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// 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.packages;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Ordering;
import com.google.common.collect.Sets;
import com.google.common.collect.Sets.SetView;
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 com.google.devtools.build.lib.syntax.ClassObject;
import com.google.devtools.build.lib.syntax.Concatable;
import com.google.devtools.build.lib.syntax.EvalException;
import com.google.devtools.build.lib.syntax.EvalUtils;
import com.google.devtools.build.lib.syntax.Printer;
import com.google.devtools.build.lib.syntax.SkylarkType;
import com.google.devtools.build.lib.util.Preconditions;
import java.io.Serializable;
import java.util.Map;
/** An implementation class of ClassObject for structs created in Skylark code. */
@SkylarkModule(
name = "struct",
category = SkylarkModuleCategory.BUILTIN,
doc =
"A special language element to support structs (i.e. simple value objects). "
+ "See the global <a href=\"globals.html#struct\">struct</a> function "
+ "for more details."
)
public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable, Serializable {
/** Error message to use when errorMessage argument is null. */
private static final String DEFAULT_ERROR_MESSAGE = "'struct' object has no attribute '%s'";
private final SkylarkClassObjectConstructor constructor;
private final ImmutableMap<String, Object> values;
private final Location creationLoc;
private final String errorMessage;
/**
* Primarily for testing purposes where no location is available and the default
* errorMessage suffices.
*/
public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
Map<String, Object> values) {
this.constructor = constructor;
this.values = copyValues(values);
this.creationLoc = null;
this.errorMessage = DEFAULT_ERROR_MESSAGE;
}
/**
* Creates a built-in struct (i.e. without creation loc). The errorMessage has to have
* exactly one '%s' parameter to substitute the struct field name.
*/
public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
Map<String, Object> values, String errorMessage) {
this.constructor = constructor;
this.values = copyValues(values);
this.creationLoc = null;
this.errorMessage = Preconditions.checkNotNull(errorMessage);
}
public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
Map<String, Object> values, Location creationLoc) {
this.constructor = constructor;
this.values = copyValues(values);
this.creationLoc = Preconditions.checkNotNull(creationLoc);
this.errorMessage = DEFAULT_ERROR_MESSAGE;
}
// Ensure that values are all acceptable to Skylark before to stuff them in a ClassObject
private ImmutableMap<String, Object> copyValues(Map<String, Object> values) {
ImmutableMap.Builder<String, Object> builder = ImmutableMap.builder();
for (Map.Entry<String, Object> e : values.entrySet()) {
builder.put(e.getKey(), SkylarkType.convertToSkylark(e.getValue(), null));
}
return builder.build();
}
@Override
public Object getValue(String name) {
return values.get(name);
}
/**
* Returns a value and try to cast it into specified type
*/
public <TYPE> TYPE getValue(String key, Class<TYPE> type) throws EvalException {
Object obj = values.get(key);
if (obj == null) {
return null;
}
SkylarkType.checkType(obj, type, key);
return type.cast(obj);
}
@Override
public ImmutableCollection<String> getKeys() {
return values.keySet();
}
public Location getCreationLoc() {
return Preconditions.checkNotNull(creationLoc,
"This struct was not created in a Skylark code");
}
@Override
public Concatter getConcatter() {
return StructConcatter.INSTANCE;
}
public SkylarkClassObjectConstructor getConstructor() {
return constructor;
}
private static class StructConcatter implements Concatter {
private static final StructConcatter INSTANCE = new StructConcatter();
private StructConcatter() {}
@Override
public SkylarkClassObject concat(
Concatable left, Concatable right, Location loc) throws EvalException {
SkylarkClassObject lval = (SkylarkClassObject) left;
SkylarkClassObject rval = (SkylarkClassObject) right;
if (!lval.constructor.equals(rval.constructor)) {
throw new EvalException(loc,
String.format("Cannot concat %s with %s",
lval.constructor.getPrintableName(),
rval.constructor.getPrintableName()));
}
SetView<String> commonFields = Sets
.intersection(lval.values.keySet(), rval.values.keySet());
if (!commonFields.isEmpty()) {
throw new EvalException(loc, "Cannot concat structs with common field(s): "
+ Joiner.on(",").join(commonFields));
}
return new SkylarkClassObject(lval.constructor,
ImmutableMap.<String, Object>builder()
.putAll(lval.values)
.putAll(rval.values)
.build(),
loc);
}
}
@Override
public String errorMessage(String name) {
String suffix =
"Available attributes: "
+ Joiner.on(", ").join(Ordering.natural().sortedCopy(values.keySet()));
return String.format(errorMessage, name) + "\n" + suffix;
}
@Override
public boolean isImmutable() {
for (Object item : values.values()) {
if (!EvalUtils.isImmutable(item)) {
return false;
}
}
return true;
}
/**
* Convert the object to string using Skylark syntax. The output tries to be
* reversible (but there is no guarantee, it depends on the actual values).
*/
@Override
public void write(Appendable buffer, char quotationMark) {
boolean first = true;
Printer.append(buffer, constructor.getPrintableName());
Printer.append(buffer, "(");
// Sort by key to ensure deterministic output.
for (String key : Ordering.natural().sortedCopy(values.keySet())) {
if (!first) {
Printer.append(buffer, ", ");
}
first = false;
Printer.append(buffer, key);
Printer.append(buffer, " = ");
Printer.write(buffer, values.get(key), quotationMark);
}
Printer.append(buffer, ")");
}
@Override
public String toString() {
return Printer.repr(this);
}
}
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