fix(mcp): use atomic.Bool for Server.readonly to prevent data races

pkg/mcp/mcp.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"os/exec"
 	"strings"
+	"sync/atomic"
 
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 )
@@ -22,7 +23,7 @@ const (
 type Server struct {
 	OnInit    func(context.Context) // Invoked when the server is initialized
 	prefix    string                // Command prefix ("func" or "kn func")
-	readonly  bool                  // disables deploy and delete when true
+	readonly  atomic.Bool           // disables deploy and delete when true
 	executor  executor
 	transport mcp.Transport // Transport to use (defaults to StdioTransport)
 	impl      *mcp.Server   // implements the protocol
@@ -58,7 +59,7 @@ func WithTransport(transport mcp.Transport) Option {
 // WithReadonly sets the server to readonly mode.
 func WithReadonly(readonly bool) Option {
 	return func(s *Server) {
-		s.readonly = readonly
+		s.readonly.Store(readonly)
 	}
 }
 
@@ -80,7 +81,7 @@ func New(options ...Option) *Server {
 			Title:   title,
 			Version: version},
 		&mcp.ServerOptions{
-			Instructions:       instructions(s.readonly),
+			Instructions:       instructions(s.readonly.Load()),
 			HasPrompts:         true,
 			HasResources:       true,
 			HasTools:           true,
@@ -146,7 +147,7 @@ func New(options ...Option) *Server {
 
 // Start the MCP server using the configured transport
 func (s *Server) Start(ctx context.Context, writeEnabled bool) error {
-	s.readonly = !writeEnabled
+	s.readonly.Store(!writeEnabled)
 	return s.impl.Run(ctx, s.transport)
 }
 

pkg/mcp/tools_delete.go

@@ -20,7 +20,7 @@ var deleteTool = &mcp.Tool{
 }
 
 func (s *Server) deleteHandler(ctx context.Context, r *mcp.CallToolRequest, input DeleteInput) (result *mcp.CallToolResult, output DeleteOutput, err error) {
-	if s.readonly {
+	if s.readonly.Load() {
 		err = fmt.Errorf("the server is currently in readonly mode.  Please set FUNC_ENABLE_MCP_WRITE and restart the client")
 		return
 	}

pkg/mcp/tools_delete_test.go

@@ -55,7 +55,7 @@ func TestTool_Delete_Args(t *testing.T) {
 		t.Fatal(err)
 	}
 	// Delete requires write mode - enable it for this test
-	server.readonly = false
+	server.readonly.Store(false)
 
 	// Build input arguments from test data
 	inputArgs := buildInputArgs(stringFlags, boolFlags)
@@ -76,3 +76,22 @@ func TestTool_Delete_Args(t *testing.T) {
 		t.Fatal("executor was not invoked")
 	}
 }
+
+// TestTool_Delete_Readonly ensures the delete tool rejects requests in readonly mode.
+func TestTool_Delete_Readonly(t *testing.T) {
+	client, _, err := newTestPairWithReadonly(t, true) // readonly = true
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	result, err := client.CallTool(t.Context(), &mcp.CallToolParams{
+		Name:      "delete",
+		Arguments: map[string]any{"name": "my-function"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !result.IsError {
+		t.Fatal("expected delete to be rejected in readonly mode")
+	}
+}

pkg/mcp/tools_deploy.go

@@ -20,7 +20,7 @@ var deployTool = &mcp.Tool{
 }
 
 func (s *Server) deployHandler(ctx context.Context, r *mcp.CallToolRequest, input DeployInput) (result *mcp.CallToolResult, output DeployOutput, err error) {
-	if s.readonly {
+	if s.readonly.Load() {
 		err = fmt.Errorf("the server is currently in readonly mode.  Please set FUNC_ENABLE_MCP_WRITE and restart the client")
 		return
 	}

pkg/mcp/tools_deploy_test.go

@@ -59,7 +59,7 @@ func TestTool_Deploy_Args(t *testing.T) {
 		t.Fatal(err)
 	}
 	// Deploy requires write mode - enable it for this test
-	server.readonly = false
+	server.readonly.Store(false)
 
 	// Build input arguments from test data
 	inputArgs := buildInputArgs(stringFlags, boolFlags)
@@ -79,3 +79,22 @@ func TestTool_Deploy_Args(t *testing.T) {
 		t.Fatal("executor was not invoked")
 	}
 }
+
+// TestTool_Deploy_Readonly ensures the deploy tool rejects requests in readonly mode.
+func TestTool_Deploy_Readonly(t *testing.T) {
+	client, _, err := newTestPairWithReadonly(t, true) // readonly = true
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	result, err := client.CallTool(t.Context(), &mcp.CallToolParams{
+		Name:      "deploy",
+		Arguments: map[string]any{"path": "."},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !result.IsError {
+		t.Fatal("expected deploy to be rejected in readonly mode")
+	}
+}