fix(build): bundle @npmcli/package-json with subpath exports

Fix the bundling system to create standalone bundles for @npmcli/package-json
and its subpath imports (lib/read-package, lib/sort), resolving module not
found errors in the editable package.json workflow.

Build changes:
- Add subpaths field to scoped package config for bundling subpath exports
- Enhance orchestrator to bundle subpaths as standalone files
- Remove directory copying (replaced with proper bundles)

Source changes:
- Create entry point for @npmcli/package-json main export
- Add entry points for lib/read-package and lib/sort subpaths

This produces 33 bundled packages (up from 31):
- dist/external/@npmcli/package-json.js (236KB)
- dist/external/@npmcli/package-json/lib/read-package.js (2.4KB)
- dist/external/@npmcli/package-json/lib/sort.js (2.2KB)

All bundles are zero-dependency standalone modules created by esbuild.

Fixes: test/packages/operations.test.ts editable package.json tests

Author: jdalton

scripts/build-externals/config.mjs

@@ -34,7 +34,12 @@ export const externalPackages = [
 
 // Scoped packages need special handling.
 export const scopedPackages = [
-  { scope: '@npmcli', name: 'promise-spawn', bundle: true },
+  {
+    scope: '@npmcli',
+    packages: ['package-json', 'promise-spawn'],
+    bundle: true,
+    subpaths: ['package-json/lib/read-package.js', 'package-json/lib/sort.js'],
+  },
   {
     scope: '@inquirer',
     packages: [

scripts/build-externals/orchestrator.mjs

@@ -12,7 +12,6 @@ import { ensureDir } from './copy-files.mjs'
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url))
 const rootDir = path.resolve(__dirname, '..', '..')
-const _srcExternalDir = path.join(rootDir, 'src', 'external')
 const distExternalDir = path.join(rootDir, 'dist', 'external')
 
 /**
@@ -43,7 +42,7 @@ async function bundleAllPackages(options = {}) {
   }
 
   // Bundle scoped packages.
-  for (const { name, optional, packages, scope } of scopedPackages) {
+  for (const { name, optional, packages, scope, subpaths } of scopedPackages) {
     const scopeDir = path.join(distExternalDir, scope)
     await ensureDir(scopeDir)
 
@@ -106,6 +105,24 @@ async function bundleAllPackages(options = {}) {
         }
       }
     }
+
+    // Bundle subpath exports (e.g., @npmcli/package-json/lib/read-package)
+    if (subpaths) {
+      for (const subpath of subpaths) {
+        const outputPath = path.join(distExternalDir, scope, subpath)
+        const packageName = `${scope}/${subpath}`
+        // Ensure parent directory exists
+        await ensureDir(path.dirname(outputPath))
+        const size = await bundlePackage(packageName, outputPath, {
+          quiet,
+          rootDir,
+        })
+        if (size) {
+          bundledCount++
+          totalSize += size
+        }
+      }
+    }
   }
 
   return { bundledCount, totalSize }

src/external/@npmcli/package-json.js

@@ -0,0 +1 @@
+module.exports = require('@npmcli/package-json')

src/external/@npmcli/package-json/lib/read-package.js

@@ -1 +1,2 @@
+// Entry point for bundling @npmcli/package-json/lib/read-package
 module.exports = require('@npmcli/package-json/lib/read-package.js')

src/external/@npmcli/package-json/lib/sort.js

@@ -1 +1,2 @@
+// Entry point for bundling @npmcli/package-json/lib/sort
 module.exports = require('@npmcli/package-json/lib/sort.js')