[MNG-7083] - introduce lazy Log message evaluation

maven-plugin-api/src/main/java/org/apache/maven/monitor/logging/DefaultLog.java

@@ -19,6 +19,7 @@
  * under the License.
  */
 
+import org.apache.maven.plugin.logging.AbstractLog;
 import org.apache.maven.plugin.logging.Log;
 import org.codehaus.plexus.logging.Logger;
 
@@ -28,7 +29,7 @@
  * @deprecated Use SLF4J directly
  */
 @Deprecated
-public class DefaultLog
+public class DefaultLog extends AbstractLog
     implements Log
 {
 

maven-plugin-api/src/main/java/org/apache/maven/plugin/logging/AbstractLog.java

@@ -0,0 +1,116 @@
+package org.apache.maven.plugin.logging;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.util.function.Supplier;
+
+/**
+ * Abstract class providing some defaults shareable implementation of some Log methods.
+ */
+public abstract class AbstractLog implements Log 
+{
+  /**
+   * @see org.apache.maven.plugin.logging.Log#debug(Supplier) 
+   */
+  public void debug( Supplier<String> messageSupplier )
+  {
+    if ( isDebugEnabled() )
+    {
+      debug( messageSupplier.get() );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#debug(Supplier, Throwable)  
+   */
+  public void debug( Supplier<String> messageSupplier, Throwable error )
+  {
+    if ( isDebugEnabled() )
+    {
+      debug( messageSupplier.get(), error );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#info(Supplier)
+   */
+  public void info( Supplier<String> messageSupplier )
+  {
+    if ( isInfoEnabled() )
+    {
+      info( messageSupplier.get() );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#info(Supplier, Throwable)
+   */
+  public void info( Supplier<String> messageSupplier, Throwable error )
+  {
+    if ( isInfoEnabled() )
+    {
+      info( messageSupplier.get(), error );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#warn(Supplier)
+   */
+  public void warn( Supplier<String> messageSupplier )
+  {
+    if ( isWarnEnabled() )
+    {
+      warn( messageSupplier.get() );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#warn(Supplier, Throwable)
+   */
+  public void warn( Supplier<String> messageSupplier, Throwable error )
+  {
+    if ( isWarnEnabled() )
+    {
+      warn( messageSupplier.get(), error );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#error(Supplier)
+   */
+  public void error( Supplier<String> messageSupplier )
+  {
+    if ( isErrorEnabled() )
+    {
+      error( messageSupplier.get() );
+    }
+  }
+
+  /**
+   * @see org.apache.maven.plugin.logging.Log#error(Supplier, Throwable)
+   */
+  public void error( Supplier<String> messageSupplier, Throwable error )
+  {
+    if ( isErrorEnabled() )
+    {
+      error( messageSupplier.get(), error );
+    }
+  }
+}

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

@@ -19,6 +19,8 @@
  * under the License.
  */
 
+import java.util.function.Supplier;
+
 /**
  * This interface supplies the API for providing feedback to the user from the <code>Mojo</code>, using standard
  * <code>Maven</code> channels.<br>
@@ -63,6 +65,23 @@ public interface Log
      */
     void debug( Throwable error );
 
+    /**
+     * Send a message to the user in the <b>debug</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isDebugEnabled() is <b>true</b>.
+     * 
+     * @param messageSupplier a non null Supplier of the message to use
+     */
+    void debug( Supplier<String> messageSupplier );
+
+    /**
+     * Send a message to the user in the <b>debug</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isDebugEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     * @param error the error that occurred and for which the log applies 
+     */
+    void debug( Supplier<String> messageSupplier, Throwable error );
+
     /**
      * @return true if the <b>info</b> error level is enabled
      */
@@ -92,6 +111,23 @@ public interface Log
      */
     void info( Throwable error );
 
+    /**
+     * Send a message to the user in the <b>info</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isInfoEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     */
+    void info( Supplier<String> messageSupplier );
+
+    /**
+     * Send a message to the user in the <b>info</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isInfoEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     * @param error the error that occurred and for which the log applies 
+     */
+    void info( Supplier<String> messageSupplier, Throwable error );
+
     /**
      * @return true if the <b>warn</b> error level is enabled
      */
@@ -121,6 +157,23 @@ public interface Log
      */
     void warn( Throwable error );
 
+    /**
+     * Send a message to the user in the <b>warn</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isWarnEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     */
+    void warn( Supplier<String> messageSupplier );
+
+    /**
+     * Send a message to the user in the <b>warn</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isWarnEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     * @param error the error that occurred and for which the log applies 
+     */
+    void warn( Supplier<String> messageSupplier, Throwable error );
+
     /**
      * @return true if the <b>error</b> error level is enabled
      */
@@ -149,4 +202,21 @@ public interface Log
      * @param error
      */
     void error( Throwable error );
+
+    /**
+     * Send a message to the user in the <b>error</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isErrorEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     */
+    void error( Supplier<String> messageSupplier );
+
+    /**
+     * Send a message to the user in the <b>error</b> error level by computing the message
+     * only when needed. The supplier will be called only if @see #isErrorEnabled() is <b>true</b>.
+     *
+     * @param messageSupplier a non null Supplier of the message to use
+     * @param error the error that occurred and for which the log applies 
+     */
+    void error( Supplier<String> messageSupplier, Throwable error );
 }

maven-plugin-api/src/main/java/org/apache/maven/plugin/logging/SystemStreamLog.java

@@ -30,7 +30,7 @@
  * @deprecated Use SLF4J directly
  */
 @Deprecated
-public class SystemStreamLog
+public class SystemStreamLog extends AbstractLog
     implements Log
 {
     /**

maven-plugin-api/src/test/java/org/apache/maven/monitor/logging/DefaultLogTest.java

@@ -0,0 +1,78 @@
+package org.apache.maven.monitor.logging;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.maven.plugin.logging.CountingCallsSupplier;
+import org.apache.maven.plugin.logging.Log;
+import org.codehaus.plexus.logging.Logger;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class DefaultLogTest
+{
+  private static final String EXPECTED_MESSAGE = "expected message";
+
+  @Test
+  public void testLazyMessageIsEvaluatedForActiveLogLevels() 
+  {
+    CountingCallsSupplier<String> messageSupplier = CountingCallsSupplier.of(EXPECTED_MESSAGE);
+
+    Throwable fakeError = new RuntimeException();
+
+    Log logger = new DefaultLog(new NoOpLogger(Logger.LEVEL_DEBUG));
+
+    logger.debug(messageSupplier);
+    logger.info(messageSupplier);
+    logger.warn(messageSupplier);
+    logger.error(messageSupplier);
+
+    logger.debug(messageSupplier, fakeError);
+    logger.info(messageSupplier, fakeError);
+    logger.warn(messageSupplier, fakeError);
+    logger.error(messageSupplier, fakeError);
+
+    // all log calls should have lead to a supplier call
+    assertEquals(8, messageSupplier.getNumberOfCalls(), "wrong number of calls to the message supplier");
+  }
+
+  @Test
+  public void testLazyMessageIsNotEvaluatedForNonActiveLogLevels()
+  {
+    CountingCallsSupplier<String> messageSupplier = CountingCallsSupplier.of(EXPECTED_MESSAGE);
+
+    Throwable fakeError = new RuntimeException();
+
+    Log logger = new DefaultLog(new NoOpLogger(Logger.LEVEL_DISABLED));
+
+    logger.debug(messageSupplier);
+    logger.info(messageSupplier);
+    logger.warn(messageSupplier);
+    logger.error(messageSupplier);
+
+    logger.debug(messageSupplier, fakeError);
+    logger.info(messageSupplier, fakeError);
+    logger.warn(messageSupplier, fakeError);
+    logger.error(messageSupplier, fakeError);
+
+    // no log calls should have lead to any supplier call
+    assertEquals(0, messageSupplier.getNumberOfCalls(), "wrong number of calls to the message supplier");
+  }
+}

maven-plugin-api/src/test/java/org/apache/maven/monitor/logging/NoOpLogger.java

@@ -0,0 +1,70 @@
+package org.apache.maven.monitor.logging;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.codehaus.plexus.logging.AbstractLogger;
+import org.codehaus.plexus.logging.Logger;
+
+/**
+ * Custom implementation for tests purpose.
+ */
+public class NoOpLogger extends AbstractLogger  
+    implements Logger {
+
+  public NoOpLogger(int threshold)
+  {
+    super(threshold, "NoOp"); 
+  }
+
+  @Override
+  public void debug(String message, Throwable throwable)
+  {
+    // no-op
+  }
+
+  @Override
+  public void info(String message, Throwable throwable)
+  {
+    // no-op
+  }
+
+  @Override
+  public void warn(String message, Throwable throwable)
+  {
+    // no-op
+  }
+
+  @Override
+  public void error(String message, Throwable throwable)
+  {
+    // no-op
+  }
+
+  @Override
+  public void fatalError(String message, Throwable throwable)
+  {
+    // no-op
+  }
+
+  @Override
+  public Logger getChildLogger(String name) {
+    return this;
+  }
+}