panic: Unexpected expression of type <nil> during --minify

[etrepum]

This was originally observed when trying to build something with vite, which minifies with esbuild by default. I've reduced the chunk and captured the bundle it's trying to minify.

esbuild 0.25.9

❯ npx esbuild --minify problematic-chunk.mjs 
✘ [ERROR] panic: Unexpected expression of type <nil> (while printing "problematic-chunk.mjs")

  debug.Stack (runtime/debug/stack.go:26)
  helpers.PrettyPrintedStack (internal/helpers/stack.go:9)
  linker.(*linkerContext).recoverInternalError (internal/linker/linker.go:7248)
  panic (runtime/panic.go:791)
  js_printer.(*printer).printExpr (internal/js_printer/js_printer.go:3347)
  js_printer.(*printer).printExpr (internal/js_printer/js_printer.go:2337)
  js_printer.(*printer).printStmt (internal/js_printer/js_printer.go:4899)
  js_printer.Print (internal/js_printer/js_printer.go:5005)
  linker.(*linkerContext).generateCodeForFileInChunkJS (internal/linker/linker.go:4973)
  linker.(*linkerContext).generateChunkJS in goroutine 11 (internal/linker/linker.go:5600)

1 error

https://esbuild.github.io/try/ doesn't produce a URL because the panic.

Here is the input: https://gist.github.com/etrepum/ca202aac6cf20c0181a8ff3ad49dd89f

Interestingly this problem requires a combination of separate modules to reproduce. It didn't happen when putting them each in separate chunks or when trying to use esbuild to minify the inputs directly. The smallest combination had two modules, which is attached. These are otherwise unmodified from the code I was trying to build.

I have not yet had the time to try and pare down the file to see what syntax exactly is the issue, and of course the go panic isn't very helpful. IIRC the inputs here are mostly already minified by terser, but might have gone through tree shaking.

[evanw]

Thanks for the report with a reproduction. Here's a reduced reproduction (live link):

function f(x) { return x }
f({ y: f({}) })

If you're looking for a quick workaround, the problem can be avoided by commenting out the code corresponding to this line:

Fl({ build: (t2, e2, n2) => at(e2), config: Kl({ disabled: false, newTab: false }), dependencies: [H], name: "@lexical/link/ClickableLink", register: (t2, e2, n2) => B(t2, n2.getOutput()) });

That value isn't stored anywhere so esbuild is attempting to remove it as an unused value, which triggers the bug.

[etrepum]

It's not quite that easy to workaround because that variable is exported in the original source, so I think there's two bugs: one in the tree-shaking that's not eliminating the expression altogether (maybe I can work around with pure annotations?) or at least not giving it a name, and then the other in the minifier when it encounters such an expression.

export const ClickableLinkExtension = defineExtension({
  build(editor, config, state) {
    return namedSignals(config);
  },
  config: safeCast<ClickableLinkConfig>({disabled: false, newTab: false}),
  dependencies: [LinkExtension],
  name: '@lexical/link/ClickableLink',
  register(editor, config, state) {
    return registerClickableLink(editor, state.getOutput());
  },
});

defineExtension and safeCast are just identity functions used for typescript inference reasons

[etrepum]

I think that adding @__NO_SIDE_EFFECTS__ to these functions was able to avoid this issue. Either way, it seems like a cluster of bugs somewhere in vite, rollup, and/or esbuild, but I am not blocked on it.