From 679f0519804afeaa5ce8b930a30976ade2860fe0 Mon Sep 17 00:00:00 2001
From: Evans Mungai <mbuevans@gmail.com>
Date: Fri, 12 Dec 2025 17:00:18 +0000
Subject: [PATCH] Preserve nil values in chart already

Signed-off-by: Evans Mungai <mbuevans@gmail.com>
---
 pkg/chart/common/util/coalesce.go      | 27 +++++++++++++++++++-------
 pkg/chart/common/util/coalesce_test.go | 13 +++++++++----
 2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/pkg/chart/common/util/coalesce.go b/pkg/chart/common/util/coalesce.go
index 3220a275c..6c72b3d56 100644
--- a/pkg/chart/common/util/coalesce.go
+++ b/pkg/chart/common/util/coalesce.go
@@ -302,23 +302,36 @@ func coalesceTablesFullKey(printf printFn, dst, src map[string]interface{}, pref
 	if dst == nil {
 		return src
 	}
+	// Track original non-nil src keys before modifying src
+	// This lets us distinguish between user nullifying a chart default vs
+	// user setting nil for a key not in chart defaults.
+	srcOriginalNonNil := make(map[string]bool)
+	for key, val := range src {
+		if val != nil {
+			srcOriginalNonNil[key] = true
+		}
+	}
+	for key, val := range dst {
+		if val == nil {
+			src[key] = nil
+		}
+	}
 	// Because dest has higher precedence than src, dest values override src
 	// values.
 	for key, val := range src {
 		fullkey := concatPrefix(prefix, key)
-		dv, ok := dst[key]
-		if !ok {
-			dst[key] = val
-		} else if dv == nil && !merge && val != nil {
+		if dv, ok := dst[key]; ok && !merge && dv == nil && srcOriginalNonNil[key] {
 			// When coalescing (not merging), if dst has nil and src has a non-nil
 			// value, the user is nullifying a chart default - remove the key.
-			// Per Helm docs: setting a key to null deletes it.
-			// But if src also has nil (or key not in src), preserve the nil (issue #31643).
+			// But if src also has nil (or key not in src), preserve the nil
 			delete(dst, key)
+		} else if !ok {
+			// key not in user values, preserve src value (including nil)
+			dst[key] = val
 		} else if istable(val) {
 			if istable(dv) {
 				coalesceTablesFullKey(printf, dv.(map[string]interface{}), val.(map[string]interface{}), fullkey, merge)
-			} else if dv != nil {
+			} else {
 				printf("warning: cannot overwrite table with non table for %s (%v)", fullkey, val)
 			}
 		} else if istable(dv) && val != nil {
diff --git a/pkg/chart/common/util/coalesce_test.go b/pkg/chart/common/util/coalesce_test.go
index 598f1f9ef..84442e6cd 100644
--- a/pkg/chart/common/util/coalesce_test.go
+++ b/pkg/chart/common/util/coalesce_test.go
@@ -491,23 +491,28 @@ func TestCoalesceTables(t *testing.T) {
 		is.Equal("pequod", dst2["boat"], "Expected boat string, got %v", dst2["boat"])
 		is.Equal("black", dst2["hole"], "Expected hole string, got %v", dst2["hole"])
 	})
-	t.Run("empty chart map with nil user value", func(t *testing.T) {
+	t.Run("chart values with nil user value", func(t *testing.T) {
 		dst := map[string]any{
 			"foo": "bar",
 			"baz": nil, // explicit nil from user
 		}
 
 		// Chart's default values (src - lower priority) - empty map
-		src := map[string]any{}
+		src := map[string]any{
+			"ben": nil,
+		}
 
 		CoalesceTables(dst, src)
 
 		// "foo" should be preserved
 		is.Equal("bar", dst["foo"])
+		_, ok := dst["ben"]
+		is.True(ok, "Expected ben key to be present")
+		is.Nil(dst["ben"], "Expected ben key to be nil but it is not")
 
-		_, ok := dst["baz"]
+		_, ok = dst["baz"]
 		is.True(ok, "Expected baz key to be present but it was removed")
-		is.True(dst["baz"] == nil, "Expected baz key to be nil but it is not")
+		is.Nil(dst["baz"], "Expected baz key to be nil but it is not")
 	})
 }