src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java - bazel - Git at Google

 // Copyright 2016 The Bazel Authors. All rights reserved.
 //
 // 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 com.google.devtools.build.lib.skylarkinterface;

 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import javax.annotation.Nullable;

 /**
  * Helpers for accessing Skylark interface annotations.
  */
 public class SkylarkInterfaceUtils {

   private static final class ClassWithAnnotation<T extends Annotation> {
     final Class<?> klass;
     final T annotation;

     ClassWithAnnotation(Class<?> klass, T annotation) {
       this.klass = klass;
       this.annotation = annotation;
     }
   }

   /**
    * Returns the more specific class of two classes. Class x is more specific than class y
    * if x is assignable to y. For example, of Integer.class and Object.class, Integer.class is more
    * specific.
    *
    * <p>If either class is null, returns the other class.</p>
    *
    * <p>If the classes are identical, returns the class.</p>
    *
    * @throws IllegalArgumentException if neither class is assignable to the other
    */
   private static <T extends Annotation> ClassWithAnnotation<T> moreSpecificClass(
       ClassWithAnnotation<T> x, ClassWithAnnotation<T> y) {
     if (x == null) {
       return y;
     } else if (y == null) {
       return x;
     }
     Class<?> xClass = x.klass;
     Class<?> yClass = y.klass;
     if (xClass.isAssignableFrom(yClass)) {
       return y;
     } else if (yClass.isAssignableFrom(xClass)) {
       return x;
     } else {
       // If this exception occurs, it indicates the following error scenario:
       //
       // Suppose class A is a subclass of both B and C, where B and C are annotated with
       // @SkylarkModule annotations (and are thus considered "skylark types"). If B is not a
       // subclass of C (nor visa versa), then it's impossible to resolve whether A is of type
       // B or if A is of type C. It's both! The way to resolve this is usually to have A be its own
       // type (annotated with @SkylarkModule), and thus have the explicit type of A be semantically
       // "B and C".
       throw new IllegalArgumentException(String.format(
           "Expected one of %s and %s to be a subclass of the other",
           xClass, yClass));
     }
   }

   /**
    * Searches a class or interface's class hierarchy for the given class annotation.
    *
    * <p>If the given class annotation appears multiple times within the class hierachy, this
    * chooses the annotation on the most-specified class in the hierarchy.</p>
    *
    * @return a {@link ClassWithAnnotation} containing the best-fit annotation and the class
    *     it was declared on
    */
   @Nullable
   private static <T extends Annotation> ClassWithAnnotation<T> searchForClassAnnotation(
       Class<?> classObj,
       Class<T> annotationClass) {
     if (classObj.isAnnotationPresent(annotationClass)) {
       return new ClassWithAnnotation<T>(classObj, classObj.getAnnotation(annotationClass));
     }
     ClassWithAnnotation<T> bestCandidate = null;

     Class<?> superclass = classObj.getSuperclass();
     if (superclass != null) {
       ClassWithAnnotation<T> result = searchForClassAnnotation(superclass, annotationClass);
       bestCandidate = moreSpecificClass(result, bestCandidate);
     }
     for (Class<?> interfaceObj : classObj.getInterfaces()) {
       ClassWithAnnotation<T> result = searchForClassAnnotation(interfaceObj, annotationClass);
       bestCandidate = moreSpecificClass(result, bestCandidate);
     }
     return bestCandidate;
   }

   /**
    * Returns the {@link SkylarkModule} annotation for the given class, if it exists, and
    * null otherwise. The first annotation found will be returned, starting with {@code classObj}
    * and following its base classes and interfaces recursively.
    */
   @Nullable
   public static SkylarkModule getSkylarkModule(Class<?> classObj) {
     ClassWithAnnotation<SkylarkModule> result =
         searchForClassAnnotation(classObj, SkylarkModule.class);
     return result == null ? null : result.annotation;
   }

   /**
    * Searches {@code classObj}'s class hierarchy and returns the first superclass or interface that
    * is annotated with {@link SkylarkModule} (including possibly {@code classObj} itself), or null
    * if none is found.
    */
   @Nullable
   public static Class<?> getParentWithSkylarkModule(Class<?> classObj) {
     ClassWithAnnotation<SkylarkModule> result =
         searchForClassAnnotation(classObj, SkylarkModule.class);
     return result == null ? null : result.klass;
   }

   /**
    * Searches {@code classObj}'s class hierarchy and for a superclass or interface that
    * is annotated with {@link SkylarkGlobalLibrary} (including possibly {@code classObj} itself),
    * and returns true if one is found.
    */
   public static boolean hasSkylarkGlobalLibrary(Class<?> classObj) {
     ClassWithAnnotation<SkylarkGlobalLibrary> result =
         searchForClassAnnotation(classObj, SkylarkGlobalLibrary.class);
     return result != null;
   }

   /**
    * Returns the {@link SkylarkCallable} annotation for the given method, if it exists, and
    * null otherwise.
    *
    * <p>Note that the annotation may be defined on a supermethod, rather than directly on the given
    * method.
    *
    * <p>{@code classObj} is the class on which the given method is defined.
    */
   @Nullable
   public static SkylarkCallable getSkylarkCallable(Class<?> classObj, Method method) {
     SkylarkCallable callable = getCallableOnClassMatchingSignature(classObj, method);
     if (callable != null) {
       return callable;
     }
     if (classObj.getSuperclass() != null) {
       SkylarkCallable annotation = getSkylarkCallable(classObj.getSuperclass(), method);
       if (annotation != null) {
         return annotation;
       }
     }
     for (Class<?> interfaceObj : classObj.getInterfaces()) {
       SkylarkCallable annotation = getSkylarkCallable(interfaceObj, method);
       if (annotation != null) {
         return annotation;
       }
     }
     return null;
   }

   /**
    * Convenience version of {@code getAnnotationsFromParentClass(Class, Method)} that uses
    * the declaring class of the method.
    */
   @Nullable
   public static SkylarkCallable getSkylarkCallable(Method method) {
     return getSkylarkCallable(method.getDeclaringClass(), method);
   }

   /**
    * Returns the {@code SkylarkCallable} annotation corresponding to the given method of the given
    * class, or null if there is no such annotation.
    *
    * <p>This method checks assignability instead of exact matches for purposes of generics. If
    * Clazz has parameters BarT (extends BarInterface) and BazT (extends BazInterface), then
    * foo(BarT, BazT) should match if the given method signature is foo(BarImpl, BazImpl). The
    * signatures are in inexact match, but an "assignable" match.
    */
   @Nullable
   private static SkylarkCallable getCallableOnClassMatchingSignature(
       Class<?> classObj, Method signatureToMatch) {
     // TODO(b/79877079): This method validates several invariants of @SkylarkCallable. These
     // invariants should be verified in annotation processor or in test, and left out of this
     // method.
     Method[] methods = classObj.getDeclaredMethods();
     Class<?>[] paramsToMatch = signatureToMatch.getParameterTypes();

     SkylarkCallable callable = null;

     for (Method method : methods) {
       if (signatureToMatch.getName().equals(method.getName())
           && method.isAnnotationPresent(SkylarkCallable.class)) {
         Class<?>[] paramTypes = method.getParameterTypes();

         if (paramTypes.length == paramsToMatch.length) {
           for (int i = 0; i < paramTypes.length; i++) {
             // This verifies assignability of the method signature to ensure this is not a
             // coincidental overload. We verify assignability instead of matching exact parameter
             // classes in order to match generic methods.
             if (!paramTypes[i].isAssignableFrom(paramsToMatch[i])) {
               throw new IllegalStateException(
                   String.format(
                       "Class %s has an incompatible overload of annotated method %s declared by %s",
                       classObj, signatureToMatch.getName(), signatureToMatch.getDeclaringClass()));
             }
           }
         }
         if (callable == null) {
           callable = method.getAnnotation(SkylarkCallable.class);
         } else {
           throw new IllegalStateException(
               String.format(
                   "Class %s has multiple overloaded methods named '%s' annotated "
                       + "with @SkylarkCallable",
                   classObj, signatureToMatch.getName()));
         }
       }
     }
     return callable;
   }
 }
	// Copyright 2016 The Bazel Authors. All rights reserved.
	//
	// 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 com.google.devtools.build.lib.skylarkinterface;

	import java.lang.annotation.Annotation;
	import java.lang.reflect.Method;
	import javax.annotation.Nullable;

	/**
	* Helpers for accessing Skylark interface annotations.
	*/
	public class SkylarkInterfaceUtils {

	private static final class ClassWithAnnotation<T extends Annotation> {
	final Class<?> klass;
	final T annotation;

	ClassWithAnnotation(Class<?> klass, T annotation) {
	this.klass = klass;
	this.annotation = annotation;
	}
	}

	/**
	* Returns the more specific class of two classes. Class x is more specific than class y
	* if x is assignable to y. For example, of Integer.class and Object.class, Integer.class is more
	* specific.
	*
	* <p>If either class is null, returns the other class.</p>
	*
	* <p>If the classes are identical, returns the class.</p>
	*
	* @throws IllegalArgumentException if neither class is assignable to the other
	*/
	private static <T extends Annotation> ClassWithAnnotation<T> moreSpecificClass(
	ClassWithAnnotation<T> x, ClassWithAnnotation<T> y) {
	if (x == null) {
	return y;
	} else if (y == null) {
	return x;
	}
	Class<?> xClass = x.klass;
	Class<?> yClass = y.klass;
	if (xClass.isAssignableFrom(yClass)) {
	return y;
	} else if (yClass.isAssignableFrom(xClass)) {
	return x;
	} else {
	// If this exception occurs, it indicates the following error scenario:
	//
	// Suppose class A is a subclass of both B and C, where B and C are annotated with
	// @SkylarkModule annotations (and are thus considered "skylark types"). If B is not a
	// subclass of C (nor visa versa), then it's impossible to resolve whether A is of type
	// B or if A is of type C. It's both! The way to resolve this is usually to have A be its own
	// type (annotated with @SkylarkModule), and thus have the explicit type of A be semantically
	// "B and C".
	throw new IllegalArgumentException(String.format(
	"Expected one of %s and %s to be a subclass of the other",
	xClass, yClass));
	}
	}

	/**
	* Searches a class or interface's class hierarchy for the given class annotation.
	*
	* <p>If the given class annotation appears multiple times within the class hierachy, this
	* chooses the annotation on the most-specified class in the hierarchy.</p>
	*
	* @return a {@link ClassWithAnnotation} containing the best-fit annotation and the class
	* it was declared on
	*/
	@Nullable
	private static <T extends Annotation> ClassWithAnnotation<T> searchForClassAnnotation(
	Class<?> classObj,
	Class<T> annotationClass) {
	if (classObj.isAnnotationPresent(annotationClass)) {
	return new ClassWithAnnotation<T>(classObj, classObj.getAnnotation(annotationClass));
	}
	ClassWithAnnotation<T> bestCandidate = null;

	Class<?> superclass = classObj.getSuperclass();
	if (superclass != null) {
	ClassWithAnnotation<T> result = searchForClassAnnotation(superclass, annotationClass);
	bestCandidate = moreSpecificClass(result, bestCandidate);
	}
	for (Class<?> interfaceObj : classObj.getInterfaces()) {
	ClassWithAnnotation<T> result = searchForClassAnnotation(interfaceObj, annotationClass);
	bestCandidate = moreSpecificClass(result, bestCandidate);
	}
	return bestCandidate;
	}

	/**
	* Returns the {@link SkylarkModule} annotation for the given class, if it exists, and
	* null otherwise. The first annotation found will be returned, starting with {@code classObj}
	* and following its base classes and interfaces recursively.
	*/
	@Nullable
	public static SkylarkModule getSkylarkModule(Class<?> classObj) {
	ClassWithAnnotation<SkylarkModule> result =
	searchForClassAnnotation(classObj, SkylarkModule.class);
	return result == null ? null : result.annotation;
	}

	/**
	* Searches {@code classObj}'s class hierarchy and returns the first superclass or interface that
	* is annotated with {@link SkylarkModule} (including possibly {@code classObj} itself), or null
	* if none is found.
	*/
	@Nullable
	public static Class<?> getParentWithSkylarkModule(Class<?> classObj) {
	ClassWithAnnotation<SkylarkModule> result =
	searchForClassAnnotation(classObj, SkylarkModule.class);
	return result == null ? null : result.klass;
	}

	/**
	* Searches {@code classObj}'s class hierarchy and for a superclass or interface that
	* is annotated with {@link SkylarkGlobalLibrary} (including possibly {@code classObj} itself),
	* and returns true if one is found.
	*/
	public static boolean hasSkylarkGlobalLibrary(Class<?> classObj) {
	ClassWithAnnotation<SkylarkGlobalLibrary> result =
	searchForClassAnnotation(classObj, SkylarkGlobalLibrary.class);
	return result != null;
	}

	/**
	* Returns the {@link SkylarkCallable} annotation for the given method, if it exists, and
	* null otherwise.
	*
	* <p>Note that the annotation may be defined on a supermethod, rather than directly on the given
	* method.
	*
	* <p>{@code classObj} is the class on which the given method is defined.
	*/
	@Nullable
	public static SkylarkCallable getSkylarkCallable(Class<?> classObj, Method method) {
	SkylarkCallable callable = getCallableOnClassMatchingSignature(classObj, method);
	if (callable != null) {
	return callable;
	}
	if (classObj.getSuperclass() != null) {
	SkylarkCallable annotation = getSkylarkCallable(classObj.getSuperclass(), method);
	if (annotation != null) {
	return annotation;
	}
	}
	for (Class<?> interfaceObj : classObj.getInterfaces()) {
	SkylarkCallable annotation = getSkylarkCallable(interfaceObj, method);
	if (annotation != null) {
	return annotation;
	}
	}
	return null;
	}

	/**
	* Convenience version of {@code getAnnotationsFromParentClass(Class, Method)} that uses
	* the declaring class of the method.
	*/
	@Nullable
	public static SkylarkCallable getSkylarkCallable(Method method) {
	return getSkylarkCallable(method.getDeclaringClass(), method);
	}

	/**
	* Returns the {@code SkylarkCallable} annotation corresponding to the given method of the given
	* class, or null if there is no such annotation.
	*
	* <p>This method checks assignability instead of exact matches for purposes of generics. If
	* Clazz has parameters BarT (extends BarInterface) and BazT (extends BazInterface), then
	* foo(BarT, BazT) should match if the given method signature is foo(BarImpl, BazImpl). The
	* signatures are in inexact match, but an "assignable" match.
	*/
	@Nullable
	private static SkylarkCallable getCallableOnClassMatchingSignature(
	Class<?> classObj, Method signatureToMatch) {
	// TODO(b/79877079): This method validates several invariants of @SkylarkCallable. These
	// invariants should be verified in annotation processor or in test, and left out of this
	// method.
	Method[] methods = classObj.getDeclaredMethods();
	Class<?>[] paramsToMatch = signatureToMatch.getParameterTypes();

	SkylarkCallable callable = null;

	for (Method method : methods) {
	if (signatureToMatch.getName().equals(method.getName())
	&& method.isAnnotationPresent(SkylarkCallable.class)) {
	Class<?>[] paramTypes = method.getParameterTypes();

	if (paramTypes.length == paramsToMatch.length) {
	for (int i = 0; i < paramTypes.length; i++) {
	// This verifies assignability of the method signature to ensure this is not a
	// coincidental overload. We verify assignability instead of matching exact parameter
	// classes in order to match generic methods.
	if (!paramTypes[i].isAssignableFrom(paramsToMatch[i])) {
	throw new IllegalStateException(
	String.format(
	"Class %s has an incompatible overload of annotated method %s declared by %s",
	classObj, signatureToMatch.getName(), signatureToMatch.getDeclaringClass()));
	}
	}
	}
	if (callable == null) {
	callable = method.getAnnotation(SkylarkCallable.class);
	} else {
	throw new IllegalStateException(
	String.format(
	"Class %s has multiple overloaded methods named '%s' annotated "
	+ "with @SkylarkCallable",
	classObj, signatureToMatch.getName()));
	}
	}
	}
	return callable;
	}
	}