fix: add --dry-run=server to helm diff for Helm 4

Helm 4 changed DryRun from boolean to DryRunStrategy enum.
The helm-diff plugin now requires --dry-run=server for
.Capabilities.APIVersions.Has to work correctly during diffs.

Closes #991

Author: mkubaczyk

internal/app/release.go

@@ -187,29 +187,32 @@ func (r *Release) uninstall(p *plan, optionalNamespace ...string) {
 	p.addCommand(cmd, priority, r, before, after)
 }
 
+// getDiffArgs returns the helm arguments for diffing a release
+func (r *Release) getDiffArgs() []string {
+	if flags.kubectlDiff {
+		return r.getHelmArgsFor("template")
+	}
+	args := []string{"diff"}
+	if !flags.showSecrets {
+		args = append(args, "--suppress-secrets")
+	}
+	if flags.noColors {
+		args = append(args, "--no-color")
+	}
+	if flags.diffContext != -1 {
+		args = append(args, "--context", strconv.Itoa(flags.diffContext))
+	}
+	if checkHelmVersion(">=4.0.0") {
+		args = append(args, "--dry-run=server")
+	}
+	return concat(args, r.getHelmArgsFor("diff"))
+}
+
 // diffRelease diffs an existing release with the specified values.yaml
 func (r *Release) diff() (string, error) {
-	var (
-		args        []string
-		maxExitCode int
-	)
-
-	if !flags.kubectlDiff {
-		args = []string{"diff"}
-		if !flags.showSecrets {
-			args = append(args, "--suppress-secrets")
-		}
-		if flags.noColors {
-			args = append(args, "--no-color")
-		}
-		if flags.diffContext != -1 {
-			args = append(args, "--context", strconv.Itoa(flags.diffContext))
-		}
-		args = concat(args, r.getHelmArgsFor("diff"))
-	} else {
-		args = r.getHelmArgsFor("template")
-	}
+	var maxExitCode int
 
+	args := r.getDiffArgs()
 	desc := "Diffing release [ " + r.Name + " ] in namespace [ " + r.Namespace + " ]"
 	cmd := CmdPipe{helmCmd(args, desc)}
 

internal/app/release_test.go

@@ -566,3 +566,73 @@ func Test_release_getChartVersion(t *testing.T) {
 		})
 	}
 }
+
+ func Test_release_getDiffArgs(t *testing.T) {
+	// Save original values to restore after test
+	originalHelmVersion := curHelmVersion
+	originalFlags := flags
+	defer func() {
+		curHelmVersion = originalHelmVersion
+		flags = originalFlags
+	}()
+
+	r := &Release{
+		Name:      "test-release",
+		Namespace: "test-ns",
+		Chart:     "repo/chart",
+		Version:   "1.0.0",
+	}
+
+	tests := []struct {
+		name        string
+		helmVersion string
+		wantFlag    string
+		shouldHave  bool
+	}{
+		{
+			name:        "helm 4.0.0 should have --dry-run=server",
+			helmVersion: "v4.0.0",
+			wantFlag:    "--dry-run=server",
+			shouldHave:  true,
+		},
+		{
+			name:        "helm 4.1.0 should have --dry-run=server",
+			helmVersion: "v4.1.0",
+			wantFlag:    "--dry-run=server",
+			shouldHave:  true,
+		},
+		{
+			name:        "helm 3.14.0 should not have --dry-run=server",
+			helmVersion: "v3.14.0",
+			wantFlag:    "--dry-run=server",
+			shouldHave:  false,
+		},
+		{
+			name:        "helm 3.99.99 should not have --dry-run=server",
+			helmVersion: "v3.99.99",
+			wantFlag:    "--dry-run=server",
+			shouldHave:  false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			curHelmVersion = tt.helmVersion
+			flags = cli{}
+
+			args := r.getDiffArgs()
+			hasFlag := false
+			for _, arg := range args {
+				if arg == tt.wantFlag {
+					hasFlag = true
+					break
+				}
+			}
+
+			if hasFlag != tt.shouldHave {
+				t.Errorf("getDiffArgs() with helm %s: got flag %s present=%v, want present=%v. Args: %v",
+					tt.helmVersion, tt.wantFlag, hasFlag, tt.shouldHave, args)
+			}
+		})
+	}
+}

internal/app/utils_test.go

@@ -285,3 +285,56 @@ func Test_eyamlSecrets(t *testing.T) {
 		})
 	}
 }
+
+func Test_checkVersion(t *testing.T) {
+	tests := []struct {
+		name       string
+		version    string
+		constraint string
+		want       bool
+	}{
+		{
+			name:       "helm 4.0.0 matches >=4.0.0",
+			version:    "v4.0.0",
+			constraint: ">=4.0.0",
+			want:       true,
+		},
+		{
+			name:       "helm 4.1.0 matches >=4.0.0",
+			version:    "v4.1.0",
+			constraint: ">=4.0.0",
+			want:       true,
+		},
+		{
+			name:       "helm 3.14.0 does not match >=4.0.0",
+			version:    "v3.14.0",
+			constraint: ">=4.0.0",
+			want:       false,
+		},
+		{
+			name:       "helm 3.99.99 does not match >=4.0.0",
+			version:    "v3.99.99",
+			constraint: ">=4.0.0",
+			want:       false,
+		},
+		{
+			name:       "helm 4.0.0 does not match <4.0.0",
+			version:    "v4.0.0",
+			constraint: "<4.0.0",
+			want:       false,
+		},
+		{
+			name:       "helm 3.14.0 matches <4.0.0",
+			version:    "v3.14.0",
+			constraint: "<4.0.0",
+			want:       true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := checkVersion(tt.version, tt.constraint); got != tt.want {
+				t.Errorf("checkVersion(%s, %s) = %v, want %v", tt.version, tt.constraint, got, tt.want)
+			}
+		})
+	}
+}