[MNG-5707] warn if Maven unsupported slf4j binding used

maven-embedder/src/main/java/org/apache/maven/cli/logging/Slf4jConfigurationFactory.java

@@ -22,8 +22,12 @@
 import java.io.IOException;
 import java.net.URL;
 import java.util.Enumeration;
+import java.util.LinkedHashMap;
+import java.util.Map;
 import java.util.Properties;
+import java.util.Set;
 
+import org.apache.maven.cli.logging.impl.UnsupportedSlf4jBindingConfiguration;
 import org.codehaus.plexus.util.PropertyUtils;
 import org.slf4j.ILoggerFactory;
 
@@ -41,24 +45,28 @@ public class Slf4jConfigurationFactory
 
     public static Slf4jConfiguration getConfiguration( ILoggerFactory loggerFactory )
     {
+        Map<URL, Set<Object>> supported = new LinkedHashMap<URL, Set<Object>>();
+
+        String slf4jBinding = loggerFactory.getClass().getCanonicalName();
+
         try
         {
             Enumeration<URL> resources = Slf4jConfigurationFactory.class.getClassLoader().getResources( RESOURCE );
 
-            String key = loggerFactory.getClass().getCanonicalName();
-
             while ( resources.hasMoreElements() )
             {
                 URL resource = resources.nextElement();
 
                 Properties conf = PropertyUtils.loadProperties( resource.openStream() );
 
-                String impl = conf.getProperty( key );
+                String impl = conf.getProperty( slf4jBinding );
 
                 if ( impl != null )
                 {
                     return (Slf4jConfiguration) Class.forName( impl ).newInstance();
                 }
+
+                supported.put( resource, conf.keySet() );
             }
         }
         catch ( IOException e )
@@ -78,6 +86,6 @@ public static Slf4jConfiguration getConfiguration( ILoggerFactory loggerFactory
             e.printStackTrace();
         }
 
-        return new BaseSlf4jConfiguration();
+        return new UnsupportedSlf4jBindingConfiguration( slf4jBinding, supported );
     }
 }

maven-embedder/src/main/java/org/apache/maven/cli/logging/impl/UnsupportedSlf4jBindingConfiguration.java

@@ -0,0 +1,72 @@
+package org.apache.maven.cli.logging.impl;
+
+/*
+ * 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.net.URL;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.maven.cli.logging.BaseSlf4jConfiguration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Pseudo-configuration for unsupported slf4j binding.
+ * 
+ * @author Hervé Boutemy
+ * @since 3.2.4
+ */
+public class UnsupportedSlf4jBindingConfiguration
+    extends BaseSlf4jConfiguration
+{
+    private final Logger logger = LoggerFactory.getLogger( UnsupportedSlf4jBindingConfiguration.class );
+
+    private String slf4jBinding;
+
+    private Map<URL, Set<Object>> supported;
+
+    public UnsupportedSlf4jBindingConfiguration( String slf4jBinding, Map<URL, Set<Object>> supported )
+    {
+        this.slf4jBinding = slf4jBinding;
+        this.supported = supported;
+    }
+
+    @Override
+    public void activate()
+    {
+        logger.warn( "The SLF4J binding actually used is not supported by Maven: " + slf4jBinding );
+        logger.warn( "Maven supported bindings are:" );
+
+        String ls = System.getProperty( "line.separator" );
+
+        for ( Map.Entry<URL, Set<Object>> entry : supported.entrySet() )
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.append( "(from " ).append( entry.getKey().toExternalForm() ).append( ")" ); 
+
+            for ( Object binding : entry.getValue() )
+            {
+                sb.append( ls ).append( "- " ).append( binding );
+            }
+
+            logger.warn( sb.toString() );
+        }
+    }
+}

maven-embedder/src/main/resources/META-INF/maven/slf4j-configuration.properties

@@ -18,5 +18,5 @@
 # key = Slf4j effective logger factory implementation
 # value = corresponding o.a.m.cli.logging.Slf4jConfiguration class
 org.slf4j.impl.SimpleLoggerFactory org.apache.maven.cli.logging.impl.Slf4jSimpleConfiguration
-org.slf4j.helpers.Log4JLoggerFactory org.apache.maven.cli.logging.impl.Log4j2Configuration
+org.slf4j.helpers.Log4jLoggerFactory org.apache.maven.cli.logging.impl.Log4j2Configuration
 ch.qos.logback.classic.LoggerContext org.apache.maven.cli.logging.impl.LogbackConfiguration