Fix escaping even more.

Change-Id: Ie958d557aae0dda68c451e9fafc615221cc07bb0

text/create.go

@@ -54,7 +54,8 @@ func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
 	if in.Help != nil {
 		n, err := fmt.Fprintf(
 			out, "# HELP %s %s\n",
-			name, strings.Replace(*in.Help, "\n", `\n`, -1))
+			name, escapeString(*in.Help, false),
+		)
 		written += n
 		if err != nil {
 			return written, err
@@ -217,7 +218,7 @@ func labelPairsToText(
 	for _, lp := range in {
 		n, err := fmt.Fprintf(
 			out, `%c%s="%s"`,
-			separator, lp.GetName(), escapeLabelValue(lp.GetValue()),
+			separator, lp.GetName(), escapeString(lp.GetValue(), true),
 		)
 		written += n
 		if err != nil {
@@ -229,7 +230,7 @@ func labelPairsToText(
 		n, err := fmt.Fprintf(
 			out, `%c%s="%s"`,
 			separator, additionalLabelName,
-			escapeLabelValue(additionalLabelValue),
+			escapeString(additionalLabelValue, true),
 		)
 		written += n
 		if err != nil {
@@ -244,16 +245,17 @@ func labelPairsToText(
 	return written, nil
 }
 
-// escapeLabelValue replaces '\' by '\\', '"' by '\"', and new line character by '\n'.
-func escapeLabelValue(v string) string {
+// escapeString replaces '\' by '\\', new line character by '\n', and - if
+// includeDoubleQuote is true - '"' by '\"'.
+func escapeString(v string, includeDoubleQuote bool) string {
 	result := bytes.NewBuffer(make([]byte, 0, len(v)))
 	for _, c := range v {
-		switch c {
-		case '\\':
+		switch {
+		case c == '\\':
 			result.WriteString(`\\`)
-		case '"':
+		case includeDoubleQuote && c == '"':
 			result.WriteString(`\"`)
-		case '\n':
+		case c == '\n':
 			result.WriteString(`\n`)
 		default:
 			result.WriteRune(c)

text/create_test.go

@@ -33,7 +33,7 @@ func testCreate(t test.Tester) {
 		{
 			in: &dto.MetricFamily{
 				Name: proto.String("name"),
-				Help: proto.String("two-line\n doc  string"),
+				Help: proto.String("two-line\n doc  str\\ing"),
 				Type: dto.MetricType_COUNTER.Enum(),
 				Metric: []*dto.Metric{
 					&dto.Metric{
@@ -69,7 +69,7 @@ func testCreate(t test.Tester) {
 					},
 				},
 			},
-			out: `# HELP name two-line\n doc  string
+			out: `# HELP name two-line\n doc  str\\ing
 # TYPE name counter
 name{labelname="val1",basename="basevalue"} NaN
 name{labelname="val2",basename="basevalue"} 0.23 1234567890
@@ -79,7 +79,7 @@ name{labelname="val2",basename="basevalue"} 0.23 1234567890
 		{
 			in: &dto.MetricFamily{
 				Name: proto.String("gauge_name"),
-				Help: proto.String("gauge\ndoc\nstring"),
+				Help: proto.String("gauge\ndoc\nstr\"ing"),
 				Type: dto.MetricType_GAUGE.Enum(),
 				Metric: []*dto.Metric{
 					&dto.Metric{
@@ -114,7 +114,7 @@ name{labelname="val2",basename="basevalue"} 0.23 1234567890
 					},
 				},
 			},
-			out: `# HELP gauge_name gauge\ndoc\nstring
+			out: `# HELP gauge_name gauge\ndoc\nstr"ing
 # TYPE gauge_name gauge
 gauge_name{name_1="val with\nnew line",name_2="val with \\backslash and \"quotes\""} +Inf
 gauge_name{name_1="Björn",name_2="佖佥"} 3.14e+42

text/parse.go

@@ -401,7 +401,7 @@ func (p *Parser) startTimestamp() stateFn {
 		return nil
 	}
 	p.currentMetric.TimestampMs = proto.Int64(timestamp)
-	if p.readTokenUntilNewline(); p.err != nil {
+	if p.readTokenUntilNewline(false); p.err != nil {
 		return nil // Unexpected end of input.
 	}
 	if p.currentToken.Len() > 0 {
@@ -419,12 +419,10 @@ func (p *Parser) readingHelp() stateFn {
 		return nil
 	}
 	// Rest of line is the docstring.
-	if p.readTokenUntilNewline(); p.err != nil {
+	if p.readTokenUntilNewline(true); p.err != nil {
 		return nil // Unexpected end of input.
 	}
-	p.currentMF.Help = proto.String(
-		strings.Replace(p.currentToken.String(), `\n`, "\n", -1),
-	)
+	p.currentMF.Help = proto.String(p.currentToken.String())
 	return p.startOfLine
 }
 
@@ -436,7 +434,7 @@ func (p *Parser) readingType() stateFn {
 		return nil
 	}
 	// Rest of line is the type.
-	if p.readTokenUntilNewline(); p.err != nil {
+	if p.readTokenUntilNewline(false); p.err != nil {
 		return nil // Unexpected end of input.
 	}
 	metricType, ok := dto.MetricType_value[strings.ToUpper(p.currentToken.String())]
@@ -490,11 +488,34 @@ func (p *Parser) readTokenUntilWhitespace() {
 // readTokenUntilNewline copies bytes from p.buf into p.currentToken.  The first
 // byte considered is the byte already read (now in p.currentByte).  The first
 // newline byte encountered is still copied into p.currentByte, but not into
-// p.currentToken.
-func (p *Parser) readTokenUntilNewline() {
+// p.currentToken. If recognizeEscapeSequence is true, two escape sequences are
+// recognized: '\\' tranlates into '\', and '\n' into a line-feed character. All
+// other escape sequences are invalid and cause an error.
+func (p *Parser) readTokenUntilNewline(recognizeEscapeSequence bool) {
 	p.currentToken.Reset()
-	for p.err == nil && p.currentByte != '\n' {
-		p.currentToken.WriteByte(p.currentByte)
+	escaped := false
+	for p.err == nil {
+		if recognizeEscapeSequence && escaped {
+			switch p.currentByte {
+			case '\\':
+				p.currentToken.WriteByte(p.currentByte)
+			case 'n':
+				p.currentToken.WriteByte('\n')
+			default:
+				p.parseError(fmt.Sprintf("invalid escape sequence '\\%c'", p.currentByte))
+				return
+			}
+			escaped = false
+		} else {
+			switch p.currentByte {
+			case '\n':
+				return
+			case '\\':
+				escaped = true
+			default:
+				p.currentToken.WriteByte(p.currentByte)
+			}
+		}
 		p.currentByte, p.err = p.buf.ReadByte()
 	}
 }

text/parse_test.go

@@ -91,9 +91,9 @@ no_labels{} 3
 # TYPE name counter
 name{labelname="val1",basename="basevalue"} NaN
 name {labelname="val2",basename="base\"v\\al\nue"} 0.23 1234567890
-# HELP name two-line\n doc  string
+# HELP name two-line\n doc  str\\ing
 
- # HELP  name2  	doc string 2
+ # HELP  name2  	doc str"ing 2
   #    TYPE    name2 gauge
 name2{labelname="val2"	,basename   =   "basevalue2"		} +Inf 54321
 name2{ labelname = "val1" }-Inf
@@ -101,7 +101,7 @@ name2{ labelname = "val1" }-Inf
 			out: []*dto.MetricFamily{
 				&dto.MetricFamily{
 					Name: proto.String("name"),
-					Help: proto.String("two-line\n doc  string"),
+					Help: proto.String("two-line\n doc  str\\ing"),
 					Type: dto.MetricType_COUNTER.Enum(),
 					Metric: []*dto.Metric{
 						&dto.Metric{
@@ -139,7 +139,7 @@ name2{ labelname = "val1" }-Inf
 				},
 				&dto.MetricFamily{
 					Name: proto.String("name2"),
-					Help: proto.String("doc string 2"),
+					Help: proto.String("doc str\"ing 2"),
 					Type: dto.MetricType_GAUGE.Enum(),
 					Metric: []*dto.Metric{
 						&dto.Metric{