chore: added some comments and renamed some functions

Author: nickytonline

packages/runtime/src/helpers/compiler.ts

@@ -4,6 +4,17 @@ import { join } from 'path'
 import { build } from '@netlify/esbuild'
 import { FSWatcher, watch } from 'chokidar'
 
+// For more information on Next.js middleware, see https://nextjs.org/docs/advanced-features/middleware
+
+// These are the locations that a middleware file can exist in a Next.js application
+// If other possible locations are added by Next.js, they should be added here.
+const MIDDLEWARE_FILE_LOCATIONS: Readonly<string[]> = [
+  'middleware.js',
+  'middleware.ts',
+  'src/middleware.js',
+  'src/middleware.ts',
+]
+
 const toFileList = (watched: Record<string, Array<string>>) =>
   Object.entries(watched).flatMap(([dir, files]) => files.map((file) => join(dir, file)))
 
@@ -66,8 +77,14 @@ const updateWatchedFiles = async (watcher: FSWatcher, base: string, isFirstRun =
   watcher.emit('build')
 }
 
-export const startWatching = (base: string) => {
-  const watcher = watch(['middleware.js', 'middleware.ts', 'src/middleware.js', 'src/middleware.ts'], {
+/**
+ * Watch for changes to the middleware file location. When a change is detected, recompile the middleware file.
+ *
+ * @param base The base directory to watch
+ * @returns a file watcher and a promise that resolves when the initial scan is complete.
+ */
+export const watchForMiddlewareChanges = (base: string) => {
+  const watcher = watch(MIDDLEWARE_FILE_LOCATIONS, {
     // Try and ensure renames just emit one event
     atomic: true,
     // Don't emit for every watched file, just once after the scan is done
@@ -93,7 +110,7 @@ export const startWatching = (base: string) => {
     watcher,
     isReady: new Promise<void>((resolve) => {
       watcher.on('ready', async () => {
-        console.log('Initial scan complete. Ready for changes')
+        console.log('Initial scan for middleware file complete. Ready for changes')
         // This only happens on the first scan
         await updateWatchedFiles(watcher, base, true)
         console.log('Ready')

packages/runtime/src/helpers/dev.ts

@@ -16,7 +16,7 @@ export const onPreDev: OnPreBuild = async ({ constants, netlifyConfig }) => {
   await writeDevEdgeFunction(constants)
   // Don't await this or it will never finish
   execa.node(
-    resolve(__dirname, '..', '..', 'lib', 'helpers', 'watcher.js'),
+    resolve(__dirname, '..', '..', 'lib', 'helpers', 'middlewareWatcher.js'),
     [base, process.env.NODE_ENV === 'test' ? '--once' : ''],
     {
       stdio: 'inherit',

packages/runtime/src/helpers/watcher.ts renamed to packages/runtime/src/helpers/middlewareWatcher.ts

@@ -1,9 +1,9 @@
 import { resolve } from 'path'
 
-import { startWatching } from './compiler'
+import { watchForMiddlewareChanges } from './compiler'
 
 const run = async () => {
-  const { isReady, watcher } = startWatching(resolve(process.argv[2]))
+  const { isReady, watcher } = watchForMiddlewareChanges(resolve(process.argv[2]))
   await isReady
   if (process.argv[3] === '--once') {
     watcher.close()

test/index.spec.js

@@ -31,7 +31,7 @@ const { downloadFile } = require('../packages/runtime/src/templates/handlerUtils
 const { getExtendedApiRouteConfigs } = require('../packages/runtime/src/helpers/functions')
 const nextRuntimeFactory = require('../packages/runtime/src')
 const nextRuntime = nextRuntimeFactory({})
-const { startWatching } = require('../packages/runtime/src/helpers/compiler')
+const { watchForMiddlewareChanges } = require('../packages/runtime/src/helpers/compiler')
 const { HANDLER_FUNCTION_NAME, ODB_FUNCTION_NAME, IMAGE_FUNCTION_NAME } = require('../packages/runtime/src/constants')
 const { join } = require('pathe')
 const {
@@ -1837,7 +1837,7 @@ fdescribe('the dev middleware watcher', () => {
     await moveNextDist('.next', true)
     await writeFile(path.join(process.cwd(), 'middleware.ts'), middlewareSourceTs)
     expect(middlewareExists()).toBeFalsy()
-    const { watcher, isReady } = startWatching(process.cwd())
+    const { watcher, isReady } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeTruthy()
@@ -1847,7 +1847,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should compile a file if it is written after the watcher starts', async () => {
     console.log('starting should compile a file if it is written after the watcher starts')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1861,7 +1861,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should remove the output if the middleware is removed after the watcher starts', async () => {
     console.log('starting should remove the output if the middleware is removed after the watcher starts')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1879,7 +1879,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should remove the output if invalid middleware is written after the watcher starts', async () => {
     console.log('starting should remove the output if invalid middleware is written after the watcher starts')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1899,7 +1899,7 @@ fdescribe('the dev middleware watcher', () => {
       'starting should recompile the middleware if it is moved into the src directory after the watcher starts',
     )
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1919,7 +1919,7 @@ fdescribe('the dev middleware watcher', () => {
       'starting should recompile the middleware if it is moved into the root directory after the watcher starts',
     )
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1940,7 +1940,7 @@ fdescribe('the dev middleware watcher', () => {
       'starting should compile the middleware if invalid source is replaced with valid source after the watcher starts',
     )
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1960,7 +1960,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should not compile middleware if more than one middleware file exists', async () => {
     console.log('starting should not compile middleware if more than one middleware file exists')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1975,7 +1975,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should not compile middleware if a second middleware file is added after the watcher starts', async () => {
     console.log('starting should not compile middleware if a second middleware file is added after the watcher starts')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -1993,7 +1993,7 @@ fdescribe('the dev middleware watcher', () => {
   it('should compile middleware if a second middleware file is removed after the watcher starts', async () => {
     console.log('starting should compile middleware if a second middleware file is removed after the watcher starts')
     await moveNextDist('.next', true)
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()
@@ -2020,7 +2020,7 @@ fdescribe('the dev middleware watcher', () => {
     const consoleErrorSpy = jest
       .spyOn(console, 'error')
       .mockImplementation((args) => console.warn(args?.errors?.[0]?.text))
-    const { watcher, isReady, nextBuild } = startWatching(process.cwd())
+    const { watcher, isReady, nextBuild } = watchForMiddlewareChanges(process.cwd())
     watchers.push(watcher)
     await isReady
     expect(middlewareExists()).toBeFalsy()