fix: clean subchart-default nils when parent sets any child value

In coalesceValues, childChartMergeTrue() was shadowing the merge
variable to true for child chart keys, which caused cleanNilValues(src)
to be skipped even during CoalesceValues (merge=false). This let nil
values from subchart defaults leak through when the parent chart
provided any user value under the subchart's namespace.

Fix by using a separate childMerge variable for childChartMergeTrue
so the original merge flag controls nil cleaning.

Fixes #32093

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/chart/common/util/coalesce.go

@@ -249,17 +249,19 @@ func coalesceValues(printf printFn, c chart.Charter, v map[string]any, prefix st
 					}
 				} else {
 					// If the key is a child chart, coalesce tables with Merge set to true
-					merge := childChartMergeTrue(c, key, merge)
+					childMerge := childChartMergeTrue(c, key, merge)
 
 					// When coalescing, clean nils from chart defaults before merging
-					// so they don't leak into the result.
+					// so they don't leak into the result. Use the original merge flag
+					// (not childMerge) because childMerge is always true for child
+					// chart keys, which would skip cleaning subchart-default nils.
 					if !merge {
 						cleanNilValues(src)
 					}
 
 					// Because v has higher precedence than nv, dest values override src
 					// values.
-					coalesceTablesFullKey(printf, dest, src, concatPrefix(subPrefix, key), merge)
+					coalesceTablesFullKey(printf, dest, src, concatPrefix(subPrefix, key), childMerge)
 				}
 			}
 		} else {

pkg/chart/common/util/coalesce_test.go

@@ -928,3 +928,94 @@ func TestCoalesceValuesSubchartNilCleanedWhenUserPartiallyOverrides(t *testing.T
 	_, ok = keyMapping["password"]
 	is.False(ok, "Expected keyMapping.password (nil from chart defaults) to be removed even when user partially overrides the map")
 }
+
+// TestCoalesceValuesSubchartDefaultNilsCleanedWithUnrelatedUserValues tests that
+// nil values in subchart defaults are cleaned even when the parent provides an
+// unrelated user value under that subchart's namespace.
+// Regression test for issue #32093.
+func TestCoalesceValuesSubchartDefaultNilsCleanedWithUnrelatedUserValues(t *testing.T) {
+	is := assert.New(t)
+
+	subchart := &chart.Chart{
+		Metadata: &chart.Metadata{Name: "child"},
+		Values: map[string]any{
+			"keyMapping": map[string]any{
+				"password": nil,
+			},
+			"ingress": map[string]any{
+				"configureCertmanager": nil,
+			},
+		},
+	}
+
+	parent := withDeps(&chart.Chart{
+		Metadata: &chart.Metadata{Name: "parent"},
+		Values:   map[string]any{},
+	}, subchart)
+
+	vals := map[string]any{
+		"child": map[string]any{
+			"someOtherKey": "value",
+		},
+	}
+
+	v, err := CoalesceValues(parent, vals)
+	is.NoError(err)
+
+	childVals, ok := v["child"].(map[string]any)
+	is.True(ok, "child values should be a map")
+
+	keyMapping, ok := childVals["keyMapping"].(map[string]any)
+	is.True(ok, "keyMapping should be a map")
+	_, ok = keyMapping["password"]
+	is.False(ok, "Expected keyMapping.password (nil from chart defaults) to be removed when parent sets unrelated child value")
+
+	ingress, ok := childVals["ingress"].(map[string]any)
+	is.True(ok, "ingress should be a map")
+	_, ok = ingress["configureCertmanager"]
+	is.False(ok, "Expected ingress.configureCertmanager (nil from chart defaults) to be removed when parent sets unrelated child value")
+}
+
+// TestCoalesceValuesSubchartDefaultNilsCleanedWithPartialOverrideSameMap tests
+// that nil values in subchart defaults are cleaned even when the user overrides
+// a sibling key within the same map.
+// Regression test for issue #32093.
+func TestCoalesceValuesSubchartDefaultNilsCleanedWithPartialOverrideSameMap(t *testing.T) {
+	is := assert.New(t)
+
+	subchart := &chart.Chart{
+		Metadata: &chart.Metadata{Name: "child"},
+		Values: map[string]any{
+			"keyMapping": map[string]any{
+				"password": nil,
+				"format":   "bcrypt",
+			},
+		},
+	}
+
+	parent := withDeps(&chart.Chart{
+		Metadata: &chart.Metadata{Name: "parent"},
+		Values:   map[string]any{},
+	}, subchart)
+
+	vals := map[string]any{
+		"child": map[string]any{
+			"keyMapping": map[string]any{
+				"format": "sha256",
+			},
+		},
+	}
+
+	v, err := CoalesceValues(parent, vals)
+	is.NoError(err)
+
+	childVals, ok := v["child"].(map[string]any)
+	is.True(ok, "child values should be a map")
+
+	keyMapping, ok := childVals["keyMapping"].(map[string]any)
+	is.True(ok, "keyMapping should be a map")
+
+	is.Equal("sha256", keyMapping["format"], "User override should be preserved")
+	_, ok = keyMapping["password"]
+	is.False(ok, "Expected keyMapping.password (nil from chart defaults) to be removed when user overrides sibling key in same map")
+}