Ensure that the webpack output filename ends with .js.

This ensures that the Webpack SourceMapDevToolPlugin can handle the file, even when it has been originally no javascript file (e.g. .ts or .feature).

Author: jp7677

index.js

@@ -76,7 +76,9 @@ const preprocessor = (options = {}) => {
     // we're provided a default output path that lives alongside Cypress's
     // app data files so we don't have to worry about where to put the bundled
     // file on disk
-    const outputPath = file.outputPath
+    const outputPath = path.extname(file.outputPath) === '.js'
+      ? file.outputPath
+      : `${file.outputPath}.js`
 
     // we need to set entry and output
     webpackOptions = Object.assign(webpackOptions, {

test/unit/index.spec.js

@@ -132,6 +132,17 @@ describe('webpack preprocessor', function () {
         })
       })
 
+      it('adds .js extension to filename when the originating file had been no javascript file', function () {
+        this.file.outputPath = 'output/output.ts'
+
+        return this.run().then(() => {
+          expect(webpack.lastCall.args[0].output).to.eql({
+            path: 'output',
+            filename: 'output.ts.js',
+          })
+        })
+      })
+
       it('enables inline source maps', function () {
         return this.run().then(() => {
           expect(webpack.lastCall.args[0].devtool).to.equal('inline-source-map')
@@ -179,6 +190,15 @@ describe('webpack preprocessor', function () {
         })
       })
 
+      it('adds .js extension and resolves with that output path when the originating file had been no javascript file', function () {
+        this.file.outputPath = 'output/output.ts'
+        const expectedOutputPath = 'output/output.ts.js'
+
+        return this.run().then((outputPath) => {
+          expect(outputPath).to.be.equal(expectedOutputPath)
+        })
+      })
+
       it('emits "rerun" when shouldWatch is true and there is an update', function () {
         this.file.shouldWatch = true
         this.compilerApi.watch.yields(null, this.statsApi)