fix(router): grow param values for contexts created before a route with more params (v4)

echo_test.go

@@ -1860,3 +1860,20 @@ func BenchmarkEchoGitHubAPIMisses(b *testing.B) {
 func BenchmarkEchoParseAPI(b *testing.B) {
 	benchmarkEchoRoutes(b, parseAPI)
 }
+
+func TestEchoAddParamRouteAfterServing(t *testing.T) {
+	e := New()
+	e.GET("/static", func(c Context) error { return c.String(http.StatusOK, "static") })
+
+	rec := httptest.NewRecorder()
+	e.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/static", nil))
+	assert.Equal(t, "static", rec.Body.String())
+
+	// the pooled context from the first request has param values sized for routes without params
+	e.GET("/users/:id", func(c Context) error { return c.String(http.StatusOK, c.Param("id")) })
+
+	rec = httptest.NewRecorder()
+	e.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/users/42", nil))
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Equal(t, "42", rec.Body.String())
+}

router.go

@@ -582,6 +582,16 @@ func optionsMethodHandler(allowMethods string) func(c Context) error {
 	}
 }
 
+// growParamValues replaces the context's pvalues when the context was created (and pooled) before a route with more
+// path params was added, so Find can set values by index. Values already set during this Find are kept and the
+// context keeps the new slice for later requests.
+func (r *Router) growParamValues(ctx *context, paramValues []string) []string {
+	grown := make([]string, *r.echo.maxParam)
+	copy(grown, paramValues)
+	ctx.pvalues = grown
+	return grown
+}
+
 // Find lookup a handler registered for method and path. It also parses URL for path
 // parameters and load them into context.
 //
@@ -730,6 +740,9 @@ func (r *Router) Find(method, path string, c Context) {
 				i = l
 			}
 
+			if paramIndex >= len(paramValues) {
+				paramValues = r.growParamValues(ctx, paramValues)
+			}
 			paramValues[paramIndex] = search[:i]
 			paramIndex++
 			search = search[i:]
@@ -742,6 +755,9 @@ func (r *Router) Find(method, path string, c Context) {
 		if child := currentNode.anyChild; child != nil {
 			// If any node is found, use remaining path for paramValues
 			currentNode = child
+			if currentNode.paramsCount > len(paramValues) {
+				paramValues = r.growParamValues(ctx, paramValues)
+			}
 			paramValues[currentNode.paramsCount-1] = search
 
 			// update indexes/search in case we need to backtrack when no handler match is found

router_test.go

@@ -2930,3 +2930,43 @@ func BenchmarkRouterGooglePlusAPIMisses(b *testing.B) {
 func BenchmarkRouterParamsAndAnyAPI(b *testing.B) {
 	benchmarkRouterRoutes(b, paramAndAnyAPI, paramAndAnyAPIToFind)
 }
+
+func TestRouterFindWithContextCreatedBeforeParamRouteAdded(t *testing.T) {
+	var testCases = []struct {
+		name        string
+		whenURL     string
+		expectRoute string
+		expectParam map[string]string
+	}{
+		{
+			name:        "ok, param route grows the context",
+			whenURL:     "/users/1/files/a.txt",
+			expectRoute: "/users/:id/files/*",
+			expectParam: map[string]string{"id": "1", "*": "a.txt"},
+		},
+		{
+			name:        "ok, any route grows the context",
+			whenURL:     "/static/css/a.css",
+			expectRoute: "/static/*",
+			expectParam: map[string]string{"*": "css/a.css"},
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			e := New()
+			// the context is created while no route has path params, so it has no room for param values
+			c := e.NewContext(nil, nil).(*context)
+
+			r := e.router
+			r.Add(http.MethodGet, "/users/:id/files/*", handlerFunc)
+			r.Add(http.MethodGet, "/static/*", handlerFunc)
+
+			r.Find(http.MethodGet, tc.whenURL, c)
+
+			assert.Equal(t, tc.expectRoute, c.Path())
+			for name, value := range tc.expectParam {
+				assert.Equal(t, value, c.Param(name))
+			}
+		})
+	}
+}