allow multiple dashes in StatsD metric names

Signed-off-by: Evan Van Dam <evan.vandam@wonolo.com>

pkg/mapper/mapper.go

@@ -30,10 +30,10 @@ import (
 
 var (
 	// The first segment of a match cannot start with a number
-	statsdMetricRE = `[a-zA-Z_](-?[a-zA-Z0-9_])*`
+	statsdMetricRE = `[a-zA-Z_]([a-zA-Z0-9_\-])*`
 	// The subsequent segments of a match can start with a number
 	// See https://github.com/prometheus/statsd_exporter/issues/328
-	statsdMetricSubsequentRE = `[a-zA-Z0-9_](-?[a-zA-Z0-9_])*`
+	statsdMetricSubsequentRE = `[a-zA-Z0-9_]([a-zA-Z0-9_\-])*`
 	templateReplaceRE        = `(\$\{?\d+\}?)`
 
 	metricLineRE = regexp.MustCompile(`^(\*|` + statsdMetricRE + `)(\.\*|\.` + statsdMetricSubsequentRE + `)*$`)

pkg/mapper/mapper_test.go

@@ -68,7 +68,7 @@ func TestMetricMapperYAML(t *testing.T) {
 mappings:
 - match: test.dispatcher.*.*.*
   name: "dispatch_events"
-  labels: 
+  labels:
     processor: "$1"
     action: "$2"
     result: "$3"
@@ -430,12 +430,27 @@ mappings:
 			testName: "Config with bad metric line",
 			config: `---
 mappings:
-- match: bad--metric-line.*.*
+- match: bad!!metric-line.*.*
   name: "foo"
   labels: {}
   `,
 			configBad: true,
 		},
+		{
+			testName: "Config with multiple dashes in metric name",
+			config: `---
+mappings:
+- match: "foo--bar.*"
+  name: "foo_bar_${1}"
+  labels: {}
+  `,
+			mappings: mappings{
+				{
+					statsdMetric: "foo--bar.count",
+					name:         "foo_bar_count",
+				},
+			},
+		},
 		{
 			testName: "Config with dynamic metric name",
 			config: `---