From 3201a51170a98f3bcc4f0e1435bf72a3c91049c9 Mon Sep 17 00:00:00 2001
From: merceyz <merceyz@users.noreply.github.com>
Date: Mon, 21 Dec 2020 02:28:15 +0100
Subject: [PATCH] feat: add config to enable ESM loader

---
 packages/plugin-pnp/sources/PnpLinker.ts       | 2 +-
 packages/plugin-pnp/sources/index.ts           | 2 +-
 packages/yarnpkg-core/sources/Configuration.ts | 8 ++++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/packages/plugin-pnp/sources/PnpLinker.ts b/packages/plugin-pnp/sources/PnpLinker.ts
index 6405d7d86664..b8a6e4936c5e 100644
--- a/packages/plugin-pnp/sources/PnpLinker.ts
+++ b/packages/plugin-pnp/sources/PnpLinker.ts
@@ -264,7 +264,7 @@ export class PnpInstaller implements Installer {
 
     await xfs.removePromise(pnpPath.other);
 
-    if (this.opts.project.topLevelWorkspace.manifest.type !== `module`)
+    if (this.opts.project.configuration.get(`enableExperimentalESMLoader`) !== true || this.opts.project.topLevelWorkspace.manifest.type !== `module`)
       await xfs.removePromise(pnpPath.esmLoader);
 
     if (this.opts.project.configuration.get(`nodeLinker`) !== `pnp`) {
diff --git a/packages/plugin-pnp/sources/index.ts b/packages/plugin-pnp/sources/index.ts
index a38dccf658de..2f320e0bbeaf 100644
--- a/packages/plugin-pnp/sources/index.ts
+++ b/packages/plugin-pnp/sources/index.ts
@@ -16,7 +16,7 @@ export const getPnpPath = (project: Project) => {
   let mainFilename;
   let otherFilename;
 
-  if (project.topLevelWorkspace.manifest.type === `module`) {
+  if (project.configuration.get(`enableExperimentalESMLoader`) === true || project.topLevelWorkspace.manifest.type === `module`) {
     mainFilename = `.pnp.cjs`;
     otherFilename = `.pnp.js`;
   } else {
diff --git a/packages/yarnpkg-core/sources/Configuration.ts b/packages/yarnpkg-core/sources/Configuration.ts
index be0f046bd179..7e3817144af4 100644
--- a/packages/yarnpkg-core/sources/Configuration.ts
+++ b/packages/yarnpkg-core/sources/Configuration.ts
@@ -429,6 +429,12 @@ export const coreDefinitions: {[coreSettingName: string]: SettingsDefinition} =
     default: `throw`,
   },
 
+  enableExperimentalESMLoader: {
+    description: `If true, an ESM loader will be added to the environment`,
+    type: SettingsType.BOOLEAN,
+    default: false,
+  },
+
   // Package patching - to fix incorrect definitions
   packageExtensions: {
     description: `Map of package corrections to apply on the dependency tree`,
@@ -547,6 +553,8 @@ export interface ConfigurationValueMap {
     peerDependencies?: Map<string, string>,
     peerDependenciesMeta?: Map<string, miscUtils.ToMapValue<{optional?: boolean}>>,
   }>>;
+
+  enableExperimentalESMLoader: boolean
 }
 
 export type PackageExtensionData = miscUtils.MapValueToObjectValue<miscUtils.MapValue<ConfigurationValueMap['packageExtensions']>>;