test(handlers): add filesystem suite for ListRegistry (plugins_listing.go)

Tests listRegistryFiltered and ListRegistry endpoint:
  - empty dir → empty list
  - files (non-dirs) → ignored
  - single plugin with plugin.yaml → appears in list
  - runtime filter: claude-code plugin matches, hermes plugin excluded
  - universal plugin (no runtimes field) → always included
  - nonexistent dir → empty list (ReadDir error is non-fatal)
  - HTTP endpoint: GET /plugins → 200 with JSON array

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/handlers/plugins_listing_test.go

@@ -0,0 +1,141 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func TestListRegistry_EmptyDir(t *testing.T) {
+	dir := t.TempDir()
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list, got %d plugins", len(got))
+	}
+}
+
+func TestListRegistry_IgnoresFiles(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "not-a-plugin.txt"), []byte("x"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list (files ignored), got %d", len(got))
+	}
+}
+
+func TestListRegistry_SinglePlugin(t *testing.T) {
+	dir := t.TempDir()
+	pluginDir := filepath.Join(dir, "my-plugin")
+	if err := os.Mkdir(pluginDir, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pluginDir, "plugin.yaml"), []byte("name: my-plugin\nversion: 1.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	got := h.listRegistryFiltered("")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 plugin, got %d", len(got))
+	}
+	if got[0].Name != "my-plugin" {
+		t.Errorf("expected name 'my-plugin', got %q", got[0].Name)
+	}
+}
+
+func TestListRegistry_FiltersByRuntime(t *testing.T) {
+	dir := t.TempDir()
+	for _, spec := range []struct{ name, yaml string }{
+		{"runtime-a", "name: runtime-a\nruntimes:\n  - claude-code\n"},
+		{"runtime-b", "name: runtime-b\nruntimes:\n  - hermes\n"},
+		{"universal", "name: universal\nversion: 1.0.0\n"},
+	} {
+		pd := filepath.Join(dir, spec.name)
+		if err := os.Mkdir(pd, 0755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte(spec.yaml), 0600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	// Filter to claude-code: runtime-a matches, universal (no runtimes field)
+	// is always included per supportsRuntime semantics.
+	got := h.listRegistryFiltered("claude-code")
+	if len(got) != 2 {
+		t.Fatalf("expected 2 (runtime-a + universal), got %d: %v", len(got), func() []string {
+			ns := make([]string, len(got))
+			for i, p := range got { ns[i] = p.Name }
+			return ns
+		}())
+	}
+}
+
+func TestListRegistry_PluginWithNoRuntimeDeclarations_AlwaysIncluded(t *testing.T) {
+	dir := t.TempDir()
+	pd := filepath.Join(dir, "universal-plugin")
+	if err := os.Mkdir(pd, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte("name: universal-plugin\nversion: 1.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	// When plugin declares no runtimes, it should always be included (try-it).
+	got := h.listRegistryFiltered("any-runtime")
+	if len(got) != 1 {
+		t.Errorf("expected 1 plugin (unspecified runtime), got %d", len(got))
+	}
+}
+
+func TestListRegistry_ReadDirError_ReturnsEmpty(t *testing.T) {
+	h := NewPluginsHandler("/nonexistent/path/for/plugins", nil, nil)
+	got := h.listRegistryFiltered("")
+	if len(got) != 0 {
+		t.Errorf("expected empty list on ReadDir error, got %d", len(got))
+	}
+}
+
+func TestListRegistry_HTTPEndpoint(t *testing.T) {
+	dir := t.TempDir()
+	pd := filepath.Join(dir, "test-plugin")
+	if err := os.Mkdir(pd, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(pd, "plugin.yaml"), []byte("name: test-plugin\nversion: 2.0.0\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	h := NewPluginsHandler(dir, nil, nil)
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest("GET", "/plugins", nil)
+	h.ListRegistry(c)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var plugins []pluginInfo
+	if err := json.Unmarshal(w.Body.Bytes(), &plugins); err != nil {
+		t.Fatalf("failed to parse JSON: %v", err)
+	}
+	if len(plugins) != 1 {
+		t.Errorf("expected 1 plugin, got %d", len(plugins))
+	}
+	if plugins[0].Name != "test-plugin" {
+		t.Errorf("expected name 'test-plugin', got %q", plugins[0].Name)
+	}
+}