Mojo API update proposal

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

@@ -143,6 +143,7 @@ public class DefaultMavenPluginManager
     private PluginVersionResolver pluginVersionResolver;
     private PluginArtifactsCache pluginArtifactsCache;
     private MavenPluginValidator pluginValidator;
+    private MojoLogFactory logFactory;
 
     private final ExtensionDescriptorBuilder extensionDescriptorBuilder = new ExtensionDescriptorBuilder();
     private final PluginDescriptorBuilder builder = new PluginDescriptorBuilder();
@@ -158,7 +159,8 @@ public DefaultMavenPluginManager(
             ExtensionRealmCache extensionRealmCache,
             PluginVersionResolver pluginVersionResolver,
             PluginArtifactsCache pluginArtifactsCache,
-            MavenPluginValidator pluginValidator )
+            MavenPluginValidator pluginValidator,
+            MojoLogFactory logFactory )
     {
         this.container = container;
         this.classRealmManager = classRealmManager;
@@ -170,6 +172,7 @@ public DefaultMavenPluginManager(
         this.pluginVersionResolver = pluginVersionResolver;
         this.pluginArtifactsCache = pluginArtifactsCache;
         this.pluginValidator = pluginValidator;
+        this.logFactory = logFactory;
     }
 
     public synchronized PluginDescriptor getPluginDescriptor( Plugin plugin, List<RemoteRepository> repositories,
@@ -569,8 +572,7 @@ else if ( cause instanceof LinkageError )
 
             if ( mojo instanceof Mojo )
             {
-                Logger mojoLogger = LoggerFactory.getLogger( mojoDescriptor.getImplementation() );
-                ( (Mojo) mojo ).setLog( new MojoLogWrapper( mojoLogger ) );
+                ( ( Mojo ) mojo ).setLog( logFactory.getLog( mojoDescriptor.getImplementation() ) );
             }
 
             Xpp3Dom dom = mojoExecution.getConfiguration();

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

@@ -0,0 +1,206 @@
+package org.apache.maven.plugin.internal;
+
+/*
+ * 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.Log;
+import org.slf4j.Logger;
+
+import javax.inject.Provider;
+
+import static java.util.Objects.requireNonNull;
+
+/**
+ * Mojo {@link Log} implementation that lazily creates {@link Logger} instances. To achieve "lazyness" it uses
+ * {@link Provider} for logger, but guarantees that {@link Provider#get()} is invoked only once, and once got
+ * Logger instance is reused.
+ *
+ * @since TBD
+ */
+public class MojoLog
+    implements Log
+{
+    private final Provider<Logger> loggerProvider;
+
+    public MojoLog( Provider<Logger> loggerProvider )
+    {
+        this.loggerProvider = memoize( loggerProvider );
+    }
+
+    private Logger getLogger()
+    {
+        return loggerProvider.get();
+    }
+
+    private String toString( CharSequence content )
+    {
+        if ( content == null )
+        {
+            return "";
+        }
+        else
+        {
+            return content.toString();
+        }
+    }
+
+    @Override
+    public void debug( CharSequence content )
+    {
+        if ( getLogger().isDebugEnabled() )
+        {
+            getLogger().debug( toString( content ) );
+        }
+    }
+
+    @Override
+    public void debug( CharSequence format, Object... arguments )
+    {
+        if ( getLogger().isDebugEnabled() )
+        {
+            getLogger().debug( toString( format ), arguments );
+        }
+    }
+
+    @Override
+    public void debug( CharSequence content, Throwable error )
+    {
+        if ( getLogger().isDebugEnabled() )
+        {
+            getLogger().debug( toString( content ), error );
+        }
+    }
+
+    @Override
+    public void debug( Throwable error )
+    {
+        getLogger().debug( "", error );
+    }
+
+    @Override
+    public void info( CharSequence content )
+    {
+        getLogger().info( toString( content ) );
+    }
+
+    @Override
+    public void info( CharSequence content, Throwable error )
+    {
+        getLogger().info( toString( content ), error );
+    }
+
+    @Override
+    public void info( Throwable error )
+    {
+        getLogger().info( "", error );
+    }
+
+    @Override
+    public void warn( CharSequence content )
+    {
+        getLogger().warn( toString( content ) );
+    }
+
+    @Override
+    public void warn( CharSequence content, Throwable error )
+    {
+        getLogger().warn( toString( content ), error );
+    }
+
+    @Override
+    public void warn( Throwable error )
+    {
+        getLogger().warn( "", error );
+    }
+
+    @Override
+    public void error( CharSequence content )
+    {
+        getLogger().error( toString( content ) );
+    }
+
+    @Override
+    public void error( CharSequence content, Throwable error )
+    {
+        getLogger().error( toString( content ), error );
+    }
+
+    @Override
+    public void error( Throwable error )
+    {
+        getLogger().error( "", error );
+    }
+
+    @Override
+    public boolean isDebugEnabled()
+    {
+        return getLogger().isDebugEnabled();
+    }
+
+    @Override
+    public boolean isInfoEnabled()
+    {
+        return getLogger().isInfoEnabled();
+    }
+
+    @Override
+    public boolean isWarnEnabled()
+    {
+        return getLogger().isWarnEnabled();
+    }
+
+    @Override
+    public boolean isErrorEnabled()
+    {
+        return getLogger().isErrorEnabled();
+    }
+
+    /**
+     * A helper bit to make users of this class easier: it wraps {@link Provider} into "memoizing" provider: the
+     * wrapped (delegate) provider will be invoked only once, and the returned value will be stored for subsequent
+     * invocations of {@link Provider#get()} on wrapper.
+     */
+    private static <T> Provider<T> memoize( Provider<T> provider )
+    {
+        requireNonNull( provider );
+        return new Provider<T>()
+        {
+            Provider<T> delegate = this::memoize;
+
+            volatile boolean memoized = false;
+
+            @Override
+            public T get()
+            {
+                return delegate.get();
+            }
+
+            private synchronized T memoize()
+            {
+                if ( !memoized )
+                {
+                    T value = provider.get();
+                    delegate = () -> value;
+                    memoized = true;
+                }
+                return delegate.get();
+            }
+        };
+    }
+}

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

@@ -0,0 +1,46 @@
+package org.apache.maven.plugin.internal;
+
+/*
+ * 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 javax.inject.Named;
+import javax.inject.Singleton;
+
+import org.apache.maven.plugin.logging.Log;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implementation of Mojo {@link Log} factory backed by Maven internal logging (slf4j).
+ *
+ * @since TBD
+ */
+@Singleton
+@Named
+public class MojoLogFactory
+{
+    public Log getLog( final Class<?> clazz )
+    {
+        return new MojoLog( () -> LoggerFactory.getLogger( clazz ) );
+    }
+
+    public Log getLog( final String name )
+    {
+        return new MojoLog( () -> LoggerFactory.getLogger( name ) );
+    }
+}