfile.

[mhegazy]

This seems right to me. with --outFile sourceFiles are "bundled" into a new node. a transformer can perform some transformations on the new file generated by the bundle if it needs to.

[LucasSloan]

Right, my problem is not that the transformer was fed a Bundle, it's that the type of an after transformer doesn't allow for the transformer to be called with a Bundle.

[mhegazy]

ah. sorry about that. we would be happy to take a PR to fix the declarations.

[jakebailey]

#31301 was supposed to close this, but the "Fixes" line was incorrectly written so GitHub didn't do it.