Fix SCM path normalization edge cases in ModelInheritanceAssembler (#274)

src/main/java/org/apache/maven/plugin/resources/remote/ModelInheritanceAssembler.java

@@ -18,13 +18,14 @@
  */
 package org.apache.maven.plugin.resources.remote;
 
+import java.io.File;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
-import java.util.StringTokenizer;
 import java.util.TreeMap;
 
 import org.apache.maven.model.Build;
@@ -568,51 +569,34 @@ protected String appendPath(String parentPath, String childPath, String pathAdju
             uncleanPath = uncleanPath.substring(protocolIdx + 3);
         }
 
-        if (uncleanPath.startsWith("/")) {
-            cleanedPath += "/";
-        }
-
         return cleanedPath + resolvePath(uncleanPath);
     }
 
-    // TODO Move this to plexus-utils' PathTool.
-    private static String resolvePath(String uncleanPath) {
-        LinkedList<String> pathElements = new LinkedList<>();
-
-        StringTokenizer tokenizer = new StringTokenizer(uncleanPath, "/");
-
-        while (tokenizer.hasMoreTokens()) {
-            String token = tokenizer.nextToken();
-
-            switch (token) {
-                case "":
-                    // Empty path entry ("...//.."), remove.
-                    break;
-                case "..":
-                    if (pathElements.isEmpty()) {
-                        // FIXME: somehow report to the user
-                        // that there are too many '..' elements.
-                        // For now, ignore the extra '..'.
-                    } else {
-                        pathElements.removeLast();
-                    }
-                    break;
-                default:
-                    pathElements.addLast(token);
-                    break;
-            }
-        }
+    /**
+     * Normalizes the path part of an SCM URL using {@link java.nio.file.Path#normalize()}.
+     * <ul>
+     *   <li>Trailing separators are significant (e.g. {@code http://host/repo/} is not
+     *       {@code http://host/repo}) and are preserved.</li>
+     *   <li>Redundant separators, {@code "."} and resolvable {@code ".."} segments are collapsed.</li>
+     *   <li>Excess {@code ".."} segments that would climb above the path root are left to the
+     *       normalizer instead of being silently dropped.</li>
+     * </ul>
+     */
+    private String resolvePath(String uncleanPath) {
+        boolean trailingSeparator = uncleanPath.endsWith("/");
 
-        StringBuilder cleanedPath = new StringBuilder();
+        String resolved;
+        try {
+            resolved = Paths.get(uncleanPath).normalize().toString().replace(File.separatorChar, '/');
+        } catch (InvalidPathException e) {
+            resolved = uncleanPath;
+        }
 
-        while (!pathElements.isEmpty()) {
-            cleanedPath.append(pathElements.removeFirst());
-            if (!pathElements.isEmpty()) {
-                cleanedPath.append('/');
-            }
+        if (trailingSeparator && !resolved.endsWith("/")) {
+            resolved += "/";
         }
 
-        return cleanedPath.toString();
+        return resolved;
     }
 
     private static void mergeExtensionLists(Build childBuild, Build parentBuild) {

src/test/java/org/apache/maven/plugin/resources/remote/ModelInheritanceAssemblerTest.java

@@ -0,0 +1,59 @@
+/*
+ * 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.plugin.resources.remote;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Unit tests for the SCM path normalization in {@link ModelInheritanceAssembler}.
+ */
+public class ModelInheritanceAssemblerTest {
+
+    private final ModelInheritanceAssembler assembler = new ModelInheritanceAssembler();
+
+    @Test
+    public void appendPathPreservesTrailingSlash() {
+        assertEquals(
+                "http://svn.example.com/repo/",
+                assembler.appendPath("http://svn.example.com/repo/", null, null, false));
+    }
+
+    @Test
+    public void appendPathAppendsChild() {
+        assertEquals(
+                "http://svn.example.com/repo/child",
+                assembler.appendPath("http://svn.example.com/repo", "child", null, true));
+    }
+
+    @Test
+    public void appendPathCollapsesDotSegment() {
+        assertEquals(
+                "http://svn.example.com/repo/child",
+                assembler.appendPath("http://svn.example.com/repo/./child", null, null, false));
+    }
+
+    @Test
+    public void appendPathResolvesParentDirectory() {
+        assertEquals(
+                "http://svn.example.com/repos",
+                assembler.appendPath("http://svn.example.com/repos/project/..", null, null, false));
+    }
+}