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// 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.syntax;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
import java.util.List;
import java.util.Objects;
/**
* 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>
*/
@SkylarkModule(
name = "select",
doc = "A selector between configuration-dependent entities.",
documented = false
)
@AutoCodec
public final class SelectorList implements SkylarkValue {
// TODO(build-team): Selectors are currently split between .packages and .syntax . They should
// really all be in .packages, but then we'd need to figure out a way how to extend binary
// operators, which is a non-trivial problem.
private final Class<?> type;
private final List<Object> elements;
@AutoCodec.VisibleForSerialization
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.
*/
public List<Object> getElements() {
return elements;
}
/**
* Returns the native type contained by this expression.
*/
public Class<?> getType() {
return type;
}
/**
* Creates a "wrapper" list that consists of a single select.
*/
public static SelectorList of(SelectorValue selector) {
return new SelectorList(selector.getType(), ImmutableList.of(selector));
}
/**
* 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
*/
public static SelectorList concat(Location location, Object value1, Object value2)
throws EvalException {
return of(location, value1, value2);
}
/**
* 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
*/
public static SelectorList of(Location location, Object... values) throws EvalException {
return SelectorList.of(location, ImmutableList.copyOf(values));
}
/**
* 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
*/
public static SelectorList of(Location location, 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).getElements());
} else {
elements.add(value);
}
if (firstValue == null) {
firstValue = value;
}
if (!canConcatenate(getNativeType(firstValue), getNativeType(value))) {
throw new EvalException(
location,
String.format(
"'+' operator applied to incompatible types (%s, %s)",
EvalUtils.getDataTypeName(firstValue, true),
EvalUtils.getDataTypeName(value, true)));
}
}
return new SelectorList(getNativeType(firstValue), elements.build());
}
private static final Class<?> NATIVE_LIST_TYPE = List.class;
private static Class<?> getNativeType(Object value) {
if (value instanceof SelectorList) {
return ((SelectorList) value).getType();
} 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;
} else if (isListType(type1) && isListType(type2)) {
return true;
} else {
return false;
}
}
@Override
public String toString() {
return Printer.repr(this);
}
@Override
public void repr(SkylarkPrinter printer) {
printer.printList(elements, "", " + ", "", null);
}
@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);
}
}
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