Nested comments aren't emitted correctly

[jam13]

🐛 bug report

I've been testing nightly builds in order to make use of some updates that aren't in 2.0.0-beta.1, and been having build problems. They occur when trying to bundle the typescript monaco worker (all other workers build fine) as outlined here:

https://github.com/microsoft/monaco-editor/blob/master/docs/integrate-esm.md#using-parcel

When building, it fails at the optimise step due to the js from the previous step containing a syntax error.

This works fine on beta.1, and I've narrowed it down to 2.0.0-nightly.522 which has the following two commits on top of 520:

• e183e32
• 601bcbd

If I disable minification then the build succeeds, but the js contains the syntax error.

🎛 Configuration (.babelrc, package.json, cli command)

I can reproduce with the default parcel config and no babelrc.

parcel build ./node_modules/monaco-editor/esm/vs/language/typescript/ts.worker.js --no-source-maps

🤔 Expected Behaviour

Optimised ts.worker.js bundle should be written to dist

😯 Current Behaviour

$ yarn monaco:worker:ts
yarn run v1.22.10
$ parcel build ./node_modules/monaco-editor/esm/vs/language/typescript/ts.worker.js --no-source-maps --dist-dir dist/monaco
🚨 Build failed.
@parcel/optimizer-terser: Unexpected token: operator (*)
  19028 |           /** @returns {number}*/
> 19029 |           /**/*/
>       |              ^ Unexpected token: operator (*)
  19030 |           /*var x = function(name) { return name.length; }*/
  19031 | } else // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement.
It's likely that Terser doesn't support this syntax yet.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

💁 Possible Solution

The problem might be due to missing whitespace and/or newlines around comments in the bundled js, as this seems to make up the majority of the diff between the two unminified versions of 520 and 522. The syntax error also looks like it occurs within a mangled comment.

🔦 Context

Can't use nightly > 520

🌍 Your Environment

Software	Version(s)
Parcel	>=2.0.0-nightly.522
Node	14.15.4
Yarn	1.22.10
Operating System	MacOS

[mischnic]

Minimal reproduction:

if (1) {
    a();
}
// /* */
else {
    b();
}

becomes

(function () {
  if (1) {
    a();
      /*/* */*/
} else // /* */
  {
    b();
  }
})();

[mischnic]

A workaround would be to remove that comment in monaco-editor/esm/vs/language/typescript/lib/typescriptServices.js:
search for Try to recognize this pattern when node and remove the block comment inside the line comment.

[jam13]

A workaround would be to remove that comment in monaco-editor/esm/vs/language/typescript/lib/typescriptServices.js:
search for Try to recognize this pattern when node and remove the block comment inside the line comment.

Thanks for the minimal test case. I'm ok to stick on the previous nightly for now, but will try this to confirm it works.

[ittaibaratz]

We had the same issue caused by highlight.js@10.3.1 . Bumping to 10.6.0 solved the problem.

[mischnic]

But the comment in the test is still duplicated because of Babel's AST format
(#5825)

Babel has recently changed the logic to check for comment identity (so a WeakSet to ensure each comment object is only printed once) instead of deduplicating via the source location. That should work in our case as well

[mischnic]

This should be fixed in the recent versions using swc