feat: add helm 4 --server-side flag support for diff and bump helm-diff to v3.15.10 (#2645)

Add appendServerSideFlagsForDiff to validate helm-diff plugin version
(v3.15.10+) before passing the --server-side flag to helm diff upgrade.
Extract resolveServerSideValue helper to share precedence logic between
upgrade and diff paths. Bump helm-diff recommended version to v3.15.10
across Dockerfiles, CI, and integration scripts.

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

pkg/app/init.go

@@ -19,7 +19,7 @@ import (
 
 const (
 	HelmRequiredVersion            = "v3.18.6" // Minimum required version (supports Helm 3.x and 4.x)
-	HelmDiffRecommendedVersion     = "v3.15.9"
+	HelmDiffRecommendedVersion     = "v3.15.10"
 	HelmRecommendedVersion         = "v4.2.1" // Recommended Helm 4 version
 	HelmSecretsRecommendedVersion  = "v4.7.4" // v4.7.0+ works with both Helm 3 (single plugin) and Helm 4 (split plugin architecture)
 	HelmGitRecommendedVersion      = "v1.3.0"

pkg/state/helmx.go

@@ -357,6 +357,21 @@ func (st *HelmState) appendTakeOwnershipFlagsForUpgrade(flags []string, helm hel
 // validServerSideValues are the allowed values for the helm 4 --server-side flag.
 var validServerSideValues = map[string]struct{}{"true": {}, "false": {}, "auto": {}}
 
+// resolveServerSideValue resolves the server-side value following precedence:
+// release-level > CLI flag > helmDefaults. Returns empty string if no value is configured.
+func (st *HelmState) resolveServerSideValue(release *ReleaseSpec, serverSide string) string {
+	switch {
+	case release.ServerSide != nil && *release.ServerSide != "":
+		return *release.ServerSide
+	case serverSide != "":
+		return serverSide
+	case st.HelmDefaults.ServerSide != nil && *st.HelmDefaults.ServerSide != "":
+		return *st.HelmDefaults.ServerSide
+	default:
+		return ""
+	}
+}
+
 // appendServerSideFlagsForUpgrade appends the helm 4 --server-side flag when appropriate.
 // Precedence: release-level > CLI flag > helmDefaults.
 func (st *HelmState) appendServerSideFlagsForUpgrade(flags []string, helm helmexec.Interface, release *ReleaseSpec, serverSide string) ([]string, error) {
@@ -372,15 +387,8 @@ func (st *HelmState) appendServerSideFlagsForUpgrade(flags []string, helm helmex
 		return flags, nil
 	}
 
-	var value string
-	switch {
-	case release.ServerSide != nil && *release.ServerSide != "":
-		value = *release.ServerSide
-	case serverSide != "":
-		value = serverSide
-	case st.HelmDefaults.ServerSide != nil && *st.HelmDefaults.ServerSide != "":
-		value = *st.HelmDefaults.ServerSide
-	default:
+	value := st.resolveServerSideValue(release, serverSide)
+	if value == "" {
 		return flags, nil
 	}
 

pkg/state/state.go

@@ -4019,7 +4019,7 @@ func (st *HelmState) flagsForDiff(helm helmexec.Interface, release *ReleaseSpec,
 	}
 
 	// append server-side flag
-	flags, err = st.appendServerSideFlagsForUpgrade(flags, helm, release, serverSide)
+	flags, err = st.appendServerSideFlagsForDiff(flags, helm, release, serverSide, pluginsDir)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -4058,6 +4058,27 @@ func (st *HelmState) appendTakeOwnershipFlagsForDiff(flags []string, release *Re
 	return flags, nil
 }
 
+// appendServerSideFlagsForDiff appends the helm 4 --server-side flag for helm-diff.
+// It requires helm-diff plugin version v3.15.10 or later.
+func (st *HelmState) appendServerSideFlagsForDiff(flags []string, helm helmexec.Interface, release *ReleaseSpec, serverSide string, pluginsDir string) ([]string, error) {
+	if helm.IsHelm4() {
+		value := st.resolveServerSideValue(release, serverSide)
+		if value != "" {
+			diffVersion, err := helmexec.GetPluginVersion("diff", pluginsDir)
+			if err != nil {
+				return flags, err
+			}
+			minVersion, _ := semver.NewVersion("v3.15.10")
+
+			if diffVersion.LessThan(minVersion) {
+				return flags, fmt.Errorf("server-side is not supported by helm-diff plugin version %s, please use at least v3.15.10", diffVersion)
+			}
+		}
+	}
+
+	return st.appendServerSideFlagsForUpgrade(flags, helm, release, serverSide)
+}
+
 func (st *HelmState) appendChartVersionFlags(flags []string, release *ReleaseSpec) []string {
 	version := release.Version
 	// Strip OCI digest from version (digest is handled in chart URL, not --version flag)