feat: expose the Prometheus Metrics library version

.github/scripts/sync-api-diffs.sh

@@ -31,8 +31,15 @@ mkdir -p "$out_dir"
 for report in "${reports[@]}"; do
 	# report path: <repo>/<module path>/target/japicmp/api-diff.diff
 	module="$(basename "$(dirname "$(dirname "$(dirname "$report")")")")"
+	# Japicmp emits a trailing blank line, which flint rejects in committed reports.
 	grep -vE '^(WARNING: You are using the option|Semantic versioning suggestion)' \
-		"$report" >"$out_dir/$module.txt"
+		"$report" | awk '
+			NF { last = NR }
+			{ lines[NR] = $0 }
+			END {
+				for (i = 1; i <= last; i++) print lines[i]
+			}
+		' >"$out_dir/$module.txt"
 done
 
 echo "Wrote ${#reports[@]} API diff report(s) to docs/apidiffs/current_vs_latest/."

docs/content/getting-started/quickstart.md

@@ -211,3 +211,15 @@ scrape_configs:
     static_configs:
       - targets: ["localhost:9400"]
 ```
+
+## Library version
+
+Get the Maven version of the Prometheus Java Metrics Library's core artifact with
+`PrometheusMetricsVersion.getVersion()`:
+
+```java
+String version = io.prometheus.metrics.core.PrometheusMetricsVersion.getVersion();
+```
+
+The result matches the `prometheus-metrics-core` artifact version, including a `-SNAPSHOT` suffix
+when present. It is not the Prometheus server version.

prometheus-metrics-core/pom.xml

@@ -72,6 +72,53 @@
 
   <build>
     <plugins>
+      <plugin>
+        <artifactId>maven-resources-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>generate-version-class</id>
+            <phase>generate-sources</phase>
+            <goals>
+              <goal>copy-resources</goal>
+            </goals>
+            <configuration>
+              <outputDirectory>${project.build.directory}/generated-sources/version</outputDirectory>
+              <resources>
+                <resource>
+                  <directory>src/main/version-template</directory>
+                  <filtering>true</filtering>
+                </resource>
+              </resources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>build-helper-maven-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>add-version-source</id>
+            <phase>generate-sources</phase>
+            <goals>
+              <goal>add-source</goal>
+            </goals>
+            <configuration>
+              <sources>
+                <source>${project.build.directory}/generated-sources/version</source>
+              </sources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <configuration>
+          <systemPropertyVariables>
+            <prometheus.metrics.core.version>${project.version}</prometheus.metrics.core.version>
+          </systemPropertyVariables>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.felix</groupId>
         <artifactId>maven-bundle-plugin</artifactId>

prometheus-metrics-core/src/main/java/io/prometheus/metrics/core/PrometheusMetricsVersion.java

@@ -0,0 +1,20 @@
+package io.prometheus.metrics.core;
+
+import io.prometheus.metrics.annotations.StableApi;
+
+/** Provides the version of the Prometheus Java Metrics Library. */
+@StableApi
+public final class PrometheusMetricsVersion {
+
+  private PrometheusMetricsVersion() {}
+
+  /**
+   * Returns the Maven version of the {@code prometheus-metrics-core} artifact containing this
+   * class.
+   *
+   * @return the artifact version, including any suffix such as {@code -SNAPSHOT}
+   */
+  public static String getVersion() {
+    return VersionInfo.VERSION;
+  }
+}

prometheus-metrics-core/src/main/version-template/io/prometheus/metrics/core/VersionInfo.java

@@ -0,0 +1,9 @@
+package io.prometheus.metrics.core;
+
+/** Generated version metadata. */
+final class VersionInfo {
+
+  static final String VERSION = "${project.version}";
+
+  private VersionInfo() {}
+}

prometheus-metrics-core/src/test/java/io/prometheus/metrics/core/PrometheusMetricsVersionTest.java

@@ -0,0 +1,16 @@
+package io.prometheus.metrics.core;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class PrometheusMetricsVersionTest {
+
+  @Test
+  void versionMatchesMavenProjectVersion() {
+    String version = PrometheusMetricsVersion.getVersion();
+
+    assertThat(version).isEqualTo(System.getProperty("prometheus.metrics.core.version"));
+    assertThat(version).isNotBlank().doesNotContain("${", "}");
+  }
+}