Guide users to apply dependency management plugin when resolution fails

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/DependencyManagementPluginActionIntegrationTests.java

@@ -16,11 +16,16 @@
 
 package org.springframework.boot.gradle.plugin;
 
+import java.io.File;
+import java.io.IOException;
+
+import org.gradle.testkit.runner.BuildResult;
 import org.gradle.testkit.runner.TaskOutcome;
 import org.junit.Rule;
 import org.junit.Test;
 
 import org.springframework.boot.gradle.testkit.GradleBuild;
+import org.springframework.util.FileSystemUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -50,4 +55,23 @@ public class DependencyManagementPluginActionIntegrationTests {
 						.isEqualTo(TaskOutcome.SUCCESS);
 	}
 
+	@Test
+	public void helpfulErrorWhenVersionlessDependencyFailsToResolve() throws IOException {
+		File examplePackage = new File(this.gradleBuild.getProjectDir(),
+				"src/main/java/com/example");
+		examplePackage.mkdirs();
+		FileSystemUtils.copyRecursively(new File("src/test/java/com/example"),
+				examplePackage);
+		BuildResult result = this.gradleBuild.buildAndFail("compileJava");
+		assertThat(result.task(":compileJava").getOutcome())
+				.isEqualTo(TaskOutcome.FAILED);
+		String output = result.getOutput();
+		assertThat(output).contains("During the build, one or more dependencies that "
+				+ "were declared without a version failed to resolve:");
+		assertThat(output).contains("org.springframework.boot:spring-boot-starter-web:");
+		assertThat(output).contains("Did you forget to apply the "
+				+ "io.spring.dependency-management plugin to the "
+				+ this.gradleBuild.getProjectDir().getName() + " project?");
+	}
+
 }

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/testkit/GradleBuild.java

@@ -126,22 +126,35 @@ public class GradleBuild implements TestRule {
 
 	public BuildResult build(String... arguments) {
 		try {
-			Files.copy(new File(this.script).toPath(),
-					new File(this.projectDir, "build.gradle").toPath(),
-					StandardCopyOption.REPLACE_EXISTING);
-			GradleRunner gradleRunner = GradleRunner.create()
-					.withProjectDir(this.projectDir).forwardOutput();
-			List<String> allArguments = new ArrayList<String>();
-			allArguments.add("-PpluginClasspath=" + pluginClasspath());
-			allArguments.add("-PbootVersion=" + getBootVersion());
-			allArguments.addAll(Arrays.asList(arguments));
-			return gradleRunner.withArguments(allArguments).build();
+			return prepareRunner(arguments).build();
 		}
 		catch (Exception ex) {
 			throw new RuntimeException(ex);
 		}
 	}
 
+	public BuildResult buildAndFail(String... arguments) {
+		try {
+			return prepareRunner(arguments).buildAndFail();
+		}
+		catch (Exception ex) {
+			throw new RuntimeException(ex);
+		}
+	}
+
+	public GradleRunner prepareRunner(String... arguments) throws IOException {
+		Files.copy(new File(this.script).toPath(),
+				new File(this.projectDir, "build.gradle").toPath(),
+				StandardCopyOption.REPLACE_EXISTING);
+		GradleRunner gradleRunner = GradleRunner.create().withProjectDir(this.projectDir)
+				.forwardOutput();
+		List<String> allArguments = new ArrayList<String>();
+		allArguments.add("-PpluginClasspath=" + pluginClasspath());
+		allArguments.add("-PbootVersion=" + getBootVersion());
+		allArguments.addAll(Arrays.asList(arguments));
+		return gradleRunner.withArguments(allArguments);
+	}
+
 	public File getProjectDir() {
 		return this.projectDir;
 	}