fn: json excess data check should ignore whitespace (#830)

* fn: json excess data check should ignore whitespace

* fn: adjustments and test case

api/agent/protocol/json.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net/http"
 	"sync"
+	"unicode"
 
 	"go.opencensus.io/trace"
 
@@ -149,9 +150,18 @@ func (h *JSONProtocol) Dispatch(ctx context.Context, ci CallInfo, w io.Writer) e
 func (h *JSONProtocol) isExcessData(err error, decoder *json.Decoder) error {
 	if err == nil {
 		// Now check for excess output, if this is the case, we can be certain that the next request will fail.
-		tmp, ok := decoder.Buffered().(*bytes.Reader)
+		reader, ok := decoder.Buffered().(*bytes.Reader)
-		if ok && tmp.Len() > 0 {
+		if ok && reader.Len() > 0 {
-			return ErrExcessData
+			// Let's check if extra data is whitespace, which is valid/ignored in json
+			for {
+				r, _, err := reader.ReadRune()
+				if err == io.EOF {
+					break
+				}
+				if !unicode.IsSpace(r) {
+					return ErrExcessData
+				}
+			}
 		}
 	}
 	return err

api/server/runner_test.go

@@ -186,6 +186,7 @@ func TestRouteRunnerIOPipes(t *testing.T) {
 
 	// sleep between logs and with debug enabled, fn-test-utils will log header/footer below:
 	immediateGarbage := `{"isDebug": true, "postOutGarbage": "YOGURT_YOGURT_YOGURT", "postSleepTime": 0}`
+	immediateJsonValidGarbage := `{"isDebug": true, "postOutGarbage": "\r", "postSleepTime": 0}`
 	delayedGarbage := `{"isDebug": true, "postOutGarbage": "YOGURT_YOGURT_YOGURT", "postSleepTime": 1000}`
 	ok := `{"isDebug": true}`
 
@@ -203,6 +204,9 @@ func TestRouteRunnerIOPipes(t *testing.T) {
 		//
 		// JSON WORLD
 		//
+		// this should go through.
+		{"/r/zoo/json/", immediateJsonValidGarbage, "GET", http.StatusOK, "", nil, 0},
+
 		// CASE I: immediate garbage: likely to be in the json decoder buffer after json resp parsing
 		{"/r/zoo/json/", immediateGarbage, "GET", http.StatusOK, "", nil, 0},
 
@@ -275,20 +279,22 @@ func TestRouteRunnerIOPipes(t *testing.T) {
 		t.Logf("Test %d: dockerId: %v", i, containerIds[i])
 		time.Sleep(test.sleepAmount)
 	}
-	jsonIds := containerIds[0:4]
+
+	jsonIds := containerIds[0:5]
 
 	// now cross check JSON container ids:
-	if jsonIds[0] != jsonIds[1] &&
+	if jsonIds[1] != jsonIds[2] &&
-		jsonIds[2] == "N/A" &&
+		jsonIds[0] == jsonIds[1] &&
-		jsonIds[1] != jsonIds[2] &&
+		jsonIds[3] == "N/A" &&
-		jsonIds[2] != jsonIds[3] {
+		jsonIds[2] != jsonIds[3] &&
+		jsonIds[3] != jsonIds[4] {
 		t.Logf("json container ids are OK, ids=%v", jsonIds)
 	} else {
 		isFailure = true
 		t.Errorf("json container ids are not OK, ids=%v", jsonIds)
 	}
 
-	httpids := containerIds[4:]
+	httpids := containerIds[5:]
 
 	// now cross check HTTP container ids:
 	if httpids[0] == httpids[1] &&