[MNG-3779] Improve error message when trying to execute moojo with no pom.xml

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-3/trunk@928903 13f79535-47bb-0310-9956-ffa450edef68

maven-core/src/main/java/org/apache/maven/lifecycle/DefaultLifecycleExecutor.java

@@ -248,8 +248,23 @@ public class DefaultLifecycleExecutor
 
         try
         {
+            if ( !session.isUsingPOMsFromFilesystem() && requiresProject( session ) )
+            {
+                throw new MissingProjectException( "The goal you specified requires a project to execute"
+                    + " but there is no POM in this directory (" + session.getExecutionRootDirectory() + ")."
+                    + " Please verify you invoked Maven from the correct directory." );
+            }
+
             projectBuilds = calculateProjectBuilds( session );
 
+            if ( projectBuilds.isEmpty() )
+            {
+                throw new NoGoalSpecifiedException( "No goals have been specified for this build."
+                    + " You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or"
+                    + " <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>."
+                    + " Available lifecycle phases are: " + getLifecyclePhaseList() + "." );
+            }
+
             projectIndex = new ProjectIndex( session.getProjects() );
         }
         catch ( Exception e )
@@ -564,7 +579,9 @@ public class DefaultLifecycleExecutor
         if ( mojoDescriptor.isProjectRequired() && !session.isUsingPOMsFromFilesystem() )
         {
             Throwable cause =
-                new IllegalStateException( "Goal requires a project to execute but there is no POM in this build." );
+                new MissingProjectException( "Goal requires a project to execute"
+                    + " but there is no POM in this directory (" + session.getExecutionRootDirectory() + ")."
+                    + " Please verify you invoked Maven from the correct directory." );
             throw new LifecycleExecutionException( mojoExecution, null, cause );
         }
 
@@ -1080,7 +1097,10 @@ public class DefaultLifecycleExecutor
 
         if ( lifecycle == null )
         {
-            throw new LifecyclePhaseNotFoundException( lifecyclePhase );
+            throw new LifecyclePhaseNotFoundException( "Unknown lifecycle phase \"" + lifecyclePhase
+                + "\". You must specify a valid lifecycle phase" + " or a goal in the format <plugin-prefix>:<goal> or"
+                + " <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are: "
+                + getLifecyclePhaseList() + ".", lifecyclePhase );
         }
 
         /*
@@ -2068,4 +2088,32 @@ public class DefaultLifecycleExecutor
         return phaseToLifecycleMap;
     }
 
+    private String getLifecyclePhaseList()
+    {
+        Set<String> phases = new LinkedHashSet<String>();
+
+        for ( Lifecycle lifecycle : lifecycles )
+        {
+            phases.addAll( lifecycle.getPhases() );
+        }
+
+        return StringUtils.join( phases.iterator(), ", " );
+    }
+
+    private boolean requiresProject( MavenSession session )
+    {
+        List<String> goals = session.getGoals();
+        if ( goals != null )
+        {
+            for ( String goal : goals )
+            {
+                if ( !isGoalSpecification( goal ) )
+                {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
 }

maven-core/src/main/java/org/apache/maven/lifecycle/LifecyclePhaseNotFoundException.java

@@ -33,13 +33,12 @@ public class LifecyclePhaseNotFoundException
     /**
      * Creates a new exception to indicate that the specified lifecycle phase is not defined by any known lifecycle.
      * 
+     * @param message The detail message, may be {@code null}.
      * @param lifecyclePhase The name of the lifecycle phase that could not be located, may be {@code null}.
      */
-    public LifecyclePhaseNotFoundException( String lifecyclePhase )
+    public LifecyclePhaseNotFoundException( String message, String lifecyclePhase )
     {
-        super( "Unknown lifecycle phase \"" + lifecyclePhase + "\". You must specify a valid lifecycle phase"
-            + " or a goal in the format <plugin-prefix>:<goal> or"
-            + " <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>" );
+        super( message );
         this.lifecyclePhase = ( lifecyclePhase != null ) ? lifecyclePhase : "";
     }
 

maven-core/src/main/java/org/apache/maven/lifecycle/MissingProjectException.java

@@ -0,0 +1,41 @@
+package org.apache.maven.lifecycle;
+
+/*
+ * 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.
+ */
+
+/**
+ * Signals a failure to execute a lifecycle phase or mojo because a project is required but not present.
+ * 
+ * @author Benjamin Bentmann
+ */
+public class MissingProjectException
+    extends Exception
+{
+
+    /**
+     * Creates a new exception.
+     * 
+     * @param message The detail message, may be {@code null}.
+     */
+    public MissingProjectException( String message )
+    {
+        super( message );
+    }
+
+}

maven-core/src/main/java/org/apache/maven/lifecycle/NoGoalSpecifiedException.java

@@ -0,0 +1,41 @@
+package org.apache.maven.lifecycle;
+
+/*
+ * 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.
+ */
+
+/**
+ * Signals a failure to build because no goal was specified.
+ * 
+ * @author Benjamin Bentmann
+ */
+public class NoGoalSpecifiedException
+    extends Exception
+{
+
+    /**
+     * Creates a new exception.
+     * 
+     * @param message The detail message, may be {@code null}.
+     */
+    public NoGoalSpecifiedException( String message )
+    {
+        super( message );
+    }
+
+}