Fix enableDNS flag missing in diff command and refactor duplicate logic (#2147)

* Initial plan

* Add enableDNS flag support to diff command

Co-authored-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

* Extract EnableDNS flag logic into reusable function

Co-authored-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

pkg/state/state.go

@@ -2699,6 +2699,14 @@ func (st *HelmState) appendKeyringFlags(flags []string, release *ReleaseSpec) []
 	return flags
 }
 
+// appendEnableDNSFlags append the helm command-line flag for DNS resolution
+func (st *HelmState) appendEnableDNSFlags(flags []string, release *ReleaseSpec) []string {
+	if release.EnableDNS != nil && *release.EnableDNS || release.EnableDNS == nil && st.HelmDefaults.EnableDNS {
+		flags = append(flags, "--enable-dns")
+	}
+	return flags
+}
+
 func (st *HelmState) kubeConnectionFlags(release *ReleaseSpec) []string {
 	flags := []string{}
 	if release.KubeContext != "" {
@@ -2774,9 +2782,7 @@ func (st *HelmState) timeoutFlags(release *ReleaseSpec, ops *SyncOpts) []string
 func (st *HelmState) flagsForUpgrade(helm helmexec.Interface, release *ReleaseSpec, workerIndex int, opt *SyncOpts) ([]string, []string, error) {
 	var flags []string
 	flags = st.appendChartVersionFlags(flags, release)
-	if release.EnableDNS != nil && *release.EnableDNS || release.EnableDNS == nil && st.HelmDefaults.EnableDNS {
+	flags = st.appendEnableDNSFlags(flags, release)
-		flags = append(flags, "--enable-dns")
-	}
 
 	flags = st.appendWaitFlags(flags, helm, release, opt)
 	flags = st.appendWaitForJobsFlags(flags, release, opt)
@@ -2901,6 +2907,7 @@ func (st *HelmState) flagsForDiff(helm helmexec.Interface, release *ReleaseSpec,
 	settings := cli.New()
 	var flags []string
 	flags = st.appendChartVersionFlags(flags, release)
+	flags = st.appendEnableDNSFlags(flags, release)
 
 	disableOpenAPIValidation := false
 	if release.DisableOpenAPIValidation != nil {

pkg/state/state_test.go

@@ -1858,14 +1858,19 @@ func TestHelmState_DiffReleases(t *testing.T) {
 }
 
 func TestHelmState_DiffFlags(t *testing.T) {
+	enable := true
+	disable := false
+
 	tests := []struct {
 		name          string
+		defaults      HelmSpec
 		releases      []ReleaseSpec
 		helm          *exectest.Helm
 		wantDiffFlags []string
 	}{
 		{
-			name: "release with api version and kubeversion",
+			name:     "release with api version and kubeversion",
+			defaults: HelmSpec{},
 			releases: []ReleaseSpec{
 				{
 					Name:        "releaseName",
@@ -1878,7 +1883,8 @@ func TestHelmState_DiffFlags(t *testing.T) {
 			wantDiffFlags: []string{"--api-versions", "helmfile.test/v1", "--api-versions", "helmfile.test/v2", "--kube-version", "1.21"},
 		},
 		{
-			name: "release with kubeversion and plain http which is ignored",
+			name:     "release with kubeversion and plain http which is ignored",
+			defaults: HelmSpec{},
 			releases: []ReleaseSpec{
 				{
 					Name:        "releaseName",
@@ -1890,13 +1896,52 @@ func TestHelmState_DiffFlags(t *testing.T) {
 			helm:          &exectest.Helm{},
 			wantDiffFlags: []string{"--kube-version", "1.21"},
 		},
+		{
+			name:     "release with enable-dns",
+			defaults: HelmSpec{EnableDNS: false},
+			releases: []ReleaseSpec{
+				{
+					Name:      "releaseName",
+					Chart:     "foo",
+					EnableDNS: &enable,
+				},
+			},
+			helm:          &exectest.Helm{},
+			wantDiffFlags: []string{"--enable-dns"},
+		},
+		{
+			name:     "release with disable-dns override",
+			defaults: HelmSpec{EnableDNS: true},
+			releases: []ReleaseSpec{
+				{
+					Name:      "releaseName",
+					Chart:     "foo",
+					EnableDNS: &disable,
+				},
+			},
+			helm:          &exectest.Helm{},
+			wantDiffFlags: nil,
+		},
+		{
+			name:     "release with enable-dns from default",
+			defaults: HelmSpec{EnableDNS: true},
+			releases: []ReleaseSpec{
+				{
+					Name:  "releaseName",
+					Chart: "foo",
+				},
+			},
+			helm:          &exectest.Helm{},
+			wantDiffFlags: []string{"--enable-dns"},
+		},
 	}
 	for i := range tests {
 		tt := tests[i]
 		t.Run(tt.name, func(t *testing.T) {
 			state := &HelmState{
 				ReleaseSetSpec: ReleaseSetSpec{
-					Releases: tt.releases,
+					Releases:     tt.releases,
+					HelmDefaults: tt.defaults,
 				},
 				logger:         logger,
 				valsRuntime:    valsRuntime,