fix: merge environment values by ovewriting with empty values (#1162)

Fixes #1154

go.mod

@@ -19,7 +19,7 @@ require (
 	github.com/hashicorp/go-version v1.2.0
 	github.com/howeyc/gopass v0.0.0-20190910152052-7cb4b85ec19c // indirect
 	github.com/huandu/xstrings v1.2.0 // indirect
-	github.com/imdario/mergo v0.3.8
+	github.com/imdario/mergo v0.3.9
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/mattn/go-colorable v0.1.4 // indirect
 	github.com/mattn/go-isatty v0.0.10 // indirect

go.sum

@@ -473,6 +473,8 @@ github.com/imdario/mergo v0.3.6 h1:xTNEAn+kxVO7dTZGu0CegyqKZmoWFI0rF8UxjlB2d28=
 github.com/imdario/mergo v0.3.6/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
 github.com/imdario/mergo v0.3.8 h1:CGgOkSJeqMRmt0D9XLWExdT4m4F1vd3FV3VPt+0VxkQ=
 github.com/imdario/mergo v0.3.8/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
+github.com/imdario/mergo v0.3.9 h1:UauaLniWCFHWd+Jp9oCEkTBj8VO/9DKg3PV3VCNMDIg=
+github.com/imdario/mergo v0.3.9/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
 github.com/influxdata/influxdb v0.0.0-20190411212539-d24b7ba8c4c4 h1:3K3KcD4S6/Y2hevi70EzUTNKOS3cryQyhUnkjE6Tz0w=
 github.com/influxdata/influxdb v0.0.0-20190411212539-d24b7ba8c4c4/go.mod h1:qZna6X/4elxqT3yI9iZYdZrWWdeFOOprn86kgg4+IzY=

pkg/environment/environment.go

@@ -58,7 +58,7 @@ func (e *Environment) Merge(other *Environment) (*Environment, error) {
 	}
 	copy := e.DeepCopy()
 	if other != nil {
-		if err := mergo.Merge(&copy, other, mergo.WithOverride); err != nil {
+		if err := mergo.Merge(&copy, other, mergo.WithOverride, mergo.WithOverwriteWithEmptyValue); err != nil {
 			return nil, err
 		}
 	}

pkg/environment/environment_test.go

@@ -0,0 +1,98 @@
+package environment
+
+import (
+	"github.com/google/go-cmp/cmp"
+	"testing"
+)
+
+// See https://github.com/roboll/helmfile/issues/1150
+func TestMerge_OverwriteNilValue_Issue1150(t *testing.T) {
+	dst := &Environment{
+		Name: "dst",
+		Values: map[string]interface{}{
+			"components": map[string]interface{}{
+				"etcd-operator": nil,
+			},
+		},
+		Defaults: nil,
+	}
+
+	src := &Environment{
+		Name: "src",
+		Values: map[string]interface{}{
+			"components": map[string]interface{}{
+				"etcd-operator": map[string]interface{}{
+					"version": "0.10.3",
+				},
+			},
+		},
+		Defaults: nil,
+	}
+
+	merged, err := dst.Merge(src)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	actual := merged.Values
+
+	expected := map[string]interface{}{
+		"components": map[string]interface{}{
+			"etcd-operator": map[string]interface{}{
+				"version": "0.10.3",
+			},
+		},
+	}
+
+	if diff := cmp.Diff(expected, actual); diff != "" {
+		t.Errorf(diff)
+	}
+}
+
+// See https://github.com/roboll/helmfile/issues/1154
+func TestMerge_OverwriteWithNilValue_Issue1154(t *testing.T) {
+	dst := &Environment{
+		Name: "dst",
+		Values: map[string]interface{}{
+			"components": map[string]interface{}{
+				"etcd-operator": map[string]interface{}{
+					"version": "0.10.0",
+				},
+			},
+		},
+		Defaults: nil,
+	}
+
+	src := &Environment{
+		Name: "src",
+		Values: map[string]interface{}{
+			"components": map[string]interface{}{
+				"etcd-operator": map[string]interface{}{
+					"version": "0.10.3",
+				},
+				"prometheus": nil,
+			},
+		},
+		Defaults: nil,
+	}
+
+	merged, err := dst.Merge(src)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	actual := merged.Values
+
+	expected := map[string]interface{}{
+		"components": map[string]interface{}{
+			"etcd-operator": map[string]interface{}{
+				"version": "0.10.3",
+			},
+			"prometheus": nil,
+		},
+	}
+
+	if diff := cmp.Diff(expected, actual); diff != "" {
+		t.Errorf(diff)
+	}
+}