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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchdefinition;
import com.yahoo.searchlib.rankingexpression.RankingExpression;
import com.yahoo.searchlib.rankingexpression.rule.*;
import com.yahoo.searchlib.rankingexpression.transform.ExpressionTransformer;
import java.util.Map;
import java.util.logging.Logger;
/**
* Transforms function nodes to reference nodes if a macro shadows a built-in function.
* This has the effect of allowing macros to redefine built-in functions.
* Another effect is that we can more or less add built-in functions over time
* without fear of breaking existing users' macros with the same name.
*
* However, there is a (largish) caveat. If a user has a macro with a certain number
* of arguments, and we add in a built-in function with a different arity,
* this will cause parse errors as the Java parser gives precedence to
* built-in functions.
*
* @author lesters
*/
class MacroShadower extends ExpressionTransformer {
private static final Logger log = Logger.getLogger(MacroShadower.class.getName());
private final Map<String, RankProfile.Macro> macros;
public MacroShadower(Map<String, RankProfile.Macro> macros) {
this.macros = macros;
}
@Override
public RankingExpression transform(RankingExpression expression) {
String name = expression.getName();
ExpressionNode node = expression.getRoot();
ExpressionNode result = transform(node);
return new RankingExpression(name, result);
}
@Override
public ExpressionNode transform(ExpressionNode node) {
if (node instanceof FunctionNode)
return transformFunctionNode((FunctionNode) node);
if (node instanceof CompositeNode)
return transformChildren((CompositeNode)node);
return node;
}
protected ExpressionNode transformFunctionNode(FunctionNode function) {
String name = function.getFunction().toString();
RankProfile.Macro macro = macros.get(name);
if (macro == null) {
return transformChildren(function);
}
int functionArity = function.getFunction().arity();
int macroArity = macro.getFormalParams() != null ? macro.getFormalParams().size() : 0;
if (functionArity != macroArity) {
log.warning("Macro \"" + name + "\" has the same name as a built-in function. Due to different number of arguments, the built-in function will be used.");
return transformChildren(function);
}
log.warning("Macro \"" + name + "\" shadows the built-in function with the same name.");
ReferenceNode node = new ReferenceNode(name, function.children(), null);
return transformChildren(node);
}
}
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