// Copyright (C) 2005 Google Inc.
//
// 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.caja.parser.js;
import com.google.caja.lexer.FilePosition;
import com.google.caja.lexer.TokenConsumer;
import com.google.caja.reporting.RenderContext;
import java.util.List;
/**
* A statement that contains an expression as its only child. When control
* reaches this statement, the expression is invoked, presumably for its side
* effects, and the value is discarded.
*
* @author mikesamuel@gmail.com
*/
public final class ExpressionStmt extends AbstractStatement {
private static final long serialVersionUID = 4277971387206538109L;
/** @param value unused. This ctor is provided for reflection. */
@ReflectiveCtor
public ExpressionStmt(
FilePosition pos, Void value, List<? extends Expression> children) {
this(pos, children.get(0));
}
public ExpressionStmt(FilePosition pos, Expression expr) {
super(pos, Expression.class);
ctorAppendChild(expr);
}
public ExpressionStmt(Expression expr) {
super(expr.getFilePosition(), Expression.class);
ctorAppendChild(expr);
}
@Override
protected void childrenChanged() {
if (1 != children().size()) { throw new IllegalStateException(); }
}
public Expression getExpression() { return (Expression) children().get(0); }
@Override
public Object getValue() { return null; }
public void render(RenderContext rc) {
TokenConsumer out = rc.getOut();
out.mark(getFilePosition());
Expression e = getExpression();
if (e instanceof FunctionConstructor
|| e instanceof ObjectConstructor
|| startsWithRegex(e)) {
// We need to parenthesize Object constructors because otherwise an
// object constructor with only one entry:
// { x : 4 }
// is ambiguous. It could be a block containing a labeled expression
// statement, and depending on semicolon insertion.
// We need to parenthesize Function constructors because otherwise
// we might output something like
// function a () {
// ;
// };
// which is interpreted as two statements -- a declaration and a noop for
// the semicolon.
// Rhino fails to parse
// if(...)/foo/.test(x)?bar:baz;
// so we parenthesize operator trees whose left-most operand is a regex
// literal.
out.consume("(");
e.render(rc);
out.consume(")");
} else {
e.render(rc);
}
}
public boolean hasHangingConditional() { return false; }
private static boolean startsWithRegex(Expression e) {
while (e instanceof Operation) {
Operation op = (Operation) e;
if (op.getOperator().getType() == OperatorType.PREFIX) { break; }
e = op.children().get(0);
}
return e instanceof RegexpLiteral;
}
}