From 648b12d8c563fa761f5643bdc790a424e2d78a4d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Mierzwa?= <l.mierzwa@gmail.com>
Date: Mon, 20 Jun 2022 16:57:34 +0100
Subject: [PATCH] Implement Unwrap() on errors returned from rulefmt
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I'd like to unwrap errors returned from rulefmt but both Error and WrappedError types are missing Unwrap() method.

Signed-off-by: Łukasz Mierzwa <l.mierzwa@gmail.com>
---
 model/rulefmt/rulefmt.go      | 10 ++++++++++
 model/rulefmt/rulefmt_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/model/rulefmt/rulefmt.go b/model/rulefmt/rulefmt.go
index 46e008007..6c8b5978d 100644
--- a/model/rulefmt/rulefmt.go
+++ b/model/rulefmt/rulefmt.go
@@ -48,6 +48,11 @@ func (err *Error) Error() string {
 	return errors.Wrapf(err.Err.err, "group %q, rule %d, %q", err.Group, err.Rule, err.RuleName).Error()
 }
 
+// Unwrap unpacks wrapped error for use in errors.Is & errors.As.
+func (err *Error) Unwrap() error {
+	return &err.Err
+}
+
 // WrappedError wraps error with the yaml node which can be used to represent
 // the line and column numbers of the error.
 type WrappedError struct {
@@ -66,6 +71,11 @@ func (we *WrappedError) Error() string {
 	return we.err.Error()
 }
 
+// Unwrap unpacks wrapped error for use in errors.Is & errors.As.
+func (we *WrappedError) Unwrap() error {
+	return we.err
+}
+
 // RuleGroups is a set of rule groups that are typically exposed in a file.
 type RuleGroups struct {
 	Groups []RuleGroup `yaml:"groups"`
diff --git a/model/rulefmt/rulefmt_test.go b/model/rulefmt/rulefmt_test.go
index 21afb0b46..f8e6869f0 100644
--- a/model/rulefmt/rulefmt_test.go
+++ b/model/rulefmt/rulefmt_test.go
@@ -15,6 +15,7 @@ package rulefmt
 
 import (
 	"errors"
+	"io"
 	"path/filepath"
 	"testing"
 
@@ -299,3 +300,27 @@ func TestWrappedError(t *testing.T) {
 		})
 	}
 }
+
+func TestErrorUnwrap(t *testing.T) {
+	err1 := errors.New("test error")
+
+	tests := []struct {
+		wrappedError   *Error
+		unwrappedError error
+	}{
+		{
+			wrappedError:   &Error{Err: WrappedError{err: err1}},
+			unwrappedError: err1,
+		},
+		{
+			wrappedError:   &Error{Err: WrappedError{err: io.ErrClosedPipe}},
+			unwrappedError: io.ErrClosedPipe,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.wrappedError.Error(), func(t *testing.T) {
+			require.ErrorIs(t, tt.wrappedError, tt.unwrappedError)
+		})
+	}
+}