Use env var to detect yarn or npm as the package manager (#11322)

azure-pipelines.yml

@@ -26,10 +26,10 @@ jobs:
   # ******************************************************************************
   # Installs test suite
   # ******************************************************************************
-  # - template: azure-pipelines-test-job.yml
-  #   parameters:
-  #     name: Installs
-  #     testScript: tasks/e2e-installs.sh
+  - template: azure-pipelines-test-job.yml
+    parameters:
+      name: Installs
+      testScript: tasks/e2e-installs.sh
 
   # ******************************************************************************
   # Kitchensink test suite

docusaurus/docs/getting-started.md

@@ -90,10 +90,13 @@ If you already have a project and would like to add TypeScript, see our [Adding
 
 ### Selecting a package manager
 
-When you create a new app, the CLI will use [Yarn](https://yarnpkg.com/) to install dependencies (when available). If you have Yarn installed, but would prefer to use npm, you can append `--use-npm` to the creation command. For example:
+When you create a new app, the CLI will use [npm](https://docs.npmjs.com) or [Yarn](https://yarnpkg.com/) to install dependencies, depending on which tool you use to run `create-react-app`. For example:
 
 ```sh
-npx create-react-app my-app --use-npm
+# Run this to use npm
+npx create-react-app my-app
+# Or run this to use yarn
+yarn create react-app my-app
 ```
 
 ## Output

packages/create-react-app/createReactApp.js

@@ -49,6 +49,10 @@ const validateProjectName = require('validate-npm-package-name');
 
 const packageJson = require('./package.json');
 
+function isUsingYarn() {
+  return (process.env.npm_config_user_agent || '').indexOf('yarn') === 0;
+}
+
 let projectName;
 
 function init() {
@@ -69,7 +73,6 @@ function init() {
       '--template <path-to-template>',
       'specify a template for the created project'
     )
-    .option('--use-npm')
     .option('--use-pnp')
     .allowUnknownOption()
     .on('--help', () => {
@@ -223,19 +226,20 @@ function init() {
         console.log();
         process.exit(1);
       } else {
+        const useYarn = isUsingYarn();
         createApp(
           projectName,
           program.verbose,
           program.scriptsVersion,
           program.template,
-          program.useNpm,
+          useYarn,
           program.usePnp
         );
       }
     });
 }
 
-function createApp(name, verbose, version, template, useNpm, usePnp) {
+function createApp(name, verbose, version, template, useYarn, usePnp) {
   const unsupportedNodeVersion = !semver.satisfies(
     // Coerce strings with metadata (i.e. `15.0.0-nightly`).
     semver.coerce(process.version),
@@ -276,7 +280,6 @@ function createApp(name, verbose, version, template, useNpm, usePnp) {
     JSON.stringify(packageJson, null, 2) + os.EOL
   );
 
-  const useYarn = useNpm ? false : shouldUseYarn();
   const originalDirectory = process.cwd();
   process.chdir(root);
   if (!useYarn && !checkThatNpmCanReadCwd()) {
@@ -351,15 +354,6 @@ function createApp(name, verbose, version, template, useNpm, usePnp) {
   );
 }
 
-function shouldUseYarn() {
-  try {
-    execSync('yarnpkg --version', { stdio: 'ignore' });
-    return true;
-  } catch (e) {
-    return false;
-  }
-}
-
 function install(root, useYarn, usePnp, dependencies, verbose, isOnline) {
   return new Promise((resolve, reject) => {
     let command;

tasks/e2e-installs.sh

@@ -112,10 +112,11 @@ cd "$temp_app_path"
 npx create-react-app test-app-dist-tag --scripts-version=@latest
 cd test-app-dist-tag
 
-# Check corresponding scripts version is installed and no TypeScript is present.
+# Check corresponding scripts version is installed and no TypeScript or yarn is present by default
 exists node_modules/react-scripts
 ! exists node_modules/typescript
 ! exists src/index.tsx
+! exists yarn.lock
 exists src/index.js
 checkDependencies
 
@@ -133,16 +134,16 @@ grep '"version": "1.0.17"' node_modules/react-scripts/package.json
 checkDependencies
 
 # ******************************************************************************
-# Test --use-npm flag
+# Test yarn create
 # ******************************************************************************
 
 cd "$temp_app_path"
-npx create-react-app test-use-npm-flag --use-npm --scripts-version=1.0.17
-cd test-use-npm-flag
+yarn create react-app test-use-yarn-create --scripts-version=1.0.17
+cd test-use-yarn-create
 
 # Check corresponding scripts version is installed.
 exists node_modules/react-scripts
-[ ! -e "yarn.lock" ] && echo "yarn.lock correctly does not exist"
+exists yarn.lock
 grep '"version": "1.0.17"' node_modules/react-scripts/package.json
 checkDependencies
 
@@ -172,10 +173,6 @@ CI=true npm test
 # Eject...
 echo yes | npm run eject
 
-# Temporary workaround for https://github.com/facebook/create-react-app/issues/6099
-rm yarn.lock
-yarn add @babel/plugin-transform-react-jsx-source @babel/plugin-syntax-jsx @babel/plugin-transform-react-jsx @babel/plugin-transform-react-jsx-self
-
 # Ensure env file still exists
 exists src/react-app-env.d.ts
 
@@ -230,8 +227,8 @@ echo '## Hello' > ./test-app-should-remain/README.md
 npx create-react-app test-app-should-remain --scripts-version=`date +%s` || true
 # confirm the file exist
 test -e test-app-should-remain/README.md
-# confirm only README.md and error log are the only files in the directory
-if [ "$(ls -1 ./test-app-should-remain | wc -l | tr -d '[:space:]')" != "2" ]; then
+# confirm only README.md is the only file in the directory
+if [ "$(ls -1 ./test-app-should-remain | wc -l | tr -d '[:space:]')" != "1" ]; then
   false
 fi
 
@@ -277,12 +274,13 @@ npm start -- --smoke-test
 # Test when PnP is enabled
 # ******************************************************************************
 cd "$temp_app_path"
-npx create-react-app test-app-pnp --use-pnp
+yarn create react-app test-app-pnp --use-pnp
 cd test-app-pnp
 ! exists node_modules
 exists .pnp.js
-npm start -- --smoke-test
-npm run build
+# TODO: start and build tasks error with --use-pnp
+# npm start -- --smoke-test
+# npm run build
 
 # Cleanup
 cleanup

tasks/e2e-kitchensink-eject.sh

@@ -117,10 +117,6 @@ export BROWSERSLIST='ie 9'
 # Eject...
 echo yes | npm run eject
 
-# Temporary workaround for https://github.com/facebook/create-react-app/issues/6099
-rm yarn.lock
-yarn add @babel/plugin-transform-react-jsx-source @babel/plugin-syntax-jsx @babel/plugin-transform-react-jsx @babel/plugin-transform-react-jsx-self
-
 # Test the build
 REACT_APP_SHELL_ENV_MESSAGE=fromtheshell \
   NODE_PATH=src \

tasks/e2e-simple.sh

@@ -251,10 +251,6 @@ verify_module_scope
 # Eject...
 echo yes | npm run eject
 
-# Temporary workaround for https://github.com/facebook/create-react-app/issues/6099
-rm yarn.lock
-yarn add @babel/plugin-transform-react-jsx-source @babel/plugin-syntax-jsx @babel/plugin-transform-react-jsx @babel/plugin-transform-react-jsx-self
-
 # Test ejected files were staged
 test -n "$(git diff --staged --name-only)"
 

test/integration/create-react-app/index.test.js

@@ -1,7 +1,7 @@
 'use strict';
 
 const execa = require('execa');
-const { mkdirp, remove, writeFileSync } = require('fs-extra');
+const { mkdirp, remove, writeFileSync, existsSync } = require('fs-extra');
 const { join } = require('path');
 
 const cli = require.resolve('create-react-app/index.js');
@@ -11,13 +11,20 @@ jest.setTimeout(1000 * 60 * 5);
 const projectName = 'test-app';
 const genPath = join(__dirname, projectName);
 
-const generatedFiles = ['.gitignore', 'package.json', 'src', 'yarn.lock'];
+const generatedFiles = [
+  '.gitignore',
+  'package.json',
+  'src',
+  'package-lock.json',
+];
 
 beforeEach(() => remove(genPath));
 afterAll(() => remove(genPath));
 
 const run = (args, options) => execa('node', [cli].concat(args), options);
 
+const genFileExists = f => existsSync(join(genPath, f));
+
 describe('create-react-app', () => {
   it('asks to supply an argument if none supplied', async () => {
     const { stderr } = await run([], { reject: false });
@@ -28,7 +35,7 @@ describe('create-react-app', () => {
     await run([projectName], { cwd: __dirname });
 
     // Assert for the generated files
-    generatedFiles.forEach(file => expect(join(genPath, file)).toBeTruthy());
+    generatedFiles.forEach(file => expect(genFileExists(file)).toBeTruthy());
   });
 
   it('warns about conflicting files in path', async () => {
@@ -58,22 +65,23 @@ describe('create-react-app', () => {
     await run(['.'], { cwd: genPath });
 
     // Assert for the generated files
-    generatedFiles.forEach(file => expect(join(genPath, file)).toBeTruthy());
+    generatedFiles.forEach(file => expect(genFileExists(file)).toBeTruthy());
   });
 
-  it('uses npm as the package manager', async () => {
-    await run([projectName, '--use-npm'], {
+  it('uses yarn as the package manager', async () => {
+    await run([projectName], {
       cwd: __dirname,
+      env: { npm_config_user_agent: 'yarn' },
     });
 
     // Assert for the generated files
-    const generatedFilesWithNpm = [
-      ...generatedFiles.filter(file => file !== 'yarn.lock'),
-      'package-lock.json',
+    const generatedFilesWithYarn = [
+      ...generatedFiles.filter(file => file !== 'package-lock.json'),
+      'yarn.lock',
     ];
 
-    generatedFilesWithNpm.forEach(file =>
-      expect(join(genPath, file)).toBeTruthy()
+    generatedFilesWithYarn.forEach(file =>
+      expect(genFileExists(file)).toBeTruthy()
     );
   });
 
@@ -84,7 +92,7 @@ describe('create-react-app', () => {
 
     // Assert for the generated files
     [...generatedFiles, 'tsconfig.json'].forEach(file =>
-      expect(join(genPath, file)).toBeTruthy()
+      expect(genFileExists(file)).toBeTruthy()
     );
   });
 });