Introduce Prometheus Java Client integration test (#1468)

And document some possible future improvements.

.github/workflows/run-integration-tests.yml

@@ -19,21 +19,27 @@ jobs:
     runs-on: ubuntu-24.04
     strategy:
       matrix:
-        integration-test: [ "checkstyle", "metrics" ]
+        integration-test: [ "checkstyle", "metrics", "prometheus-java-client" ]
     steps:
       - name: Install Harden-Runner
         uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
         with:
           disable-sudo: true
           egress-policy: block
           allowed-endpoints: >
+            # XXX: After updating the validation build flags in
+            # `integration-tests/prometheus-java-client.sh`, review whether the
+            # Docker domains specified here can be dropped.
             api.adoptium.net:443
+            auth.docker.io:443
             checkstyle.org:443
             example.com:80
             github.com:443
             objects.githubusercontent.com:443
             oss.sonatype.org:443
+            production.cloudflare.docker.com:443
             raw.githubusercontent.com:443
+            registry-1.docker.io:443
             repo.maven.apache.org:443
             repository.sonatype.org:443
       - name: Check out code and set up JDK and Maven

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/JUnitMethodDeclaration.java

@@ -101,6 +101,8 @@ private void reportMethodRenameBlocker(MethodTree tree, String reason, VisitorSt
             .build());
   }
 
+  // XXX: Consider dropping leading underscores that otherwise result when canonicalizing
+  // `test_some_method_name`.
   private static Optional<String> tryCanonicalizeMethodName(MethodSymbol symbol) {
     return Optional.of(symbol.getQualifiedName().toString())
         .filter(name -> name.startsWith(TEST_PREFIX))

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/StringJoin.java

@@ -36,7 +36,9 @@
  */
 // XXX: What about `v1 + "sep" + v2` and similar expressions? Do we want to rewrite those to
 // `String.join`, or should some `String.join` invocations be rewritten to use the `+` operator?
-// (The latter suggestion would conflict with the `FormatStringConcatenation` check.)
+// (The latter suggestion would conflict with the `FormatStringConcatenation` check, but does make
+// more sense when `"sep"` is a long string. Similarly for `String.format("%s some long text %s",
+// arg1, arg2)`.)
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Prefer `String#join` over `String#format`",