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// 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.Iterables;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.syntax.FuncallExpression.MethodDescriptor;
import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
import com.google.devtools.build.lib.syntax.compiler.DebugInfo;
import com.google.devtools.build.lib.syntax.compiler.VariableScope;
import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
import net.bytebuddy.implementation.bytecode.Duplication;
import net.bytebuddy.implementation.bytecode.constant.TextConstant;
import java.util.ArrayList;
import java.util.List;
/**
* Syntax node for a dot expression.
* e.g. obj.field, but not obj.method()
*/
public final class DotExpression extends Expression {
private final Expression obj;
private final Identifier field;
public DotExpression(Expression obj, Identifier field) {
this.obj = obj;
this.field = field;
}
public Expression getObj() {
return obj;
}
public Identifier getField() {
return field;
}
@Override
public String toString() {
return obj + "." + field;
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
Object objValue = obj.eval(env);
String name = field.getName();
Object result = eval(objValue, name, getLocation(), env);
return checkResult(objValue, result, name, getLocation());
}
/**
* Throws the correct error message if the result is null depending on the objValue.
*/
public static Object checkResult(Object objValue, Object result, String name, Location loc)
throws EvalException {
if (result == null) {
if (objValue instanceof ClassObject) {
String customErrorMessage = ((ClassObject) objValue).errorMessage(name);
if (customErrorMessage != null) {
throw new EvalException(loc, customErrorMessage);
}
}
throw new EvalException(loc, Printer.format("Object of type '%s' has no field %r",
EvalUtils.getDataTypeName(objValue), name));
}
return result;
}
/**
* Returns the field of the given name of the struct objValue, or null if no such field exists.
*/
public static Object eval(Object objValue, String name,
Location loc, Environment env) throws EvalException {
if (objValue instanceof ClassObject) {
Object result = null;
try {
result = ((ClassObject) objValue).getValue(name);
} catch (IllegalArgumentException ex) {
throw new EvalException(loc, ex);
}
// ClassObjects may have fields that are annotated with @SkylarkCallable.
// Since getValue() does not know about those, we cannot expect that result is a valid object.
if (result != null) {
result = SkylarkType.convertToSkylark(result, env);
// If we access NestedSets using ClassObject.getValue() we won't know the generic type,
// so we have to disable it. This should not happen.
SkylarkType.checkTypeAllowedInSkylark(result, loc);
return result;
}
}
List<MethodDescriptor> methods =
FuncallExpression.getMethods(objValue.getClass(), name, 0, loc);
if (methods != null && !methods.isEmpty()) {
MethodDescriptor method = Iterables.getOnlyElement(methods);
if (method.getAnnotation().structField()) {
return FuncallExpression.callMethod(method, name, objValue, new Object[] {}, loc, env);
}
}
return null;
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
void validate(ValidationEnvironment env) throws EvalException {
obj.validate(env);
}
@Override
ByteCodeAppender compile(VariableScope scope, DebugInfo debugInfo) throws EvalException {
List<ByteCodeAppender> code = new ArrayList<>();
code.add(obj.compile(scope, debugInfo));
TextConstant name = new TextConstant(field.getName());
ByteCodeUtils.append(
code,
Duplication.SINGLE,
name,
debugInfo.add(this).loadLocation,
scope.loadEnvironment(),
ByteCodeUtils.invoke(DotExpression.class, "eval", Object.class, String.class,
Location.class, Environment.class),
// at this point we have the value of obj and the result of eval on the stack
name,
debugInfo.add(this).loadLocation,
ByteCodeUtils.invoke(DotExpression.class, "checkResult", Object.class, Object.class,
String.class, Location.class)
);
return ByteCodeUtils.compoundAppender(code);
}
}
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