expfmt: format OpenMetrics 2.0 float values and validate units (#969)

- Use writeOpenMetricsFloat in writeOpenMetrics20Sample and writeExemplar20 so integral floats render with .0.
- Validate in.Unit against newlines and carriage returns.
- Update test cases to reflect float formatting and add unit newline error tests.

Signed-off-by: David Ashpole <dashpole@google.com>

Author: dashpole

expfmt/openmetrics_2_0_create.go

@@ -42,6 +42,9 @@ func MetricFamilyToOpenMetrics20(out io.Writer, in *dto.MetricFamily, options ..
 	if containsRawNewline(name) {
 		return 0, fmt.Errorf("MetricFamily name %q contains raw newlines", name)
 	}
+	if in.Unit != nil && containsRawNewline(*in.Unit) {
+		return 0, fmt.Errorf("MetricFamily unit %q contains raw newlines", *in.Unit)
+	}
 
 	// Try the interface upgrade. If it doesn't work, we'll use a
 	// bufio.Writer from the sync.Pool.
@@ -222,7 +225,7 @@ func writeOpenMetrics20Sample(w enhancedWriter, name string, metric *dto.Metric,
 	if useIntValue {
 		n, err = writeUint(w, intValue)
 	} else {
-		n, err = writeFloat(w, floatValue)
+		n, err = writeOpenMetricsFloat(w, floatValue)
 	}
 	written += n
 	if err != nil {
@@ -305,7 +308,7 @@ func writeExemplar20(w enhancedWriter, e *dto.Exemplar) (int, error) {
 	if err != nil {
 		return written, err
 	}
-	n, err = writeFloat(w, e.GetValue())
+	n, err = writeOpenMetricsFloat(w, e.GetValue())
 	written += n
 	if err != nil {
 		return written, err

expfmt/openmetrics_2_0_create_test.go

@@ -52,7 +52,7 @@ func TestCreateOpenMetrics20(t *testing.T) {
 			},
 			out: `# HELP http_requests_total Total number of HTTP requests.
 # TYPE http_requests_total counter
-http_requests_total{method="GET",code="200"} 1027 st@1234567890
+http_requests_total{method="GET",code="200"} 1027.0 st@1234567890
 `,
 		},
 		{
@@ -76,7 +76,7 @@ http_requests_total{method="GET",code="200"} 1027 st@1234567890
 			},
 			out: `# HELP http_requests_total Total number of HTTP requests.
 # TYPE http_requests_total counter
-http_requests_total{method="GET",code="200"} 1027 st@1234567890.987654321
+http_requests_total{method="GET",code="200"} 1027.0 st@1234567890.987654321
 `,
 		},
 		{
@@ -160,7 +160,7 @@ node_memory_active_bytes 1.2345e+09 1234567890
 				},
 			},
 			out: `# TYPE http_requests_total counter
-http_requests_total 1027 1234567891 st@1234567890 # {trace_id="1234"} 1 1234567890.5
+http_requests_total 1027.0 1234567891 st@1234567890 # {trace_id="1234"} 1.0 1234567890.5
 `,
 		},
 		{
@@ -181,7 +181,7 @@ http_requests_total 1027 1234567891 st@1234567890 # {trace_id="1234"} 1 12345678
 				},
 			},
 			out: `# TYPE http_requests_total counter
-http_requests_total 1027 # {} 1 1234567890.5
+http_requests_total 1027.0 # {} 1.0 1234567890.5
 `,
 		},
 		{
@@ -204,7 +204,7 @@ http_requests_total 1027 # {} 1 1234567890.5
 				},
 			},
 			out: `# TYPE http_requests_total counter
-http_requests_total 1027
+http_requests_total 1027.0
 `,
 		},
 		{
@@ -228,7 +228,7 @@ http_requests_total 1027
 				},
 			},
 			out: `# TYPE http_requests_total counter
-http_requests_total 1027 # {trace_id="1234"} NaN 1234567890
+http_requests_total 1027.0 # {trace_id="1234"} NaN 1234567890
 `,
 		},
 		{
@@ -262,7 +262,7 @@ test_metric 1.23
 				},
 			},
 			out: `# TYPE http_requests_total counter
-http_requests_total 1027
+http_requests_total 1027.0
 `,
 		},
 		{
@@ -282,7 +282,7 @@ http_requests_total 1027
 				},
 			},
 			out: `# TYPE "你好_total" counter
-{"你好_total","🌎"="🌍"} 1027
+{"你好_total","🌎"="🌍"} 1027.0
 `,
 		},
 	}
@@ -491,6 +491,30 @@ func TestCreateOpenMetrics20_Errors(t *testing.T) {
 			},
 			expectedErr: "contains raw newlines",
 		},
+		{
+			name: "NewlineInUnit",
+			in: &dto.MetricFamily{
+				Name: proto.String("test_counter_total"),
+				Type: dto.MetricType_COUNTER.Enum(),
+				Unit: proto.String("seconds\n"),
+				Metric: []*dto.Metric{
+					{Counter: &dto.Counter{Value: proto.Float64(1.0)}},
+				},
+			},
+			expectedErr: "contains raw newlines",
+		},
+		{
+			name: "CarriageReturnInUnit",
+			in: &dto.MetricFamily{
+				Name: proto.String("test_counter_total"),
+				Type: dto.MetricType_COUNTER.Enum(),
+				Unit: proto.String("seconds\r"),
+				Metric: []*dto.Metric{
+					{Counter: &dto.Counter{Value: proto.Float64(1.0)}},
+				},
+			},
+			expectedErr: "contains raw newlines",
+		},
 		{
 			name: "NilMetric",
 			in: &dto.MetricFamily{
@@ -614,7 +638,7 @@ func TestCreateOpenMetrics20_SimpleWriter(t *testing.T) {
 	}
 
 	expected := `# TYPE http_requests_total counter
-http_requests_total 1027
+http_requests_total 1027.0
 `
 	if buf.String() != expected {
 		t.Errorf("expected %q, got %q", expected, buf.String())