grpcreplay: remove extra spaces from prototext output (#54)

This should reduce spurious diffs in PRs/CLs.

grpcreplay/grpcreplay_test.go

@@ -703,5 +703,4 @@ func TestSetInitial(t *testing.T) {
 	if got, want := rep.Initial(), initialState; !bytes.Equal(got, want) {
 		t.Errorf("got initial state %q, want %q", got, want)
 	}
-
 }

grpcreplay/text_format.go

@@ -55,13 +55,39 @@ func (w *textWriter) writeEntry(e *entry) error {
 	if err != nil {
 		return err
 	}
+	bytes = removeExtraSpaces(bytes)
 	if _, err := fmt.Fprintln(w.w, len(bytes)); err != nil {
 		return err
 	}
 	_, err = fmt.Fprint(w.w, string(bytes))
 	return err
 }
 
+// Remove extra spaces after a colon in "field: value" lines.
+// prototext inserts these to discourage its use as a stable format,
+// but the more stability the better to avoid spurious diffs in CLs.
+func removeExtraSpaces(bs []byte) []byte {
+	var buf bytes.Buffer
+	for len(bs) > 0 {
+		var line []byte
+		var nlfound bool
+		line, bs, nlfound = bytes.Cut(bs, []byte{'\n'})
+		field, value, found := bytes.Cut(line, []byte{':'})
+		if !found {
+			buf.Write(line)
+		} else {
+			buf.Write(field)
+			buf.WriteByte(':')
+			buf.WriteByte(' ')
+			buf.Write(bytes.TrimSpace(value))
+		}
+		if nlfound {
+			buf.WriteByte('\n')
+		}
+	}
+	return buf.Bytes()
+}
+
 type textReader struct {
 	r    *bufio.Reader
 	file string

grpcreplay/text_format_test.go

@@ -0,0 +1,54 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package grpcreplay
+
+import "testing"
+
+func TestRemoveExtraSpaces(t *testing.T) {
+	in := `
+      fields: {
+        key:  "value"
+        value:    {
+          array_value: {
+            values:  	{
+              double_value: 0.30135461688041687
+            }
+            values: {
+              double_value: 0.3094993531703949
+            }
+          }
+        }
+      }
+`
+	want := `
+      fields: {
+        key: "value"
+        value: {
+          array_value: {
+            values: {
+              double_value: 0.30135461688041687
+            }
+            values: {
+              double_value: 0.3094993531703949
+            }
+          }
+        }
+      }
+`
+	got := string(removeExtraSpaces([]byte(in)))
+	if got != want {
+		t.Errorf("got\n%s\nwant\n%s", got, want)
+	}
+}