Add a strategy to resolve the dependency management plugin version

Closes gh-977

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/DependencyManagementPluginVersionResolver.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2012-2019 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.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.project.ResolvedProjectDescription;
+
+/**
+ * Strategy for resolving a dependency management plugin version from a platform version.
+ *
+ * @author Stephane Nicoll
+ */
+@FunctionalInterface
+public interface DependencyManagementPluginVersionResolver {
+
+	/**
+	 * Resolves the dependency management plugin version to use for the generation of the
+	 * project with the given {@code description}.
+	 * @param description the description of the project being generated
+	 * @return the corresponding version for the {@code io.spring.dependency-management}
+	 * plugin
+	 */
+	String resolveDependencyManagementPluginVersion(ResolvedProjectDescription description);
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfiguration.java

@@ -245,12 +245,15 @@ public class GradleProjectGenerationConfiguration {
 
 		@Bean
 		BuildCustomizer<GradleBuild> springBootPluginContributor(ResolvedProjectDescription projectDescription,
+				ObjectProvider<DependencyManagementPluginVersionResolver> versionResolver,
 				InitializrMetadata metadata) {
 			return (build) -> {
 				build.plugins().add("org.springframework.boot",
 						(plugin) -> plugin.setVersion(projectDescription.getPlatformVersion().toString()));
-				build.plugins().add("io.spring.dependency-management", (plugin) -> plugin.setVersion(
-						metadata.getConfiguration().getEnv().getGradle().getDependencyManagementPluginVersion()));
+				build.plugins().add("io.spring.dependency-management",
+						(plugin) -> plugin.setVersion(versionResolver
+								.getIfAvailable(() -> new InitializrDependencyManagementPluginVersionResolver(metadata))
+								.resolveDependencyManagementPluginVersion(projectDescription)));
 			};
 		}
 

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/InitializrDependencyManagementPluginVersionResolver.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2019 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.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.project.ResolvedProjectDescription;
+import io.spring.initializr.metadata.InitializrMetadata;
+
+/**
+ * {@link DependencyManagementPluginVersionResolver} that resolves the version from the
+ * {@link InitializrMetadata}.
+ *
+ * @author Stephane Nicoll
+ */
+public class InitializrDependencyManagementPluginVersionResolver implements DependencyManagementPluginVersionResolver {
+
+	private final InitializrMetadata metadata;
+
+	public InitializrDependencyManagementPluginVersionResolver(InitializrMetadata metadata) {
+		this.metadata = metadata;
+	}
+
+	@Override
+	public String resolveDependencyManagementPluginVersion(ResolvedProjectDescription description) {
+		return this.metadata.getConfiguration().getEnv().getGradle().getDependencyManagementPluginVersion();
+	}
+
+}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GradleKtsProjectGenerationConfigurationTests.java

@@ -126,6 +126,26 @@ class GradleKtsProjectGenerationConfigurationTests {
 				"    testImplementation(\"org.springframework.boot:spring-boot-starter-test\")", "}");
 	}
 
+	@Test
+	void dependencyManagementPluginFallbacksToMetadataIfNotPresent() {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse("2.1.0.RELEASE"));
+		description.setLanguage(new JavaLanguage("11"));
+		List<String> lines = this.projectTester.generate(description).readAllLines("build.gradle.kts");
+		assertThat(lines).contains("    id(\"io.spring.dependency-management\") version \"1.0.6.RELEASE\"");
+	}
+
+	@Test
+	void dependencyManagementPluginVersionResolverIsUsedIfPresent() {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse("2.1.0.RELEASE"));
+		description.setLanguage(new JavaLanguage("11"));
+		List<String> lines = this.projectTester
+				.withBean(DependencyManagementPluginVersionResolver.class, () -> (d) -> "1.5.1.RC1")
+				.generate(description).readAllLines("build.gradle.kts");
+		assertThat(lines).contains("    id(\"io.spring.dependency-management\") version \"1.5.1.RC1\"");
+	}
+
 	@Test
 	void warPluginIsAppliedWhenBuildingProjectThatUsesWarPackaging() {
 		ProjectDescription description = new ProjectDescription();