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// Copyright 2014 Google Inc. 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.Joiner;
import com.google.common.base.Preconditions;
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.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.events.Location;
import java.io.Serializable;
import java.util.Map;
import javax.annotation.Nullable;
/**
* An interface for objects behaving like Skylark structs.
*/
// TODO(bazel-team): type checks
public interface ClassObject {
/**
* Returns the value associated with the name field in this struct,
* or null if the field does not exist.
*/
@Nullable
Object getValue(String name);
/**
* Returns the fields of this struct.
*/
ImmutableCollection<String> getKeys();
/**
* Returns a customized error message to print if the name is not a valid struct field
* of this struct, or returns null to use the default error message.
*/
@Nullable String errorMessage(String name);
/**
* An implementation class of ClassObject for structs created in Skylark code.
*/
// TODO(bazel-team): maybe move the SkylarkModule annotation to the ClassObject interface?
@Immutable
@SkylarkModule(name = "struct",
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, 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 ImmutableMap<String, Object> values;
private final Location creationLoc;
private final String errorMessage;
/**
* 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(Map<String, Object> values, String errorMessage) {
this.values = ImmutableMap.copyOf(values);
this.creationLoc = null;
this.errorMessage = Preconditions.checkNotNull(errorMessage);
}
public SkylarkClassObject(Map<String, Object> values, Location creationLoc) {
this.values = ImmutableMap.copyOf(values);
this.creationLoc = Preconditions.checkNotNull(creationLoc);
this.errorMessage = DEFAULT_ERROR_MESSAGE;
}
@Override
public Object getValue(String name) {
return values.get(name);
}
@Override
public ImmutableCollection<String> getKeys() {
return values.keySet();
}
public Location getCreationLoc() {
return Preconditions.checkNotNull(creationLoc,
"This struct was not created in a Skylark code");
}
static SkylarkClassObject concat(
SkylarkClassObject lval, SkylarkClassObject rval, Location loc) throws EvalException {
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(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;
}
/**
* 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 String toString() {
StringBuilder builder = new StringBuilder();
boolean first = true;
builder.append("struct(");
// Sort by key to ensure deterministic output.
for (String key : Ordering.natural().sortedCopy(values.keySet())) {
if (!first) {
builder.append(", ");
}
first = false;
builder.append(key);
builder.append(" = ");
Printer.write(builder, values.get(key));
}
builder.append(")");
return builder.toString();
}
}
}
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