fix yarn publish warning (#9073)

* fix yarn publish warning

* note

.yarn/plugins/strip-publish-config.cjs

@@ -0,0 +1,33 @@
+const APPLIED_FIELDS = [
+  'type',
+  'main',
+  'browser',
+  'module',
+  'exports',
+  'imports',
+  'bin',
+  'types',
+  'typings',
+];
+
+module.exports = {
+  name: 'strip-publish-config',
+  factory: () => ({
+    hooks: {
+      beforeWorkspacePacking(workspace, rawManifest) {
+        const publishConfig = rawManifest.publishConfig;
+        if (!publishConfig) {
+          return;
+        }
+
+        for (const field of APPLIED_FIELDS) {
+          delete publishConfig[field];
+        }
+
+        if (Object.keys(publishConfig).length === 0) {
+          delete rawManifest.publishConfig;
+        }
+      },
+    },
+  }),
+};

.yarnrc.yml

@@ -16,3 +16,8 @@ enableScripts: false
 # days ago, giving the community time to catch compromised releases. Trusted
 # packages that need immediate updates can be listed in npmPreapprovedPackages.
 npmMinimalAgeGate: '3d'
+
+# yarn pack applies publishConfig overrides but leaves them in the packed
+# manifest, which npm publish warns about. Strip the applied fields.
+plugins:
+  - path: .yarn/plugins/strip-publish-config.cjs

upcoming-release-notes/strip-publish-config.md

@@ -0,0 +1,6 @@
+---
+category: Maintenance
+authors: [matt-fidd]
+---
+
+Remove the npm warning about unknown `publishConfig` fields when publishing packages.