| // 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.query2.engine; |
| |
| import com.google.common.base.Function; |
| import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryTaskFuture; |
| import com.google.devtools.build.lib.query2.engine.QueryEnvironment.ThreadSafeMutableSet; |
| import java.util.Collection; |
| import java.util.regex.Pattern; |
| |
| /** |
| * A let expression. |
| * |
| * <pre>expr ::= LET WORD = expr IN expr</pre> |
| */ |
| public class LetExpression extends QueryExpression { |
| |
| private static final String VAR_NAME_PATTERN = "[a-zA-Z_][a-zA-Z0-9_]*$"; |
| |
| // Variables names may be any legal identifier in the C programming language |
| private static final Pattern NAME_PATTERN = Pattern.compile("^" + VAR_NAME_PATTERN); |
| |
| // Variable references are prepended with the "$" character. |
| // A variable named "x" is referenced as "$x". |
| private static final Pattern REF_PATTERN = Pattern.compile("^\\$" + VAR_NAME_PATTERN); |
| |
| static boolean isValidVarReference(String varName) { |
| return REF_PATTERN.matcher(varName).matches(); |
| } |
| |
| public static String getNameFromReference(String reference) { |
| return reference.substring(1); |
| } |
| |
| private final String varName; |
| private final QueryExpression varExpr; |
| private final QueryExpression bodyExpr; |
| |
| public LetExpression(String varName, QueryExpression varExpr, QueryExpression bodyExpr) { |
| this.varName = varName; |
| this.varExpr = varExpr; |
| this.bodyExpr = bodyExpr; |
| } |
| |
| public String getVarName() { |
| return varName; |
| } |
| |
| public QueryExpression getVarExpr() { |
| return varExpr; |
| } |
| |
| public QueryExpression getBodyExpr() { |
| return bodyExpr; |
| } |
| |
| @Override |
| public <T> QueryTaskFuture<Void> eval( |
| final QueryEnvironment<T> env, |
| final QueryExpressionContext<T> context, |
| final Callback<T> callback) { |
| if (!NAME_PATTERN.matcher(varName).matches()) { |
| return env.immediateFailedFuture( |
| new QueryException(this, "invalid variable name '" + varName + "' in let expression")); |
| } |
| QueryTaskFuture<ThreadSafeMutableSet<T>> varValueFuture = |
| QueryUtil.evalAll(env, context, varExpr); |
| Function<ThreadSafeMutableSet<T>, QueryTaskFuture<Void>> evalBodyAsyncFunction = |
| varValue -> { |
| QueryExpressionContext<T> bodyContext = context.with(varName, varValue); |
| return env.eval(bodyExpr, bodyContext, callback); |
| }; |
| return env.transformAsync(varValueFuture, evalBodyAsyncFunction); |
| } |
| |
| @Override |
| public void collectTargetPatterns(Collection<String> literals) { |
| varExpr.collectTargetPatterns(literals); |
| bodyExpr.collectTargetPatterns(literals); |
| } |
| |
| @Override |
| public <T, C> T accept(QueryExpressionVisitor<T, C> visitor, C context) { |
| return visitor.visit(this, context); |
| } |
| |
| @Override |
| public String toString() { |
| return "let " + varName + " = " + varExpr + " in " + bodyExpr; |
| } |
| } |