feat(serve-static): introduce onNotFound option (#119)

* feat(serve-static): introduce `onNotFound` option

* tweak

README.md

@@ -162,6 +162,22 @@ app.use(
 )
 ```
 
+#### `onNotFound`
+
+The `onNotFound` is useful for debugging. You can write a handle for when a file is not found.
+
+```ts
+app.use(
+  '/static/*',
+  serveStatic({
+    root: './non-existent-dir',
+    onNotFound: (path, c) => {
+      console.log(`${path} is not found, request to ${c.req.path}`)
+    },
+  })
+)
+```
+
 ## Related projects
 
 - Hono - <https://hono.dev>

src/serve-static.ts

@@ -1,6 +1,6 @@
-import type { ReadStream} from 'fs'
+import type { ReadStream } from 'fs'
 import { createReadStream, existsSync, lstatSync } from 'fs'
-import type { MiddlewareHandler } from 'hono'
+import type { Context, MiddlewareHandler } from 'hono'
 import { getFilePath } from 'hono/utils/filepath'
 import { getMimeType } from 'hono/utils/mime'
 
@@ -12,6 +12,7 @@ export type ServeStaticOptions = {
   path?: string
   index?: string // default is 'index.html'
   rewriteRequestPath?: (path: string) => string
+  onNotFound?: (path: string, c: Context) => void | Promise<void>
 }
 
 const createStreamBody = (stream: ReadStream) => {
@@ -51,6 +52,7 @@ export const serveStatic = (options: ServeStaticOptions = { root: '' }): Middlew
     path = `./${path}`
 
     if (!existsSync(path)) {
+      await options.onNotFound?.(path, c)
       return next()
     }
 

test/serve-static.test.ts

@@ -16,6 +16,17 @@ describe('Serve Static Middleware', () => {
     })
   )
 
+  let notFoundMessage = ''
+  app.use(
+    '/on-not-found/*',
+    serveStatic({
+      root: './not-found',
+      onNotFound: (path, c) => {
+        notFoundMessage = `${path} is not found, request to ${c.req.path}`
+      },
+    })
+  )
+
   const server = createAdaptorServer(app)
 
   it('Should return index.html', async () => {
@@ -110,4 +121,12 @@ describe('Serve Static Middleware', () => {
     expect(res.text.length).toBe(17)
     expect(res.text).toBe('This is plain.txt')
   })
+
+  it('Should handle the `onNotFound` option', async () => {
+    const res = await request(server).get('/on-not-found/foo.txt')
+    expect(res.status).toBe(404)
+    expect(notFoundMessage).toBe(
+      './not-found/on-not-found/foo.txt is not found, request to /on-not-found/foo.txt'
+    )
+  })
 })