fix(babel-highlight::index.ts): Short-circuit empty source highlighting

[a20185]

Short-circuit empty source highlighting to prevent infinite iteration.

Q	A
Fixed Issues?	NONE
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link	No
Any Dependency Changes?	No
License	MIT

When we are using babel-highlight to highlight the stylelint output results, we surprisingly found that babel-highlight plugin fails on empty source files: While passing '' to tokenize function, it will end up in an infinite iterator.

IMO I thought the empty source is worthless for highlighting(since the result won't disappear to be different after highlighting), so maybe a short-circuit guard will be a solution to this case 😄

FYI，the case we've encountered in this situation：

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/51536/

[a20185]

@nicolo-ribaudo @zxbodya @CommanderRoot @blankPen
If you have time, please help to check if this modification is okay.
It's really nesassary for us, thanks a lot! ❤

[JLHwung]

We already guard against the empty source in #14165. The highlightTokens is an internal function, I don't think we need to check that again. Can you post your use case?

[a20185]

We already guard against the empty source in #14165. The highlightTokens is an internal function, I don't think we need to check that again. Can you post your use case?

Ah，#14165 should solve the problem we've encountered, and seemed to be a better solution.

The situation we've been in is that we've using stylelint for style linting in vue-cli. When calling vue-cli-service lint:style, it will call stylelint to lint scss files.

When we've create empty files in the project, the stylelint creates warning for empty file, showing that it conflicts with no-empty-source, using babel-highlight for highlighting outputs, passing '' to the highlighter, and eventually trapped in the infinite loop of highlightTokens.

IMO this is nesassary for us, since it's not only awkward for not knowing what REALLY HAPPENS in linting styles by actually shows nothing but a forever spinning icon, but also stuck our building CI/CD procedure.

Really looking forward for the bugfix releases, can you please to help for a faster progress?

[a20185]

This PR should be closed since #14165 could be a better solution.

[nicolo-ribaudo]

It has been released in v7.16.10 🤔

[a20185]

It has been released in v7.16.10 🤔

Thanks! ❤