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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.Streams;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.util.SpellChecker;
import java.io.IOException;
import java.util.Optional;
/** Syntax node for a dot expression. e.g. obj.field, but not obj.method() */
public final class DotExpression extends Expression {
private final Expression object;
private final Identifier field;
public DotExpression(Expression object, Identifier field) {
this.object = object;
this.field = field;
}
public Expression getObject() {
return object;
}
public Identifier getField() {
return field;
}
@Override
public void prettyPrint(Appendable buffer) throws IOException {
object.prettyPrint(buffer);
buffer.append('.');
field.prettyPrint(buffer);
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
Object objValue = object.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) {
return result;
}
throw getMissingFieldException(objValue, name, loc, "field");
}
static EvalException getMissingFieldException(
Object objValue, String name, Location loc, String accessName) {
String suffix = "";
EvalException toSuppress = null;
if (objValue instanceof ClassObject) {
String customErrorMessage = ((ClassObject) objValue).getErrorMessageForUnknownField(name);
if (customErrorMessage != null) {
return new EvalException(loc, customErrorMessage);
}
try {
suffix = SpellChecker.didYouMean(name, ((ClassObject) objValue).getFieldNames());
} catch (EvalException ee) {
toSuppress = ee;
}
} else {
suffix =
SpellChecker.didYouMean(
name,
FuncallExpression.getStructFieldNames(
objValue instanceof Class ? (Class<?>) objValue : objValue.getClass()));
}
if (suffix.isEmpty() && hasMethod(objValue, name)) {
// If looking up the field failed, then we know that this method must have struct_field=false
suffix = ", however, a method of that name exists";
}
EvalException ee =
new EvalException(
loc,
String.format(
"object of type '%s' has no %s '%s'%s",
EvalUtils.getDataTypeName(objValue), accessName, name, suffix));
if (toSuppress != null) {
ee.addSuppressed(toSuppress);
}
return ee;
}
/** Returns whether the given object has a method with the given name. */
static boolean hasMethod(Object obj, String name) {
Class<?> cls = obj instanceof Class ? (Class<?>) obj : obj.getClass();
if (Runtime.getBuiltinRegistry().getFunctionNames(cls).contains(name)) {
return true;
}
return FuncallExpression.getMethodNames(cls).contains(name);
}
/**
* 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, InterruptedException {
Iterable<MethodDescriptor> methods =
objValue instanceof Class<?>
? FuncallExpression.getMethods((Class<?>) objValue, name)
: FuncallExpression.getMethods(objValue.getClass(), name);
if (methods != null) {
Optional<MethodDescriptor> method =
Streams.stream(methods).filter(MethodDescriptor::isStructField).findFirst();
if (method.isPresent() && method.get().isStructField()) {
return method
.get()
.call(
objValue,
FuncallExpression.extraInterpreterArgs(method.get(), /* ast = */ null, loc, env)
.toArray(),
loc,
env);
}
}
if (objValue instanceof SkylarkClassObject) {
try {
return ((SkylarkClassObject) objValue).getValue(name);
} catch (IllegalArgumentException ex) {
throw new EvalException(loc, ex);
}
} else 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;
}
}
return null;
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
public Kind kind() {
return Kind.DOT;
}
}
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