Fix a mistake in chunk name generation (vercel#4573)

This fixes a missed bug introduced in vercel#4510.

Because the regexp was `/-[^-]*/` and not `/-[^-]*$/`, a wrong part of the filename was being removed:

```
bad:
'foo-bar-0123456789abcdef-0123456789abcdef.js' -> 'foo-0123456789abcdef-0123456789abcdef.js'

good:
'foo-bar-0123456789abcdef-0123456789abcdef.js' -> 'foo-bar-0123456789abcdef'
```

By a stroke of luck this didn't affect the existing dynamically generated chunks. To prevent regression I've added unit tests for the function that generates the name.

Btw. in the original issue (vercel#4433) I used the right regexp, I just used the wrong regexp in vercel#4510.

cc @timneutkens

Author: fatfisz

server/utils.js

@@ -4,6 +4,10 @@ import { readdirSync, existsSync } from 'fs'
 export const IS_BUNDLED_PAGE = /^bundles[/\\]pages.*\.js$/
 export const MATCH_ROUTE_NAME = /^bundles[/\\]pages[/\\](.*)\.js$/
 
+export function getChunkNameFromFilename (filename) {
+  return filename.replace(/-[^-]*$/, '')
+}
+
 export function getAvailableChunks (distDir) {
   const chunksDir = join(distDir, 'chunks')
   if (!existsSync(chunksDir)) return {}
@@ -13,7 +17,7 @@ export function getAvailableChunks (distDir) {
 
   chunkFiles.forEach(filename => {
     if (/\.js$/.test(filename)) {
-      const chunkName = filename.replace(/-[^-]*/, '')
+      const chunkName = getChunkNameFromFilename(filename)
       chunksMap[chunkName] = filename
     }
   })

test/unit/server-utils.test.js

@@ -0,0 +1,17 @@
+/* global describe, it, expect */
+
+import { getChunkNameFromFilename } from '../../dist/server/utils'
+
+describe('Server utils', () => {
+  describe('getChunkNameFromFilename', () => {
+    it('should strip the hash from the filename', () => {
+      const filename = 'foo_bar_0123456789abcdef-0123456789abcdef.js'
+      expect(getChunkNameFromFilename(filename)).toBe('foo_bar_0123456789abcdef')
+    })
+
+    it('should only strip the part after the last hyphen in the filename', () => {
+      const filename = 'foo-bar-0123456789abcdef-0123456789abcdef.js'
+      expect(getChunkNameFromFilename(filename)).toBe('foo-bar-0123456789abcdef')
+    })
+  })
+})