added formatter and tests

cmd/grpcurl/grpcurl.go

@@ -109,6 +109,8 @@ var (
 		will accept. If not specified, defaults to 4,194,304 (4 megabytes).`))
 	emitDefaults = flags.Bool("emit-defaults", false, prettify(`
 		Emit default values for JSON-encoded responses.`))
+	jsonError = flags.Bool("json-error", false, prettify(`
+		Emit error response as JSON.`))
 	protosetOut = flags.String("protoset-out", "", prettify(`
 		The name of a file to be written that will contain a FileDescriptorSet
 		proto. With the list and describe verbs, the listed or described
@@ -652,7 +654,11 @@ func main() {
 			fmt.Printf("Sent %d request%s and received %d response%s\n", reqCount, reqSuffix, h.NumResponses, respSuffix)
 		}
 		if h.Status.Code() != codes.OK {
-			grpcurl.PrintStatus(os.Stderr, h.Status, formatter)
+			if *jsonError {
+				grpcurl.PrintJSONStatus(os.Stderr, h.Status)
+			} else {
+				grpcurl.PrintStatus(os.Stderr, h.Status, formatter)
+			}
 			exit(1)
 		}
 	}

format.go

@@ -467,3 +467,12 @@ func PrintStatus(w io.Writer, stat *status.Status, formatter Formatter) {
 		}
 	}
 }
+
+// PrintJSONStatus returns the grpc status response as a JSON object
+func PrintJSONStatus(w io.Writer, stat *status.Status) {
+	jsonStatus, err := (&jsonpb.Marshaler{}).MarshalToString(stat.Proto())
+	if err != nil {
+		fmt.Fprintf(w, "ERROR: %v", err.Error())
+	}
+	fmt.Fprint(w, jsonStatus)
+}

format_test.go

@@ -11,7 +11,9 @@ import (
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes/struct"
 	"github.com/jhump/protoreflect/desc"
+	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
 )
 
 func TestRequestParser(t *testing.T) {
@@ -173,6 +175,25 @@ func TestHandler(t *testing.T) {
 	}
 }
 
+func TestPrintJSONStatus(t *testing.T) {
+	testCases := []struct {
+		input          *status.Status
+		expectedOutput string
+	}{{
+		input:          status.New(codes.InvalidArgument, "Missing Argument"),
+		expectedOutput: statusAsJSON,
+	}}
+
+	for _, tc := range testCases {
+		var b bytes.Buffer
+		PrintJSONStatus(&b, tc.input)
+		got := b.String()
+		if !compare(tc.expectedOutput, got) {
+			t.Errorf("Incorrect output. Expected:\n%s\nGot:\n%s", tc.expectedOutput, got)
+		}
+	}
+}
+
 // compare checks that actual and expected are equal, returning true if so.
 // A simple equality check (==) does not suffice because jsonpb formats
 // structpb.Value strangely. So if that formatting gets fixed, we don't
@@ -244,6 +265,7 @@ Response contents:
   "null": null
 }
 `
+	statusAsJSON  = `{"code":3,"message":"Missing Argument"} `
 	messageAsText = `struct_value: <
   fields: <
     key: "bar"