Issue with Antlr4 Java 7 Grammar expression Parser rule

[sufail]

I found this issue for the following input

public String publishAbsencesApprovalsEvent(Map<String,Object> absenceValues) {

// inside this method there is a pretty much long string which spans around 150 lines.

}

When I try to create a ParseTree for this input file, it's got hanged like forever. I guess there is a decision-making issue for the grammar for the below two rules.

typeArguments
: '<' typeArgument (',' typeArgument)* '>'
;

expression
: //many alternatives
| expression ('<=' | '>=' | '>' | '<') expression #logical

When I commented out the #logical alternative and re-ran it's worked.

I guess there is a token matching decision from lexer to Parser level which makes it hang forever.
Please let me know if there is a solution for this without altering much of the grammar file.

[parrt]

Is this java or java8 grammar? it is hitting a nonlinearity. not a bug but not fun either. ;)

[sufail]

@parrt Well it still seems a for me.
I am using Java7 grammar. https://github.com/antlr/grammars-v4/blob/master/java/Java.g4
Please have a look at the following input file snippet

public class AbsencesApprovalsEventsAMImpl extends ApplicationModuleImpl {

    public Object publishAbsencesApprovalsEvent(Map<String,Integer>  absenceValues) {

    if (!(transactionId.equals(null)) && !(requestor.equals(null))) {


        String payload = "<AbsencesApprovalsRequest xmlns=\"http://xmlns.oracle.com/apps/hcm/globalAbsences/approvals/model/entity/events/schema/AbsencesApprovalsEvent\">"
                + "<TransactionId>"
                + transactionId
                + "</TransactionId>"
                + "<Requestor>"
                + requestor
                + "</Requestor>"
                + "<PersonName>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml(personName)
                + "</PersonName>"
                + "<AbsenceType>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml(absenceType)
                + "</AbsenceType>"
                + "<AbsenceStartDate>"
                + absenceStartDate
                + "</AbsenceStartDate>"
                + "<AbsenceEndDate>"
                + absenceEndDate
                + "</AbsenceEndDate>"
                + "<AbsenceStatusCd>"
                + AbsenceStatusCd
                + "</AbsenceStatusCd>"
                + "<SubmittedDate>"
                + SubmittedDate
                + "</SubmittedDate>"
                + "<StartDate>"
                + StartDate
                + "</StartDate>"
                + "<DiseaseCode>"+

                (String) absenceValues.get("DiseaseCode")
                + "</DiseaseCode>"
                + "<LegalEntity>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues
                                .get("LegalEntity"))
                + "</LegalEntity>"
                + "<LegislativeDataGroup>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues
                                .get("LegislativeDataGroup"))
                + "</LegislativeDataGroup>"
                + "<AbsenceTypeReasons>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues
                                .get("AbsenceTypeReasons"))
                + "</AbsenceTypeReasons>"
                + "<AbsencePatternCd>"
                + (String) absenceValues.get("AbsencePatternCd")
                + "</AbsencePatternCd>"
                + "<AbsenceStatusCd>"
                + (String) absenceValues.get("AbsenceStatusCd")
                + "</AbsenceStatusCd>"
                + "<ChildEventTypeCd>"
                + (String) absenceValues.get("ChildEventTypeCd")
                + "</ChildEventTypeCd>"
                + "<ConfirmedDate>"
                +

                (Date) absenceValues.get("ConfirmedDate")
                + "</ConfirmedDate>"
                + "<Duration>"
                + (BigDecimal) absenceValues.get("Duration")
                + "</Duration>"
                + "<StartTime>"
                +

                (Timestamp) absenceValues.get("StartTime")
                + "</StartTime>"
                + "<EndTime>"
                + (Timestamp) absenceValues.get("EndTime")
                + "</EndTime>"
                + "<OpenEndedFlag>"
                + (String) absenceValues.get("OpenEndedFlag")
                + "</OpenEndedFlag>"
                + "<PlannedEndDate>"
                + (Date) absenceValues.get("PlannedEndDate")
                +

                "</PlannedEndDate>"
                + "<Uom>"
                + (String) absenceValues.get("Uom")
                + "</Uom>"
                + "<SingleDayFlag>"

                +

                (String) absenceValues.get("SingleDayFlag")
                + "</SingleDayFlag>"
                + "<StartDateDuration>"
                + (BigDecimal) absenceValues.get("StartDateDuration")
                + "</StartDateDuration>"
                + "<EndDateDuration>"
                + (BigDecimal) absenceValues.get("EndDateDuration")
                + "</EndDateDuration>"
                + "<Comments>"
                +

                org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues.get("Comments"))
                + "</Comments>"
                + "<CreatedBy>"
                + (String) absenceValues.get("CreatedBy")
                + "</CreatedBy>"
                + "<CreationDate>"
                + (Timestamp) absenceValues.get("CreationDate")
                + "</CreationDate>"
                + "<LastUpdateDate>"
                + (Timestamp) absenceValues.get("LastUpdateDate")
                + "</LastUpdateDate>"
                + "<LastUpdateLogin>"
                + (String) absenceValues.get("LastUpdateLogin")
                + "</LastUpdateLogin>"
                + "<LastUpdatedBy>"
                + (String) absenceValues.get("LastUpdatedBy")
                + "</LastUpdatedBy>"
                + "<SubmittedDate>"
                + (Date) absenceValues.get("SubmittedDate")
                + "</SubmittedDate>"
                + "<AbsenceEntryBasicFlag>"
                +

                (String) absenceValues.get("AbsenceEntryBasicFlag")
                + "</AbsenceEntryBasicFlag>"
                + "<IllnessStartDate>"
                + (Date) absenceValues.get("IllnessStartDate")
                + "</IllnessStartDate>"
                + "<StartDatetime>"
                + (Timestamp) absenceValues.get("StartDatetime")
                + "</StartDatetime>"
                + "<EndDatetime>"
                + (Timestamp) absenceValues.get("EndDatetime")
                + "</EndDatetime>"
                + "<AbsenceDispStatusCd>"
                + (String) absenceValues.get("AbsenceDispStatusCd")
                + "</AbsenceDispStatusCd>"
                + "<Durationuomname>"
                + (String) absenceValues.get("Durationuomname")
                + "</Durationuomname>"
                + "<Statuslookupname>"
                + (String) absenceValues.get("Statuslookupname")
                + "</Statuslookupname>"
                + "<Typename>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues.get("Typename"))
                + "</Typename>"
                + "<Employername>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues
                                .get("Employername"))
                + "</Employername>"
                + "<PartialDay>"
                + (String) absenceValues.get("PartialDay")
                + "</PartialDay>"
                + "<MapEventTypeCd>"
                + (String) absenceValues.get("MapEventTypeCd")
                + "</MapEventTypeCd>"
                + "<EmpLockIfConfirmCd>"
                + (String) absenceValues.get("EmpLockIfConfirmCd")
                + "</EmpLockIfConfirmCd>"
                + "<EmpAllowUpdatesCd>"
                + (String) absenceValues.get("EmpAllowUpdatesCd")
                + "</EmpAllowUpdatesCd>"
                + "<MinDuration>"
                + (BigDecimal) absenceValues.get("MinDuration")
                + "</MinDuration>"
                + "<MaxDuration>"
                + (BigDecimal) absenceValues.get("MaxDuration")
                + "</MaxDuration>"
                + "<MinDurationRuleCd>"
                + (String) absenceValues.get("MinDurationRuleCd")
                + "</MinDurationRuleCd>"
                + "<MaxDurationRuleCd>"
                + (String) absenceValues.get("MaxDurationRuleCd")
                + "</MaxDurationRuleCd>"
                + "<MaxDurationRuleCd>"
                + (String) absenceValues.get("MaxDurationRuleCd")
                + "</MaxDurationRuleCd>"
                + "<AllowDeleteDate>"
                + (Date) absenceValues.get("AllowDeleteDate")
                + "</AllowDeleteDate>"
                + "<MgrLockIfConfirmCd>"
                + (String) absenceValues.get("MgrLockIfConfirmCd")
                + "</MgrLockIfConfirmCd>"
                + "<MgrAllowUpdatesCd>"
                + (String) absenceValues.get("MgrAllowUpdatesCd")
                + "</MgrAllowUpdatesCd>"
                + "<NotificationDate>"
                + (Date) absenceValues.get("NotificationDate")
                + "</NotificationDate>"
                + "<SplCondition>"
                + (String) absenceValues.get("SplCondition")
                + "</SplCondition>"
                + "<LateNotifyFlag>"
                +

                (String) absenceValues.get("LateNotifyFlag")
                + "</LateNotifyFlag>"
                + "<InitialTimelyNotifyFlag>"
                + (String) absenceValues.get("InitialTimelyNotifyFlag")
                + "</InitialTimelyNotifyFlag>"
                + "<TimelinessOverrideDate>"
                + (Date) absenceValues.get("TimelinessOverrideDate")
                + "</TimelinessOverrideDate>"
                + "<CertificationAuthFlag>"
                + (String) absenceValues.get("CertificationAuthFlag")
                + "</CertificationAuthFlag>"
                + "<AuthStatusUpdateDate>"
                + (Date) absenceValues.get("AuthStatusUpdateDate")
                + "</AuthStatusUpdateDate>"
                + "<PeriodOfIncapToWorkFlag>"
                + (String) absenceValues.get("PeriodOfIncapToWorkFlag")
                + "</PeriodOfIncapToWorkFlag>"
                + "<EstablishmentDate>"
                + (Date) absenceValues.get("EstablishmentDate")
                + "</EstablishmentDate>"
                + "<UserMode>"
                + (String) absenceValues.get("UserMode")
                + "</UserMode>"
                + "<LegislationCode>"
                + (String) absenceValues.get("LegislationCode")
                + "</LegislationCode>"
                + "<Name>"
                + (String) absenceValues.get("Name")
                + "</Name>"
                + "<AbsenceDispStatus>"
                +

                org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues
                                .get("AbsenceDispStatus"))
                + "</AbsenceDispStatus>"
                + "<AbsenceDispDate>"
                + (String) absenceValues.get("AbsenceDispDate")
                + "</AbsenceDispDate>"
                + "<TimeFormat>"
                + (String) absenceValues.get("TimeFormat")
                + "</TimeFormat>"
                + "<IntendToWork>"
                + (String) absenceValues.get("IntendToWork")
                + "</IntendToWork>"
                + "<StartDtPartialDay>"
                + (String) absenceValues.get("StartDtPartialDay")
                + "</StartDtPartialDay>"
                + "<EndDtPartialDay>"
                + (String) absenceValues.get("EndDtPartialDay")
                + "</EndDtPartialDay>"
                + "<DispTypeName>"
                + (String) absenceValues.get("DispTypeName")
                + "</DispTypeName>"
                + "<AllowUpdateFlag>"
                + (String) absenceValues.get("AllowUpdateFlag")
                + "</AllowUpdateFlag>"
                + "<BindpEmpAllowUpdatesCd>"
                + (String) absenceValues.get("BindpEmpAllowUpdatesCd")
                + "</BindpEmpAllowUpdatesCd>"
                + "<BindpMgrAllowUpdatesCd>"
                + (String) absenceValues.get("BindpMgrAllowUpdatesCd")
                + "</BindpMgrAllowUpdatesCd>"
                + "<BlockedLeaveCandidate>"
                + (String) absenceValues.get("BlockedLeaveCandidate")
                + "</BlockedLeaveCandidate>"
                + "<EmpUserId>"
                + org.apache.commons.lang.StringEscapeUtils
                        .escapeXml((String) absenceValues.get("EmpUserId"))
                + "</EmpUserId>"
                + "<PersonId>"
                + personId
                + "</PersonId>"
                + "<AssignmentId>"
                + assignmentId
                + "</AssignmentId>"
                + "<NotificationName>"
                + rowStatus
                + "</NotificationName>"
                + "<ApprovalType>"
                + " "
                + "</ApprovalType>"
                + "</AbsencesApprovalsRequest>";

        String eventNameSpace = "http://xmlns.oracle.com/apps/hcm/globalAbsences/approvals/model/entity/events/edl/AbsencesApprovalsEvent";
        String eventName = "AbsencesApprovalsEvent";

        try {

        } catch (Exception e) {
            if (conn != null) {
                conn.close();
            }
            throw new JboException(e);
        }

        retStatus = "SUCCESS";

    }
    return retStatus;
}

}
`
If you parse the above file using the grammar for java7, it will halt , like forever.

Now if I change something in the input file like what follows.

case 1:
public Object publishAbsencesApprovalsEvent(Map<String,Integer> absenceValues) {

Removing the Generic Symbols from the method argument. That is changing

Map<String,Integer> absenceValues to Map abscenceValues ( or like anything without "<" and ">" symbols)

Keeping the rest of the code as they are.

case 2:

Keeping the method argument as it is and reducing the length of the String payload ( the payload string spans across multiple lines from line number 11 to line number 291)
I reduced the string to span across from line 11 to line say, 41.
Keeping the rest of the code as they are.

In both cases, it Works.

When I tried with Java8 grammar (https://github.com/antlr/grammars-v4/blob/master/java8/Java8.g4), it worked.

For some reasons, I can't change my underlying grammar. I need to get this done using Java7 grammar itself. I tried almost everything, from using to unbuffered streams to setting SSL prediction but nothing worked for me.
I have a strong feeling that this is because Antlr failed to make a prediction for these tokens "<" ">" as these tokens appear in two ambiguous rules.

typeParameters
: '<' typeParameter (',' typeParameter)* '>'
;

expression
: // many alternatives
| expression ('<=' | '>=' | '>' | '<') expression #logical

I changed the expression rule to something like this

expression
: //many alternatives
| logicalExpression #logical

and

logicalExpression
: logicalOperands ('<=' | '>=' | '>' | '<') logicalOperands
;
logicalOperands
: logicalOperand ('+' logicalOperand)* ;

logicalOperand
: Identifier
| Identifier '(' ')'
| Identifier '(' expression ')'
;

For my next run, it worked.

I have written some APIs targeting Java7.g4 grammar and can't move straight away to Java8.g4 as the rule name among them are entirely different.

[parrt]

Yes, ANTLR's ALL(*) is O(n^4) worst case and you hit it with that. The java8 grammar doesn't use left-recursive expr and so performs better in this case.

[parrt]

Dup of #994