Restore NUL convention for helper name

[NMinhNguyen]

The null character \0 seems to have first been introduced by d169da1.

Fixes #197

[NMinhNguyen]

Question: running npm install results in the following change to package-lock.json, but I wasn't sure if I should commit that too?

- "version": "4.0.0-beta.1",
+ "version": "4.0.0-beta.2",

[Andarist]

You have mentioned that you would like to setup an integration test for this - is this still your intent? Could you also share a repository with the issue reproduced?

Question: running npm install results in the following change to package-lock.json, but I wasn't sure if I should commit that too?

Also not sure 😜 I guess yes, just add it to the commit and we'll decide before merging this in

[NMinhNguyen]

@Andarist My bad, I just wanted to get the PR ready before 😜But I was working on the repro, and here it is: https://github.com/NMinhNguyen/rollup-plugin-babel-null-convention. Integration test may be a little harder/take more time though!

[NMinhNguyen]

So I have my first stab at an integration test here. It does depend on rollup-plugin-node-resolve@^2.1.1 and the test does fail if you remove the \0 from the helper name. I dug into this a little more, and it appears that rollup-plugin-node-resolve@^3.2.0 works because of this breaking change in v3, especially https://github.com/rollup/rollup-plugin-node-resolve/pull/90/files?w=1#diff-1fdf421c05c1140f6d71444ea2b27638L74:

-						if ( err ) {
-							if ( skip === true ) accept( false );
-							else reject( Error( `Could not resolve '${importee}' from ${normalize( importer )}` ) );
-						} else {

Interestingly, in the screenshot below, you can see that resolveId still returns an error, but due to the different branching logic in v3, the promise ends up being resolved with undefined:

@Andarist, could you perhaps help reproduce the issue you were experiencing with acorn? And lastly, the reason I'm not so keen on upgrading to v3 in my project is because of the several issues reported in that PR around the removal of skip option: rollup/rollup-plugin-node-resolve#90, as well as rollup/rollup-plugin-node-resolve#72

[Andarist]

Cannot reproduce my previous issue with acorn.

Thanks for the report, report and explaining the issue. Good work!