Polish

Polish micrometer-metricsgh-4608
The test was not testing the changes made (it would have passed before the changes to main code), so I removed it.
Removed the unused constructor in MicrometerCollector because it is a package private class we know all the callsites.

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/MicrometerCollector.java

@@ -44,14 +44,9 @@ class MicrometerCollector extends Collector implements Collector.Describable {
 
     private final String help;
 
-    public MicrometerCollector(Meter.Id id, NamingConvention convention, PrometheusConfig config) {
-        this.id = id;
-        this.conventionName = id.getConventionName(convention);
-        this.tagKeys = id.getConventionTags(convention).stream().map(Tag::getKey).collect(toList());
-        this.help = config.descriptions() ? Optional.ofNullable(id.getDescription()).orElse(" ") : " ";
-    }
-
-    public MicrometerCollector(String name, Meter.Id id, NamingConvention convention, PrometheusConfig config) {
+    // take name to avoid calling NamingConvention#name after the callsite has already
+    // done it
+    MicrometerCollector(String name, Meter.Id id, NamingConvention convention, PrometheusConfig config) {
         this.id = id;
         this.conventionName = name;
         this.tagKeys = id.getConventionTags(convention).stream().map(Tag::getKey).collect(toList());

implementations/micrometer-registry-prometheus/src/test/java/io/micrometer/prometheus/MicrometerCollectorTest.java

@@ -31,11 +31,14 @@
 
 class MicrometerCollectorTest {
 
+    NamingConvention convention = NamingConvention.snakeCase;
+
     @Issue("#769")
     @Test
     void manyTags() {
         Meter.Id id = Metrics.counter("my.counter").getId();
-        MicrometerCollector collector = new MicrometerCollector(id, NamingConvention.dot, PrometheusConfig.DEFAULT);
+        MicrometerCollector collector = new MicrometerCollector(id.getConventionName(convention), id, convention,
+                PrometheusConfig.DEFAULT);
 
         for (Integer i = 0; i < 20_000; i++) {
             Collector.MetricFamilySamples.Sample sample = new Collector.MetricFamilySamples.Sample("my_counter",
@@ -52,7 +55,8 @@ void manyTags() {
     @Test
     void sameValuesDifferentOrder() {
         Meter.Id id = Metrics.counter("my.counter").getId();
-        MicrometerCollector collector = new MicrometerCollector(id, NamingConvention.dot, PrometheusConfig.DEFAULT);
+        MicrometerCollector collector = new MicrometerCollector(id.getConventionName(convention), id, convention,
+                PrometheusConfig.DEFAULT);
 
         Collector.MetricFamilySamples.Sample sample = new Collector.MetricFamilySamples.Sample("my_counter",
                 asList("k", "k2"), asList("v1", "v2"), 1.0);