esbuild does not tree shake known globals

[moos]

esbuild:

$ echo "class A extends HTMLElement {}" | npx esbuild --bundle --format=esm
// <stdin>
var A = class extends HTMLElement {
};

Rollup:

$ echo "class A extends HTMLElement {}" | npx rollup
- → stdout...
(!) Generated an empty chunk
-

For unknown globals (e.g., "class A extends Foo {}"), both esbuild and rollup keep the definition.

It would be great if esbuild could also filter for known globals.

Related:

• [QUESTION] Why is this code not tree shaked? #756 (issue is with HTMLElement and not with lit-element)
• rollup/#3115
• shoelace-style/#180

[evanw]

There is limited support for this already in esbuild here:

esbuild/internal/config/globals.go

Lines 15 to 24 in f50aa9a

	var knownGlobals = [][]string{
	// These global identifiers should exist in all JavaScript environments
	{"Array"},
	{"Boolean"},
	{"Function"},
	{"Math"},
	{"Number"},
	{"Object"},
	{"RegExp"},
	{"String"},

This does not yet encode DOM globals, however.

[moos]

Ah good to know. I'm not a Go programmer but willing to give it a "go" if you want some help. Let me know.

[evanw]

It's ok, this is easy for me. I've got this one.