test(mcp): add subsystem tests with IPC round-trip verification

Fix cyclic type panic in contextmenu tools by using map[string]any
for ContextMenuDef which contains self-referencing MenuItemDef.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/mcp/mcp_test.go

@@ -0,0 +1,60 @@
+// pkg/mcp/mcp_test.go
+package mcp
+
+import (
+	"context"
+	"testing"
+
+	"forge.lthn.ai/core/go/pkg/core"
+	"forge.lthn.ai/core/gui/pkg/clipboard"
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSubsystem_Good_Name(t *testing.T) {
+	c, _ := core.New(core.WithServiceLock())
+	sub := New(c)
+	assert.Equal(t, "display", sub.Name())
+}
+
+func TestSubsystem_Good_RegisterTools(t *testing.T) {
+	c, _ := core.New(core.WithServiceLock())
+	sub := New(c)
+	// RegisterTools should not panic with a real mcp.Server
+	server := mcp.NewServer(&mcp.Implementation{Name: "test", Version: "0.1.0"}, nil)
+	assert.NotPanics(t, func() { sub.RegisterTools(server) })
+}
+
+// Integration test: verify the IPC round-trip that MCP tool handlers use.
+
+type mockClipPlatform struct {
+	text string
+	ok   bool
+}
+
+func (m *mockClipPlatform) Text() (string, bool)  { return m.text, m.ok }
+func (m *mockClipPlatform) SetText(t string) bool  { m.text = t; m.ok = t != ""; return true }
+
+func TestMCP_Good_ClipboardRoundTrip(t *testing.T) {
+	c, err := core.New(
+		core.WithService(clipboard.Register(&mockClipPlatform{text: "hello", ok: true})),
+		core.WithServiceLock(),
+	)
+	require.NoError(t, err)
+	require.NoError(t, c.ServiceStartup(context.Background(), nil))
+
+	// Verify the IPC path that clipboard_read tool handler uses
+	result, handled, err := c.QUERY(clipboard.QueryText{})
+	require.NoError(t, err)
+	assert.True(t, handled)
+	content, _ := result.(clipboard.ClipboardContent)
+	assert.Equal(t, "hello", content.Text)
+}
+
+func TestMCP_Bad_NoServices(t *testing.T) {
+	c, _ := core.New(core.WithServiceLock())
+	// Without any services, QUERY should return handled=false
+	_, handled, _ := c.QUERY(clipboard.QueryText{})
+	assert.False(t, handled)
+}

pkg/mcp/tools_contextmenu.go

@@ -3,6 +3,7 @@ package mcp
 
 import (
 	"context"
+	"encoding/json"
 
 	"forge.lthn.ai/core/gui/pkg/contextmenu"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
@@ -10,16 +11,23 @@ import (
 
 // --- contextmenu_add ---
 
+// ContextMenuAddInput uses map[string]any for the menu definition because
+// contextmenu.ContextMenuDef contains self-referencing MenuItemDef (Items []MenuItemDef)
+// which the MCP SDK schema generator cannot handle (cycle detection panic).
 type ContextMenuAddInput struct {
-	Name string                    `json:"name"`
-	Menu contextmenu.ContextMenuDef `json:"menu"`
+	Name string         `json:"name"`
+	Menu map[string]any `json:"menu"`
 }
 type ContextMenuAddOutput struct {
 	Success bool `json:"success"`
 }
 
 func (s *Subsystem) contextMenuAdd(_ context.Context, _ *mcp.CallToolRequest, input ContextMenuAddInput) (*mcp.CallToolResult, ContextMenuAddOutput, error) {
-	_, _, err := s.core.PERFORM(contextmenu.TaskAdd{Name: input.Name, Menu: input.Menu})
+	// Convert map[string]any to ContextMenuDef via JSON round-trip
+	menuJSON, _ := json.Marshal(input.Menu)
+	var menuDef contextmenu.ContextMenuDef
+	_ = json.Unmarshal(menuJSON, &menuDef)
+	_, _, err := s.core.PERFORM(contextmenu.TaskAdd{Name: input.Name, Menu: menuDef})
 	if err != nil {
 		return nil, ContextMenuAddOutput{}, err
 	}
@@ -49,7 +57,7 @@ type ContextMenuGetInput struct {
 	Name string `json:"name"`
 }
 type ContextMenuGetOutput struct {
-	Menu *contextmenu.ContextMenuDef `json:"menu"`
+	Menu map[string]any `json:"menu"`
 }
 
 func (s *Subsystem) contextMenuGet(_ context.Context, _ *mcp.CallToolRequest, input ContextMenuGetInput) (*mcp.CallToolResult, ContextMenuGetOutput, error) {
@@ -58,14 +66,21 @@ func (s *Subsystem) contextMenuGet(_ context.Context, _ *mcp.CallToolRequest, in
 		return nil, ContextMenuGetOutput{}, err
 	}
 	menu, _ := result.(*contextmenu.ContextMenuDef)
-	return nil, ContextMenuGetOutput{Menu: menu}, nil
+	if menu == nil {
+		return nil, ContextMenuGetOutput{}, nil
+	}
+	// Convert to map[string]any via JSON round-trip to avoid cyclic type in schema
+	menuJSON, _ := json.Marshal(menu)
+	var menuMap map[string]any
+	_ = json.Unmarshal(menuJSON, &menuMap)
+	return nil, ContextMenuGetOutput{Menu: menuMap}, nil
 }
 
 // --- contextmenu_list ---
 
 type ContextMenuListInput struct{}
 type ContextMenuListOutput struct {
-	Menus map[string]contextmenu.ContextMenuDef `json:"menus"`
+	Menus map[string]any `json:"menus"`
 }
 
 func (s *Subsystem) contextMenuList(_ context.Context, _ *mcp.CallToolRequest, _ ContextMenuListInput) (*mcp.CallToolResult, ContextMenuListOutput, error) {
@@ -74,7 +89,11 @@ func (s *Subsystem) contextMenuList(_ context.Context, _ *mcp.CallToolRequest, _
 		return nil, ContextMenuListOutput{}, err
 	}
 	menus, _ := result.(map[string]contextmenu.ContextMenuDef)
-	return nil, ContextMenuListOutput{Menus: menus}, nil
+	// Convert to map[string]any via JSON round-trip to avoid cyclic type in schema
+	menusJSON, _ := json.Marshal(menus)
+	var menusMap map[string]any
+	_ = json.Unmarshal(menusJSON, &menusMap)
+	return nil, ContextMenuListOutput{Menus: menusMap}, nil
 }
 
 // --- Registration ---