From bbfc771618c46eca67ccea92f721f8cf14faa503 Mon Sep 17 00:00:00 2001
From: Miguel Serra <Miguel.Serra@criticaltechworks.com>
Date: Tue, 2 Jun 2020 18:10:39 +0100
Subject: [PATCH] Add 405 allow header

---
 gin.go         | 9 ++++++---
 routes_test.go | 2 ++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/gin.go b/gin.go
index 1e126179..c3efbde1 100644
--- a/gin.go
+++ b/gin.go
@@ -440,18 +440,18 @@ func (engine *Engine) handleHTTPRequest(c *Context) {
 			}
 			if value := tree.root.getValue(rPath, nil, unescape); value.handlers != nil {
 				c.handlers = engine.allNoMethod
-				serveError(c, http.StatusMethodNotAllowed, default405Body)
+				serveError(c, http.StatusMethodNotAllowed, default405Body, &httpMethod)
 				return
 			}
 		}
 	}
 	c.handlers = engine.allNoRoute
-	serveError(c, http.StatusNotFound, default404Body)
+	serveError(c, http.StatusNotFound, default404Body, nil)
 }
 
 var mimePlain = []string{MIMEPlain}
 
-func serveError(c *Context, code int, defaultMessage []byte) {
+func serveError(c *Context, code int, defaultMessage []byte, allowedMethod *string) {
 	c.writermem.status = code
 	c.Next()
 	if c.writermem.Written() {
@@ -459,6 +459,9 @@ func serveError(c *Context, code int, defaultMessage []byte) {
 	}
 	if c.writermem.Status() == code {
 		c.writermem.Header()["Content-Type"] = mimePlain
+		if allowedMethod != nil {
+			c.writermem.Header()["Allow"] = []string{*allowedMethod}
+		}
 		_, err := c.Writer.Write(defaultMessage)
 		if err != nil {
 			debugPrint("cannot write message to writer during serve error: %v", err)
diff --git a/routes_test.go b/routes_test.go
index 11ff71a6..64842838 100644
--- a/routes_test.go
+++ b/routes_test.go
@@ -374,12 +374,14 @@ func TestRouteNotAllowedEnabled(t *testing.T) {
 	router.POST("/path", func(c *Context) {})
 	w := performRequest(router, http.MethodGet, "/path")
 	assert.Equal(t, http.StatusMethodNotAllowed, w.Code)
+	assert.Equal(t, "GET", w.Result().Header["Allow"][0])
 
 	router.NoMethod(func(c *Context) {
 		c.String(http.StatusTeapot, "responseText")
 	})
 	w = performRequest(router, http.MethodGet, "/path")
 	assert.Equal(t, "responseText", w.Body.String())
+	assert.NotContains(t, w.Result().Header, "Allow")
 	assert.Equal(t, http.StatusTeapot, w.Code)
 }