[MNG-7644] Fix version comparison where .X1 < -X2 for any string qualifier X

This #932

maven-artifact/src/main/java/org/apache/maven/artifact/versioning/ComparableVersion.java

@@ -52,7 +52,10 @@ import java.util.Properties;
  *     </ul>
  *     Unknown qualifiers are considered after known qualifiers, with lexical order (always case insensitive),
  *   </li>
- * <li>a hyphen usually precedes a qualifier, and is always less important than something preceded with a dot.</li>
+ * <li>a hyphen usually precedes a qualifier, and is always less important than digits/number, for example
+ *   {@code 1.0.RC2 < 1.0-RC3 < 1.0.1}; but prefer {@code 1.0.0-RC1} over {@code 1.0.0.RC1}, and more
+ *   generally: {@code 1.0.X2 < 1.0-X3 < 1.0.1} for any string {@code X}; but prefer {@code 1.0.0-X1}
+ *   over {@code 1.0.0.X1}.</li>
  * </ul>
  *
  * @see <a href="https://cwiki.apache.org/confluence/display/MAVENOLD/Versioning">"Versioning" on Maven Wiki</a>
@@ -570,6 +573,13 @@ public class ComparableVersion implements Comparable<ComparableVersion> {
                 stack.push(list);
             } else if (Character.isDigit(c)) {
                 if (!isDigit && i > startIndex) {
+                    // 1.0.0.X1 < 1.0.0-X2
+                    // treat .X as -X for any string qualifier X
+                    if (!list.isEmpty()) {
+                        list.add(list = new ListItem());
+                        stack.push(list);
+                    }
+
                     list.add(new StringItem(version.substring(startIndex, i), true));
                     startIndex = i;
 
@@ -592,6 +602,13 @@ public class ComparableVersion implements Comparable<ComparableVersion> {
         }
 
         if (version.length() > startIndex) {
+            // 1.0.0.X1 < 1.0.0-X2
+            // treat .X as -X for any string qualifier X
+            if (!isDigit && !list.isEmpty()) {
+                list.add(list = new ListItem());
+                stack.push(list);
+            }
+
             list.add(parseItem(isDigit, version.substring(startIndex)));
         }
 

maven-artifact/src/test/java/org/apache/maven/artifact/versioning/ComparableVersionTest.java

@@ -71,8 +71,8 @@ public class ComparableVersionTest {
     };
 
     private static final String[] VERSIONS_NUMBER = {
-        "2.0", "2-1", "2.0.a", "2.0.0.a", "2.0.2", "2.0.123", "2.1.0", "2.1-a", "2.1b", "2.1-c", "2.1-1", "2.1.0.1",
+        "2.0", "2.0.a", "2-1", "2.0.2", "2.0.123", "2.1.0", "2.1-a", "2.1b", "2.1-c", "2.1-1", "2.1.0.1", "2.2",
-        "2.2", "2.123", "11.a2", "11.a11", "11.b2", "11.b11", "11.m2", "11.m11", "11", "11.a", "11b", "11c", "11m"
+        "2.123", "11.a2", "11.a11", "11.b2", "11.b11", "11.m2", "11.m11", "11", "11.a", "11b", "11c", "11m"
     };
 
     private void checkVersionsOrder(String[] versions) {
@@ -346,4 +346,21 @@ public class ComparableVersionTest {
 
         assertEquals(c1, c2, "reused instance should be equivalent to new instance");
     }
+
+    /**
+     * Test <a href="https://issues.apache.org/jira/browse/MNG-7644">MNG-7644</a> edge cases
+     * 1.0.0.RC1 < 1.0.0-RC2 and more generally:
+     * 1.0.0.X1 < 1.0.0-X2 for any string X
+     */
+    @Test
+    public void testMng7644() {
+        for (String x : new String[] {"abc", "alpha", "a", "beta", "b", "def", "milestone", "m", "RC"}) {
+            // 1.0.0.X1 < 1.0.0-X2 for any string x
+            checkVersionsOrder("1.0.0." + x + "1", "1.0.0-" + x + "2");
+            // 2.0.X == 2-X == 2.0.0.X for any string x
+            checkVersionsEqual("2-" + x, "2.0." + x); // previously ordered, now equals
+            checkVersionsEqual("2-" + x, "2.0.0." + x); // previously ordered, now equals
+            checkVersionsEqual("2.0." + x, "2.0.0." + x); // previously ordered, now equals
+        }
+    }
 }