[MNG-7597] Fix infinite loop when iterating PropertiesAsMap (#872)

maven-core/src/main/java/org/apache/maven/internal/impl/PropertiesAsMap.java

@@ -47,50 +47,61 @@ class PropertiesAsMap extends AbstractMap<String, String>
                 Iterator<Entry<Object, Object>> iterator = properties.entrySet().iterator();
                 return new Iterator<Entry<String, String>>()
                 {
-                    Entry<Object, Object> next;
+                    Entry<String, String> next;
 
-                    @Override
-                    public boolean hasNext()
                     {
-                        while ( next == null && iterator.hasNext() )
+                        advance();
+                    }
+
+                    private void advance()
+                    {
+                        next = null;
+                        while ( iterator.hasNext() )
                         {
                             Entry<Object, Object> e = iterator.next();
                             if ( PropertiesAsMap.matches( e ) )
                             {
-                                next = e;
+                                next = new Entry<String, String>()
+                                {
+                                    @Override
+                                    public String getKey()
+                                    {
+                                        return (String) e.getKey();
+                                    }
+
+                                    @Override
+                                    public String getValue()
+                                    {
+                                        return (String) e.getValue();
+                                    }
+
+                                    @Override
+                                    public String setValue( String value )
+                                    {
+                                        return (String) e.setValue( value );
+                                    }
+                                };
                                 break;
                             }
                         }
+                    }
+
+                    @Override
+                    public boolean hasNext()
+                    {
                         return next != null;
                     }
 
                     @Override
                     public Entry<String, String> next()
                     {
-                        if ( next == null )
+                        Entry<String, String> item = next;
+                        if ( item == null )
                         {
                             throw new NoSuchElementException();
                         }
-                        return new Entry<String, String>()
-                        {
-                            @Override
-                            public String getKey()
-                            {
-                                return (String) next.getKey();
-                            }
-
-                            @Override
-                            public String getValue()
-                            {
-                                return (String) next.getValue();
-                            }
-
-                            @Override
-                            public String setValue( String value )
-                            {
-                                return (String) next.setValue( value );
-                            }
-                        };
+                        advance();
+                        return item;
                     }
                 };
             }

maven-core/src/test/java/org/apache/maven/internal/impl/PropertiesAsMapTest.java

@@ -0,0 +1,61 @@
+package org.apache.maven.internal.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.util.Iterator;
+import java.util.Map.Entry;
+import java.util.NoSuchElementException;
+import java.util.Properties;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class PropertiesAsMapTest
+{
+
+    @Test
+    public void testPropertiesAsMap()
+    {
+        Properties props = new Properties();
+        props.setProperty( "foo1", "bar1" );
+        props.setProperty( "foo2", "bar2" );
+        PropertiesAsMap pam = new PropertiesAsMap( props );
+        assertEquals( 2, pam.size() );
+        Set<Entry<String, String>> set = pam.entrySet();
+        assertNotNull( set );
+        assertEquals( 2, set.size() );
+        Iterator<Entry<String, String>> iterator = set.iterator();
+        assertNotNull( iterator );
+        assertTrue( iterator.hasNext() );
+        assertTrue( iterator.hasNext() );
+        Entry<String, String> entry = iterator.next();
+        assertNotNull( entry );
+        entry = iterator.next();
+        assertNotNull( entry );
+        assertThrows(NoSuchElementException.class, () -> iterator.next() );
+        assertFalse( iterator.hasNext() );
+    }
+}