Deno.emit() not respecting compilerOptions.target when use with bundle:esm

[yw662]

The code to compile :

export class A {
    static a = 'b'
}

Static member should be compiled into A.a = 'b' if targeting lower versions.

The code calling Deno.emit:

#! /usr/bin/env deno run -A --unstable
const sources = {
  '/foo.ts': `
        export class A {
            static a = 'b'
        }
        `
}
console.log(
  '\nno bundling:\n',
  (await Deno.emit('/foo.ts', { sources })).files['file:///foo.ts.js'],
  '\nbundle:esm:\n',
  (await Deno.emit('/foo.ts', { sources, bundle: 'esm' })).files[
    'deno:///bundle.js'
  ],
  '\nbundle:esm, target:es6:\n',
  (
    await Deno.emit('/foo.ts', {
      sources,
      bundle: 'esm',
      compilerOptions: { target: 'es6' }
    })
  ).files['deno:///bundle.js']
)

The output:

no bundling:
 export class A {
}
A.a = 'b';
 

bundle:esm:
 class A1 {
    static a = 'b';
}
export { A1 as A };
 

bundle:esm, target:es6:
 class A1 {
    static a = 'b';
}
export { A1 as A };

The behavior of bundle:esm, target:es6 is incorrect, static a = 'b' should be compiled into A.a = 'b', but actually not.

[yw662]

I found a work around for that, which I would call "double emit":

const sources = {
  '/foo.ts': `
        export class A {
            static a = 'b'
        }
        `
}
Deno.emit('/foo.ts', {
  sources,
  bundle: 'esm',
  compilerOptions: { target: 'es6' }
})
  .then(result => result.files['deno:///bundle.js'])
  .then(src =>
    Deno.emit('/src.js', {
      sources: {
        '/src.js': src
      },
      compilerOptions: { target: 'es6' }
    })
  )
  .then(result => result.files['file:///src.js.js'])
  .then(src => console.log(src))

This may not be efficient but can be use as a workaround.

[yw662]

This issue still exists in deno 1.10.2. compilerOptions.target still does not work with bundle:module.

[kitsonk]

That is why the issue isn't closed.

[dgreensp]

Same with "bundle": "classic", FWIW. I'm grateful for the workaround. I wonder if this renders source maps worthless (I haven't gotten them working yet).

[KnorpelSenf]

The workaround did not work for me (Deno 1.16.3). The transpilation was skipped.

I could fix it by using /src.ts instead of /src.js as the intermediate file name. New workaround:

const source = "/path/or/url/to/mod.ts";
// bundling
const bundled = await Deno.emit(source, { bundle: "module" });
const bundledCode = bundled.files["deno:///bundle.js"];
// transpilation
const transpiled = await Deno.emit("/src.ts", {
    sources: { "/src.ts": bundledCode },
    compilerOptions: { target: "es6" },
});
const transpiledCode = transpiled.files["file:///src.ts.js"];
// write output file
await Deno.writeTextFile("/tmp/bundle.js", out);

[johnspurlock]

Just ran into this issue on deno 1.18.2

The workaround from @KnorpelSenf worked for me - but it would be excellent if it wasn't needed