Preserve null collections in effective YAML

internal/app/config_commands_test.go

@@ -207,6 +207,56 @@ scriptorium:
 	}
 }
 
+func TestConfigShowPreservesNullAndEmptyCollections(t *testing.T) {
+	dir := t.TempDir()
+	pipelinePath := filepath.Join(dir, "pipeline.yml")
+	mustWriteTestFile(t, pipelinePath, `workspace:
+  root: /tmp/narratio-work
+whisperx:
+  transcribe_url: https://transcription.example.test/transcribe
+audita:
+  modules: null
+scriptorium:
+  artifacts: null
+`)
+	mustWriteTestFile(t, filepath.Join(dir, "profiles", "empty.yml"), `audita:
+  modules: []
+scriptorium:
+  artifacts: {}
+`)
+
+	var base, empty bytes.Buffer
+	if err := ConfigShow(context.Background(), []string{"--config", pipelinePath}, &base); err != nil {
+		t.Fatal(err)
+	}
+	if err := ConfigShow(context.Background(), []string{"--config", pipelinePath, "--profile", "empty"}, &empty); err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"modules: null\n", "artifacts: null\n"} {
+		if !strings.Contains(base.String(), want) {
+			t.Fatalf("base show output missing %q:\n%s", want, base.String())
+		}
+	}
+	for _, want := range []string{"modules: []\n", "artifacts: {}\n"} {
+		if !strings.Contains(empty.String(), want) {
+			t.Fatalf("empty-profile show output missing %q:\n%s", want, empty.String())
+		}
+	}
+
+	var diff bytes.Buffer
+	if err := ConfigDiff(context.Background(), []string{"default", "empty", "--config", pipelinePath}, &diff); err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{
+		"changed\taudita.modules\tnull\t[]\n",
+		"changed\tscriptorium.artifacts\tnull\t{}\n",
+	} {
+		if !strings.Contains(diff.String(), want) {
+			t.Fatalf("diff output missing %q:\n%s", want, diff.String())
+		}
+	}
+}
+
 func TestConfigDiffComparesExpandedFamiliesAndPublishRules(t *testing.T) {
 	pipelinePath, campaignPath := writeInspectionFamilyConfig(t)
 	writeInspectionProfiles(t, pipelinePath, `scriptorium: