Ignore node_modules in verifyNoTypeScript (#6022)

packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js

@@ -22,7 +22,7 @@ function writeJson(fileName, object) {
 }
 
 function verifyNoTypeScript() {
-  const typescriptFiles = globby('**/*.(ts|tsx)', { cwd: paths.appSrc });
+  const typescriptFiles = globby(['**/*.(ts|tsx)', '!**/node_modules'], { cwd: paths.appSrc });
   if (typescriptFiles.length > 0) {
     console.warn(
       chalk.yellow(

test/fixtures/issue-5947-not-typescript/index.test.js

@@ -0,0 +1,36 @@
+const testSetup = require('../__shared__/test-setup');
+const path = require('path');
+const fs = require('fs');
+
+test('Ignores node_modules when detecting TypeScript', async () => {
+  // CRA build will check for TypeScript files by
+  // globbing for src/**/*.ts however this shouldn't
+  // include any node_modules directories within src.
+  // See https://github.com/facebook/create-react-app/issues/5947
+
+  const tsConfigPath = path.join(testSetup.testDirectory, 'tsconfig.json');
+  const tsPackagePath = [
+    testSetup.testDirectory,
+    'src',
+    'node_modules',
+    'package',
+    'index.ts',
+  ];
+  const tsSrcPath = path.join(testSetup.testDirectory, 'src', 'index.ts');
+
+  // Step 1.
+  // See if src/node_modules/package/index.ts is treated
+  // as a JS project
+  fs.mkdirSync(path.join(...tsPackagePath.slice(0, 2)));
+  fs.mkdirSync(path.join(...tsPackagePath.slice(0, 3)));
+  fs.mkdirSync(path.join(...tsPackagePath.slice(0, 4)));
+  fs.writeFileSync(path.join(...tsPackagePath));
+  await testSetup.scripts.build();
+  expect(fs.existsSync(tsConfigPath)).toBe(false);
+
+  // Step 2.
+  // Add TS and ensure tsconfig.json is generated
+  fs.writeFileSync(tsSrcPath);
+  await testSetup.scripts.build();
+  expect(fs.existsSync(tsConfigPath)).toBe(true);
+});

test/fixtures/issue-5947-not-typescript/package.json

@@ -0,0 +1,3 @@
+{
+  "dependencies": {}
+}