Fix isExplicitEmptyOverride for empty maps handling

Enhanced the isExplicitEmptyOverride function to correctly identify
empty maps and placeholders created by --set key={}, preventing
unintentional reintroduction of chart defaults. Added regression
tests to ensure proper treatment of empty map placeholders and
validated that CLI values maintain empty maps after coalescing.

Signed-off-by: Siew Kam Onn <kosiew@gmail.com>

pkg/chart/common/util/coalesce.go

@@ -382,10 +382,33 @@ func istable(v interface{}) bool {
 
 func isExplicitEmptyOverride(v interface{}) bool {
 	switch vv := v.(type) {
+	case map[string]interface{}:
+		return len(vv) == 0
+	case map[interface{}]interface{}:
+		return len(vv) == 0
 	case []interface{}:
-		return len(vv) == 0 || (len(vv) == 1 && vv[0] == "")
+		switch len(vv) {
+		case 0:
+			return true
+		case 1:
+			switch item := vv[0].(type) {
+			case string:
+				return item == ""
+			default:
+				return isExplicitEmptyOverride(item)
+			}
+		default:
+			return false
+		}
 	case []string:
-		return len(vv) == 0 || (len(vv) == 1 && vv[0] == "")
+		switch len(vv) {
+		case 0:
+			return true
+		case 1:
+			return vv[0] == ""
+		default:
+			return false
+		}
 	default:
 		return false
 	}

pkg/chart/common/util/coalesce_test.go

@@ -306,6 +306,19 @@ func TestCoalesceValuesEmptySliceOverrideForMap(t *testing.T) {
 		assert.Empty(t, config, "expected config map to be empty")
 	})
 
+	t.Run("explicit empty map placeholder", func(t *testing.T) {
+		overrides := map[string]interface{}{
+			"config": []interface{}{map[string]interface{}{}},
+		}
+
+		result, err := CoalesceValues(newChart(), overrides)
+		require.NoError(t, err)
+
+		config, ok := result["config"].(map[string]interface{})
+		require.Truef(t, ok, "expected config to remain a map, got %T", result["config"])
+		assert.Empty(t, config, "expected config map to be empty")
+	})
+
 	t.Run("nested empty slice", func(t *testing.T) {
 		overrides := map[string]interface{}{
 			"config": map[string]interface{}{

pkg/cli/values/options_test.go

@@ -26,6 +26,11 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"helm.sh/helm/v4/pkg/chart/common/util"
+	chart "helm.sh/helm/v4/pkg/chart/v2"
 	"helm.sh/helm/v4/pkg/getter"
 )
 
@@ -248,6 +253,58 @@ func TestReadFile(t *testing.T) {
 	}
 }
 
+func TestMergeValuesExplicitEmptyOverrides(t *testing.T) {
+	newChart := func() *chart.Chart {
+		return &chart.Chart{
+			Metadata: &chart.Metadata{Name: "emptymap"},
+			Values: map[string]interface{}{
+				"key": map[string]interface{}{"default": true},
+			},
+		}
+	}
+
+	tests := []struct {
+		name  string
+		setup func(t *testing.T) *Options
+	}{
+		{
+			name: "empty map from values file",
+			setup: func(t *testing.T) *Options {
+				dir := t.TempDir()
+				file := filepath.Join(dir, "values.yaml")
+				require.NoError(t, os.WriteFile(file, []byte("key: {}\n"), 0o600))
+				return &Options{ValueFiles: []string{file}}
+			},
+		},
+		{
+			name: "empty map from set flag",
+			setup: func(_ *testing.T) *Options {
+				return &Options{Values: []string{"key={}"}}
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			opts := tt.setup(t)
+
+			overrides, err := opts.MergeValues(getter.Providers{})
+			require.NoError(t, err)
+
+			result, err := util.CoalesceValues(newChart(), overrides)
+			require.NoError(t, err)
+
+			raw, ok := result["key"]
+			require.True(t, ok, "expected key to be present")
+
+			actual, ok := raw.(map[string]interface{})
+			require.True(t, ok, "expected key to be a map but got %T", raw)
+			assert.Empty(t, actual)
+		})
+	}
+}
+
 // TestReadFileErrorMessages tests specific error scenarios and their messages
 func TestReadFileErrorMessages(t *testing.T) {
 	tests := []struct {