NullPointerException in ATNConfig.hashCode

[JFinis]

NullPointerException in ATNConfig.hashCode

[sharwell]

Do you happen to know which commit you're using? (Ideally the SHA hash for it)

[JFinis]

Yes, it is
28ee391
from parrt/antlr4

[sharwell]

Can you add the following assertions to track down the source of failure?

In the two ATNConfig constructors that set state and semanticContext, add:

assert state != null;
assert semanticContext != null;

[JFinis]

okay, here we go:

Exception in thread "main" java.lang.AssertionError: state is null
    at org.antlr.v4.runtime.atn.ATNConfig.<init>(ATNConfig.java:112)
    at org.antlr.v4.runtime.atn.ATNConfig.<init>(ATNConfig.java:98)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.actionTransition(ParserATNSimulator.java:1043)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.getEpsilonTarget(ParserATNSimulator.java:1032)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:990)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:946)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:1012)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.closure(ParserATNSimulator.java:912)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.computeReachSet(ParserATNSimulator.java:711)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.execATN(ParserATNSimulator.java:521)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.predictATN(ParserATNSimulator.java:331)
    at org.antlr.v4.runtime.atn.ParserATNSimulator.adaptivePredict(ParserATNSimulator.java:296)
    at org.eeve.antlrgen.parser.ANTLRv4Parser.strongExpr(ANTLRv4Parser.java:886)
    at org.eeve.antlrgen.parser.ANTLRv4Parser.expr(ANTLRv4Parser.java:1146)
    at org.eeve.antlrgen.parser.ANTLRv4Parser.grammarRule(ANTLRv4Parser.java:398)
    at org.eeve.antlrgen.parser.ANTLRv4Parser.gramma(ANTLRv4Parser.java:150)
    at org.eeve.antlrgen.ANTLRGenTest.parseStatic(ANTLRGenTest.java:92)
    at org.eeve.antlrgen.ANTLRGenTest.main(ANTLRGenTest.java:38)

[sharwell]

It would definitely help if you are able to post an example grammar and input for me to duplicate this issue. You may not have to post input - it looks like you have a case where Transition is being constructed with target==null. You could add an assertion to the Transition constructor as a check.

Have you tried regenerating the code?

[JFinis]

Okay, here is the grammar

grammar ANTLRv4;

ruler returns [String r]
  :  t=ID  ':' alts+=expr ('|' alts+= expr)* ';'
      {  $r = "x"; }
   ;

strongExpr returns [String r]
  : ID                      { $r = "x"; }
  | '(' ep=parenExpr ')'            { $r = "x"; }
  | e1=strongExpr '?'             { $r = "x"; }
  ;  

expr returns [String r]
  : e=strongExpr (e2=expr)? { $r = "x"; }
  | e1=expr '->' ID {$r = "x"; }
  ;

parenExpr returns [String r]
  : e1=expr '|' e2=parenExpr { $r = "x"; }
  | expr              {$r = $expr.r; }
  ;

ID  :   ('A'..'Z'|'a'..'z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*
    ;    

And here is a test input:

x:x;

Code for parser execution:

ANTLRv4Lexer lex = new ANTLRv4Lexer(new ANTLRInputStream(new FileInputStream(new File("test.input"))));
CommonTokenStream tokens = new CommonTokenStream(lex);

new ANTLRv4Parser(tokens).ruler();

[sharwell]

Thanks, that's perfect. I was able to derive the following grammar as a unit test for the issue which I'm now working to fix.

grammar T;
start
  : ID ':' expr
  ;
expr
  : primary expr? {}
  | expr '->' ID
  ;
primary
  : ID
  ;

ID : [a-z]+;

Input: x:x

[JFinis]

well, after merging your commits, I get the anticipated exception during parser building

    [java] Exception in thread "main" java.lang.IllegalStateException: Cannot serialize a transition to a removed state.
    [java]  at org.antlr.v4.automata.ATNSerializer.serialize(ATNSerializer.java:138)
    [java]  at org.antlr.v4.automata.ATNSerializer.getSerialized(ATNSerializer.java:281)
    [java]  at org.antlr.v4.codegen.model.SerializedATN.<init>(SerializedATN.java:43)
    [java]  at org.antlr.v4.codegen.model.Parser.<init>(Parser.java:86)
    [java]  at org.antlr.v4.codegen.ParserFactory.parser(ParserFactory.java:54)
    [java]  at org.antlr.v4.codegen.OutputModelController.parser(OutputModelController.java:145)
    [java]  at org.antlr.v4.codegen.OutputModelController.buildParserOutputModel(OutputModelController.java:84)
    [java]  at org.antlr.v4.codegen.CodeGenerator.generateParser(CodeGenerator.java:132)
    [java]  at org.antlr.v4.codegen.CodeGenPipeline.process(CodeGenPipeline.java:51)
    [java]  at org.antlr.v4.Tool.processNonCombinedGrammar(Tool.java:353)
    [java]  at org.antlr.v4.Tool.process(Tool.java:319)
    [java]  at org.antlr.v4.Tool.processGrammarsOnCommandLine(Tool.java:283)
    [java]  at org.antlr.v4.Tool.main(Tool.java:173)

While this is better than a fail at runtime, it is still not satisfactory, as I don't know what I have done wrong.

[sharwell]

Once this issue is corrected, it will be tagged with "status:pull-request" until it gets closed. :) The test I've implemented so far is in place to help track down the issue, but like you saw it doesn't create a working grammar.

[sharwell]

I am no longer able to reproduce this bug.