test: validate Micrometer opt-in compatibility

.github/renovate-tracked-deps.json

@@ -36,6 +36,11 @@
         "mise"
       ]
     },
+    ".github/workflows/micrometer-compatibility.yml": {
+      "regex": [
+        "mise"
+      ]
+    },
     ".github/workflows/lint.yml": {
       "regex": [
         "mise"
@@ -125,6 +130,7 @@
         "hugo",
         "java",
         "lychee",
+        "maven",
         "node",
         "npm:renovate",
         "protoc",

.github/workflows/micrometer-compatibility.yml

@@ -0,0 +1,43 @@
+---
+name: Micrometer Opt-In Compatibility
+
+on:
+  pull_request:
+  workflow_dispatch:
+    inputs:
+      micrometer-repository:
+        description: Micrometer repository to test, in owner/name form
+        required: false
+        default: zeitlinger/micrometer
+      micrometer-ref:
+        description: Micrometer branch, tag, or commit to test
+        required: false
+        default: feat/prometheus-client-opt-in
+
+permissions: {}
+
+jobs:
+  micrometer-compatibility:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          persist-credentials: false
+      - uses: jdx/mise-action@1648a7812b9aeae629881980618f079932869151 # v4.0.1
+        with:
+          version: v2026.5.5
+          sha256: 3aaab5c05a8a94a93b42b4f581779bbd5c44ddb251e7f3639fc671ec5c6aab8a
+      - name: Cache local Maven repository
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
+      - name: Run Micrometer compatibility tests
+        run: |
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            export MICROMETER_REPOSITORY="${{ github.event.inputs.micrometer-repository }}"
+            export MICROMETER_REF="${{ github.event.inputs.micrometer-ref }}"
+          fi
+          mise run micrometer:test

.mise/lib/micrometer_compat.py

@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+
+from __future__ import annotations
+
+import os
+import subprocess
+import xml.etree.ElementTree as ET
+from pathlib import Path
+from typing import Optional
+
+
+DEFAULT_MICROMETER_DIR = Path(
+    os.environ.get("MICROMETER_DIR", "/tmp/micrometer-compat")
+)
+DEFAULT_MICROMETER_REPOSITORY = os.environ.get(
+    "MICROMETER_REPOSITORY", "zeitlinger/micrometer"
+)
+DEFAULT_MICROMETER_REMOTE = os.environ.get("MICROMETER_REMOTE", "origin")
+DEFAULT_MICROMETER_REF = os.environ.get(
+    "MICROMETER_REF", "feat/prometheus-client-opt-in"
+)
+DEFAULT_INIT_SCRIPT = Path(
+    os.environ.get("MICROMETER_INIT_SCRIPT", "/tmp/micrometer-prom-local.init.gradle")
+)
+DEFAULT_PROM_VERSION = os.environ.get("PROM_VERSION")
+
+
+def run_cmd(cmd: list[str], cwd: Optional[Path] = None) -> None:
+    subprocess.run(cmd, cwd=cwd, check=True)
+
+
+def micrometer_repository_url(repository: str) -> str:
+    return f"https://github.com/{repository}.git"
+
+
+def check_clean_worktree(micrometer_dir: Path) -> None:
+    result = subprocess.run(
+        ["git", "status", "--short"],
+        cwd=micrometer_dir,
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+    if result.stdout.strip():
+        raise RuntimeError(
+            f"{micrometer_dir} has uncommitted changes; use a clean clone or set MICROMETER_DIR"
+        )
+
+
+def get_prom_version(root_dir: Path = Path.cwd()) -> str:
+    configured_version = DEFAULT_PROM_VERSION
+    if configured_version:
+        return configured_version
+    pom = ET.parse(root_dir / "pom.xml")
+    root = pom.getroot()
+    version = root.findtext("./{*}version")
+    if not version:
+        version = root.findtext("./{*}parent/{*}version")
+    if not version:
+        raise RuntimeError("could not determine Prometheus version from pom.xml")
+    return version
+
+
+def write_init_script(
+    init_script: Path = DEFAULT_INIT_SCRIPT, prom_version: Optional[str] = None
+) -> None:
+    if prom_version is None:
+        prom_version = get_prom_version()
+    init_script.write_text(
+        f"""allprojects {{
+    repositories {{
+        mavenLocal()
+        mavenCentral()
+        gradlePluginPortal()
+    }}
+    configurations.configureEach {{
+        resolutionStrategy.eachDependency {{ details ->
+            if (details.requested.group == 'io.prometheus') {{
+                details.useVersion('{prom_version}')
+                details.because(
+                    'Use local prom_client_java artifacts for downstream compatibility testing'
+                )
+            }}
+        }}
+    }}
+}}
+""",
+        encoding="utf-8",
+    )
+
+
+def prepare_repo(
+    micrometer_dir: Path = DEFAULT_MICROMETER_DIR,
+    repository: str = DEFAULT_MICROMETER_REPOSITORY,
+    remote: str = DEFAULT_MICROMETER_REMOTE,
+    ref: str = DEFAULT_MICROMETER_REF,
+) -> None:
+    repository_url = micrometer_repository_url(repository)
+    if (micrometer_dir / ".git").is_dir():
+        check_clean_worktree(micrometer_dir)
+        run_cmd(
+            ["git", "remote", "set-url", remote, repository_url], cwd=micrometer_dir
+        )
+        run_cmd(["git", "fetch", remote, ref], cwd=micrometer_dir)
+    else:
+        run_cmd(
+            [
+                "git",
+                "clone",
+                repository_url,
+                str(micrometer_dir),
+            ]
+        )
+        run_cmd(["git", "fetch", remote, ref], cwd=micrometer_dir)
+    run_cmd(
+        ["git", "checkout", "-B", "codex-micrometer-compat", "FETCH_HEAD"],
+        cwd=micrometer_dir,
+    )
+
+
+def install_local_artifacts(root_dir: Path = Path.cwd()) -> None:
+    run_cmd(
+        [
+            "./mvnw",
+            "install",
+            "-DskipTests",
+            "-Dcoverage.skip=true",
+            "-Dcheckstyle.skip=true",
+            "-Dwarnings=-nowarn",
+        ],
+        cwd=root_dir,
+    )
+
+
+def run_gradle_test(
+    test_selector: Optional[str] = None,
+    micrometer_dir: Path = DEFAULT_MICROMETER_DIR,
+    init_script: Path = DEFAULT_INIT_SCRIPT,
+) -> None:
+    cmd = [
+        "./gradlew",
+        "--no-daemon",
+        "-I",
+        str(init_script),
+        ":micrometer-registry-prometheus:test",
+    ]
+    if test_selector:
+        cmd.extend(["--tests", test_selector])
+    run_cmd(cmd, cwd=micrometer_dir)

.mise/tasks/micrometer/prepare.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+# [MISE] description="Install local artifacts and check out a target Micrometer ref"
+# [MISE] alias="micrometer:prepare"
+
+import sys
+
+
+sys.path.insert(0, ".mise/lib")
+
+
+def main() -> int:
+    from micrometer_compat import (
+        install_local_artifacts,
+        prepare_repo,
+        write_init_script,
+    )
+
+    install_local_artifacts()
+    prepare_repo()
+    write_init_script()
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

.mise/tasks/micrometer/test-class.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+# [MISE] description="Run Micrometer PrometheusMeterRegistryTest against a target Micrometer ref"
+# [MISE] alias="micrometer:test-class"
+
+import sys
+
+
+sys.path.insert(0, ".mise/lib")
+
+
+def main() -> int:
+    from micrometer_compat import (
+        install_local_artifacts,
+        prepare_repo,
+        run_gradle_test,
+        write_init_script,
+    )
+
+    install_local_artifacts()
+    prepare_repo()
+    write_init_script()
+    run_gradle_test("io.micrometer.prometheusmetrics.PrometheusMeterRegistryTest")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

.mise/tasks/micrometer/test.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+# [MISE] description="Run Micrometer Prometheus registry tests against a target Micrometer ref"
+# [MISE] alias="micrometer:test"
+
+import sys
+
+
+sys.path.insert(0, ".mise/lib")
+
+
+def main() -> int:
+    from micrometer_compat import (
+        install_local_artifacts,
+        prepare_repo,
+        run_gradle_test,
+        write_init_script,
+    )
+
+    install_local_artifacts()
+    prepare_repo()
+    write_init_script()
+    run_gradle_test()
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

mise.toml

@@ -2,6 +2,7 @@
 "go:github.com/grafana/oats" = "0.6.1"
 hugo = "0.161.1"
 java = "temurin-25.0.3+9.0.LTS"
+maven = "3.9.15"
 node = "24.15.0"
 protoc = "34.1"
 

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/CounterSnapshot.java

@@ -179,6 +179,14 @@ public Builder dataPoint(CounterDataPointSnapshot dataPoint) {
       return this;
     }
 
+    @Override
+    protected MetricMetadata buildMetadata() {
+      if (name == null) {
+        throw new IllegalArgumentException("Missing required field: name is null");
+      }
+      return MetricMetadataSupport.counterMetadata(name, help, unit);
+    }
+
     @Override
     public CounterSnapshot build() {
       return new CounterSnapshot(buildMetadata(), dataPoints);

prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/InfoSnapshot.java

@@ -118,6 +118,14 @@ public Builder unit(@Nullable Unit unit) {
       throw new IllegalArgumentException("Info metric cannot have a unit.");
     }
 
+    @Override
+    protected MetricMetadata buildMetadata() {
+      if (name == null) {
+        throw new IllegalArgumentException("Missing required field: name is null");
+      }
+      return MetricMetadataSupport.infoMetadata(name, help);
+    }
+
     @Override
     public InfoSnapshot build() {
       return new InfoSnapshot(buildMetadata(), dataPoints);