feat: add --ignore-not-found flag to 'flux diff ks' command

Signed-off-by: rycli <cyril@ryc.li>
Assisted-by: claude-code/claude-opus-4-6

cmd/flux/diff_kustomization_test.go

@@ -48,7 +48,7 @@ func TestDiffKustomization(t *testing.T) {
 			name:       "diff nothing deployed",
 			args:       "diff kustomization podinfo --path ./testdata/build-kustomization/podinfo --progress-bar=false",
 			objectFile: "",
-			assert:     assertGoldenFile("./testdata/diff-kustomization/nothing-is-deployed.golden"),
+			assert:     assertGoldenFile("./testdata/diff-kustomization/diff-new-kustomization.golden"),
 		},
 		{
 			name:       "diff with a deployment object",
@@ -96,7 +96,7 @@ func TestDiffKustomization(t *testing.T) {
 			name:       "diff where kustomization file has multiple objects with the same name",
 			args:       "diff kustomization podinfo --path ./testdata/build-kustomization/podinfo --progress-bar=false --kustomization-file ./testdata/diff-kustomization/flux-kustomization-multiobj.yaml",
 			objectFile: "",
-			assert:     assertGoldenFile("./testdata/diff-kustomization/nothing-is-deployed.golden"),
+			assert:     assertGoldenFile("./testdata/diff-kustomization/diff-new-kustomization.golden"),
 		},
 		{
 			name:       "diff with recursive",
@@ -138,6 +138,118 @@ func TestDiffKustomization(t *testing.T) {
 	}
 }
 
+// TestDiffKustomizationNotDeployed tests `flux diff ks` when the Kustomization
+// CR does not exist in the cluster but is provided via --kustomization-file.
+// Reproduces https://github.com/fluxcd/flux2/issues/5439
+func TestDiffKustomizationNotDeployed(t *testing.T) {
+	// Use a dedicated namespace with NO setup() -- the Kustomization CR
+	// intentionally does not exist in the cluster.
+	tmpl := map[string]string{
+		"fluxns": allocateNamespace("flux-system"),
+	}
+	setupTestNamespace(tmpl["fluxns"], t)
+
+	tests := []struct {
+		name   string
+		args   string
+		assert assertFunc
+	}{
+		{
+			name: "fails without --ignore-not-found",
+			args: "diff kustomization podinfo --path ./testdata/build-kustomization/podinfo --progress-bar=false " +
+				"--kustomization-file ./testdata/diff-kustomization/flux-kustomization-local-only.yaml",
+			assert: assertError("failed to get kustomization object: kustomizations.kustomize.toolkit.fluxcd.io \"podinfo\" not found"),
+		},
+		{
+			name: "succeeds with --ignore-not-found and --kustomization-file",
+			args: "diff kustomization podinfo --path ./testdata/build-kustomization/podinfo --progress-bar=false " +
+				"--kustomization-file ./testdata/diff-kustomization/flux-kustomization-local-only.yaml " +
+				"--ignore-not-found",
+			assert: assertGoldenFile("./testdata/diff-kustomization/diff-new-kustomization.golden"),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cmd := cmdTestCase{
+				args:   tt.args + " -n " + tmpl["fluxns"],
+				assert: tt.assert,
+			}
+			cmd.runTestCmd(t)
+		})
+	}
+}
+
+// TestDiffKustomizationTakeOwnership tests `flux diff ks` when taking ownership
+// of existing resources on the cluster. A "pre-existing" configmap is applied
+// to the cluster, and the kustomization contains a matching configmap; the
+// diff should show the labels added by flux
+func TestDiffKustomizationTakeOwnership(t *testing.T) {
+	tmpl := map[string]string{
+		"fluxns": allocateNamespace("flux-system"),
+	}
+	setupTestNamespace(tmpl["fluxns"], t)
+
+	b, _ := build.NewBuilder("configmaps", "", build.WithClientConfig(kubeconfigArgs, kubeclientOptions))
+	resourceManager, err := b.Manager()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Pre-create the "existing" configmap in the cluster without Flux labels
+	if _, err := resourceManager.ApplyAll(context.Background(), createObjectFromFile("./testdata/diff-kustomization/existing-configmap.yaml", tmpl, t), ssa.DefaultApplyOptions()); err != nil {
+		t.Fatal(err)
+	}
+
+	cmd := cmdTestCase{
+		args: "diff kustomization configmaps --path ./testdata/build-kustomization/configmaps --progress-bar=false " +
+			"--kustomization-file ./testdata/diff-kustomization/flux-kustomization-configmaps.yaml " +
+			"--ignore-not-found" +
+			" -n " + tmpl["fluxns"],
+		assert: assertGoldenFile("./testdata/diff-kustomization/diff-taking-ownership.golden"),
+	}
+	cmd.runTestCmd(t)
+}
+
+// TestDiffKustomizationNewNamespaceAndConfigmap runs `flux diff ks` when the
+// kustomization creates a new namespace and resources inside it. The server-side
+// dry-run cannot resolve resources in a namespace that doesn't exist yet,
+// consistent with `kubectl diff --server-side` behavior.
+func TestDiffKustomizationNewNamespaceAndConfigmap(t *testing.T) {
+	tmpl := map[string]string{
+		"fluxns": allocateNamespace("flux-system"),
+	}
+	setupTestNamespace(tmpl["fluxns"], t)
+
+	cmd := cmdTestCase{
+		args: "diff kustomization new-namespace-and-configmap --path ./testdata/build-kustomization/new-namespace-and-configmap --progress-bar=false " +
+			"--kustomization-file ./testdata/diff-kustomization/flux-kustomization-new-namespace-and-configmap.yaml " +
+			"--ignore-not-found" +
+			" -n " + tmpl["fluxns"],
+		assert: assertError("ConfigMap/new-ns/app-config not found: namespaces \"new-ns\" not found"),
+	}
+	cmd.runTestCmd(t)
+}
+
+// TestDiffKustomizationNewNamespaceOnly runs `flux diff ks` when the
+// kustomization creates only a new namespace. The diff should show the
+// namespace as created.
+func TestDiffKustomizationNewNamespaceOnly(t *testing.T) {
+	tmpl := map[string]string{
+		"fluxns": allocateNamespace("flux-system"),
+	}
+	setupTestNamespace(tmpl["fluxns"], t)
+
+	cmd := cmdTestCase{
+		args: "diff kustomization new-namespace-only --path ./testdata/build-kustomization/new-namespace-only --progress-bar=false " +
+			"--kustomization-file ./testdata/diff-kustomization/flux-kustomization-new-namespace-only.yaml " +
+			"--ignore-not-found" +
+			" -n " + tmpl["fluxns"],
+		assert: assertGoldenFile("./testdata/diff-kustomization/diff-new-namespace-only.golden"),
+	}
+	cmd.runTestCmd(t)
+}
+
 func createObjectFromFile(objectFile string, templateValues map[string]string, t *testing.T) []*unstructured.Unstructured {
 	buf, err := os.ReadFile(objectFile)
 	if err != nil {