feat: add getCurrentPackageManager (#9505)

Co-authored-by: Niklas Mischkulnig <4586894+mischnic@users.noreply.github.com>

packages/core/package-manager/src/getCurrentPackageManager.js

@@ -0,0 +1,17 @@
+// @flow
+
+export default function getCurrentPackageManager(
+  userAgent: ?string = process.env.npm_config_user_agent,
+): ?{|name: string, version: string|} {
+  if (!userAgent) {
+    return undefined;
+  }
+
+  const pmSpec = userAgent.split(' ')[0];
+  const separatorPos = pmSpec.lastIndexOf('/');
+  const name = pmSpec.substring(0, separatorPos);
+  return {
+    name: name,
+    version: pmSpec.substring(separatorPos + 1),
+  };
+}

packages/core/package-manager/src/installPackage.js

@@ -26,6 +26,7 @@ import {Npm} from './Npm';
 import {Yarn} from './Yarn';
 import {Pnpm} from './Pnpm.js';
 import {getConflictingLocalDependencies} from './utils';
+import getCurrentPackageManager from './getCurrentPackageManager';
 import validateModuleSpecifier from './validateModuleSpecifier';
 
 async function install(
@@ -173,6 +174,15 @@ async function determinePackageInstaller(
     return new Yarn();
   }
 
+  let currentPackageManager = getCurrentPackageManager()?.name;
+  if (currentPackageManager === 'npm') {
+    return new Npm();
+  } else if (currentPackageManager === 'yarn') {
+    return new Yarn();
+  } else if (currentPackageManager === 'pnpm') {
+    return new Pnpm();
+  }
+
   if (await Yarn.exists()) {
     return new Yarn();
   } else if (await Pnpm.exists()) {

packages/core/package-manager/test/getCurrentPackageManager.test.js

@@ -0,0 +1,28 @@
+// @flow
+import assert from 'assert';
+import getCurrentPackageManager from '../src/getCurrentPackageManager';
+
+describe('getCurrentPackageManager', () => {
+  it('yarn', () => {
+    const npm_config_user_agent = 'yarn/1.22.21 npm/? node/v21.1.0 darwin x64';
+    const currentPackageManager = getCurrentPackageManager(
+      npm_config_user_agent,
+    );
+    assert(currentPackageManager?.name, 'yarn');
+  });
+  it('npm', () => {
+    const npm_config_user_agent =
+      'npm/10.2.0 node/v21.1.0 darwin x64 workspaces/true';
+    const currentPackageManager = getCurrentPackageManager(
+      npm_config_user_agent,
+    );
+    assert(currentPackageManager?.name, 'npm');
+  });
+  it('pnpm', () => {
+    const npm_config_user_agent = 'pnpm/8.14.2 npm/? node/v18.17.1 darwin x64';
+    const currentPackageManager = getCurrentPackageManager(
+      npm_config_user_agent,
+    );
+    assert(currentPackageManager?.name, 'pnpm');
+  });
+});