| // Copyright 2015 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.packages; |
| |
| import com.google.common.base.Preconditions; |
| import com.google.common.collect.ImmutableList; |
| import com.google.common.collect.Iterables; |
| import com.google.devtools.build.lib.cmdline.Label; |
| import com.google.devtools.build.lib.collect.nestedset.Depset; |
| import java.util.Arrays; |
| import java.util.List; |
| import java.util.Objects; |
| import javax.annotation.Nullable; |
| import net.starlark.java.annot.StarlarkBuiltin; |
| import net.starlark.java.eval.Dict; |
| import net.starlark.java.eval.EvalException; |
| import net.starlark.java.eval.HasBinary; |
| import net.starlark.java.eval.Printer; |
| import net.starlark.java.eval.Starlark; |
| import net.starlark.java.eval.StarlarkValue; |
| import net.starlark.java.syntax.TokenKind; |
| |
| /** |
| * An attribute value consisting of a concatenation of native types and selects, e.g: |
| * |
| * <pre> |
| * rule( |
| * name = 'myrule', |
| * deps = |
| * [':defaultdep'] |
| * + select({ |
| * 'a': [':adep'], |
| * 'b': [':bdep'],}) |
| * + select({ |
| * 'c': [':cdep'], |
| * 'd': [':ddep'],}) |
| * ) |
| * </pre> |
| */ |
| @StarlarkBuiltin( |
| name = "select", |
| doc = "A selector between configuration-dependent entities.", |
| documented = false) |
| public final class SelectorList implements StarlarkValue, HasBinary { |
| |
| // TODO(adonovan): combine Selector{List,Value} and BuildType.SelectorList. |
| // We don't need three classes for the same concept |
| |
| private final Class<?> type; |
| private final List<Object> elements; |
| |
| private SelectorList(Class<?> type, List<Object> elements) { |
| this.type = type; |
| this.elements = elements; |
| } |
| |
| /** |
| * Returns an ordered list of the elements in this expression. Each element may be a native type |
| * or a select. |
| */ |
| List<Object> getElements() { |
| return elements; |
| } |
| |
| /** Returns the native type contained by this expression. */ |
| Class<?> getType() { |
| return type; |
| } |
| |
| /** Implementation of the Starlark {@code select} function exposed to BUILD and .bzl files. */ |
| public static Object select(Dict<?, ?> dict, String noMatchError) throws EvalException { |
| if (dict.isEmpty()) { |
| throw Starlark.errorf( |
| "select({}) with an empty dictionary can never resolve because it includes no conditions" |
| + " to match"); |
| } |
| for (Object key : dict.keySet()) { |
| if (!(key instanceof String || key instanceof Label)) { |
| throw Starlark.errorf( |
| "select: got %s for dict key, want a Label or label string", Starlark.type(key)); |
| } |
| } |
| return SelectorList.of(new SelectorValue(dict, noMatchError)); |
| } |
| |
| /** Creates a "wrapper" list that consists of a single select. */ |
| static SelectorList of(SelectorValue selector) { |
| return new SelectorList(selector.getType(), ImmutableList.of(selector)); |
| } |
| |
| /** |
| * Creates a list from the given sequence of values, which must be non-empty. Each value may be a |
| * native type, a select over that type, or a selector list over that type. |
| * |
| * @throws EvalException if all values don't have the same underlying type |
| */ |
| static SelectorList of(Iterable<?> values) throws EvalException { |
| Preconditions.checkArgument(!Iterables.isEmpty(values)); |
| ImmutableList.Builder<Object> elements = ImmutableList.builder(); |
| Object firstValue = null; |
| |
| for (Object value : values) { |
| if (value instanceof SelectorList) { |
| elements.addAll(((SelectorList) value).elements); |
| } else { |
| elements.add(value); |
| } |
| if (firstValue == null) { |
| firstValue = value; |
| } |
| if (!canConcatenate(getNativeType(firstValue), getNativeType(value))) { |
| throw Starlark.errorf( |
| "'+' operator applied to incompatible types (%s, %s)", |
| getTypeName(firstValue), getTypeName(value)); |
| } |
| } |
| |
| return new SelectorList(getNativeType(firstValue), elements.build()); |
| } |
| |
| /** |
| * Creates a list that concatenates two values, where each value may be a native type, a select |
| * over that type, or a selector list over that type. |
| * |
| * @throws EvalException if the values don't have the same underlying type |
| */ |
| static SelectorList concat(Object x, Object y) throws EvalException { |
| return of(Arrays.asList(x, y)); |
| } |
| |
| @Override |
| @Nullable |
| public SelectorList binaryOp(TokenKind op, Object that, boolean thisLeft) throws EvalException { |
| if (op == TokenKind.PLUS) { |
| return thisLeft ? concat(this, that) : concat(that, this); |
| } |
| return null; |
| } |
| |
| private static final Class<?> NATIVE_LIST_TYPE = List.class; |
| |
| private static String getTypeName(Object x) { |
| if (x instanceof SelectorList) { |
| return "select of " + Depset.ElementType.of(((SelectorList) x).type); |
| } else if (x instanceof SelectorValue) { |
| return "select of " + Depset.ElementType.of(((SelectorValue) x).getType()); |
| } else { |
| return Starlark.type(x); |
| } |
| } |
| |
| private static Class<?> getNativeType(Object value) { |
| if (value instanceof SelectorList) { |
| return ((SelectorList) value).type; |
| } else if (value instanceof SelectorValue) { |
| return ((SelectorValue) value).getType(); |
| } else { |
| return value.getClass(); |
| } |
| } |
| |
| private static boolean isListType(Class<?> type) { |
| return NATIVE_LIST_TYPE.isAssignableFrom(type); |
| } |
| |
| private static boolean canConcatenate(Class<?> type1, Class<?> type2) { |
| if (type1 == type2) { |
| return true; |
| } |
| return isListType(type1) && isListType(type2); |
| } |
| |
| @Override |
| public String toString() { |
| return Starlark.repr(this); |
| } |
| |
| @Override |
| public void repr(Printer printer) { |
| printer.printList(elements, "", " + ", ""); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hash(type, elements); |
| } |
| |
| @Override |
| public boolean equals(Object other) { |
| if (this == other) { |
| return true; |
| } |
| if (!(other instanceof SelectorList)) { |
| return false; |
| } |
| SelectorList that = (SelectorList) other; |
| return Objects.equals(this.type, that.type) && Objects.equals(this.elements, that.elements); |
| } |
| } |