service/dap: Add panic guard to DAP handlers

go.mod

@@ -5,7 +5,7 @@ go 1.11
 require (
 	github.com/cosiner/argv v0.0.0-20170225145430-13bacc38a0a5
 	github.com/cpuguy83/go-md2man v1.0.8 // indirect
-	github.com/google/go-dap v0.1.0
+	github.com/google/go-dap v0.2.0
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/mattn/go-colorable v0.0.0-20170327083344-ded68f7a9561

go.sum

@@ -10,6 +10,8 @@ github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/go-dap v0.1.0 h1:UzVzngq6yBR+bJVnTM8mjcdKrQnYR7m7U7JpNSnEo48=
 github.com/google/go-dap v0.1.0/go.mod h1:5q8aYQFnHOAZEMP+6vmq25HKYAEwE+LF5yh7JKrrhSQ=
+github.com/google/go-dap v0.2.0 h1:whjIGQRumwbR40qRU7CEKuFLmePUUc2s4Nt9DoXXxWk=
+github.com/google/go-dap v0.2.0/go.mod h1:5q8aYQFnHOAZEMP+6vmq25HKYAEwE+LF5yh7JKrrhSQ=
 github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=

service/dap/daptest/client.go

@@ -192,14 +192,6 @@ func (c *Client) UnkownRequest() {
 	c.send(request)
 }
 
-// UnkownProtocolMessage triggers dap.DecodeProtocolMessageFieldError.
-func (c *Client) UnkownProtocolMessage() {
-	m := &dap.ProtocolMessage{}
-	m.Seq = -1
-	m.Type = "unknown"
-	c.send(m)
-}
-
 // UnknownEvent triggers dap.DecodeProtocolMessageFieldError.
 func (c *Client) UnknownEvent() {
 	event := &dap.Event{}

service/dap/error_ids.go

@@ -3,6 +3,7 @@ package dap
 // Unique identifiers for messages returned for errors from requests.
 const (
 	UnsupportedCommand int = 9999
+	InternalError      int = 8888
 
 	// The values below come from the vscode-go debug adaptor.
 	// Although the spec says they should be unique, the adaptor

service/dap/server.go

@@ -21,11 +21,10 @@ import (
 	"github.com/go-delve/delve/service"
 	"github.com/go-delve/delve/service/api"
 	"github.com/go-delve/delve/service/debugger"
-	"github.com/google/go-dap"  // dap
+	"github.com/google/go-dap"
 	"github.com/sirupsen/logrus"
 )
 
-
 // Server implements a DAP server that can accept a single client for
 // a single debug session. It does not support restarting.
 // The server operates via two goroutines:
@@ -161,13 +160,19 @@ func (s *Server) serveDAPCodec() {
 			}
 			return
 		}
-		// TODO(polina) Add a panic guard,
-		// so we do not kill user's process when delve panics.
 		s.handleRequest(request)
 	}
 }
 
 func (s *Server) handleRequest(request dap.Message) {
+	defer func() {
+		// In case a handler panics, we catch the panic and send an error response
+		// back to the client.
+		if ierr := recover(); ierr != nil {
+			s.sendInternalErrorResponse(request.GetSeq(), fmt.Sprintf("%v", ierr))
+		}
+	}()
+
 	jsonmsg, _ := json.Marshal(request)
 	s.log.Debug("[<- from client]", string(jsonmsg))
 
@@ -253,11 +258,8 @@ func (s *Server) handleRequest(request dap.Message) {
 	default:
 		// This is a DAP message that go-dap has a struct for, so
 		// decoding succeeded, but this function does not know how
-		// to handle. We should be sending an ErrorResponse, but
-		// we cannot get to Seq and other fields from dap.Message.
-		// TODO(polina): figure out how to handle this better.
-		// Consider adding GetSeq() method to dap.Message interface.
-		s.log.Errorf("Unable to process %#v\n", request)
+		// to handle.
+		s.sendInternalErrorResponse(request.GetSeq(), fmt.Sprintf("Unable to process %#v\n", request))
 	}
 }
 
@@ -410,6 +412,21 @@ func (s *Server) sendErrorResponse(request dap.Request, id int, summary string,
 	s.send(er)
 }
 
+// sendInternalErrorResponse sends an "internal error" response back to the client.
+// We only take a seq here because we don't want to make assumptions about the
+// kind of message received by the server that this error is a reply to.
+func (s *Server) sendInternalErrorResponse(seq int, details string) {
+	er := &dap.ErrorResponse{}
+	er.Type = "response"
+	er.RequestSeq = seq
+	er.Success = false
+	er.Message = "Internal Error"
+	er.Body.Error.Id = InternalError
+	er.Body.Error.Format = fmt.Sprintf("%s: %s", er.Message, details)
+	s.log.Error(er.Body.Error.Format)
+	s.send(er)
+}
+
 func (s *Server) sendUnsupportedErrorResponse(request dap.Request) {
 	s.sendErrorResponse(request, UnsupportedCommand, "Unsupported command",
 		fmt.Sprintf("cannot process '%s' request", request.Command))