fix(gin): literal colon routes not working with engine.Handler()

gin.go

@@ -23,10 +23,12 @@ import (
 	"golang.org/x/net/http2/h2c"
 )
 
-const defaultMultipartMemory = 32 << 20 // 32 MB
-const escapedColon = "\\:"
-const colon = ":"
-const backslash = "\\"
+const (
+	defaultMultipartMemory = 32 << 20 // 32 MB
+	escapedColon           = "\\:"
+	colon                  = ":"
+	backslash              = "\\"
+)
 
 var (
 	default404Body = []byte("404 page not found")
@@ -46,8 +48,10 @@ var defaultTrustedCIDRs = []*net.IPNet{
 	},
 }
 
-var regSafePrefix = regexp.MustCompile("[^a-zA-Z0-9/-]+")
-var regRemoveRepeatedChar = regexp.MustCompile("/{2,}")
+var (
+	regSafePrefix         = regexp.MustCompile("[^a-zA-Z0-9/-]+")
+	regRemoveRepeatedChar = regexp.MustCompile("/{2,}")
+)
 
 // HandlerFunc defines the handler used by gin middleware as return value.
 type HandlerFunc func(*Context)
@@ -94,6 +98,10 @@ const (
 type Engine struct {
 	RouterGroup
 
+	// routeTreesUpdated ensures that the initialization or update of the route trees
+	// (used for routing HTTP requests) happens only once, even if called multiple times concurrently.
+	routeTreesUpdated sync.Once
+
 	// RedirectTrailingSlash enables automatic redirection if the current route can't be matched but a
 	// handler for the path with (without) the trailing slash exists.
 	// For example if /foo/ is requested but a route only exists for /foo, the
@@ -635,6 +643,10 @@ func (engine *Engine) RunListener(listener net.Listener) (err error) {
 
 // ServeHTTP conforms to the http.Handler interface.
 func (engine *Engine) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	engine.routeTreesUpdated.Do(func() {
+		engine.updateRouteTrees()
+	})
+
 	c := engine.pool.Get().(*Context)
 	c.writermem.reset(w)
 	c.Request = req

gin_test.go

@@ -913,3 +913,102 @@ func TestMethodNotAllowedNoRoute(t *testing.T) {
 	assert.NotPanics(t, func() { g.ServeHTTP(resp, req) })
 	assert.Equal(t, http.StatusNotFound, resp.Code)
 }
+
+// Test the fix for https://github.com/gin-gonic/gin/pull/4415
+func TestLiteralColonWithRun(t *testing.T) {
+	SetMode(TestMode)
+	router := New()
+
+	router.GET(`/test\:action`, func(c *Context) {
+		c.JSON(http.StatusOK, H{"path": "literal_colon"})
+	})
+
+	router.updateRouteTrees()
+
+	w := httptest.NewRecorder()
+
+	req, _ := http.NewRequest(http.MethodGet, "/test:action", nil)
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "literal_colon")
+}
+
+func TestLiteralColonWithDirectServeHTTP(t *testing.T) {
+	SetMode(TestMode)
+	router := New()
+
+	router.GET(`/test\:action`, func(c *Context) {
+		c.JSON(http.StatusOK, H{"path": "literal_colon"})
+	})
+
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/test:action", nil)
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "literal_colon")
+}
+
+func TestLiteralColonWithHandler(t *testing.T) {
+	SetMode(TestMode)
+	router := New()
+
+	router.GET(`/test\:action`, func(c *Context) {
+		c.JSON(http.StatusOK, H{"path": "literal_colon"})
+	})
+
+	handler := router.Handler()
+
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/test:action", nil)
+	handler.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "literal_colon")
+}
+
+func TestLiteralColonWithHTTPServer(t *testing.T) {
+	SetMode(TestMode)
+	router := New()
+
+	router.GET(`/test\:action`, func(c *Context) {
+		c.JSON(http.StatusOK, H{"path": "literal_colon"})
+	})
+
+	router.GET("/test/:param", func(c *Context) {
+		c.JSON(http.StatusOK, H{"param": c.Param("param")})
+	})
+
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/test:action", nil)
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "literal_colon")
+
+	w2 := httptest.NewRecorder()
+	req2, _ := http.NewRequest(http.MethodGet, "/test/foo", nil)
+	router.ServeHTTP(w2, req2)
+
+	assert.Equal(t, http.StatusOK, w2.Code)
+	assert.Contains(t, w2.Body.String(), "foo")
+}
+
+// Test that updateRouteTrees is called only once
+func TestUpdateRouteTreesCalledOnce(t *testing.T) {
+	SetMode(TestMode)
+	router := New()
+
+	router.GET(`/test\:action`, func(c *Context) {
+		c.String(http.StatusOK, "ok")
+	})
+
+	for range 5 {
+		w := httptest.NewRecorder()
+		req, _ := http.NewRequest(http.MethodGet, "/test:action", nil)
+		router.ServeHTTP(w, req)
+		assert.Equal(t, http.StatusOK, w.Code)
+		assert.Equal(t, "ok", w.Body.String())
+	}
+}