| // 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.collect.ImmutableList; |
| import com.google.devtools.build.lib.events.Location; |
| import com.google.devtools.build.lib.skylarkinterface.SkylarkModule; |
| import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory; |
| import com.google.devtools.build.lib.skylarkinterface.SkylarkValue; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.RandomAccess; |
| import javax.annotation.Nullable; |
| |
| /** |
| * A Sequence is a finite sequence of Starlark values, such as a list or tuple. |
| * |
| * <p>Although this implements the {@link List} interface, it is not mutable via that interface's |
| * methods. Instead, use the mutators that take in a {@link Mutability} object. |
| */ |
| @SkylarkModule( |
| name = "sequence", |
| documented = false, |
| category = SkylarkModuleCategory.BUILTIN, |
| doc = "common type of lists and tuples.") |
| public interface Sequence<E> extends SkylarkValue, List<E>, RandomAccess, SkylarkIndexable { |
| |
| @Override |
| default boolean truth() { |
| return !isEmpty(); |
| } |
| |
| /** Returns an ImmutableList object with the current underlying contents of this Sequence. */ |
| default ImmutableList<E> getImmutableList() { |
| return ImmutableList.copyOf(this); |
| } |
| |
| /** |
| * Retrieve an entry from a Sequence. |
| * |
| * @param key the index |
| * @param loc a {@link Location} in case of error |
| * @throws EvalException if the key is invalid |
| */ |
| @Override |
| default E getIndex(Object key, Location loc) throws EvalException { |
| return get(EvalUtils.getSequenceIndex(key, size(), loc)); |
| } |
| |
| @Override |
| default boolean containsKey(Object key, Location loc) throws EvalException { |
| return contains(key); |
| } |
| |
| /** |
| * Constructs a version of this {@code Sequence} containing just the items in a slice. |
| * |
| * <p>{@code mutability} will be used for the resulting list. If it is null, the list will be |
| * immutable. For {@code Tuple}s, which are always immutable, this argument is ignored. |
| * |
| * @see EvalUtils#getSliceIndices |
| * @throws EvalException if the key is invalid; uses {@code loc} for error reporting |
| */ |
| Sequence<E> getSlice(Object start, Object end, Object step, Location loc, Mutability mutability) |
| throws EvalException; |
| |
| /** |
| * Casts a {@code List<?>} to an unmodifiable {@code List<T>}, after checking that its contents |
| * all have type {@code type}. |
| * |
| * <p>The returned list may or may not be a view that is affected by updates to the original list. |
| * |
| * @param list the original list to cast |
| * @param type the expected type of all the list's elements |
| * @param description a description of the argument being converted, or null, for debugging |
| */ |
| // We could have used bounded generics to ensure that only downcasts are possible (i.e. cast |
| // List<S> to List<T extends S>), but this would be less convenient for some callers, and it would |
| // disallow casting an empty list to any type. |
| // TODO(adonovan): this method doesn't belong here. |
| @SuppressWarnings("unchecked") |
| public static <T> List<T> castList(List<?> list, Class<T> type, @Nullable String description) |
| throws EvalException { |
| Object desc = description == null ? null : Printer.formattable("'%s' element", description); |
| for (Object value : list) { |
| SkylarkType.checkType(value, type, desc); |
| } |
| return Collections.unmodifiableList((List<T>) list); |
| } |
| |
| /** |
| * If {@code obj} is a {@code Sequence}, casts it to an unmodifiable {@code List<T>} after |
| * checking that each element has type {@code type}. If {@code obj} is {@code None} or null, |
| * treats it as an empty list. For all other values, throws an {@link EvalException}. |
| * |
| * <p>The returned list may or may not be a view that is affected by updates to the original list. |
| * |
| * @param obj the object to cast. null and None are treated as an empty list. |
| * @param type the expected type of all the list's elements |
| * @param description a description of the argument being converted, or null, for debugging |
| */ |
| // TODO(adonovan): this method doesn't belong here. |
| public static <T> List<T> castSkylarkListOrNoneToList( |
| Object obj, Class<T> type, @Nullable String description) throws EvalException { |
| if (EvalUtils.isNullOrNone(obj)) { |
| return ImmutableList.of(); |
| } |
| if (obj instanceof Sequence) { |
| return ((Sequence<?>) obj).getContents(type, description); |
| } |
| throw new EvalException(null, |
| String.format("Illegal argument: %s is not of expected type list or NoneType", |
| description == null ? Printer.repr(obj) : String.format("'%s'", description))); |
| } |
| |
| /** |
| * Casts this list as an unmodifiable {@code List<T>}, after checking that each element has type |
| * {@code type}. |
| * |
| * @param type the expected type of all the list's elements |
| * @param description a description of the argument being converted, or null, for debugging |
| */ |
| // TODO(adonovan): this method doesn't belong here. |
| default <T> List<T> getContents(Class<T> type, @Nullable String description) |
| throws EvalException { |
| return castList(this, type, description); |
| } |
| |
| /** |
| * Creates an immutable StarlarkList with the given elements. |
| * |
| * <p>The caller must ensure that the elements of {@code contents} are not mutable. |
| */ |
| // TODO(adonovan): move to StarlarkList. |
| public static <E> Sequence<E> createImmutable(Iterable<? extends E> contents) { |
| return StarlarkList.copyOf(Mutability.IMMUTABLE, contents); |
| } |
| } |