Resolves mojohaus#973: NPE if actual version is null for a dependency

versions-common/src/main/java/org/codehaus/mojo/versions/api/AbstractVersionDetails.java

@@ -82,11 +82,12 @@ protected ArtifactVersion getHighestLowerBound(ArtifactVersion lowerBoundVersion
      * If the artifact is bound by one or more version ranges, returns the restriction that constitutes
      * the version range containing the selected actual version.
      * If there are no version ranges, returns the provided version.
-     * @param selectedVersion actual version used
+     * @param selectedVersion actual version used, may not be {@code null}
      * @return restriction containing the version range selected by the given version,
      * or {@link Optional#empty()} if there are no ranges
      */
     protected Optional<Restriction> getSelectedRestriction(ArtifactVersion selectedVersion) {
+        assert selectedVersion != null;
         return Optional.ofNullable(getCurrentVersionRange())
                 .map(VersionRange::getRestrictions)
                 .flatMap(r -> r.stream()
@@ -116,7 +117,8 @@ public Restriction restrictionForSelectedSegment(ArtifactVersion lowerBound, Opt
     public Restriction restrictionForUnchangedSegment(
             ArtifactVersion actualVersion, Optional<Segment> unchangedSegment, boolean allowDowngrade)
             throws InvalidSegmentException {
-        Optional<Restriction> selectedRestriction = getSelectedRestriction(actualVersion);
+        Optional<Restriction> selectedRestriction =
+                Optional.ofNullable(actualVersion).flatMap(this::getSelectedRestriction);
         ArtifactVersion selectedRestrictionUpperBound =
                 selectedRestriction.map(Restriction::getUpperBound).orElse(actualVersion);
         ArtifactVersion lowerBound = allowDowngrade

versions-common/src/main/java/org/codehaus/mojo/versions/api/DefaultVersionsHelper.java

@@ -528,6 +528,7 @@ public Map<Dependency, ArtifactVersions> lookupDependenciesUpdates(
         try {
             Map<Dependency, ArtifactVersions> dependencyUpdates = new TreeMap<>(DependencyComparator.INSTANCE);
             List<Future<? extends Pair<Dependency, ArtifactVersions>>> futures = dependencies.stream()
+                    .filter(d -> d.getVersion() != null)
                     .map(dependency -> executor.submit(() -> new ImmutablePair<>(
                             dependency,
                             lookupDependencyUpdates(

versions-common/src/test/java/org/codehaus/mojo/versions/api/AbstractVersionDetailsTest.java

@@ -30,6 +30,7 @@
 import static org.codehaus.mojo.versions.utils.ArtifactVersionUtils.version;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.fail;
 
 /**
  * Unit tests for {@link AbstractVersionDetails}
@@ -156,4 +157,24 @@ public void testRestrictionForUnchangedSegmentWithTwoNotConnectingRanges4()
                         .containsVersion(version("2.0.0-1")),
                 is(true));
     }
+
+    @Test
+    public void testRestrictionForUnchangedSegmentWithoutVersionInformation()
+            throws InvalidSegmentException, InvalidVersionSpecificationException {
+        instance.setCurrentVersionRange(VersionRange.createFromVersionSpec("[,0]"));
+        assertThat(
+                instance.restrictionForUnchangedSegment(null, empty(), false).containsVersion(version("1.0.0")),
+                is(true));
+    }
+
+    @Test
+    public void testGetSelectedRestrictionForNoVersion()
+            throws InvalidVersionSpecificationException, InvalidSegmentException {
+        instance.setCurrentVersionRange(VersionRange.createFromVersionSpec("[,0]"));
+        try {
+            instance.getSelectedRestriction(null);
+            fail("Expected a NullPointerException to be thrown or assertions are not enabled.");
+        } catch (AssertionError ignored) {
+        }
+    }
 }

versions-maven-plugin/src/it/it-display-dependency-updates-issue-973-versionless/invoker.properties

@@ -0,0 +1,2 @@
+invoker.goals = ${project.groupId}:${project.artifactId}:${project.version}:display-dependency-updates
+invoker.mavenOpts = -Dversions.outputFile=./output.txt -DoutputEncoding=UTF-8

versions-maven-plugin/src/it/it-display-dependency-updates-issue-973-versionless/pom.xml

@@ -0,0 +1,37 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>localhost</groupId>
+  <artifactId>it-display-dependency-updates-002</artifactId>
+  <version>1.0</version>
+  <packaging>pom</packaging>
+  <name>display-dependency-updates-from-plugins</name>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>localhost</groupId>
+        <artifactId>dummy-api</artifactId>
+        <version>1.1</version>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+
+  <build>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>localhost</groupId>
+          <artifactId>dummy-maven-plugin</artifactId>
+          <dependencies>
+            <dependency>
+              <groupId>localhost</groupId>
+              <artifactId>dummy-api</artifactId>
+            </dependency>
+          </dependencies>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+
+</project>

versions-maven-plugin/src/it/it-display-dependency-updates-issue-973-versionless/verify.groovy

@@ -0,0 +1,6 @@
+import java.util.regex.Matcher
+
+def output = new File(basedir, "output.txt").text
+def matcher = output =~ /\Qlocalhost:dummy-api\E.*->\s+\Q3.0\E\b/
+assert matcher instanceof Matcher
+assert matcher.results().count() == 1