Backport Log API enhancements and mojo MDC to 4.0.x

api/maven-api-core/src/main/java/org/apache/maven/api/plugin/Log.java

@@ -36,13 +36,70 @@
 @Experimental
 @Provider
 public interface Log {
+    /**
+     * {@return true if the <b>trace</b> error level is enabled}
+     */
+    boolean isTraceEnabled();
+
+    /**
+     * Sends a message to the user in the <b>trace</b> error level.
+     * <p>
+     * Trace is the most verbose level, intended for Maven core internals
+     * such as resolver negotiation, model interpolation, and lifecycle
+     * ordering details.  Use {@link #debug(CharSequence)} instead for
+     * messages that help <em>users</em> investigate their build
+     * (e.g. why a module was recompiled).
+     *
+     * @param content the message to log
+     */
+    void trace(CharSequence content);
+
+    /**
+     * Sends a message (and accompanying exception) to the user at the <b>trace</b> error level.
+     * The error's stacktrace will be output when this error level is enabled.
+     *
+     * @param content the message to log
+     * @param error the error that caused this log
+     */
+    void trace(CharSequence content, Throwable error);
+
+    /**
+     * Sends an exception to the user in the <b>trace</b> error level.
+     * The stack trace for this exception will be output when this error level is enabled.
+     *
+     * @param error the error that caused this log
+     */
+    void trace(Throwable error);
+
+    /**
+     * Sends a lazily-computed message in the <b>trace</b> error level.
+     * The supplier is only evaluated if trace is enabled.
+     *
+     * @param content the message supplier
+     */
+    void trace(Supplier<String> content);
+
+    /**
+     * Sends a lazily-computed message (and accompanying exception) in the <b>trace</b> error level.
+     * The supplier is only evaluated if trace is enabled.
+     *
+     * @param content the message supplier
+     * @param error the error that caused this log
+     */
+    void trace(Supplier<String> content, Throwable error);
+
     /**
      * {@return true if the <b>debug</b> error level is enabled}
      */
     boolean isDebugEnabled();
 
     /**
      * Sends a message to the user in the <b>debug</b> error level.
+     * <p>
+     * Debug is intended for messages that help <em>users</em> investigate
+     * their build — for example, why a module was recompiled or what
+     * classpath was resolved.  For Maven core internals, use
+     * {@link #trace(CharSequence)} instead.
      *
      * @param content the message to log
      */
@@ -167,4 +224,27 @@ public interface Log {
     void error(Supplier<String> content);
 
     void error(Supplier<String> content, Throwable error);
+
+    /**
+     * Returns a child logger whose name is derived from this logger's name
+     * by appending a dot and the given suffix.
+     *
+     * <p>For example, if a plugin's logger is named
+     * {@code "org.apache.maven.plugins.compiler.CompilerMojo"},
+     * then {@code child("diagnostics")} returns a logger named
+     * {@code "org.apache.maven.plugins.compiler.CompilerMojo.diagnostics"}.
+     * This lets sub-components log under an independently filterable name
+     * without requiring a separate injection point.</p>
+     *
+     * <p>The default implementation returns {@code this}, so existing
+     * {@code Log} implementations continue to work without changes.
+     * Implementations that wrap a hierarchical logging backend (such as
+     * SLF4J) should override this to create a real child logger.</p>
+     *
+     * @param name the suffix to append (must not be {@code null} or blank)
+     * @return a child logger — never {@code null}
+     */
+    default Log child(String name) {
+        return this;
+    }
 }

impl/maven-core/src/main/java/org/apache/maven/internal/impl/DefaultLog.java

@@ -22,6 +22,7 @@
 
 import org.apache.maven.api.plugin.Log;
 import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import static java.util.Objects.requireNonNull;
 
@@ -32,6 +33,46 @@ public DefaultLog(Logger logger) {
         this.logger = requireNonNull(logger);
     }
 
+    @Override
+    public boolean isTraceEnabled() {
+        return logger.isTraceEnabled();
+    }
+
+    @Override
+    public void trace(CharSequence content) {
+        if (isTraceEnabled()) {
+            logger.trace(toString(content));
+        }
+    }
+
+    @Override
+    public void trace(CharSequence content, Throwable error) {
+        if (isTraceEnabled()) {
+            logger.trace(toString(content), error);
+        }
+    }
+
+    @Override
+    public void trace(Throwable error) {
+        if (isTraceEnabled()) {
+            logger.trace("", error);
+        }
+    }
+
+    @Override
+    public void trace(Supplier<String> content) {
+        if (isTraceEnabled()) {
+            logger.trace(content.get());
+        }
+    }
+
+    @Override
+    public void trace(Supplier<String> content, Throwable error) {
+        if (isTraceEnabled()) {
+            logger.trace(content.get(), error);
+        }
+    }
+
     @Override
     public void debug(CharSequence content) {
         if (isDebugEnabled()) {
@@ -48,7 +89,9 @@ public void debug(CharSequence content, Throwable error) {
 
     @Override
     public void debug(Throwable error) {
-        logger.debug("", error);
+        if (isDebugEnabled()) {
+            logger.debug("", error);
+        }
     }
 
     @Override
@@ -81,7 +124,9 @@ public void info(CharSequence content, Throwable error) {
 
     @Override
     public void info(Throwable error) {
-        logger.info("", error);
+        if (isInfoEnabled()) {
+            logger.info("", error);
+        }
     }
 
     @Override
@@ -114,7 +159,9 @@ public void warn(CharSequence content, Throwable error) {
 
     @Override
     public void warn(Throwable error) {
-        logger.warn("", error);
+        if (isWarnEnabled()) {
+            logger.warn("", error);
+        }
     }
 
     @Override
@@ -127,7 +174,7 @@ public void warn(Supplier<String> content) {
     @Override
     public void warn(Supplier<String> content, Throwable error) {
         if (isWarnEnabled()) {
-            logger.info(content.get(), error);
+            logger.warn(content.get(), error);
         }
     }
 
@@ -147,7 +194,9 @@ public void error(CharSequence content, Throwable error) {
 
     @Override
     public void error(Throwable error) {
-        logger.error("", error);
+        if (isErrorEnabled()) {
+            logger.error("", error);
+        }
     }
 
     @Override
@@ -184,6 +233,12 @@ public boolean isErrorEnabled() {
         return logger.isErrorEnabled();
     }
 
+    @Override
+    public Log child(String name) {
+        requireNonNull(name, "name");
+        return new DefaultLog(LoggerFactory.getLogger(logger.getName() + "." + name));
+    }
+
     private String toString(CharSequence content) {
         return content != null ? content.toString() : "";
     }

impl/maven-core/src/main/java/org/apache/maven/logging/LoggingExecutionListener.java

@@ -121,19 +121,22 @@ public void projectSkipped(ExecutionEvent event) {
     @Override
     public void mojoStarted(ExecutionEvent event) {
         setMdc(event);
+        setMojoMdc(event);
         buildEventListener.mojoStarted(event);
         delegate.mojoStarted(event);
     }
 
     @Override
     public void mojoSucceeded(ExecutionEvent event) {
         setMdc(event);
+        ProjectBuildLogAppender.setMojoId(null);
         delegate.mojoSucceeded(event);
     }
 
     @Override
     public void mojoFailed(ExecutionEvent event) {
         setMdc(event);
+        ProjectBuildLogAppender.setMojoId(null);
         delegate.mojoFailed(event);
     }
 
@@ -187,4 +190,12 @@ private void setMdc(ExecutionEvent event) {
             ProjectBuildLogAppender.setProjectId(event.getProject().getArtifactId());
         }
     }
+
+    private void setMojoMdc(ExecutionEvent event) {
+        if (event.getMojoExecution() != null) {
+            String mojoId = event.getMojoExecution().getMojoDescriptor().getFullGoalName() + "@"
+                    + event.getMojoExecution().getExecutionId();
+            ProjectBuildLogAppender.setMojoId(mojoId);
+        }
+    }
 }

impl/maven-core/src/main/java/org/apache/maven/logging/ProjectBuildLogAppender.java

@@ -27,7 +27,9 @@
 public class ProjectBuildLogAppender implements AutoCloseable {
 
     private static final String KEY_PROJECT_ID = "maven.project.id";
+    private static final String KEY_MOJO_ID = "maven.mojo.id";
     private static final ThreadLocal<String> PROJECT_ID = new InheritableThreadLocal<>();
+    private static final ThreadLocal<String> MOJO_ID = new InheritableThreadLocal<>();
     private static final ThreadLocal<String> FORKING_PROJECT_ID = new InheritableThreadLocal<>();
 
     public static String getProjectId() {
@@ -52,6 +54,31 @@ public static void setProjectId(String projectId) {
         }
     }
 
+    public static String getMojoId() {
+        return MOJO_ID.get();
+    }
+
+    /**
+     * Sets or clears the mojo execution identifier in both the thread-local
+     * and the SLF4J MDC.  The value is available to any SLF4J appender via
+     * the MDC key {@code maven.mojo.id} and to JUL-bridged messages through
+     * the same MDC path.
+     * <p>
+     * Format: {@code "prefix:goal@executionId"}
+     * (e.g. {@code "compiler:compile@default-compile"}).
+     *
+     * @param mojoId the mojo identifier, or {@code null} to clear
+     */
+    public static void setMojoId(String mojoId) {
+        if (mojoId != null) {
+            MOJO_ID.set(mojoId);
+            MDC.put(KEY_MOJO_ID, mojoId);
+        } else {
+            MOJO_ID.remove();
+            MDC.remove(KEY_MOJO_ID);
+        }
+    }
+
     public static void setForkingProjectId(String forkingProjectId) {
         if (forkingProjectId != null) {
             FORKING_PROJECT_ID.set(forkingProjectId);

impl/maven-core/src/main/java/org/apache/maven/plugin/DefaultBuildPluginManager.java

@@ -125,7 +125,7 @@ public void executeMojo(MavenSession session, MojoExecution mojoExecution)
             scope.seed(
                     org.apache.maven.api.plugin.Log.class,
                     new DefaultLog(LoggerFactory.getLogger(
-                            mojoExecution.getMojoDescriptor().getFullGoalName())));
+                            mojoExecution.getMojoDescriptor().getImplementation())));
             InternalMavenSession sessionV4 = InternalMavenSession.from(session.getSession());
             scope.seed(Project.class, sessionV4.getProject(project));
             scope.seed(org.apache.maven.api.MojoExecution.class, new DefaultMojoExecution(sessionV4, mojoExecution));

impl/maven-core/src/main/java/org/apache/maven/plugin/internal/DefaultMavenPluginManager.java

@@ -555,7 +555,7 @@ private <T> T loadV4Mojo(
 
         org.apache.maven.api.MojoExecution execution = new DefaultMojoExecution(sessionV4, mojoExecution);
         org.apache.maven.api.plugin.Log log = new DefaultLog(
-                LoggerFactory.getLogger(mojoExecution.getMojoDescriptor().getFullGoalName()));
+                LoggerFactory.getLogger(mojoExecution.getMojoDescriptor().getImplementation()));
         try {
             Injector injector = Injector.create();
             injector.discover(pluginRealm);