feat(trailing-slash): add skip option (#4862)

Author: yusukebe

src/middleware/trailing-slash/index.test.ts

@@ -255,6 +255,63 @@ describe('Resolve trailing slash', () => {
     })
   })
 
+  describe('appendTrailingSlash middleware with skip option', () => {
+    const hasExtension = (path: string): boolean => /\.\w+$/.test(path.split('/').at(-1) ?? '')
+    const app = new Hono({ strict: true })
+    app.use('*', appendTrailingSlash({ skip: hasExtension }))
+
+    app.get('/page/', (c) => c.text('ok'))
+
+    it('should not redirect paths with file extensions', async () => {
+      const resp = await app.request('/foo.html')
+
+      expect(resp.status).toBe(404)
+    })
+
+    it('should redirect paths without file extensions', async () => {
+      const resp = await app.request('/page')
+
+      expect(resp.status).toBe(301)
+      const loc = new URL(resp.headers.get('location')!)
+      expect(loc.pathname).toBe('/page/')
+    })
+  })
+
+  describe('appendTrailingSlash middleware with alwaysRedirect and skip options', () => {
+    const hasExtension = (path: string): boolean => /\.\w+$/.test(path.split('/').at(-1) ?? '')
+    const app = new Hono()
+    app.use('*', appendTrailingSlash({ alwaysRedirect: true, skip: hasExtension }))
+
+    app.get('/', (c) => c.text('ok'))
+    app.get('/my-path/*', (c) => c.text('wildcard'))
+
+    it('should redirect paths without extensions', async () => {
+      const resp = await app.request('/my-path/something')
+      const loc = new URL(resp.headers.get('location')!)
+
+      expect(resp.status).toBe(301)
+      expect(loc.pathname).toBe('/my-path/something/')
+    })
+
+    it('should not redirect paths with file extensions', async () => {
+      const resp = await app.request('/my-path/style.css')
+
+      expect(resp.status).toBe(200)
+    })
+
+    it('should not redirect paths with extensions like .html', async () => {
+      const resp = await app.request('/my-path/page.html')
+
+      expect(resp.status).toBe(200)
+    })
+
+    it('should handle HEAD request for paths with extensions', async () => {
+      const resp = await app.request('/my-path/script.js', { method: 'HEAD' })
+
+      expect(resp.status).toBe(200)
+    })
+  })
+
   describe('appendTrailingSlash middleware with alwaysRedirect option', () => {
     const app = new Hono()
     app.use('*', appendTrailingSlash({ alwaysRedirect: true }))

src/middleware/trailing-slash/index.ts

@@ -82,6 +82,22 @@ type AppendTrailingSlashOptions = {
    * @default false
    */
   alwaysRedirect?: boolean
+  /**
+   * A function that determines whether to skip the redirect for a given path.
+   * If the function returns `true`, the redirect will be skipped.
+   * @param path - The request path
+   * @returns `true` to skip the redirect
+   *
+   * @example
+   * ```ts
+   * // Skip redirect for paths with file extensions
+   * app.use(appendTrailingSlash({
+   *   alwaysRedirect: true,
+   *   skip: (path) => /\.\w+$/.test(path),
+   * }))
+   * ```
+   */
+  skip?: (path: string) => boolean
 }
 
 /**
@@ -112,7 +128,11 @@ type AppendTrailingSlashOptions = {
 export const appendTrailingSlash = (options?: AppendTrailingSlashOptions): MiddlewareHandler => {
   return async function appendTrailingSlash(c, next) {
     if (options?.alwaysRedirect) {
-      if ((c.req.method === 'GET' || c.req.method === 'HEAD') && c.req.path.at(-1) !== '/') {
+      if (
+        (c.req.method === 'GET' || c.req.method === 'HEAD') &&
+        c.req.path.at(-1) !== '/' &&
+        !options.skip?.(c.req.path)
+      ) {
         const url = new URL(c.req.url)
         url.pathname += '/'
 
@@ -126,7 +146,8 @@ export const appendTrailingSlash = (options?: AppendTrailingSlashOptions): Middl
       !options?.alwaysRedirect &&
       c.res.status === 404 &&
       (c.req.method === 'GET' || c.req.method === 'HEAD') &&
-      c.req.path.at(-1) !== '/'
+      c.req.path.at(-1) !== '/' &&
+      !options?.skip?.(c.req.path)
     ) {
       const url = new URL(c.req.url)
       url.pathname += '/'