es6 modules without imports or nontrivial exports compile to ambiguous output

[dgoldstein0]

TypeScript Version: 3.2.2

Search Terms:
ambiguous es6 modules

Code

// asdf.ts
export {};

compile with tsc --module ES6 asdf.ts

Expected behavior:

compiles to something that is obviously a module, e.g. preserves the export {}.

Actual behavior:

output is an empty file which could be a script instead of a module.

This causes issues in complex build pipelines - e.g. if we then try to put the output through tsc --module amd, the output differs from if we had only done tsc --module amd in the first place.

Playground Link: http://www.typescriptlang.org/play/#src=export%20%7B%20%7D%3B

I can't get es6 output in the playground for this

Related Issues: n/a

[weswigham]

I agree, if --module es6 is set, we aughta be preserving export {};.

[dgoldstein0]

this probably deserves a Domain: ES Modules tag? don't know how to add that

[BPScott]

Fixed in #38696