Add LogErrorFunc to recover middleware (#2072)

LogErrorFunc provides more general interface to handle errors in the recover middleware.

middleware/recover.go

@@ -9,6 +9,9 @@ import (
 )
 
 type (
+	// LogErrorFunc defines a function for custom logging in the middleware.
+	LogErrorFunc func(c echo.Context, err error, stack []byte) error
+
 	// RecoverConfig defines the config for Recover middleware.
 	RecoverConfig struct {
 		// Skipper defines a function to skip middleware.
@@ -30,6 +33,10 @@ type (
 		// LogLevel is log level to printing stack trace.
 		// Optional. Default value 0 (Print).
 		LogLevel log.Lvl
+
+		// LogErrorFunc defines a function for custom logging in the middleware.
+		// If it's set you don't need to provide LogLevel for config.
+		LogErrorFunc LogErrorFunc
 	}
 )
 
@@ -41,6 +48,7 @@ var (
 		DisableStackAll:   false,
 		DisablePrintStack: false,
 		LogLevel:          0,
+		LogErrorFunc:      nil,
 	}
 )
 
@@ -73,9 +81,18 @@ func RecoverWithConfig(config RecoverConfig) echo.MiddlewareFunc {
 					if !ok {
 						err = fmt.Errorf("%v", r)
 					}
-					stack := make([]byte, config.StackSize)
+					var stack []byte
-					length := runtime.Stack(stack, !config.DisableStackAll)
+					var length int
+
 					if !config.DisablePrintStack {
+						stack = make([]byte, config.StackSize)
+						length = runtime.Stack(stack, !config.DisableStackAll)
+						stack = stack[:length]
+					}
+
+					if config.LogErrorFunc != nil {
+						err = config.LogErrorFunc(c, err, stack)
+					} else if !config.DisablePrintStack {
 						msg := fmt.Sprintf("[PANIC RECOVER] %v %s\n", err, stack[:length])
 						switch config.LogLevel {
 						case log.DEBUG:

middleware/recover_test.go

@@ -2,6 +2,7 @@ package middleware
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -81,3 +82,55 @@ func TestRecoverWithConfig_LogLevel(t *testing.T) {
 		})
 	}
 }
+
+func TestRecoverWithConfig_LogErrorFunc(t *testing.T) {
+	e := echo.New()
+	e.Logger.SetLevel(log.DEBUG)
+
+	buf := new(bytes.Buffer)
+	e.Logger.SetOutput(buf)
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+	c := e.NewContext(req, rec)
+
+	testError := errors.New("test")
+	config := DefaultRecoverConfig
+	config.LogErrorFunc = func(c echo.Context, err error, stack []byte) error {
+		msg := fmt.Sprintf("[PANIC RECOVER] %v %s\n", err, stack)
+		if errors.Is(err, testError) {
+			c.Logger().Debug(msg)
+		} else {
+			c.Logger().Error(msg)
+		}
+		return err
+	}
+
+	t.Run("first branch case for LogErrorFunc", func(t *testing.T) {
+		buf.Reset()
+		h := RecoverWithConfig(config)(echo.HandlerFunc(func(c echo.Context) error {
+			panic(testError)
+		}))
+
+		h(c)
+		assert.Equal(t, http.StatusInternalServerError, rec.Code)
+
+		output := buf.String()
+		assert.Contains(t, output, "PANIC RECOVER")
+		assert.Contains(t, output, `"level":"DEBUG"`)
+	})
+
+	t.Run("else branch case for LogErrorFunc", func(t *testing.T) {
+		buf.Reset()
+		h := RecoverWithConfig(config)(echo.HandlerFunc(func(c echo.Context) error {
+			panic("other")
+		}))
+
+		h(c)
+		assert.Equal(t, http.StatusInternalServerError, rec.Code)
+
+		output := buf.String()
+		assert.Contains(t, output, "PANIC RECOVER")
+		assert.Contains(t, output, `"level":"ERROR"`)
+	})
+}