RFC: Return an instance of `*fiber.Error` when no handler found (#1847)

* Return an instance of `*fiber.Error` when no handler found

When a handler cannot be found for a given path, previously Fiber
would construct a plaintext response that cannot be modified.

This commit switches to returning a new instance of `*fiber.Error`
with identical error message so that users can customise the look
of their 404 pages.

Signed-off-by: AKP <tom@tdpain.net>

* Fix `Test_App_Next_Method`

This test was failing as the error returned by `c.Next()` that's
required to generate the correct 404 status code was not being
passed through the middleware and being silently ignored.

Signed-off-by: AKP <tom@tdpain.net>

* Fix `Test_Logger_All`

Signed-off-by: AKP <tom@tdpain.net>

* Fix `Test_Cache_WithHeadThenGet` test

As far as I can tell, this test is meant to check that a cached
HEAD request to a given endpoint does not return the cached
content to a GET request to the same endpoint, and the test has
been altered to correctly check for this.

Signed-off-by: AKP <tom@tdpain.net>

app_test.go

@@ -1089,9 +1089,9 @@ func Test_App_Next_Method(t *testing.T) {
 
 	app.Use(func(c *Ctx) error {
 		utils.AssertEqual(t, MethodGet, c.Method())
-		c.Next()
+		err := c.Next()
 		utils.AssertEqual(t, MethodGet, c.Method())
-		return nil
+		return err
 	})
 
 	resp, err := app.Test(httptest.NewRequest(MethodGet, "/", nil))

middleware/cache/cache_test.go

@@ -391,32 +391,32 @@ func Test_Cache_WithHead(t *testing.T) {
 func Test_Cache_WithHeadThenGet(t *testing.T) {
 	app := fiber.New()
 	app.Use(New())
-	app.Get("/get", func(c *fiber.Ctx) error {
+	app.Get("/", func(c *fiber.Ctx) error {
 		return c.SendString(c.Query("cache"))
 	})
 
-	headResp, err := app.Test(httptest.NewRequest("HEAD", "/head?cache=123", nil))
+	headResp, err := app.Test(httptest.NewRequest("HEAD", "/?cache=123", nil))
 	utils.AssertEqual(t, nil, err)
 	headBody, err := ioutil.ReadAll(headResp.Body)
 	utils.AssertEqual(t, nil, err)
 	utils.AssertEqual(t, "", string(headBody))
 	utils.AssertEqual(t, cacheMiss, headResp.Header.Get("X-Cache"))
 
-	headResp, err = app.Test(httptest.NewRequest("HEAD", "/head?cache=123", nil))
+	headResp, err = app.Test(httptest.NewRequest("HEAD", "/?cache=123", nil))
 	utils.AssertEqual(t, nil, err)
 	headBody, err = ioutil.ReadAll(headResp.Body)
 	utils.AssertEqual(t, nil, err)
 	utils.AssertEqual(t, "", string(headBody))
 	utils.AssertEqual(t, cacheHit, headResp.Header.Get("X-Cache"))
 
-	getResp, err := app.Test(httptest.NewRequest("GET", "/get?cache=123", nil))
+	getResp, err := app.Test(httptest.NewRequest("GET", "/?cache=123", nil))
 	utils.AssertEqual(t, nil, err)
 	getBody, err := ioutil.ReadAll(getResp.Body)
 	utils.AssertEqual(t, nil, err)
 	utils.AssertEqual(t, "123", string(getBody))
 	utils.AssertEqual(t, cacheMiss, getResp.Header.Get("X-Cache"))
 
-	getResp, err = app.Test(httptest.NewRequest("GET", "/get?cache=123", nil))
+	getResp, err = app.Test(httptest.NewRequest("GET", "/?cache=123", nil))
 	utils.AssertEqual(t, nil, err)
 	getBody, err = ioutil.ReadAll(getResp.Body)
 	utils.AssertEqual(t, nil, err)

middleware/logger/logger_test.go

@@ -148,7 +148,7 @@ func Test_Logger_All(t *testing.T) {
 	utils.AssertEqual(t, nil, err)
 	utils.AssertEqual(t, fiber.StatusNotFound, resp.StatusCode)
 
-	expected := fmt.Sprintf("%dHost=example.comhttp0.0.0.0example.com/?foo=bar/%s%s%s%s%s%s%s%s%s-", os.Getpid(), cBlack, cRed, cGreen, cYellow, cBlue, cMagenta, cCyan, cWhite, cReset)
+	expected := fmt.Sprintf("%dHost=example.comhttp0.0.0.0example.com/?foo=bar/%s%s%s%s%s%s%s%s%sCannot GET /", os.Getpid(), cBlack, cRed, cGreen, cYellow, cBlue, cMagenta, cCyan, cWhite, cReset)
 	utils.AssertEqual(t, expected, buf.String())
 }
 

router.go

@@ -134,8 +134,7 @@ func (app *App) next(c *Ctx) (match bool, err error) {
 	}
 
 	// If c.Next() does not match, return 404
-	_ = c.SendStatus(StatusNotFound)
+	err = NewError(StatusNotFound, "Cannot " + c.method + " " + c.pathOriginal)
-	_ = c.SendString("Cannot " + c.method + " " + c.pathOriginal)
 
 	// If no match, scan stack again if other methods match the request
 	// Moved from app.handler because middleware may break the route chain