Add ServiceLoader for AST transformations

The loading is via a marker interface SpringBootAstTransformation
to avoid clashing with other services registered as org.groovy.*

Fixes gh-1392

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

@@ -24,6 +24,7 @@ import org.codehaus.groovy.ast.ModuleNode;
 import org.codehaus.groovy.control.SourceUnit;
 import org.codehaus.groovy.transform.ASTTransformation;
 import org.springframework.boot.cli.compiler.grape.DependencyResolutionContext;
+import org.springframework.core.annotation.Order;
 
 /**
  * {@link ASTTransformation} to apply
@@ -34,8 +35,11 @@ import org.springframework.boot.cli.compiler.grape.DependencyResolutionContext;
  * @author Dave Syer
  * @author Andy Wilkinson
  */
+@Order(DependencyAutoConfigurationTransformation.ORDER)
 public class DependencyAutoConfigurationTransformation implements ASTTransformation {
 
+	public static final int ORDER = GrabMetadataTransformation.ORDER + 100;
+
 	private final GroovyClassLoader loader;
 
 	private final DependencyResolutionContext dependencyResolutionContext;

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

@@ -43,6 +43,8 @@ import org.springframework.boot.dependency.tools.Dependencies;
 import org.springframework.boot.dependency.tools.ManagedDependencies;
 import org.springframework.boot.dependency.tools.PropertiesFileDependencies;
 import org.springframework.boot.groovy.GrabMetadata;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
 
 /**
  * {@link ASTTransformation} for processing {@link GrabMetadata @GrabMetadata}
@@ -50,8 +52,11 @@ import org.springframework.boot.groovy.GrabMetadata;
  * @author Andy Wilkinson
  * @since 1.1.0
  */
+@Order(GrabMetadataTransformation.ORDER)
 public class GrabMetadataTransformation extends AnnotatedNodeASTTransformation {
 
+	public static final int ORDER = Ordered.HIGHEST_PRECEDENCE;
+
 	private static final Set<String> GRAB_METADATA_ANNOTATION_NAMES = Collections
 			.unmodifiableSet(new HashSet<String>(Arrays.asList(
 					GrabMetadata.class.getName(), GrabMetadata.class.getSimpleName())));

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

@@ -29,6 +29,7 @@ import org.codehaus.groovy.ast.expr.ClosureExpression;
 import org.codehaus.groovy.ast.stmt.BlockStatement;
 import org.codehaus.groovy.control.SourceUnit;
 import org.codehaus.groovy.transform.ASTTransformation;
+import org.springframework.core.annotation.Order;
 
 /**
  * {@link ASTTransformation} to resolve beans declarations inside application source
@@ -38,8 +39,11 @@ import org.codehaus.groovy.transform.ASTTransformation;
  *
  * @author Dave Syer
  */
+@Order(GroovyBeansTransformation.ORDER)
 public class GroovyBeansTransformation implements ASTTransformation {
 
+	public static final int ORDER = GrabMetadataTransformation.ORDER + 200;
+
 	@Override
 	public void visit(ASTNode[] nodes, SourceUnit source) {
 		for (ASTNode node : nodes) {

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

@@ -47,6 +47,7 @@ import org.springframework.boot.cli.compiler.grape.AetherGrapeEngineFactory;
 import org.springframework.boot.cli.compiler.grape.DependencyResolutionContext;
 import org.springframework.boot.cli.compiler.grape.GrapeEngineInstaller;
 import org.springframework.boot.cli.util.ResourceUtils;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 
 /**
  * Compiler for Groovy sources. Primarily a simple Facade for
@@ -112,6 +113,11 @@ public class GroovyCompiler {
 			this.transformations.add(new ResolveDependencyCoordinatesTransformation(
 					resolutionContext));
 		}
+		for (ASTTransformation transformation : ServiceLoader
+				.load(SpringBootAstTransformation.class)) {
+			this.transformations.add(transformation);
+		}
+		Collections.sort(this.transformations, AnnotationAwareOrderComparator.INSTANCE);
 	}
 
 	/**

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

@@ -29,6 +29,7 @@ import org.codehaus.groovy.ast.expr.ConstantExpression;
 import org.codehaus.groovy.ast.expr.Expression;
 import org.codehaus.groovy.transform.ASTTransformation;
 import org.springframework.boot.cli.compiler.grape.DependencyResolutionContext;
+import org.springframework.core.annotation.Order;
 
 /**
  * {@link ASTTransformation} to resolve {@link Grab} artifact coordinates.
@@ -36,9 +37,12 @@ import org.springframework.boot.cli.compiler.grape.DependencyResolutionContext;
  * @author Andy Wilkinson
  * @author Phillip Webb
  */
+@Order(ResolveDependencyCoordinatesTransformation.ORDER)
 public class ResolveDependencyCoordinatesTransformation extends
 		AnnotatedNodeASTTransformation {
 
+	public static final int ORDER = GrabMetadataTransformation.ORDER + 300;
+
 	private static final Set<String> GRAB_ANNOTATION_NAMES = Collections
 			.unmodifiableSet(new HashSet<String>(Arrays.asList(Grab.class.getName(),
 					Grab.class.getSimpleName())));

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

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2014 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
+ *
+ *      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.
+ */
+
+package org.springframework.boot.cli.compiler;
+
+import org.codehaus.groovy.transform.ASTTransformation;
+
+/**
+ * Marker interface for AST transformations that should be installed automatically from
+ * META-INF/services
+ *
+ * @author Dave Syer
+ */
+public interface SpringBootAstTransformation extends ASTTransformation {
+
+}