Return 0.0.1 with no version for backwards compatibility

Signed-off-by: Goutham Veeramachaneni <[email protected]>

Author: gouthamve

expfmt/encode.go

@@ -100,10 +100,10 @@ func NegotiateIncludingOpenMetrics(h http.Header) Format {
 			return FmtText
 		}
 		if ac.Type+"/"+ac.SubType == OpenMetricsType && (ver == OpenMetricsVersion_0_0_1 || ver == OpenMetricsVersion_1_0_0 || ver == "") {
-			if ver == OpenMetricsVersion_0_0_1 {
-				return FmtOpenMetrics_0_0_1
+			if ver == OpenMetricsVersion_1_0_0 {
+				return FmtOpenMetrics_1_0_0
 			}
-			return FmtOpenMetrics_1_0_0
+			return FmtOpenMetrics_0_0_1
 		}
 	}
 	return FmtText

expfmt/encode_test.go

@@ -72,7 +72,7 @@ func TestNegotiateOpenMetrics(t *testing.T) {
 		{
 			name:              "OM format, no version",
 			acceptHeaderValue: "application/openmetrics-text",
-			expectedFmt:       string(FmtOpenMetrics_1_0_0),
+			expectedFmt:       string(FmtOpenMetrics_0_0_1),
 		},
 		{
 			name:              "OM format, 0.0.1 version",