pkg/gobuild/gobuild.go

@@ -90,7 +90,7 @@ func goBuildArgs(debugname string, pkgs []string, buildflags string, isTest bool
 	return args
 }
 
-// goBuildArgs2 is like goBuildArgs, but takes either string, []string, or []interface{}.
+// goBuildArgs2 is like goBuildArgs, but takes either string or []string.
 func goBuildArgs2(debugname string, pkgs []string, buildflags interface{}, isTest bool) ([]string, error) {
 	var args []string
     switch buildflags := buildflags.(type) {
@@ -99,15 +99,6 @@ func goBuildArgs2(debugname string, pkgs []string, buildflags interface{}, isTes
 	case nil:
 	case []string:
 		args = append(args, buildflags...)
-	case []interface{}:
-		for _, flag := range buildflags {
-			switch flag := flag.(type) {
-			case string:
-				args = append(args, flag)
-			default:
-				return nil, fmt.Errorf("invalid buildflags element type %T (%q)", flag, flag)
-			}
-		}
 	default:
 		return nil, fmt.Errorf("invalid buildflags type %T", buildflags)
 	}

service/dap/server.go

@@ -982,9 +982,9 @@ func (s *Session) onLaunchRequest(request *dap.LaunchRequest) {
 
 		switch args.Mode {
 		case "debug":
-			cmd, out, err = gobuild.GoBuildCombinedOutput(args.Output, []string{args.Program}, args.BuildFlags)
+			cmd, out, err = gobuild.GoBuildCombinedOutput(args.Output, []string{args.Program}, args.BuildFlags.value)
 		case "test":
-			cmd, out, err = gobuild.GoTestBuildCombinedOutput(args.Output, []string{args.Program}, args.BuildFlags)
+			cmd, out, err = gobuild.GoTestBuildCombinedOutput(args.Output, []string{args.Program}, args.BuildFlags.value)
 		}
 		args.DlvCwd, _ = filepath.Abs(args.DlvCwd)
 		s.config.log.Debugf("building from %q: [%s]", args.DlvCwd, cmd)

service/dap/server_test.go

@@ -6316,7 +6316,7 @@ func TestBadLaunchRequests(t *testing.T) {
 		// Bad "buildFlags"
 		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "buildFlags": 123})
 		checkFailedToLaunchWithMessage(client.ExpectVisibleErrorResponse(t),
-			"Failed to launch: invalid debug configuration - cannot unmarshal number into \"buildFlags\" of type string")
+			"Failed to launch: invalid debug configuration - cannot unmarshal number into \"buildFlags\" of type []string or string")
 
 		// Bad "backend"
 		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "backend": 123})

service/dap/types.go

@@ -110,7 +110,7 @@ type LaunchConfig struct {
 	// or
 	//    "buildFlags": ["-tags=integration", "-ldflags=-X main.Hello=World"]
 	// Using other types is an error.
-	BuildFlags interface{} `json:"buildFlags,omitempty"`
+	BuildFlags BuildFlags `json:"buildFlags,omitempty"`
 
 	// Output path for the binary of the debuggee.
 	// Relative path is interpreted as the path relative to
@@ -274,3 +274,30 @@ func prettyPrint(config interface{}) string {
 	}
 	return string(pretty)
 }
+
+// BuildFlags is either string or []string.
+type BuildFlags struct{
+	value interface{}
+}
+
+func (s *BuildFlags) UnmarshalJSON(b []byte) error {
+	if v := string(b); v == "" || v == "null" {
+		s.value = nil
+		return nil
+	}
+	var strs []string
+	if err := json.Unmarshal(b, &strs); err == nil {
+		s.value = strs
+		return nil
+	}
+	var str string
+	if err := json.Unmarshal(b, &str); err != nil {
+		s.value = nil
+		if uerr, ok := err.(*json.UnmarshalTypeError); ok {
+			return fmt.Errorf(`cannot unmarshal %v into "buildFlags" of type []string or string`, uerr.Value)
+		}
+		return err
+	}
+	s.value = str
+	return nil	
+}