handle empty content type

Signed-off-by: Lixia (Sylvia) Lei <[email protected]>

internal/trace/transport.go

@@ -103,6 +103,9 @@ func logResponseBody(resp *http.Response) string {
 
 	// non-applicable body is not printed and remains untouched for subsequent processing
 	contentType := resp.Header.Get("Content-Type")
+	if contentType == "" {
+		return "   Response body without a content type is not printed"
+	}
 	if !isPrintableContentType(contentType) {
 		return fmt.Sprintf("   Response body of content type %q is not printed", contentType)
 	}
@@ -137,10 +140,6 @@ func logResponseBody(resp *http.Response) string {
 
 // isPrintableContentType returns true if the content of contentType is printable.
 func isPrintableContentType(contentType string) bool {
-	if len(contentType) == 0 {
-		return false
-	}
-
 	mediaType, _, err := mime.ParseMediaType(contentType)
 	if err != nil {
 		return false

internal/trace/transport_test.go

@@ -178,6 +178,25 @@ func Test_logResponseBody(t *testing.T) {
 			},
 			want: "whatever",
 		},
+		{
+			name:     "Missing content type header",
+			wantData: []byte("whatever"),
+			resp: &http.Response{
+				Body:          io.NopCloser(bytes.NewReader([]byte("whatever"))),
+				ContentLength: 8,
+			},
+			want: "   Response body without a content type is not printed",
+		},
+		{
+			name:     "Empty content type header",
+			wantData: []byte("whatever"),
+			resp: &http.Response{
+				Body:          io.NopCloser(bytes.NewReader([]byte("whatever"))),
+				ContentLength: 8,
+				Header:        http.Header{"Content-Type": []string{""}},
+			},
+			want: "   Response body without a content type is not printed",
+		},
 		{
 			name:     "Non-printable content type",
 			wantData: []byte("binary data"),