Honour ext and classifier on @Grabbed dependencies

We currently honour type, but ignore ext. Aether doesn't make a
distinction between the two so a Grab that specifies both type and ext
but with different values is considered to be an error.

Fixes #995

spring-boot-cli/src/main/java/org/springframework/boot/cli/compiler/grape/AetherGrapeEngine.java

@@ -168,7 +168,27 @@ public class AetherGrapeEngine implements GrapeEngine {
 		String group = (String) dependencyMap.get("group");
 		String module = (String) dependencyMap.get("module");
 		String version = (String) dependencyMap.get("version");
-		return new DefaultArtifact(group, module, "jar", version);
+		String classifier = (String) dependencyMap.get("classifier");
+		String type = determineType(dependencyMap);
+
+		return new DefaultArtifact(group, module, classifier, type, version);
+	}
+
+	private String determineType(Map<?, ?> dependencyMap) {
+		String type = (String) dependencyMap.get("type");
+		String ext = (String) dependencyMap.get("ext");
+
+		if (type == null) {
+			type = ext;
+			if (type == null) {
+				type = "jar";
+			}
+		}
+		else if (ext != null && !type.equals(ext)) {
+			throw new IllegalArgumentException(
+					"If both type and ext are specified they must have the same value");
+		}
+		return type;
 	}
 
 	private boolean isTransitive(Map<?, ?> dependencyMap) {

spring-boot-cli/src/test/java/org/springframework/boot/cli/compiler/grape/AetherGrapeEngineTests.java

@@ -19,13 +19,16 @@ package org.springframework.boot.cli.compiler.grape;
 import groovy.lang.GroovyClassLoader;
 
 import java.net.URI;
+import java.net.URL;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
 import org.junit.Test;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 /**
  * Tests for {@link AetherGrapeEngine}.
@@ -99,6 +102,53 @@ public class AetherGrapeEngineTests {
 		assertEquals(1, this.groovyClassLoader.getURLs().length);
 	}
 
+	@Test(expected = IllegalArgumentException.class)
+	public void differingTypeAndExt() {
+		Map<String, Object> dependency = createDependency("org.grails",
+				"grails-dependencies", "2.4.0");
+		dependency.put("type", "foo");
+		dependency.put("ext", "bar");
+		this.grapeEngine.grab(Collections.emptyMap(), dependency);
+	}
+
+	@Test
+	public void pomDependencyResolutionViaType() {
+		Map<String, Object> args = new HashMap<String, Object>();
+		Map<String, Object> dependency = createDependency("org.springframework",
+				"spring-framework-bom", "4.0.5.RELEASE");
+		dependency.put("type", "pom");
+		this.grapeEngine.grab(args, dependency);
+		URL[] urls = this.groovyClassLoader.getURLs();
+		assertEquals(1, urls.length);
+		assertTrue(urls[0].toExternalForm().endsWith(".pom"));
+	}
+
+	@Test
+	public void pomDependencyResolutionViaExt() {
+		Map<String, Object> args = new HashMap<String, Object>();
+		Map<String, Object> dependency = createDependency("org.springframework",
+				"spring-framework-bom", "4.0.5.RELEASE");
+		dependency.put("ext", "pom");
+		this.grapeEngine.grab(args, dependency);
+		URL[] urls = this.groovyClassLoader.getURLs();
+		assertEquals(1, urls.length);
+		assertTrue(urls[0].toExternalForm().endsWith(".pom"));
+	}
+
+	@Test
+	public void resolutionWithClassifier() {
+		Map<String, Object> args = new HashMap<String, Object>();
+
+		Map<String, Object> dependency = createDependency("org.springframework",
+				"spring-jdbc", "3.2.4.RELEASE", false);
+		dependency.put("classifier", "sources");
+		this.grapeEngine.grab(args, dependency);
+
+		URL[] urls = this.groovyClassLoader.getURLs();
+		assertEquals(1, urls.length);
+		assertTrue(urls[0].toExternalForm().endsWith("-sources.jar"));
+	}
+
 	private Map<String, Object> createDependency(String group, String module,
 			String version) {
 		Map<String, Object> dependency = new HashMap<String, Object>();