[patch] added Is & Unwrap methods for the error type

Author: bnkamalesh

errors.go

@@ -98,6 +98,24 @@ func (e *Error) Message() string {
 	return e.message
 }
 
+// Unwrap implement's Go 1.13's Unwrap interface exposing the wrapped error
+func (e *Error) Unwrap() error {
+	if e.original == nil {
+		return nil
+	}
+
+	return e.original
+}
+
+// Is implements the Is interface required by Go
+func (e *Error) Is(err error) bool {
+	o, _ := err.(*Error)
+	if o == nil {
+		return false
+	}
+	return o == e
+}
+
 // HTTPStatusCode is a convenience method used to get the appropriate HTTP response status code for the respective error type
 func (e *Error) HTTPStatusCode() int {
 	status := http.StatusInternalServerError

mirror_test.go

@@ -0,0 +1,108 @@
+package errors
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestUnwrap(t *testing.T) {
+	type args struct {
+		err error
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{
+			name: "wrapped",
+			args: args{err: NewWithErrMsgType(
+				New("level 0"),
+				"level 1",
+				TypeInternal,
+			)},
+			wantErr: true,
+		},
+		{
+			name: "no wrapping",
+			args: args{err: NewWithErrMsgType(
+				nil,
+				"level 1",
+				TypeInternal,
+			)},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := Unwrap(tt.args.err); (err != nil) != tt.wantErr {
+				t.Errorf("Unwrap() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func TestIs(t *testing.T) {
+	target := New("level 0")
+	type args struct {
+		err    error
+		target error
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			name: "has err in the chain",
+			args: args{
+				err: NewWithErrMsgType(
+					NewWithErrMsgType(
+						target,
+						"level 1",
+						TypeInputBody,
+					),
+					"level 2",
+					TypeNotFound,
+				),
+				target: target,
+			},
+			want: true,
+		},
+		{
+			name: "no matching err in the chain",
+			args: args{
+				err: NewWithErrMsgType(
+					NewWithErrMsgType(
+						New("level 0"),
+						"level 1",
+						TypeInputBody,
+					),
+					"level 2",
+					TypeNotFound,
+				),
+				target: target,
+			},
+			want: false,
+		},
+		{
+			name: "external target error",
+			args: args{
+				err: NewWithErrMsgType(
+					nil,
+					"level 2",
+					TypeNotFound,
+				),
+				target: errors.New("external"),
+			},
+			want: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Is(tt.args.err, tt.args.target); got != tt.want {
+				t.Errorf("Is() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}