[MNG-7827] Ensure maven 4 Log API is the primary and documented API for mojos

maven-plugin-api/pom.xml

@@ -52,6 +52,20 @@ under the License.
       <groupId>org.codehaus.plexus</groupId>
       <artifactId>plexus-classworlds</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>maven-api-core</artifactId>
+      <version>${project.version}</version>
+      <scope>provided</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-jdk14</artifactId>
+      <version>${slf4jVersion}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

maven-plugin-api/src/main/java/org/apache/maven/plugin/AbstractMojo.java

@@ -18,11 +18,18 @@
  */
 package org.apache.maven.plugin;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
 import java.util.Map;
+import java.util.function.Supplier;
 
 import org.apache.maven.plugin.logging.Log;
 import org.apache.maven.plugin.logging.SystemStreamLog;
 
+import static java.util.Optional.ofNullable;
+
 /**
  * Abstract class to provide most of the infrastructure required to implement a <code>Mojo</code> except for
  * the execute method.<br>
@@ -147,7 +154,7 @@ public abstract class AbstractMojo implements Mojo, ContextEnabled {
     private Map pluginContext;
 
     /**
-     * @deprecated Use SLF4J directly
+     * @deprecated Use an injected {@link Log} instead in the mojo or component.
      */
     @Deprecated
     @Override
@@ -167,13 +174,48 @@ public void setLog(Log log) {
      * method directly whenever you need the logger, it is fast enough and needs no caching.
      *
      * @see org.apache.maven.plugin.Mojo#getLog()
-     * @deprecated Use SLF4J directly
+     * @deprecated Use an injected {@link org.apache.maven.api.plugin.Log} instead in the mojo or component.
      */
     @Deprecated
     @Override
     public Log getLog() {
         if (log == null) {
-            log = new SystemStreamLog();
+            // unlikely for a standard plugin, idea is to try to fallback on maven-core impl else use stdout/stderr
+            try {
+                // ensure we have slf4j
+                final ClassLoader loader = ofNullable(getClass().getClassLoader())
+                        .orElseGet(() -> Thread.currentThread().getContextClassLoader());
+                final Class<?> lf = loader.loadClass("org.slf4j.LoggerFactory");
+                final Method getLogger = lf.getDeclaredMethod("getLogger", Class.class);
+                if (!getLogger.isAccessible()) {
+                    getLogger.setAccessible(true);
+                }
+
+                // ensure we have maven-core - else we don't care to align on it
+                final Constructor<?> delegatingLogConstructor = loader.loadClass(
+                                "org.apache.maven.internal.impl.DefaultLog")
+                        .getDeclaredConstructor(getLogger.getReturnType());
+                if (!delegatingLogConstructor.isAccessible()) {
+                    delegatingLogConstructor.setAccessible(true);
+                }
+
+                // load the slf4j logger and its log impl + create a facade to comply the deprecated API
+                final Object logger = getLogger.invoke(null, getClass());
+                final Object delegate = delegatingLogConstructor.newInstance(logger);
+                log = (Log) Proxy.newProxyInstance( // Supplier is mainly an "unwrap" impl for advanced cases
+                        loader, new Class<?>[] {Log.class, Supplier.class}, (proxy, method, args) -> {
+                            if (method.getDeclaringClass() == Supplier.class) {
+                                return delegate;
+                            }
+                            try {
+                                return method.invoke(delegate, args);
+                            } catch (InvocationTargetException ite) {
+                                throw ite.getTargetException();
+                            }
+                        });
+            } catch (Error | Exception e) {
+                log = new SystemStreamLog();
+            }
         }
 
         return log;

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

@@ -20,16 +20,17 @@
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.util.function.Supplier;
 
 /**
  * Logger with "standard" output and error output stream.
  *
  * @author jdcasey
  *
- * @deprecated Use SLF4J directly
+ * @deprecated Use directly {@link org.apache.maven.api.plugin.Log} instead.
  */
 @Deprecated
-public class SystemStreamLog implements Log {
+public class SystemStreamLog implements Log, org.apache.maven.api.plugin.Log {
     /**
      * @see org.apache.maven.plugin.logging.Log#debug(java.lang.CharSequence)
      */
@@ -51,6 +52,16 @@ public void debug(Throwable error) {
         print("debug", error);
     }
 
+    @Override
+    public void debug(final Supplier<String> content) {
+        debug(content.get());
+    }
+
+    @Override
+    public void debug(final Supplier<String> content, final Throwable error) {
+        debug(content.get(), error);
+    }
+
     /**
      * @see org.apache.maven.plugin.logging.Log#info(java.lang.CharSequence)
      */
@@ -72,6 +83,16 @@ public void info(Throwable error) {
         print("info", error);
     }
 
+    @Override
+    public void info(final Supplier<String> content) {
+        info(content.get());
+    }
+
+    @Override
+    public void info(final Supplier<String> content, final Throwable error) {
+        info(content.get(), error);
+    }
+
     /**
      * @see org.apache.maven.plugin.logging.Log#warn(java.lang.CharSequence)
      */
@@ -93,6 +114,16 @@ public void warn(Throwable error) {
         print("warn", error);
     }
 
+    @Override
+    public void warn(final Supplier<String> content) {
+        warn(content.get());
+    }
+
+    @Override
+    public void warn(final Supplier<String> content, final Throwable error) {
+        warn(content.get(), error);
+    }
+
     /**
      * @see org.apache.maven.plugin.logging.Log#error(java.lang.CharSequence)
      */
@@ -109,8 +140,7 @@ public void error(CharSequence content, Throwable error) {
 
         error.printStackTrace(pWriter);
 
-        System.err.println(
-                "[error] " + content.toString() + System.lineSeparator() + System.lineSeparator() + sWriter.toString());
+        System.err.println("[error] " + content.toString() + System.lineSeparator() + System.lineSeparator() + sWriter);
     }
 
     /**
@@ -122,7 +152,17 @@ public void error(Throwable error) {
 
         error.printStackTrace(pWriter);
 
-        System.err.println("[error] " + sWriter.toString());
+        System.err.println("[error] " + sWriter);
+    }
+
+    @Override
+    public void error(final Supplier<String> content) {
+        error(content.get());
+    }
+
+    @Override
+    public void error(final Supplier<String> content, final Throwable error) {
+        error(content.get(), error);
     }
 
     /**
@@ -164,7 +204,7 @@ private void print(String prefix, Throwable error) {
 
         error.printStackTrace(pWriter);
 
-        System.out.println("[" + prefix + "] " + sWriter.toString());
+        System.out.println("[" + prefix + "] " + sWriter);
     }
 
     private void print(String prefix, CharSequence content, Throwable error) {
@@ -173,7 +213,7 @@ private void print(String prefix, CharSequence content, Throwable error) {
 
         error.printStackTrace(pWriter);
 
-        System.out.println("[" + prefix + "] " + content.toString() + System.lineSeparator() + System.lineSeparator()
-                + sWriter.toString());
+        System.out.println(
+                "[" + prefix + "] " + content.toString() + System.lineSeparator() + System.lineSeparator() + sWriter);
     }
 }

maven-plugin-api/src/test/java/org/apache/maven/internal/impl/DefaultLog.java

@@ -0,0 +1,118 @@
+/*
+ * 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.
+ */
+package org.apache.maven.internal.impl;
+
+import java.util.function.Supplier;
+
+import org.apache.maven.api.plugin.Log;
+import org.slf4j.Logger;
+
+// to not depend on maven-core we copy it to pass tests
+public class DefaultLog implements Log {
+    private final Logger logger;
+
+    public DefaultLog(final Logger logger) {
+        this.logger = logger;
+    }
+
+    // @VisibleForTests
+    public Logger getLogger() {
+        return logger;
+    }
+
+    @Override
+    public boolean isDebugEnabled() {
+        return false;
+    }
+
+    @Override
+    public void debug(final CharSequence content) {}
+
+    @Override
+    public void debug(final CharSequence content, final Throwable error) {}
+
+    @Override
+    public void debug(final Throwable error) {}
+
+    @Override
+    public void debug(final Supplier<String> content) {}
+
+    @Override
+    public void debug(final Supplier<String> content, final Throwable error) {}
+
+    @Override
+    public boolean isInfoEnabled() {
+        return false;
+    }
+
+    @Override
+    public void info(final CharSequence content) {}
+
+    @Override
+    public void info(final CharSequence content, final Throwable error) {}
+
+    @Override
+    public void info(final Throwable error) {}
+
+    @Override
+    public void info(final Supplier<String> content) {}
+
+    @Override
+    public void info(final Supplier<String> content, final Throwable error) {}
+
+    @Override
+    public boolean isWarnEnabled() {
+        return false;
+    }
+
+    @Override
+    public void warn(final CharSequence content) {}
+
+    @Override
+    public void warn(final CharSequence content, final Throwable error) {}
+
+    @Override
+    public void warn(final Throwable error) {}
+
+    @Override
+    public void warn(final Supplier<String> content) {}
+
+    @Override
+    public void warn(final Supplier<String> content, final Throwable error) {}
+
+    @Override
+    public boolean isErrorEnabled() {
+        return false;
+    }
+
+    @Override
+    public void error(final CharSequence content) {}
+
+    @Override
+    public void error(final CharSequence content, final Throwable error) {}
+
+    @Override
+    public void error(final Throwable error) {}
+
+    @Override
+    public void error(final Supplier<String> content) {}
+
+    @Override
+    public void error(final Supplier<String> content, final Throwable error) {}
+}