Add support for --noEmitUnderscoreUnderscoreESModule flag

[johnsoncodehk]

The '__esModule' is a standard for CommonJS, but forcing the emit '__esModule' does cause problems for many users.

Issues: #30718 #30166 #22879 #15795 #15685 #14351 #13709 (comment)

For me, I have a script that converts the CommonJS code into a baas cloud code, but the Typescript API has no way to remove '__esModule', I can only do replace string of this code:

Object.defineProperty(exports, "__esModule", { value: true });

But this is not safe, I am not sure if Typescript will change this code in the future:

[typescript-bot]

Thanks for the PR! It looks like you've changed the TSServer protocol in some way. Please ensure that any changes here don't break consumers of the current TSServer API. For some extra review, we'll ping @sheetalkamat, @amcasey, @mjbvz, @minestarks for you. Feel free to loop in other consumers/maintainers if necessary

[msftclas]

All CLA requirements met.

[YoungNovice]

good

[gavar]

any updates on that?

[RyanCavanaugh]

Which issue is approved to take a PR (i.e. is in the Backlog milestone) ?

[johnsoncodehk]

This problem may never be concerned about.
But here is a quick fix:
Search and replace all !currentModuleInfo.exportEquals to false under TYPESCRIPT_DIR/lib/

[RyanCavanaugh]

We need an approved issue for a PR to be looked at, but there doesn't appear to be one.

Logged #32934 as the typeof check seems reasonable

[bdero]

I'm using Typescript in an embedded V8 context, and the engine does not assign exports automatically. Instead it only populates module.exports.

In my case, my code is not intended to run in any other JavaScript environment, so as a quick and dirty hack to delete these lines in the meantime, I'm using the tsc-watch tool to fire a script after successful watch builds in order to automatically delete the lines.

package.json scripts:

  "scripts": {
    "watch": "sh node_modules/.bin/tsc-watch --onSuccess 'npm run patchTSOutput'",
    "patchTSOutput": "find . -path ./node_modules -prune -o -print | grep \\.js$ | xargs -n 1 ex '+g/^Object\\.defineProperty(exports,/d' -cwq"
  },

Just thought I'd share for other onlookers in the same situation. If you're running into this problem and you want to target many JavaScript environments, you'd probably be better off inserting undefined guards instead (similar to the suggestion in #32934).

[Reality2byte]

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