| Exception when testing language [message #800914] |
Fri, 17 February 2012 12:25  |
Eclipse User |
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Hi!
I am using org.eclipselabs.xtext.utils.unittesting to test my grammar and for a certain construct I get the exception below.
First of all, I'd like to know if the problem seems to be with xtext or with xtext.unittesting.
Second, is this something known or that someone can help me with from just this small bit of information?
If not, I will try to get a minimal example and file a bugzilla report.
best regards,
Vlad
java.lang.NullPointerException
at org.eclipse.xtext.serializer.analysis.SemanticSequencerNfaProvider$SemStateFactory.create(SemanticSequencerNfaProvider.java:123)
at org.eclipse.xtext.serializer.analysis.SemanticSequencerNfaProvider$SemStateFactory.create(SemanticSequencerNfaProvider.java:1)
at org.eclipse.xtext.util.formallang.NfaUtil.create(NfaUtil.java:238)
at org.eclipse.xtext.serializer.analysis.SemanticSequencerNfaProvider.getNFA(SemanticSequencerNfaProvider.java:152)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:397)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_Expr700(AbstractErlangSemanticSequencer.java:1463)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:889)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptAction(SequenceFeeder.java:292)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.accept(SequenceFeeder.java:95)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.accept(BacktrackingSemanticSequencer.java:389)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:423)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_Expr700(AbstractErlangSemanticSequencer.java:1454)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:514)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptEObjectRuleCall(SequenceFeeder.java:299)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptRuleCall(SequenceFeeder.java:325)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.accept(SequenceFeeder.java:239)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.accept(BacktrackingSemanticSequencer.java:380)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:423)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_Expressions(AbstractErlangSemanticSequencer.java:1535)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:449)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptEObjectRuleCall(SequenceFeeder.java:299)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptRuleCall(SequenceFeeder.java:325)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.accept(SequenceFeeder.java:222)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.accept(BacktrackingSemanticSequencer.java:387)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:423)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_FunctionClause(AbstractErlangSemanticSequencer.java:1590)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:581)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptEObjectRuleCall(SequenceFeeder.java:299)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptRuleCall(SequenceFeeder.java:325)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.accept(SequenceFeeder.java:239)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.accept(BacktrackingSemanticSequencer.java:380)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:423)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_Function(AbstractErlangSemanticSequencer.java:1599)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:575)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptEObjectRuleCall(SequenceFeeder.java:299)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.acceptRuleCall(SequenceFeeder.java:325)
at org.eclipse.xtext.serializer.acceptor.SequenceFeeder.accept(SequenceFeeder.java:239)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.accept(BacktrackingSemanticSequencer.java:380)
at org.eclipse.xtext.serializer.sequencer.BacktrackingSemanticSequencer.createSequence(BacktrackingSemanticSequencer.java:423)
at org.erlide.serializer.AbstractErlangSemanticSequencer.sequence_Module(AbstractErlangSemanticSequencer.java:1725)
at org.erlide.serializer.AbstractErlangSemanticSequencer.createSequence(AbstractErlangSemanticSequencer.java:765)
at org.eclipse.xtext.serializer.impl.Serializer.serialize(Serializer.java:84)
at org.eclipse.xtext.serializer.impl.Serializer.serialize(Serializer.java:103)
at org.eclipse.xtext.serializer.impl.Serializer.serialize(Serializer.java:125)
at org.eclipse.xtext.resource.XtextResource.doSave(XtextResource.java:313)
at org.eclipse.emf.ecore.resource.impl.ResourceImpl.save(ResourceImpl.java:1423)
at org.eclipselabs.xtext.utils.unittesting.XtextTest.loadAndSaveModule(XtextTest.java:380)
at org.eclipselabs.xtext.utils.unittesting.XtextTest.testFile(XtextTest.java:178)
at org.erlide.erlang.FilesTest.test3(FilesTest.java:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.eclipse.xtext.junit4.XtextRunner$1.evaluate(XtextRunner.java:55)
at org.eclipselabs.xtext.utils.unittesting.XtextRunner2$1.evaluate(XtextRunner2.java:36)
at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
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| Re: Exception when testing language [message #801536 is a reply to message #801447] |
Sat, 18 February 2012 10:04  |
| Eclipse User |
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On 2012-18-02 12:51, Vlad Dumitrescu wrote:
> Hello Henrik and thanks for your heroic attempt to make sense of my
> scribblings! I probably tried too hard to simplify the context.
>
> There are two issues in my mind:
> 1. if the grammar is nonsense, couldn't the compiler give a warning or
> error? It feels like the root cause for a NPE in the serializer could
> have been detected by the compiler.
>
An NPE is never good, should have done something else. Note that there
are valid grammars that are not serializeable - they still serve a
purpose but are essentially one way (they can be used to parse). The
serialization validation should have caught the problem IMO.
> 2. what would be the right way to write the grammar rules?
>
Depends on what you really want... which is what I am trying to figure
out :)
> There are four expressions that I need to parse here:
> * ExprMax * ExprMax(arg) which is a function call
> * ExprMax#type which is a typed expression
> * #type which is a type constructor
>
> The way I started with it was something like
>
>
> Expression: FunCall | TypedExpr;
> FunCall: ExprMax ('(' ')')?;
> TypedExpr: ExprMax? => '#' ID;
>
>
This is ambiguous since a FunCall can consist of only an ExprMax, and it
is impossible to detect if a following '#' ID belongs to the ExprMax or
is free standing. Using 'a' for literal, given "a#b" is this a FunCall
followed by a TypedExpr or a TypedExpr?
Try something like:
Expression : TypedExpression ;
TypedExpression
: FunctionCall
({TypedExpression.left = current}
'#' type = ID)?
;
FunctionCall
: PrimaryExpression
({FunctionCall.left = current}
'(' args += Expression* ')')?
;
PrimaryExpression
: Literal
| ParenthesizedExpression
;
Literal : value = ID;
ParenthesizedExpression : '(' Expression ')' ;
This allows any primary expression to be used as LHS in FunctionCall,
and anything can be typed. If you need to disallow certain input - say
"(a)#b" simply add validation to TypedExpression and check the class of
the LHS. Likewise, if you do not allow "(a)()", simply check LHS of
FunctionCall for acceptable class.
a => (Literal a)
a#b => (TypedExpression (Literal a) b)
a() => (FunctionCall (Literal a))
a()#b => (TypeExpression (FunctionCall (Literal a)) b)
etc.
Did you want #ID to mean "type creation expression"? You could do this:
PrimaryExpression
: Literal
| ParenthesizedExpression
| TypeDeclaration
;
TypeDeclaration
: '#' type = ID
;
You also need to have a separator (e.g. ',') between the arguments in
the function call as Expression* becomes ambiguous.
This could work but results in possibility to express things that seems
nonsensical - i.e. passing a TypeDeclaration as an argument, calling it
etc. i.e. these expression would be valid:
#b
#b()
#b#c
a(#b, #c)
....
You probably want to have it at a higher level in the grammar.
Something like this perhaps:
Statements :
statements += Statement+
Statement : Expression '.' | TypeDeclaration ;
Note that a separator between expressions is required.
> but that is ambiguos on ExprMax. Maybe it would be enough to set "k=2"
> on the ANTLR grammar? Problem is that I get syntax errors when I try it
> - "backtrack=true" works, but "k=2" gives "no viable alternative at
> input '2'"...
>
These are the kinds of things that are getting you into trouble - you
have to start with a grammar that is not ambiguous. When you turn on
backtracking without knowing why, you are basically letting the parser
guess for you. If you set k to a number you are basically setting
look-ahead to 2, better to leave it to its default.
> best regards,
> Vlad
>
Hope that helps you.
- henrik
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