From 67c2acd75aaaaa724386acdf1cd629f20ebaecde Mon Sep 17 00:00:00 2001
From: Ferenc Fabian <qwer.kocka@gmail.com>
Date: Wed, 8 Jan 2020 19:41:10 +0100
Subject: [PATCH] Merge PR #5484: Add errors.Is support to the wrappedError

---
 types/errors/errors.go      | 28 +++++++++++++++++++++
 types/errors/errors_test.go | 50 +++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/types/errors/errors.go b/types/errors/errors.go
index 49624f7847..3179aed263 100644
--- a/types/errors/errors.go
+++ b/types/errors/errors.go
@@ -263,6 +263,34 @@ func (e *wrappedError) Cause() error {
 	return e.parent
 }
 
+// Is reports whether any error in e's chain matches a target.
+func (e *wrappedError) Is(target error) bool {
+	if target == nil {
+		return e == target
+	}
+
+	w := e.Cause()
+
+	for {
+		if w == target {
+			return true
+		}
+
+		x, ok := w.(causer)
+		if ok {
+			w = x.Cause()
+		}
+		if x == nil {
+			return false
+		}
+	}
+}
+
+// Unwrap implements the built-in errors.Unwrap
+func (e *wrappedError) Unwrap() error {
+	return e.parent
+}
+
 // Recover captures a panic and stop its propagation. If panic happens it is
 // transformed into a ErrPanic instance and assigned to given error. Call this
 // function using defer in order to work as expected.
diff --git a/types/errors/errors_test.go b/types/errors/errors_test.go
index a669ee150f..f6e6e8cd7f 100644
--- a/types/errors/errors_test.go
+++ b/types/errors/errors_test.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/pkg/errors"
 )
 
@@ -158,3 +160,51 @@ func TestWrapEmpty(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestWrappedIs(t *testing.T) {
+	err := Wrap(ErrTxTooLarge, "context")
+	require.True(t, stdlib.Is(err, ErrTxTooLarge))
+
+	err = Wrap(err, "more context")
+	require.True(t, stdlib.Is(err, ErrTxTooLarge))
+
+	err = Wrap(err, "even more context")
+	require.True(t, stdlib.Is(err, ErrTxTooLarge))
+
+	err = Wrap(ErrInsufficientFee, "...")
+	require.False(t, stdlib.Is(err, ErrTxTooLarge))
+}
+
+func TestWrappedIsMultiple(t *testing.T) {
+	var errTest = errors.New("test error")
+	var errTest2 = errors.New("test error 2")
+	err := Wrap(errTest2, Wrap(errTest, "some random description").Error())
+	require.True(t, stdlib.Is(err, errTest2))
+}
+
+func TestWrappedIsFail(t *testing.T) {
+	var errTest = errors.New("test error")
+	var errTest2 = errors.New("test error 2")
+	err := Wrap(errTest2, Wrap(errTest, "some random description").Error())
+	require.False(t, stdlib.Is(err, errTest))
+}
+
+func TestWrappedUnwrap(t *testing.T) {
+	var errTest = errors.New("test error")
+	err := Wrap(errTest, "some random description")
+	require.Equal(t, errTest, stdlib.Unwrap(err))
+}
+
+func TestWrappedUnwrapMultiple(t *testing.T) {
+	var errTest = errors.New("test error")
+	var errTest2 = errors.New("test error 2")
+	err := Wrap(errTest2, Wrap(errTest, "some random description").Error())
+	require.Equal(t, errTest2, stdlib.Unwrap(err))
+}
+
+func TestWrappedUnwrapFail(t *testing.T) {
+	var errTest = errors.New("test error")
+	var errTest2 = errors.New("test error 2")
+	err := Wrap(errTest2, Wrap(errTest, "some random description").Error())
+	require.NotEqual(t, errTest, stdlib.Unwrap(err))
+}