Re: [Hibernate] introductions of new keywords to ql (Welcome to parser land!)

Max Rydahl Andersen Wed, 15 Dec 2004 23:27:03 -0800

Hi,

Now when we are adding EJBQL support is there a "easy" (read not to hacky) way of e.g. letting the parser complain if a user is actually using HQL only syntax ?

I'm just thinking that from a user point of view it would be nice to run in a "ejb3 only" mode and be told if he crosses the line into the other side ;)

/max

On Wed, 15 Dec 2004 23:16:45 -0500, Joshua Davis <[EMAIL PROTECTED]> wrote:

Alexey,
I've spent a little time getting your example grammar modification to work. In the tokens section, I added:
    // --- EJBQL keywords ---
    OBJECT="object";
In the rules, I added:
selectClause : SELECT^ // NOTE: The '^' after a token causes the corresponding AST node to be the root of the sub-tree. (DISTINCT)? ( selectedPropertiesList | newExpression | selectObject ) ;
selectObject
    : OBJECT^ OPEN! identifier CLOSE!
    ;
Just as you had experienced, my changes made the HqlParserTest fail. Welcome to parser land!

The identPrimary rule fails because the new keyword is recognized in *three* tokens of lookahead in this context. Since the parser needs the lookahead to resolve the optional DOT^ "class" clause in primaryExpression, the weakKeywords() method would not work properly no matter where you put it. So, I changed identPrimary to allow the new keyword after the DOT and then placed a semantic action there to mutate the OBJECT node into an IDENT node if it sees it.

// identifier, followed by member refs (dot ident), or method calls. identPrimary : identifier ( options { greedy=true; } : DOT^ ( identifier | ELEMENTS | o:OBJECT { #o.setType(IDENT); } ) )* ( options { greedy=true; } : ( op:OPEN^ { #op.setType(METHOD_CALL);} exprList CLOSE! ) )? // Also allow special 'aggregate functions' such as count(), avg(), etc. | aggregate ;

In general, we need to be very careful when adding keywords to the language, as there can be many seemingly strange side effects.
Joshua Davis wrote:
You are correct, this would affect 'java.lang.Object'
because the OBJECT token is being used to branch into
the new rule.
I was going to look into modifying 'path' to force the
token after the dot to be an identifier, no matter
what it is, which is similar to what weakKeywords()
does.
--- Alexey  Loubyansky <[EMAIL PROTECTED]> wrote:
Ok, thanks. I also see you have some workarounds
using weakKeywords and
handleIdentifierError but haven't yet figured it out
how to fix this.
Note, this also affects java.lang.Object.
-----Original Message----- From: Joshua Davis [mailto:[EMAIL PROTECTED] Sent: Wednesday, December 15, 2004 4:02 PM To: Alexey Loubyansky Cc: [EMAIL PROTECTED] Subject: RE: [Hibernate] introductions of new
keywords to ql
Aha... So you've introduced a new keyword, and
also a new
clause in the the select expression with the new
keyword
being the token that allows the parser to
distinguish between
the two branches.
I've got some ideas about what the problem is, but
I'll have
to test some things out to make sure.  I should be
able to do
that tonight.
--- Alexey  Loubyansky <[EMAIL PROTECTED]> wrote:
I did modify hql.g. I.e. added OBJECT token and
selectClause
        : SELECT^       // NOTE: The '^' after a token causes
the
corresponding AST node to be the root of the
sub-tree.
                (DISTINCT)? ( selectedPropertiesList |
newExpression |
selectObject)
        ;
selectObject
  : OBJECT^ OPEN! identifier CLOSE!
  ;
If I comment out selectObject in selectClause,
the test passes.
Thanks.
-----Original Message-----
From: Joshua Davis [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 15, 2004 2:13 PM
To: Alexey Loubyansky
Cc: [EMAIL PROTECTED]
Subject: Re: [Hibernate] introductions of new
keywords to ql
Actually, the HQL parser is capable of using
keywords as
identifiers in some contexts.   I'm not sure what you're
saying
here, have
you modified
the grammar and this caused HqlParserTest to
fail?
 If that
is the case
then there may be something wrong with the
modified grammar that is
preventing the 'keyword as identifier' from
working. If
not, then I'm
not really sure what the problem is.
Alexey Loubyansky wrote:
Hi Joshua & Steve,
I started working on the EJBQL syntaxes that
are
not
supported yet. I
will need to add some new keywords that might
cause some
existing tests
to fail. E.g. adding "object" causes the
following test to fail
input: ->from org.hibernate.test.Bar bar
where
bar.object.id = ? and
bar.object.class = ?<-
msg=HQL syntax error : unexpected token: .
near
line 1, column 42
There was 1 failure:
1)
testUnitTestHql(org.hibernate.test.hql.HqlParserTest)junit.fr
amework.As
s
ertionFailedError: At least one error
occurred
during parsing!
expected:<0> but was:<2>
        at
org.hibernate.test.hql.HqlParserTest.doParse(HqlParserTest.java:990)
        at
org.hibernate.test.hql.HqlParserTest.parse(HqlParserTest.java:966)
        at
org.hibernate.test.hql.HqlParserTest.testUnitTestHql(HqlParse
rTest.java:
663)
        at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native
Method)
        at
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown
Source)
        at
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown
Source)
        at
org.hibernate.test.AllTests.main(AllTests.java:120)
Am I missing something or there is really no
way
to fix this
except for
disallowing the use of 'object' even in
paths?
Thanks.
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--
Max Rydahl Andersen
callto://max.rydahl.andersen

Hibernate
[EMAIL PROTECTED]
http://hibernate.org

JBoss Inc
[EMAIL PROTECTED]
http://jboss.com

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Re: [Hibernate] introductions of new keywords to ql (Welcome to parser land!)

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