throw an error if typescript is installed, but a tsconfig.json cannot be found

Author: AtofStryker

npm/webpack-batteries-included-preprocessor/index.js

@@ -5,6 +5,13 @@ const webpackPreprocessor = require('@cypress/webpack-preprocessor')
 
 const debug = Debug('cypress:webpack-batteries-included-preprocessor')
 
+class TsConfigNotFoundError extends Error {
+  constructor () {
+    super('No tsconfig.json found, but typescript is installed. ts-loader needs a tsconfig.json file to work. Please add one to your project in either the root or the cypress directory.')
+    this.name = 'TsConfigNotFoundError'
+  }
+}
+
 const hasTsLoader = (rules) => {
   return rules.some((rule) => {
     if (!rule.use || !Array.isArray(rule.use)) return false
@@ -40,7 +47,13 @@ const addTypeScriptConfig = (file, options) => {
   // returns null if tsconfig cannot be found in the path/parent hierarchy
   const configFile = getTsConfig.getTsconfig(file.filePath)
 
-  configFile ? debug(`found user tsconfig.json at ${configFile?.path} with compilerOptions: ${JSON.stringify(configFile?.config?.compilerOptions)}`) : debug('no user tsconfig.json found')
+  if (!configFile && typescriptExtensionRegex.test(file.filePath)) {
+    debug('no user tsconfig.json found. Throwing TsConfigNotFoundError')
+    // @see https://github.com/cypress-io/cypress/issues/18938
+    throw new TsConfigNotFoundError()
+  }
+
+  debug(`found user tsconfig.json at ${configFile?.path} with compilerOptions: ${JSON.stringify(configFile?.config?.compilerOptions)}`)
 
   webpackOptions.module.rules.push({
     test: /\.tsx?$/,

npm/webpack-batteries-included-preprocessor/test/unit/index.spec.js

@@ -104,30 +104,21 @@ describe('webpack-batteries-included-preprocessor', () => {
       })
     })
 
-    it('always returns loader options even if there is an error discovering the user\'s tsconfig.json', () => {
+    // @see https://github.com/cypress-io/cypress/issues/18938. ts-loader needs a tsconfig.json file to work.
+    it('throws an error if the user\'s tsconfig.json is not found', () => {
       getTsConfigMock.returns(null)
 
       const preprocessorCB = preprocessor({
         typescript: true,
         webpackOptions,
       })
 
-      preprocessorCB({
-        filePath: 'foo.ts',
-        outputPath: '.js',
-      })
-
-      const tsLoader = webpackOptions.module.rules[0].use[0]
-
-      expect(tsLoader.loader).to.contain('ts-loader')
-
-      expect(tsLoader.options.compiler).to.be.true
-      expect(tsLoader.options.logLevel).to.equal('error')
-      expect(tsLoader.options.silent).to.be.true
-      expect(tsLoader.options.transpileOnly).to.be.true
-
-      // compilerOptions are overridden (sourceMap=true) by `@cypress/webpack-preprocessor` if ts-loader is present
-      expect(tsLoader.options.compilerOptions).to.be.undefined
+      expect(() => {
+        return preprocessorCB({
+          filePath: 'foo.ts',
+          outputPath: '.js',
+        })
+      }).to.throw('No tsconfig.json found, but typescript is installed. ts-loader needs a tsconfig.json file to work. Please add one to your project in either the root or the cypress directory.')
     })
   })
 })