Uncaught SyntaxError: Unexpected token ')' in watch mode

[jtojnar]

🐛 bug report

When I try to build a module depending on netlify-cms using parcel, I get the following error:

Uncaught SyntaxError: Unexpected token ')' (at index.b379fa61.js:135076:47)

It seems to work when building using parcel build.

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

Building with npx parcel admin/index.html --dist-dir public/admin/ --public-url .

No special configuration, see the minimal example.

🤔 Expected Behavior

The code should be produced without error.

😯 Current Behavior

Viewing the generated file in Firefox or Chromium reveals a syntax error.

🔦 Context

The line points to the following code:

function oe() {
    var e, t, n, r = 35 * G + 0, o = Z[r];
    if (o) return G = o.nextPos, o.result;
    for(e = G, t = [], n = ae(); n !== i674;)t.push(n), n = ae();
    return t !== i674 && (), e = t, Z[r] = {
    //                   ^
    // It’s these parens causing the error.
        nextPos: G,
        result: e
    }, e;
}

For some reason neither Chromium nor Firefox seems to use the source maps for this so I cannot determine the original source code.

💻 Code Sample

https://github.com/jtojnar/repro/tree/738c2d442b504378b145edde2fdc52c8b2e217a0/parcel-netlify-cms

🌍 Your Environment

Software	Version(s)
Parcel	2.4.1
Node	16.14.2
npm/Yarn	8.5.0
Operating System	NixOS

[devongovett]

Possibly fixed by #7886, which hasn't been released yet. You could try the latest nightly version and see if that fixes it?

[jtojnar]

I can still reproduce this on 2.0.0-nightly.1039+211502e55.

[devongovett]

Original code (from https://unpkg.com/netlify-cms@2.10.190/dist/cms.js):

function oe() {
    var e, t, n, r = 35 * G + 0,
        o = Z[r];
    if (o) return G = o.nextPos, o.result;
    for (e = G, t = [], n = ae(); n !== i;) t.push(n), n = ae();
    return t !== i && (e, t = t), e = t, Z[r] = {
        nextPos: G,
        result: e
    }, e
}

Probably due to:

parcel/packages/transformers/js/core/src/lib.rs

Lines 344 to 348 in 211502e

	paren_remover(Some(&comments)),
	// Simplify expressions and remove dead branches so that we
	// don't include dependencies inside conditionals that are always false.
	expr_simplifier(Default::default()),
	dead_branch_remover(),

Should the paren_remover be after the expr simplifier? cc. @mischnic

[mischnic]

As far as I understand it, paren_remover doesn't actually remove comments, it just attaches the comments correctly so that they doesn't get removed. swc-project/swc#3115 (comment)

Also, this is caused by the dead_branch_remover: swc-project/swc#4272