Java tutorial
// Copyright 2014 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.syntax; import com.google.common.annotations.VisibleForTesting; import com.google.common.base.Joiner; import com.google.common.cache.CacheBuilder; import com.google.common.cache.CacheLoader; import com.google.common.cache.LoadingCache; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableMap; import com.google.common.collect.Lists; import com.google.devtools.build.lib.events.Location; import com.google.devtools.build.lib.skylarkinterface.Param; import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable; import com.google.devtools.build.lib.skylarkinterface.SkylarkInterfaceUtils; import com.google.devtools.build.lib.skylarkinterface.SkylarkModule; import com.google.devtools.build.lib.syntax.EvalException.EvalExceptionWithJavaCause; import com.google.devtools.build.lib.syntax.Runtime.NoneType; import com.google.devtools.build.lib.util.Pair; import com.google.devtools.build.lib.util.Preconditions; import com.google.devtools.build.lib.util.StringUtilities; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import java.util.Set; import java.util.concurrent.ExecutionException; import javax.annotation.Nullable; /** * Syntax node for a function call expression. */ public final class FuncallExpression extends Expression { /** * A value class to store Methods with their corresponding SkylarkCallable annotations. * This is needed because the annotation is sometimes in a superclass. */ public static final class MethodDescriptor { private final Method method; private final SkylarkCallable annotation; private MethodDescriptor(Method method, SkylarkCallable annotation) { this.method = method; this.annotation = annotation; } Method getMethod() { return method; } /** * Returns the SkylarkCallable annotation corresponding to this method. */ public SkylarkCallable getAnnotation() { return annotation; } } private static final LoadingCache<Class<?>, Map<String, List<MethodDescriptor>>> methodCache = CacheBuilder .newBuilder().initialCapacity(10).maximumSize(100) .build(new CacheLoader<Class<?>, Map<String, List<MethodDescriptor>>>() { @Override public Map<String, List<MethodDescriptor>> load(Class<?> key) throws Exception { Map<String, List<MethodDescriptor>> methodMap = new HashMap<>(); for (Method method : key.getMethods()) { // Synthetic methods lead to false multiple matches if (method.isSynthetic()) { continue; } SkylarkCallable callable = SkylarkInterfaceUtils.getSkylarkCallable(method); if (callable == null) { continue; } Preconditions.checkArgument(callable.parameters().length == 0 || !callable.structField(), "Method " + method + " was annotated with both structField and parameters."); if (callable.parameters().length > 0 || callable.mandatoryPositionals() >= 0) { int nbArgs = callable.parameters().length + Math.max(0, callable.mandatoryPositionals()); Preconditions.checkArgument(nbArgs == method.getParameterTypes().length, "Method " + method + " was annotated for " + nbArgs + " arguments " + "but accept only " + method.getParameterTypes().length + " arguments."); } String name = callable.name(); if (name.isEmpty()) { name = StringUtilities.toPythonStyleFunctionName(method.getName()); } if (methodMap.containsKey(name)) { methodMap.get(name).add(new MethodDescriptor(method, callable)); } else { methodMap.put(name, Lists.newArrayList(new MethodDescriptor(method, callable))); } } return ImmutableMap.copyOf(methodMap); } }); /** * Returns a map of methods and corresponding SkylarkCallable annotations of the methods of the * classObj class reachable from Skylark. */ public static ImmutableMap<Method, SkylarkCallable> collectSkylarkMethodsWithAnnotation(Class<?> classObj) { ImmutableMap.Builder<Method, SkylarkCallable> methodMap = ImmutableMap.builder(); for (Method method : classObj.getMethods()) { // Synthetic methods lead to false multiple matches if (!method.isSynthetic()) { SkylarkCallable annotation = SkylarkInterfaceUtils.getSkylarkCallable(classObj, method); if (annotation != null) { methodMap.put(method, annotation); } } } return methodMap.build(); } private static class ArgumentListConversionResult { private final ImmutableList<Object> arguments; private final String error; private ArgumentListConversionResult(ImmutableList<Object> arguments, String error) { this.arguments = arguments; this.error = error; } public static ArgumentListConversionResult fromArgumentList(ImmutableList<Object> arguments) { return new ArgumentListConversionResult(arguments, null); } public static ArgumentListConversionResult fromError(String error) { return new ArgumentListConversionResult(null, error); } public String getError() { return error; } public ImmutableList<Object> getArguments() { return arguments; } } /** * An exception class to handle exceptions in direct Java API calls. */ public static final class FuncallException extends Exception { public FuncallException(String msg) { super(msg); } } @Nullable private final Expression obj; private final Identifier func; private final List<Argument.Passed> args; private final int numPositionalArgs; public FuncallExpression(@Nullable Expression obj, Identifier func, List<Argument.Passed> args) { this.obj = obj; this.func = func; this.args = args; // we assume the parser validated it with Argument#validateFuncallArguments() this.numPositionalArgs = countPositionalArguments(); } public FuncallExpression(Identifier func, List<Argument.Passed> args) { this(null, func, args); } /** * Returns the number of positional arguments. */ private int countPositionalArguments() { int num = 0; for (Argument.Passed arg : args) { if (arg.isPositional()) { num++; } } return num; } /** * Returns the function expression. */ public Identifier getFunction() { return func; } /** * Returns the object the function called on. * It's null if the function is not called on an object. */ public Expression getObject() { return obj; } /** * Returns an (immutable, ordered) list of function arguments. The first n are * positional and the remaining ones are keyword args, where n = * getNumPositionalArguments(). */ public List<Argument.Passed> getArguments() { return Collections.unmodifiableList(args); } /** * Returns the number of arguments which are positional; the remainder are * keyword arguments. */ public int getNumPositionalArguments() { return numPositionalArgs; } @Override public String toString() { StringBuilder sb = new StringBuilder(); if (obj != null) { sb.append(obj).append("."); } sb.append(func); Printer.printList(sb, args, "(", ", ", ")", /* singletonTerminator */ null, Printer.SUGGESTED_CRITICAL_LIST_ELEMENTS_COUNT, Printer.SUGGESTED_CRITICAL_LIST_ELEMENTS_STRING_LENGTH); return sb.toString(); } /** * Returns the list of Skylark callable Methods of objClass with the given name and argument * number. */ public static List<MethodDescriptor> getMethods(Class<?> objClass, String methodName) { try { return methodCache.get(objClass).get(methodName); } catch (ExecutionException e) { throw new IllegalStateException("method invocation failed: " + e); } } /** * Returns a set of the Skylark name of all Skylark callable methods for object of type {@code * objClass}. */ public static Set<String> getMethodNames(Class<?> objClass) { try { return methodCache.get(objClass).keySet(); } catch (ExecutionException e) { throw new IllegalStateException("method invocation failed: " + e); } } static Object callMethod(MethodDescriptor methodDescriptor, String methodName, Object obj, Object[] args, Location loc, Environment env) throws EvalException { try { Method method = methodDescriptor.getMethod(); if (obj == null && !Modifier.isStatic(method.getModifiers())) { throw new EvalException(loc, "method '" + methodName + "' is not static"); } // This happens when the interface is public but the implementation classes // have reduced visibility. method.setAccessible(true); Object result = method.invoke(obj, args); if (method.getReturnType().equals(Void.TYPE)) { return Runtime.NONE; } if (result == null) { if (methodDescriptor.getAnnotation().allowReturnNones()) { return Runtime.NONE; } else { throw new EvalException(loc, "method invocation returned None, please file a bug report: " + methodName + Printer.listString(ImmutableList.copyOf(args), "(", ", ", ")", null)); } } // TODO(bazel-team): get rid of this, by having everyone use the Skylark data structures result = SkylarkType.convertToSkylark(result, method, env); if (result != null && !EvalUtils.isSkylarkAcceptable(result.getClass())) { throw new EvalException(loc, Printer.format("method '%s' returns an object of invalid type %r", methodName, result.getClass())); } return result; } catch (IllegalAccessException e) { // TODO(bazel-team): Print a nice error message. Maybe the method exists // and an argument is missing or has the wrong type. throw new EvalException(loc, "Method invocation failed: " + e); } catch (InvocationTargetException e) { if (e.getCause() instanceof FuncallException) { throw new EvalException(loc, e.getCause().getMessage()); } else if (e.getCause() != null) { throw new EvalExceptionWithJavaCause(loc, e.getCause()); } else { // This is unlikely to happen throw new EvalException(loc, "method invocation failed: " + e); } } } // TODO(bazel-team): If there's exactly one usable method, this works. If there are multiple // matching methods, it still can be a problem. Figure out how the Java compiler does it // exactly and copy that behaviour. // Throws an EvalException when it cannot find a matching function. private Pair<MethodDescriptor, List<Object>> findJavaMethod(Class<?> objClass, String methodName, List<Object> args, Map<String, Object> kwargs) throws EvalException { Pair<MethodDescriptor, List<Object>> matchingMethod = null; List<MethodDescriptor> methods = getMethods(objClass, methodName); ArgumentListConversionResult argumentListConversionResult = null; if (methods != null) { for (MethodDescriptor method : methods) { if (method.getAnnotation().structField()) { return new Pair<>(method, null); } else { argumentListConversionResult = convertArgumentList(args, kwargs, method); if (argumentListConversionResult.getArguments() != null) { if (matchingMethod == null) { matchingMethod = new Pair<MethodDescriptor, List<Object>>(method, argumentListConversionResult.getArguments()); } else { throw new EvalException(getLocation(), String.format("type '%s' has multiple matches for function %s", EvalUtils.getDataTypeNameFromClass(objClass), formatMethod(args, kwargs))); } } } } } if (matchingMethod == null) { String errorMessage; if (argumentListConversionResult == null || argumentListConversionResult.getError() == null) { errorMessage = String.format("type '%s' has no method %s", EvalUtils.getDataTypeNameFromClass(objClass), formatMethod(args, kwargs)); } else { errorMessage = String.format("%s, in method %s of '%s'", argumentListConversionResult.getError(), formatMethod(args, kwargs), EvalUtils.getDataTypeNameFromClass(objClass)); } throw new EvalException(getLocation(), errorMessage); } return matchingMethod; } private static SkylarkType getType(Param param) { SkylarkType type = param.generic1() != Object.class ? SkylarkType.of(param.type(), param.generic1()) : SkylarkType.of(param.type()); return type; } /** * Constructs the parameters list to actually pass to the method, filling with default values if * any. If there is a type or argument mismatch, returns a result containing an error message. */ private ArgumentListConversionResult convertArgumentList(List<Object> args, Map<String, Object> kwargs, MethodDescriptor method) { ImmutableList.Builder<Object> builder = ImmutableList.builder(); Class<?>[] params = method.getMethod().getParameterTypes(); SkylarkCallable callable = method.getAnnotation(); int mandatoryPositionals = callable.mandatoryPositionals(); if (mandatoryPositionals < 0) { if (callable.parameters().length > 0) { mandatoryPositionals = 0; } else { mandatoryPositionals = params.length; } } if (mandatoryPositionals > args.size() || args.size() > mandatoryPositionals + callable.parameters().length) { return ArgumentListConversionResult.fromError("too many arguments"); } // First process the legacy positional parameters. int i = 0; if (mandatoryPositionals > 0) { for (Class<?> param : params) { Object value = args.get(i); if (!param.isAssignableFrom(value.getClass())) { return ArgumentListConversionResult.fromError( String.format("Cannot convert parameter at position %d from type %s to type %s", i, EvalUtils.getDataTypeName(value), param.toString())); } builder.add(value); i++; if (mandatoryPositionals >= 0 && i >= mandatoryPositionals) { // Stops for specified parameters instead. break; } } } // Then the parameters specified in callable.parameters() Set<String> keys = new HashSet<>(kwargs.keySet()); for (Param param : callable.parameters()) { SkylarkType type = getType(param); if (param.noneable()) { type = SkylarkType.Union.of(type, SkylarkType.NONE); } Object value = null; if (i < args.size()) { value = args.get(i); if (!param.positional()) { return ArgumentListConversionResult .fromError(String.format("Parameter '%s' is not positional", param.name())); } else if (!type.contains(value)) { return ArgumentListConversionResult.fromError(String .format("Cannot convert parameter '%s' to type %s", param.name(), type.toString())); } i++; } else if (param.named() && keys.remove(param.name())) { // Named parameters value = kwargs.get(param.name()); if (!type.contains(value)) { return ArgumentListConversionResult.fromError(String .format("Cannot convert parameter '%s' to type %s", param.name(), type.toString())); } } else { // Use default value if (param.defaultValue().isEmpty()) { return ArgumentListConversionResult .fromError(String.format("parameter '%s' has no default value", param.name())); } value = SkylarkSignatureProcessor.getDefaultValue(param, null); } builder.add(value); if (!param.noneable() && value instanceof NoneType) { return ArgumentListConversionResult .fromError(String.format("parameter '%s' cannot be None", param.name())); } } if (i < args.size() || !keys.isEmpty()) { return ArgumentListConversionResult.fromError("too many arguments"); } return ArgumentListConversionResult.fromArgumentList(builder.build()); } private String formatMethod(List<Object> args, Map<String, Object> kwargs) { StringBuilder sb = new StringBuilder(); sb.append(func.getName()).append("("); boolean first = true; for (Object obj : args) { if (!first) { sb.append(", "); } sb.append(EvalUtils.getDataTypeName(obj)); first = false; } for (Map.Entry<String, Object> kwarg : kwargs.entrySet()) { if (!first) { sb.append(", "); } sb.append(EvalUtils.getDataTypeName(kwarg.getValue())); sb.append(" "); sb.append(kwarg.getKey()); first = false; } return sb.append(")").toString(); } /** * Add one argument to the keyword map, registering a duplicate in case of conflict. * * <p>public for reflection by the compiler and calls from compiled functions */ public static void addKeywordArg(Map<String, Object> kwargs, String name, Object value, ImmutableList.Builder<String> duplicates) { if (kwargs.put(name, value) != null) { duplicates.add(name); } } /** * Add multiple arguments to the keyword map (**kwargs), registering duplicates * * <p>public for reflection by the compiler and calls from compiled functions */ public static void addKeywordArgs(Map<String, Object> kwargs, Object items, ImmutableList.Builder<String> duplicates, Location location) throws EvalException { if (!(items instanceof Map<?, ?>)) { throw new EvalException(location, "argument after ** must be a dictionary, not '" + EvalUtils.getDataTypeName(items) + "'"); } for (Map.Entry<?, ?> entry : ((Map<?, ?>) items).entrySet()) { if (!(entry.getKey() instanceof String)) { throw new EvalException(location, "keywords must be strings, not '" + EvalUtils.getDataTypeName(entry.getKey()) + "'"); } addKeywordArg(kwargs, (String) entry.getKey(), entry.getValue(), duplicates); } } /** * Checks whether the given object is a {@link BaseFunction}. * * <p>Public for reflection by the compiler and access from generated byte code. * * @throws EvalException If not a BaseFunction. */ public static BaseFunction checkCallable(Object functionValue, Location location) throws EvalException { if (functionValue instanceof BaseFunction) { return (BaseFunction) functionValue; } else { throw new EvalException(location, "'" + EvalUtils.getDataTypeName(functionValue) + "' object is not callable"); } } /** * Check the list from the builder and report an {@link EvalException} if not empty. * * <p>public for reflection by the compiler and calls from compiled functions */ public static void checkDuplicates(ImmutableList.Builder<String> duplicates, String function, Location location) throws EvalException { List<String> dups = duplicates.build(); if (!dups.isEmpty()) { throw new EvalException(location, "duplicate keyword" + (dups.size() > 1 ? "s" : "") + " '" + Joiner.on("', '").join(dups) + "' in call to " + function); } } /** * Call a method depending on the type of an object it is called on. * * <p>Public for reflection by the compiler and access from generated byte code. * * @param positionals The first object is expected to be the object the method is called on. * @param call the original expression that caused this call, needed for rules especially */ public Object invokeObjectMethod(String method, ImmutableList<Object> positionals, ImmutableMap<String, Object> keyWordArgs, FuncallExpression call, Environment env) throws EvalException, InterruptedException { Location location = call.getLocation(); Object value = positionals.get(0); ImmutableList<Object> positionalArgs = positionals.subList(1, positionals.size()); BaseFunction function = Runtime.getFunction(EvalUtils.getSkylarkType(value.getClass()), method); if (function != null) { if (!isNamespace(value.getClass())) { // Use self as an implicit parameter in front. positionalArgs = positionals; } return function.call(positionalArgs, ImmutableMap.<String, Object>copyOf(keyWordArgs), call, env); } else if (value instanceof ClassObject) { Object fieldValue = ((ClassObject) value).getValue(method); if (fieldValue == null) { throw new EvalException(location, String.format("struct has no method '%s'", method)); } if (!(fieldValue instanceof BaseFunction)) { throw new EvalException(location, String.format("struct field '%s' is not a function", method)); } function = (BaseFunction) fieldValue; return function.call(positionalArgs, ImmutableMap.<String, Object>copyOf(keyWordArgs), call, env); } else { // When calling a Java method, the name is not in the Environment, // so evaluating 'func' would fail. Class<?> objClass; Object obj; if (value instanceof Class<?>) { // Static call obj = null; objClass = (Class<?>) value; } else { obj = value; objClass = value.getClass(); } Pair<MethodDescriptor, List<Object>> javaMethod = call.findJavaMethod(objClass, method, positionalArgs, keyWordArgs); if (javaMethod.first.getAnnotation().structField()) { // Not a method but a callable attribute try { return callFunction(javaMethod.first.getMethod().invoke(obj), env); } catch (IllegalAccessException e) { throw new EvalException(getLocation(), "method invocation failed: " + e); } catch (InvocationTargetException e) { if (e.getCause() instanceof FuncallException) { throw new EvalException(getLocation(), e.getCause().getMessage()); } else if (e.getCause() != null) { throw new EvalExceptionWithJavaCause(getLocation(), e.getCause()); } else { // This is unlikely to happen throw new EvalException(getLocation(), "method invocation failed: " + e); } } } return callMethod(javaMethod.first, method, obj, javaMethod.second.toArray(), location, env); } } @SuppressWarnings("unchecked") private void evalArguments(ImmutableList.Builder<Object> posargs, Map<String, Object> kwargs, Environment env) throws EvalException, InterruptedException { ImmutableList.Builder<String> duplicates = new ImmutableList.Builder<>(); // Iterate over the arguments. We assume all positional arguments come before any keyword // or star arguments, because the argument list was already validated by // Argument#validateFuncallArguments, as called by the Parser, // which should be the only place that build FuncallExpression-s. for (Argument.Passed arg : args) { Object value = arg.getValue().eval(env); if (arg.isPositional()) { posargs.add(value); } else if (arg.isStar()) { // expand the starArg if (value instanceof Iterable) { posargs.addAll((Iterable<Object>) value); } } else if (arg.isStarStar()) { // expand the kwargs addKeywordArgs(kwargs, value, duplicates, getLocation()); } else { addKeywordArg(kwargs, arg.getName(), value, duplicates); } } checkDuplicates(duplicates, func.getName(), getLocation()); } @VisibleForTesting public static boolean isNamespace(Class<?> classObject) { return classObject.isAnnotationPresent(SkylarkModule.class) && classObject.getAnnotation(SkylarkModule.class).namespace(); } @Override Object doEval(Environment env) throws EvalException, InterruptedException { return (obj != null) ? invokeObjectMethod(env) : invokeGlobalFunction(env); } /** * Invokes obj.func() and returns the result. */ private Object invokeObjectMethod(Environment env) throws EvalException, InterruptedException { Object objValue = obj.eval(env); ImmutableList.Builder<Object> posargs = new ImmutableList.Builder<>(); posargs.add(objValue); // We copy this into an ImmutableMap in the end, but we can't use an ImmutableMap.Builder, or // we'd still have to have a HashMap on the side for the sake of properly handling duplicates. Map<String, Object> kwargs = new LinkedHashMap<>(); evalArguments(posargs, kwargs, env); return invokeObjectMethod(func.getName(), posargs.build(), ImmutableMap.<String, Object>copyOf(kwargs), this, env); } /** * Invokes func() and returns the result. */ private Object invokeGlobalFunction(Environment env) throws EvalException, InterruptedException { Object funcValue = func.eval(env); return callFunction(funcValue, env); } /** * Calls a function object */ private Object callFunction(Object funcValue, Environment env) throws EvalException, InterruptedException { ImmutableList.Builder<Object> posargs = new ImmutableList.Builder<>(); // We copy this into an ImmutableMap in the end, but we can't use an ImmutableMap.Builder, or // we'd still have to have a HashMap on the side for the sake of properly handling duplicates. Map<String, Object> kwargs = new LinkedHashMap<>(); BaseFunction function = checkCallable(funcValue, getLocation()); evalArguments(posargs, kwargs, env); return function.call(posargs.build(), ImmutableMap.copyOf(kwargs), this, env); } /** * Returns the value of the argument 'name' (or null if there is none). * This function is used to associate debugging information to rules created by skylark "macros". */ @Nullable public String getNameArg() { for (Argument.Passed arg : args) { if (arg != null) { String name = arg.getName(); if (name != null && name.equals("name")) { Expression expr = arg.getValue(); return (expr instanceof StringLiteral) ? ((StringLiteral) expr).getValue() : null; } } } return null; } @Override public void accept(SyntaxTreeVisitor visitor) { visitor.visit(this); } @Override void validate(ValidationEnvironment env) throws EvalException { if (obj != null) { obj.validate(env); } else { func.validate(env); } for (Argument.Passed arg : args) { arg.getValue().validate(env); } } @Override protected boolean isNewScope() { return true; } }