Add more descriptive library name message

Author: christophersmith262

lib/DrupalLibrariesPlugin.js

@@ -115,7 +115,7 @@ class DrupalLibrariesPlugin {
         const metadata = new DrupalLibraryMetadata(libraryName, chunk)
 
         if (entries[metadata.name]) {
-          throw new DrupalLibraryMetadata.KeyCollisionError('Two webpack chunks resulted in the same library name.')
+          throw new DrupalLibraryMetadata.KeyCollisionError(`Two webpack chunks resulted in the same library name: "${metadata.name}"`)
         }
 
         const promises = []

test/collision.test.js

@@ -0,0 +1,13 @@
+const path = require('path'),
+  runWebpack = require('./lib/webpack-wrapper')
+
+test('Stops the webpack build if two chunks generate the same library name', async () => {
+  await expect(
+    runWebpack({
+      entry: {
+        'a': path.resolve(__dirname, './fixtures/a.es6.js'),
+        'b': path.resolve(__dirname, './fixtures/b.es6.js'),
+      },
+    }, { nameGenerator: chunk => 'test' })
+  ).rejects.toEqual(new Error('Two webpack chunks resulted in the same library name: "test"'))
+})