feat: add webpack stats debug output (#81)

README.md

@@ -151,6 +151,21 @@ module.exports = (on) => {
 }
 ```
 
+## Debugging
+
+You can see debug messages from this module by running with environment variable
+
+```
+DEBUG=cypress:webpack
+```
+
+You can see Webpack bundle diagnostic output (timings, chunks, sizes) by running with environment variable
+
+```
+DEBUG=cypress:webpack:stats
+```
+![Webpack stats](images/webpack-stats.png)
+
 ## Contributing
 
 Use the [version of Node that matches Cypress](https://github.com/cypress-io/cypress/blob/develop/.node-version).

index.js

@@ -1,6 +1,7 @@
 const path = require('path')
 const webpack = require('webpack')
 const debug = require('debug')('cypress:webpack')
+const debugStats = require('debug')('cypress:webpack:stats')
 
 const createDeferred = require('./deferred')
 const stubbableRequire = require('./stubbable-require')
@@ -149,6 +150,11 @@ const preprocessor = (options = {}) => {
       }
 
       debug('finished bundling', outputPath)
+      if (debugStats.enabled) {
+        /* eslint-disable-next-line no-console */
+        console.error(stats.toString({ colors: true }))
+      }
+
       // resolve with the outputPath so Cypress knows where to serve
       // the file from
       latestBundle.resolve(outputPath)