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/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.runtime;
import org.antlr.v4.runtime.atn.ATNConfig;
import org.antlr.v4.runtime.atn.ATNConfigSet;
import org.antlr.v4.runtime.dfa.DFA;
import org.antlr.v4.runtime.misc.Interval;
import java.util.BitSet;
/**
* This implementation of {@link ANTLRErrorListener} can be used to identify
* certain potential correctness and performance problems in grammars. "Reports"
* are made by calling {@link Parser#notifyErrorListeners} with the appropriate
* message.
*
* <ul>
* <li><b>Ambiguities</b>: These are cases where more than one path through the
* grammar can match the input.</li>
* <li><b>Weak context sensitivity</b>: These are cases where full-context
* prediction resolved an SLL conflict to a unique alternative which equaled the
* minimum alternative of the SLL conflict.</li>
* <li><b>Strong (forced) context sensitivity</b>: These are cases where the
* full-context prediction resolved an SLL conflict to a unique alternative,
* <em>and</em> the minimum alternative of the SLL conflict was found to not be
* a truly viable alternative. Two-stage parsing cannot be used for inputs where
* this situation occurs.</li>
* </ul>
*
* @author Sam Harwell
*/
public class DiagnosticErrorListener extends BaseErrorListener {
/**
* When {@code true}, only exactly known ambiguities are reported.
*/
protected final boolean exactOnly;
/**
* Initializes a new instance of {@link DiagnosticErrorListener} which only
* reports exact ambiguities.
*/
public DiagnosticErrorListener() {
this(true);
}
/**
* Initializes a new instance of {@link DiagnosticErrorListener}, specifying
* whether all ambiguities or only exact ambiguities are reported.
*
* @param exactOnly {@code true} to report only exact ambiguities, otherwise
* {@code false} to report all ambiguities.
*/
public DiagnosticErrorListener(boolean exactOnly) {
this.exactOnly = exactOnly;
}
@Override
public void reportAmbiguity(Parser recognizer,
DFA dfa,
int startIndex,
int stopIndex,
boolean exact,
BitSet ambigAlts,
ATNConfigSet configs)
{
if (exactOnly && !exact) {
return;
}
String format = "reportAmbiguity d=%s: ambigAlts=%s, input='%s'";
String decision = getDecisionDescription(recognizer, dfa);
BitSet conflictingAlts = getConflictingAlts(ambigAlts, configs);
String text = recognizer.getTokenStream().getText(Interval.of(startIndex, stopIndex));
String message = String.format(format, decision, conflictingAlts, text);
recognizer.notifyErrorListeners(message);
}
@Override
public void reportAttemptingFullContext(Parser recognizer,
DFA dfa,
int startIndex,
int stopIndex,
BitSet conflictingAlts,
ATNConfigSet configs)
{
String format = "reportAttemptingFullContext d=%s, input='%s'";
String decision = getDecisionDescription(recognizer, dfa);
String text = recognizer.getTokenStream().getText(Interval.of(startIndex, stopIndex));
String message = String.format(format, decision, text);
recognizer.notifyErrorListeners(message);
}
@Override
public void reportContextSensitivity(Parser recognizer,
DFA dfa,
int startIndex,
int stopIndex,
int prediction,
ATNConfigSet configs)
{
String format = "reportContextSensitivity d=%s, input='%s'";
String decision = getDecisionDescription(recognizer, dfa);
String text = recognizer.getTokenStream().getText(Interval.of(startIndex, stopIndex));
String message = String.format(format, decision, text);
recognizer.notifyErrorListeners(message);
}
protected String getDecisionDescription(Parser recognizer, DFA dfa) {
int decision = dfa.decision;
int ruleIndex = dfa.atnStartState.ruleIndex;
String[] ruleNames = recognizer.getRuleNames();
if (ruleIndex < 0 || ruleIndex >= ruleNames.length) {
return String.valueOf(decision);
}
String ruleName = ruleNames[ruleIndex];
if (ruleName == null || ruleName.isEmpty()) {
return String.valueOf(decision);
}
return String.format("%d (%s)", decision, ruleName);
}
/**
* Computes the set of conflicting or ambiguous alternatives from a
* configuration set, if that information was not already provided by the
* parser.
*
* @param reportedAlts The set of conflicting or ambiguous alternatives, as
* reported by the parser.
* @param configs The conflicting or ambiguous configuration set.
* @return Returns {@code reportedAlts} if it is not {@code null}, otherwise
* returns the set of alternatives represented in {@code configs}.
*/
protected BitSet getConflictingAlts(BitSet reportedAlts, ATNConfigSet configs) {
if (reportedAlts != null) {
return reportedAlts;
}
BitSet result = new BitSet();
for (ATNConfig config : configs) {
result.set(config.alt);
}
return result;
}
}
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