feat: support keepNames and ignoreAnnotations options of esm.sh field in package.json

[ije]

esm.sh supports configuring the build options by adding the esm.sh field to your package.json:

{
  "name": "your-package",
  "esm.sh": {
    // disable the default bundling behavior
    "bundle": false,
    // prevent class/function names erasing
    "keepNames": false,
    // some libs maybe use wrong side-effect annotations
    "ignoreAnnotations": false
  }
}

close #1340

[Copilot]

Pull request overview

Adds support for package-author-controlled esbuild behaviors via the esm.sh field in package.json, specifically enabling packages to opt into preserving function/class names and ignoring side-effect annotations without requiring consumers to pass query flags.

Changes:

• Read esm.sh.keepNames and esm.sh.ignoreAnnotations from package.json and apply them to esbuild options.
• Refactor bundling decision logic by replacing isNoBundle() with shouldBundle().
• Consolidate types/typings handling by mapping typings into Types, and update routing/type resolution logic accordingly.
• Document esm.sh configuration in the README.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
server/build.go	Applies keepNames / ignoreAnnotations from package.json and refactors bundling decision logic.
internal/npm/package_json.go	Removes Typings from the normalized struct and falls back Types to raw typings.
server/router.go	Drops explicit typings handling for @types/* redirects, relying on Types fallback.
server/build_resolver.go	Drops explicit typings handling and updates DTS resolution condition.
README.md	Documents esm.sh configuration options in package.json.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The example values for keepNames and ignoreAnnotations are set to false, but the inline comments describe enabling those behaviors (preserving names / ignoring annotations). This is likely to confuse users; consider setting these to true in the example (or rewording the comments to clarify these are defaults and true enables the behavior).

Suggested change

	"keepNames": false,
	// set to true to ignore side-effect annotations
	"ignoreAnnotations": false
	"keepNames": true,
	// set to true to ignore side-effect annotations
	"ignoreAnnotations": true

[Copilot]

This change introduces a new behavior where typings is treated as a fallback for types by populating PackageJSON.Types when types is empty. There are existing tests in internal/npm but none covering this mapping; adding a unit test for ToNpmPackage (or PackageJSON.UnmarshalJSON) would help prevent regressions for packages that only specify typings.