Work around Gradle-5-published metadata breaking pom resolution

Fixes gh-263

src/main/java/io/spring/gradle/dependencymanagement/internal/maven/ConfigurationModelResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2016 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,15 +38,19 @@
  */
 class ConfigurationModelResolver implements ModelResolver {
 
+    private final Map<String, FileModelSource> pomCache = new HashMap<String, FileModelSource>();
+
     private final Project project;
 
     private final DependencyManagementConfigurationContainer configurationContainer;
 
-    private final Map<String, FileModelSource> pomCache = new HashMap<String, FileModelSource>();
+    private final PlatformCategoryAttributeConfigurer attributeConfigurer;
 
-    ConfigurationModelResolver(Project project,  DependencyManagementConfigurationContainer configurationContainer) {
+    ConfigurationModelResolver(Project project,  DependencyManagementConfigurationContainer configurationContainer,
+            PlatformCategoryAttributeConfigurer attributeConfigurer) {
         this.project = project;
         this.configurationContainer = configurationContainer;
+        this.attributeConfigurer = attributeConfigurer;
     }
 
     @Override
@@ -61,8 +65,9 @@ public ModelSource resolveModel(String groupId, String artifactId, String versio
         return pom;
     }
 
-    private FileModelSource resolveModel(String coordinates) {
+    private FileModelSource resolveModel(final String coordinates) {
         Dependency dependency = this.project.getDependencies().create(coordinates);
+        this.attributeConfigurer.configureCategoryAttribute(dependency);
         Configuration configuration = this.configurationContainer.newConfiguration(dependency);
         return new FileModelSource(configuration.resolve().iterator().next());
     }

src/main/java/io/spring/gradle/dependencymanagement/internal/maven/EffectiveModelBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2018 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -53,8 +53,8 @@ final class EffectiveModelBuilder {
     private final ModelResolver modelResolver;
 
     EffectiveModelBuilder(Project project,
-            DependencyManagementConfigurationContainer configurationContainer) {
-        this.modelResolver = new ConfigurationModelResolver(project, configurationContainer);
+            DependencyManagementConfigurationContainer configurationContainer, PlatformCategoryAttributeConfigurer attributeConfigurer) {
+        this.modelResolver = new ConfigurationModelResolver(project, configurationContainer, attributeConfigurer);
     }
 
     Model buildModel(File pom, PropertySource properties) {

src/main/java/io/spring/gradle/dependencymanagement/internal/maven/MavenPomResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2017 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -52,6 +52,8 @@
  */
 public class MavenPomResolver implements PomResolver {
 
+    private final PlatformCategoryAttributeConfigurer attributeConfigurer = new PlatformCategoryAttributeConfigurer();
+
     private final DependencyManagementConfigurationContainer configurationContainer;
 
     private final EffectiveModelBuilder effectiveModelBuilder;
@@ -67,7 +69,7 @@ public class MavenPomResolver implements PomResolver {
      */
     public MavenPomResolver(Project project, DependencyManagementConfigurationContainer configurationContainer) {
         this.configurationContainer = configurationContainer;
-        this.effectiveModelBuilder = new EffectiveModelBuilder(project, configurationContainer);
+        this.effectiveModelBuilder = new EffectiveModelBuilder(project, configurationContainer, this.attributeConfigurer);
         this.dependencyHandler = project.getDependencies();
     }
 
@@ -87,9 +89,11 @@ public List<Pom> resolvePoms(List<PomReference> pomReferences, PropertySource pr
     private Configuration createConfiguration(List<PomReference> pomReferences) {
         Configuration configuration = this.configurationContainer.newConfiguration();
         for (PomReference pomReference: pomReferences) {
-            Coordinates coordinates = pomReference.getCoordinates();
-            configuration.getDependencies().add(this.dependencyHandler.create(coordinates.getGroupId() + ":"
-                    + coordinates.getArtifactId() + ":" + coordinates.getVersion() + "@pom"));
+            final Coordinates coordinates = pomReference.getCoordinates();
+            org.gradle.api.artifacts.Dependency dependency = this.dependencyHandler.create(coordinates.getGroupId() + ":"
+                    + coordinates.getArtifactId() + ":" + coordinates.getVersion() + "@pom");
+            this.attributeConfigurer.configureCategoryAttribute(dependency);
+            configuration.getDependencies().add(dependency);
         }
         return configuration;
     }

src/main/java/io/spring/gradle/dependencymanagement/internal/maven/PlatformCategoryAttributeConfigurer.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2014-2020 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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 io.spring.gradle.dependencymanagement.internal.maven;
+
+import java.lang.reflect.Method;
+
+import org.gradle.api.Action;
+import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.artifacts.ModuleDependency;
+import org.gradle.util.GradleVersion;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Support class for configuring the {@code org.gradle.category} attribute on a {@link ModuleDependency}
+ * with a value of {@code platform}. The configuration is done reflectively as the necessary APIs are not available
+ * in the version of Gradle against which the code is compiled.
+ * <p/>
+ * Configuring the attribute works around a problem in Gradle 5 that prevents resolution of a pom for which Gradle 5 has
+ * been used to publish Gradle module metadata. The problem does not occur with Gradle 6 as it ignores metadata
+ * published by Gradle 5.
+ *
+ * @author Andy Wilkinson
+ */
+class PlatformCategoryAttributeConfigurer {
+
+    private static final Logger logger = LoggerFactory.getLogger(PlatformCategoryAttributeConfigurer.class);
+
+    void configureCategoryAttribute(Dependency dependency) {
+        if (!(dependency instanceof ModuleDependency) || !isGradle5()) {
+            return;
+        }
+        try {
+            Method attributes = dependency.getClass().getMethod("attributes", Action.class);
+            attributes.invoke(dependency, new Action<Object>() {
+
+                @Override
+                public void execute(Object container) {
+                    try {
+                        Class<?> attributeClass = Class.forName("org.gradle.api.attributes.Attribute");
+                        Object attribute = attributeClass.getMethod("of", String.class, Class.class)
+                                .invoke(null, "org.gradle.category", String.class);
+                        Class.forName("org.gradle.api.attributes.AttributeContainer")
+                                .getMethod("attribute", attributeClass, Object.class)
+                                .invoke(container, attribute, "platform");
+                    }
+                    catch (Throwable ex) {
+                        logger.debug("Failed to configure platform attribute", ex);
+                    }
+                }
+
+            });
+        }
+        catch (Throwable ex) {
+            logger.debug("Failed to configure platform attribute", ex);
+        }
+    }
+
+    private boolean isGradle5() {
+        return GradleVersion.current().getNextMajor().getVersion().startsWith("6.");
+    }
+
+}