From 7a31e0f9219255ead771009e1946b6091ee1501e Mon Sep 17 00:00:00 2001
From: Khushi Jain <khushi.jain@elastic.co>
Date: Mon, 4 Nov 2024 15:53:44 +0530
Subject: [PATCH] Do not throw error if `alterFunc` does not change the
 original key (#249)

* Do not throw error if alterfunc does not change the key

* test case explanation

* Update mapstr/mapstr_test.go

Co-authored-by: Denis <denis@rdner.de>

* update

---------

Co-authored-by: Denis <denis@rdner.de>
---
 mapstr/mapstr.go      | 10 ++++++++--
 mapstr/mapstr_test.go | 16 ++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/mapstr/mapstr.go b/mapstr/mapstr.go
index 9d92b71..b3e16a1 100644
--- a/mapstr/mapstr.go
+++ b/mapstr/mapstr.go
@@ -218,6 +218,12 @@ func (m M) AlterPath(path string, mode TraversalMode, alterFunc AlterFunc) (err
 		if newKey == "" {
 			return fmt.Errorf("replacement key for %q cannot be empty", key)
 		}
+
+		// if altered key is equal to the original key, skip below delete/put func
+		if newKey == key {
+			return nil
+		}
+
 		_, exists := level[newKey]
 		if exists {
 			return fmt.Errorf("replacement key %q already exists: %w", newKey, ErrKeyCollision)
@@ -271,7 +277,7 @@ func (m M) Traverse(path string, mode TraversalMode, visitor TraversalVisitor) (
 
 	for i, segment := range segments {
 		if !found {
-			return ErrKeyNotFound
+			return fmt.Errorf("could not fetch value for key: %s, Error: %w ", path, ErrKeyNotFound)
 		}
 		found = false
 
@@ -316,7 +322,7 @@ func (m M) Traverse(path string, mode TraversalMode, visitor TraversalVisitor) (
 	}
 
 	if !found {
-		return ErrKeyNotFound
+		return fmt.Errorf("could not fetch value for key: %s, Error: %w", path, ErrKeyNotFound)
 	}
 
 	return nil
diff --git a/mapstr/mapstr_test.go b/mapstr/mapstr_test.go
index 2d3a791..8fbbf5d 100644
--- a/mapstr/mapstr_test.go
+++ b/mapstr/mapstr_test.go
@@ -1264,6 +1264,22 @@ func TestAlterPath(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:      "does not return an error if alterFunc returns the key unchanged",
+			from:      "level1_field1.key",
+			mode:      CaseInsensitiveMode,
+			alterFunc: lower,
+			m: M{
+				"level1_field1": M{
+					"Key": "value1",
+				},
+			},
+			exp: M{
+				"level1_field1": M{ //first level is unchanged - already in lowercase
+					"key": "value1",
+				},
+			},
+		},
 		{
 			name:      "alters keys on all nested levels with case-insensitive matching",
 			from:      "level1_field1.level2_field1.level3_field1",