error if attempting to preprocess typescript file but typescript opti…

…on is not set

index.js

@@ -14,6 +14,7 @@ const typescriptExtensionRegex = /\.tsx?$/
 const errorTypes = {
   TYPESCRIPT_AND_TSIFY: 'TYPESCRIPT_AND_TSIFY',
   TYPESCRIPT_NONEXISTENT: 'TYPESCRIPT_NONEXISTENT',
+  TYPESCRIPT_NOT_CONFIGURED: 'TYPESCRIPT_NOT_CONFIGURED',
   TYPESCRIPT_NOT_STRING: 'TYPESCRIPT_NOT_STRING',
 }
 
@@ -193,6 +194,15 @@ const preprocessor = (options = {}) => {
     const browserifyOptions = await getBrowserifyOptions(filePath, options.browserifyOptions, options.typescript)
     const watchifyOptions = Object.assign({}, defaultOptions.watchifyOptions, options.watchifyOptions)
 
+    if (!options.typescript && typescriptExtensionRegex.test(filePath)) {
+      throwError({
+        type: errorTypes.TYPESCRIPT_NOT_CONFIGURED,
+        message: `You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.
+
+The file: ${filePath}`,
+      })
+    }
+
     const bundler = browserify(browserifyOptions)
 
     if (file.shouldWatch) {

test/unit/index_spec.js

@@ -486,6 +486,32 @@ describe('browserify preprocessor', function () {
             expect(err.message).to.include(`It looks like you passed the 'typescript' option and also specified a browserify transform for TypeScript. This may cause conflicts`)
           })
         })
+
+        it('throws error when processing .ts file and typescript option is not set', function () {
+          this.options.typescript = undefined
+          this.file.filePath = 'path/to/file.ts'
+
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            verifyErrorIncludesPrefix(err)
+            expect(err.type).to.equal(preprocessor.errorTypes.TYPESCRIPT_NOT_CONFIGURED)
+            expect(err.message).to.include(`You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support`)
+            expect(err.message).to.include('path/to/file.ts')
+          })
+        })
+
+        it('throws error when processing .tsx file and typescript option is not set', function () {
+          this.options.typescript = undefined
+          this.file.filePath = 'path/to/file.tsx'
+
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            verifyErrorIncludesPrefix(err)
+            expect(err.type).to.equal(preprocessor.errorTypes.TYPESCRIPT_NOT_CONFIGURED)
+            expect(err.message).to.include(`You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support`)
+            expect(err.message).to.include('path/to/file.tsx')
           })
         })
       })