Resolve plugins declared in pluginManagement for resolve-plugins and go-offline

src/it/projects/resolve-plugins/pom.xml

@@ -44,6 +44,11 @@
           <artifactId>maven-assembly-plugin</artifactId>
           <version>3.7.1</version>
         </plugin>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-dependency-plugin</artifactId>
+          <version>3.10.0</version>
+        </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-surefire-plugin</artifactId>

src/it/projects/resolve-plugins/verify.groovy

@@ -0,0 +1,27 @@
+/*
+ * 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.
+ */
+
+def resolvedPlugins = new File(basedir, "target/resolved.txt").text
+
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-assembly-plugin:jar:") : "Expected plugin not found in resolved plugins"
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-dependency-plugin:jar:") : "Expected plugin not found in resolved plugins"
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-surefire-plugin:jar:") : "Expected plugin not found in resolved plugins"
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-project-info-reports-plugin:jar:") : "Expected plugin not found in resolved plugins"
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-failsafe-plugin:jar:") : "Expected plugin not found in resolved plugins"
+assert resolvedPlugins.contains("   org.apache.maven.plugins:maven-surefire-report-plugin:jar:") : "Expected plugin not found in resolved plugins"

src/main/java/org/apache/maven/plugins/dependency/utils/ResolverUtil.java

@@ -38,6 +38,7 @@
 import org.apache.maven.model.ModelBase;
 import org.apache.maven.model.Plugin;
 import org.apache.maven.model.PluginContainer;
+import org.apache.maven.model.PluginManagement;
 import org.apache.maven.model.ReportPlugin;
 import org.apache.maven.model.Reporting;
 import org.apache.maven.project.MavenProject;
@@ -342,7 +343,7 @@ private ArtifactType getArtifactType(String packaging) {
     }
 
     /**
-     * Retrieve all plugins used in project either in build or reporting section.
+     * Retrieve all plugins used in a project either in the build, plugin management, or reporting section.
      *
      * @param project a maven project
      * @return a collection of plugins
@@ -358,9 +359,14 @@ public Collection<Plugin> getProjectPlugins(MavenProject project) {
 
         List<Plugin> projectPlugins = project.getBuild().getPlugins();
 
+        List<Plugin> managementPlugins = Optional.ofNullable(project.getPluginManagement())
+                .map(PluginManagement::getPlugins)
+                .orElse(Collections.emptyList());
+
         LinkedHashSet<Plugin> result = new LinkedHashSet<>(reportPlugins.size() + projectPlugins.size());
         result.addAll(reportPlugins);
         result.addAll(projectPlugins);
+        result.addAll(managementPlugins);
         return result;
     }