I'll update svn.openlaszlo.org/vendor/ and the wiki pages [1,2] later.
[1] http://wiki.openlaszlo.org/SubversionBuildInstructions#Install_JavaCC
[2]
http://wiki.openlaszlo.org/NativeWindows7SubversionBuildInstructions#Install_javacc
Change bargull-20110202-U3G by bargull@Bargull02 on 2011-02-02 17:03:34
in /home/anba/src/svn/openlaszlo/trunk
for http://svn.openlaszlo.org/openlaszlo/trunk
Summary: Upgrade to JavaCC5, fix ASI bugs in parser
New Features: LPP-8788 (We should use a more modern version of JavaCC)
Bugs Fixed: LPP-9714 (Parser does not enfore no-line-terminator in
break/continue/throw/postfix-op statements), LPP-9719 (Semicolon after
do-while creates empty statement), LPP-9720 (Newline in multi-line
comment not treated as newline for ASI), LPP-9721 (TypeIdentifier()
should enforce NoLineTerminator before Nullable()/NonNullable()),
LPP-9722 (Multi-line comment not handled when computing ASI)
Technical Reviewer: ptw, dda
QA Reviewer: (pending)
Overview:
JavaCC 5 has got a bug with javacode non-terminals, somehow the
tokenstream isn't rewinded properly in a (deeply?) nested syntactic
lookahead if used in conjunction with javacode non-terminals (e.g. see
lookahead for ModifiedDefinition() in Directive() and the Sc()
non-terminal). Even using a no-op javacode non-terminal broke the parser
(JAVACODE void Nop () {/*empty*/}). Because of that reason I had to
re-implement the whole optional semicolon mechanism in the parser. While
doing this rework, I've encountered a couple of bugs (LPP-9714,
LPP-9719, LPP-9720, LPP-9721, LPP-9722).
Details:
All Sc() non-terminals for optional semicolons have been rewritten to
use a semantic lookahead: [LOOKAHEAD({Sc()}) ";"]
The new Sc() function simply returns `true` if the next token in the
stream is a semicolon, this semicolon will then simply be consumed. If
the next token is not a semicolon, but an acceptable choice for
automatic semicolon insertion (ASI), Sc() returns `false`. So the
lookahead is unsuccessful and by that the optional block [...] is not
processed any further. If the next token is neither a semicolon nor an
acceptable choice for ASI, a parser exception is thrown.
JavaCC cannot infer the content a javacode non-terminal, therefore it
couldn't warn for possible ambiguities in the grammar after Sc() calls.
As the old Sc() non-terminal is gone, I had to add additional lookaheads
to resolve these ambiguities. See CallExpression(),
AdditiveExpression(), RelationalExpression() productions.
LPP-9714 (no-line-terminator rule):
The ECMAScript grammar has got restricted productions for the
PostfixExpression, ContinueStatement, BreakStatement, ThrowStatement and
ReturnStatement productions. For these productions, line terminators are
strictly prohibited. This restriction was only implemented for the
ReturnStatement, it's now implemented for the other productions as well.
The pattern used to implement the restriction is simply:
[LOOKAHEAD(NonTerminal(), {NoLineTerminator()}) NonTerminal()]. So a
combination of syntactic and semantic lookahead: if the next token(s)
can be parsed as NonTerminal() and there are no intervening newlines,
consume the tokens, otherwise just proceed. I've added an extra function
to produce a nice error message for the ThrowStatement production, so
it's easier for the user to understand what's going wrong when she added
a newline after the `throw` statement. The default error message by
JavaCC is pretty useless here: Encountered "" at line 1, column 61. Was
expecting one of: (empty list here)
LPP-9719 (do-while loop):
Just added the optional semicolon predicate for the do-while loop in
IterationStatement().
LPP-9720 (newline in multi-line comment):
Scan for newlines in multi-line comments, they count as newlines for the
syntactic grammar, cf. ECMAScript 5, 7.4 Comments
LPP-9721 (restriced production for TypeIdentifier):
TypeIdentifier was not a restricted production, but it should be,
otherwise "var x:Boolean \n !x;", where \n denotes a line break, is not
parsed as "var x:Boolean; !x;".
LPP-9722 (multi-line comment for ASI):
The (now removed) optionalSc() function just used the first special
token, but special tokens are chained, e.g. consider multiple
single-line and multi-line comments appearing next to each other.
Therefore it's necessary to loop over the specialToken field, just like
it's now done in NoLineTerminator().
Token.java:
JavaCC 5 requires a new interface in Token: Token.newToken(int, String).
TestParserASI.java:
JUnit test case for LPP-9714, LPP-9719, LPP-9720, LPP-9721, LPP-9722
build.xml:
- update 1.4 -> 1.5
- comment out org/openlaszlo/iv/flash/context package, this was recently
discussed on laszlo-dev
- explicitly add EDU/oswego package for build, sometimes my ant doesn't
pick it up, so make it explicit
- add TestParserASI to the "test" target
Tests:
TestParserASI test case, lfc compiles, smokecheck and alldata (swf10,
dhtml)x(Firefox, Opera, Safari, IE)
(Don't forget to download and install JavaCC 5 and update your
JAVACC_HOME environment variable accordingly!)
Files:
M WEB-INF/lib/javacc.jar
M WEB-INF/lps/server/build.xml
A WEB-INF/lps/server/src/org/openlaszlo/test/TestParserASI.java
M WEB-INF/lps/server/sc/src/org/openlaszlo/sc/Parser.jjt
M WEB-INF/lps/server/sc/src/org/openlaszlo/sc/parser/Token.java
Changeset:
http://svn.openlaszlo.org/openlaszlo/patches/bargull-20110202-U3G.tar
