Webpack 5.96 Breaking Change

[jteppinette]

Result
The gzip and parsed treemap sizes are missing and the following error is being thrown in the console:

Error parsing bundle asset "/Users/<correct-path>/root.bc550a233bc7d9561c2f.js": 'import' and 'export' may appear only with 'sourceType: module' (1:0)

No bundles were parsed. Analyzer will show only original module sizes from stats file.

Cause
Upgrading Webpack 5.95.X to 5.96.X.

Time Since Regression
Webpack v5.96 was released on October 31.

Reproduction

• https://github.com/jteppinette/webpack-bundle-analyzer-regression-reproduction

[valscion]

Can you create a minimal reproduction case? And maybe look around if you could find another issue for this same topic. I think I've seen this reported somewhere else earlier but can't remember where

[jteppinette]

Here is the reproduction.

I have seen many issues related to this (i.e. same result), but with a different cause.

[jteppinette]

@valscion any thoughts? I can dig into this more, but a slight point in the right direction would be helpful.

[valscion]

Thanks for the reproduction!

Ah so it's most likely output.module = true that creates a bundle which the acorn parser even fails to start parsing.

Here's the function which probably would need attention to figure this out:

webpack-bundle-analyzer/src/parseUtils.js

Lines 9 to 17 in f8d4711

	function parseBundle(bundlePath) {
	const content = fs.readFileSync(bundlePath, 'utf8');
	const ast = acorn.parse(content, {
	sourceType: 'script',
	// I believe in a bright future of ECMAScript!
	// Actually, it's set to `2050` to support the latest ECMAScript version that currently exists.
	// Seems like `acorn` supports such weird option value.
	ecmaVersion: 2050
	});

My hunch is that the sourceType: 'script' is what causes this breakage.

I don't know if changing the sourceType would break parsing other, more commonly used output formats, though. The tests should fail if so, though.