From 9ca9d6c4bdf205445aca8625aebfd145902dd0a2 Mon Sep 17 00:00:00 2001
From: john <john@johng.cn>
Date: Tue, 9 Jul 2019 10:40:26 +0800
Subject: [PATCH] add Cause function for gerror

---
 g/errors/gerror/gerror.go       | 10 ++++++++++
 g/errors/gerror/gerror_error.go | 17 +++++++++++++++++
 g/errors/gerror/gerror_test.go  | 26 ++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/g/errors/gerror/gerror.go b/g/errors/gerror/gerror.go
index 29605bb1e..99f52fad2 100644
--- a/g/errors/gerror/gerror.go
+++ b/g/errors/gerror/gerror.go
@@ -58,6 +58,16 @@ func Wrapf(err error, format string, args ...interface{}) error {
 	}
 }
 
+// Cause returns the root cause error.
+func Cause(err error) error {
+	if err != nil {
+		if e, ok := err.(*Error); ok {
+			return e.Cause()
+		}
+	}
+	return err
+}
+
 // Stack returns the stack callers as string.
 // It returns an empty string id the <err> does not support stacks.
 func Stack(err error) string {
diff --git a/g/errors/gerror/gerror_error.go b/g/errors/gerror/gerror_error.go
index c92158159..95f6c1bb7 100644
--- a/g/errors/gerror/gerror_error.go
+++ b/g/errors/gerror/gerror_error.go
@@ -47,6 +47,23 @@ func (err *Error) Error() string {
 	return err.error.Error()
 }
 
+// Cause returns the root cause error.
+func (err *Error) Cause() error {
+	loop := err
+	for loop != nil {
+		if loop.error != nil {
+			if e, ok := loop.error.(*Error); ok {
+				loop = e
+			} else {
+				return loop.error
+			}
+		} else {
+			return loop
+		}
+	}
+	return nil
+}
+
 // Format formats the frame according to the fmt.Formatter interface.
 //
 // %v, %s   : Print the error string;
diff --git a/g/errors/gerror/gerror_test.go b/g/errors/gerror/gerror_test.go
index b14053ea9..e1a040f33 100644
--- a/g/errors/gerror/gerror_test.go
+++ b/g/errors/gerror/gerror_test.go
@@ -48,6 +48,32 @@ func Test_Wrap(t *testing.T) {
 	})
 }
 
+func Test_Cause(t *testing.T) {
+	gtest.Case(t, func() {
+		err := errors.New("1")
+		gtest.Assert(gerror.Cause(err), err)
+	})
+
+	gtest.Case(t, func() {
+		err := errors.New("1")
+		err = gerror.Wrap(err, "2")
+		err = gerror.Wrap(err, "3")
+		gtest.Assert(gerror.Cause(err), "1")
+	})
+
+	gtest.Case(t, func() {
+		err := gerror.New("1")
+		gtest.Assert(gerror.Cause(err), "1")
+	})
+
+	gtest.Case(t, func() {
+		err := gerror.New("1")
+		err = gerror.Wrap(err, "2")
+		err = gerror.Wrap(err, "3")
+		gtest.Assert(gerror.Cause(err), "1")
+	})
+}
+
 func Test_Format(t *testing.T) {
 	gtest.Case(t, func() {
 		err := errors.New("1")