module ANTLR3::Debug::EventListener

A listener that simply records text representations of the events. Useful for debugging the debugging facility ;) Subclasses can override the record() method (which defaults to printing to stdout) to record the events in a different way.

Constants

EVENTS
PROTOCOL_VERSION

Public Instance Methods

add_child( root, child ) click to toggle source

Make childID a child of rootID. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only IDs are set. @see antlr3.tree.TreeAdaptor.addChild()

# File lib/antlr3/debug.rb, line 663
def add_child( root, child )
  # do nothing
end
backtrack( level ) { |self| ... } click to toggle source
# File lib/antlr3/debug.rb, line 479
def backtrack( level )
  begin_backtrack( level )
  successful = yield( self )
  end_backtrack( level, successful )
end
become_root( new_root, old_root ) click to toggle source

Make a node the new root of an existing root. Note: the newRootID parameter is possibly different than the TreeAdaptor.becomeRoot() newRoot parameter. In our case, it will always be the result of calling TreeAdaptor.becomeRoot() and not root_n or whatever. The listener should assume that this event occurs only when the current subrule (or rule) subtree is being reset to newRootID. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only IDs are set. @see antlr3.tree.TreeAdaptor.becomeRoot()

# File lib/antlr3/debug.rb, line 654
def become_root( new_root, old_root )
  # do nothing
end
begin_backtrack( level ) click to toggle source
# File lib/antlr3/debug.rb, line 471
def begin_backtrack( level )
  # do nothing
end
begin_resync() click to toggle source

Indicates the recognizer is about to consume tokens to resynchronize the parser. Any consume events from here until the recovered event are not part of the parse–they are dead tokens.

# File lib/antlr3/debug.rb, line 554
def begin_resync()
  # do nothing
end
commence( ) click to toggle source

Announce that parsing has begun. Not technically useful except for sending events over a socket. A GUI for example will launch a thread to connect and communicate with a remote parser. The thread will want to notify the GUI when a connection is made. ANTLR parsers trigger this upon entry to the first rule (the ruleLevel is used to figure this out).

# File lib/antlr3/debug.rb, line 589
def commence(  )
  # do nothing
end
consume_hidden_token( tree ) click to toggle source

An off-channel input token was consumed. Trigger after the token was matched by things like match(), matchAny(). (unless of course the hidden token is first stuff in the input stream).

# File lib/antlr3/debug.rb, line 441
def consume_hidden_token( tree )
  # do nothing
end
consume_node( tree ) click to toggle source

Input for a tree parser is an AST, but we know nothing for sure about a node except its type and text (obtained from the adaptor). This is the analog of the consumeToken method. Again, the ID is the hashCode usually of the node so it only works if hashCode is not implemented. If the type is UP or DOWN, then the ID is not really meaningful as it’s fixed–there is just one UP node and one DOWN navigation node.

# File lib/antlr3/debug.rb, line 610
def consume_node( tree )
  # do nothing
end
consume_token( tree ) click to toggle source

An input token was consumed; matched by any kind of element. Trigger after the token was matched by things like match(), matchAny().

# File lib/antlr3/debug.rb, line 433
def consume_token( tree )
  # do nothing
end
create_node( node, token = nil ) click to toggle source

Announce a new node built from token elements such as type etc… If you are receiving this event over a socket via RemoteDebugEventSocketListener then only tree.ID, type, text are set.

# File lib/antlr3/debug.rb, line 638
def create_node( node, token = nil )
  # do nothing
end
end_backtrack( level, successful ) click to toggle source
# File lib/antlr3/debug.rb, line 475
def end_backtrack( level, successful )
  # do nothing
end
end_resync() click to toggle source

Indicates that the recognizer has finished consuming tokens in order to resychronize. There may be multiple beginResync/endResync pairs before the recognizer comes out of errorRecovery mode (in which multiple errors are suppressed). This will be useful in a gui where you want to probably grey out tokens that are consumed but not matched to anything in grammar. Anything between a beginResync/endResync pair was tossed out by the parser.

# File lib/antlr3/debug.rb, line 566
def end_resync()
  # do nothing
end
enter_alternative( alt ) click to toggle source

Because rules can have lots of alternatives, it is very useful to know which alt you are entering. This is 1..n for n alts.

# File lib/antlr3/debug.rb, line 391
def enter_alternative( alt )
  # do nothing
end
enter_decision( decision_number ) click to toggle source

Every decision, fixed k or arbitrary, has an enter/exit event so that a GUI can easily track what look/consume events are associated with prediction. You will see a single enter/exit subrule but multiple enter/exit decision events, one for each loop iteration.

# File lib/antlr3/debug.rb, line 422
def enter_decision( decision_number )
  # do nothing
end
enter_rule( grammar_file, rule_name ) click to toggle source

The parser has just entered a rule. No decision has been made about which alt is predicted. This is fired AFTER init actions have been executed. Attributes are defined and available etc… The grammarFileName allows composite grammars to jump around among multiple grammar files.

# File lib/antlr3/debug.rb, line 384
def enter_rule( grammar_file, rule_name )
  # do nothing
end
enter_subrule( decision_number ) click to toggle source

Track entry into any (…) subrule other EBNF construct

# File lib/antlr3/debug.rb, line 408
def enter_subrule( decision_number )
  # do nothing
end
error_node( tree ) click to toggle source

Upon syntax error, recognizers bracket the error with an error node if they are building ASTs.

# File lib/antlr3/debug.rb, line 629
def error_node( tree )
  # do nothing
end
examine_rule_memoization( rule ) click to toggle source
# File lib/antlr3/debug.rb, line 675
def examine_rule_memoization( rule )
  # do nothing
end
exit_decision( decision_number ) click to toggle source
# File lib/antlr3/debug.rb, line 426
def exit_decision( decision_number )
  # do nothing
end
exit_rule( grammar_file, rule_name ) click to toggle source

This is the last thing executed before leaving a rule. It is executed even if an exception is thrown. This is triggered after error reporting and recovery have occurred (unless the exception is not caught in this rule). This implies an “exitAlt” event. The grammarFileName allows composite grammars to jump around among multiple grammar files.

# File lib/antlr3/debug.rb, line 402
def exit_rule( grammar_file, rule_name )
  # do nothing
end
exit_subrule( decision_number ) click to toggle source
# File lib/antlr3/debug.rb, line 412
def exit_subrule( decision_number )
  # do nothing
end
flat_node( tree ) click to toggle source

A nil was created (even nil nodes have a unique ID… they are not “null” per se). As of 4/28/2006, this seems to be uniquely triggered when starting a new subtree such as when entering a subrule in automatic mode and when building a tree in rewrite mode. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only tree.ID is set.

# File lib/antlr3/debug.rb, line 622
def flat_node( tree )
  # do nothing
end
location( line, position ) click to toggle source

To watch a parser move through the grammar, the parser needs to inform the debugger what line/charPos it is passing in the grammar. For now, this does not know how to switch from one grammar to the other and back for island grammars etc… This should also allow breakpoints because the debugger can stop the parser whenever it hits this line/pos.

# File lib/antlr3/debug.rb, line 492
def location( line, position )
  # do nothing
end
look( i, tree ) click to toggle source

Somebody (anybody) looked ahead. Note that this actually gets triggered by both peek and look calls. The debugger will want to know which Token object was examined. Like consumeToken, this indicates what token was seen at that depth. A remote debugger cannot look ahead into a file it doesn’t have so look events must pass the token even if the info is redundant.

# File lib/antlr3/debug.rb, line 452
def look( i, tree )
  # do nothing
end
mark( marker ) click to toggle source

The parser is going to look arbitrarily ahead; mark this location, the token stream’s marker is sent in case you need it.

# File lib/antlr3/debug.rb, line 459
def mark( marker )
  # do nothing
end
on( event_name, &block ) click to toggle source
# File lib/antlr3/debug.rb, line 679
def on( event_name, &block )
  sclass = class << self; self; end
  sclass.send( :define_method, event_name, &block )
end
recognition_exception( exception ) click to toggle source

A recognition exception occurred such as NoViableAltError. I made this a generic event so that I can alter the exception hierachy later without having to alter all the debug objects. Upon error, the stack of enter rule/subrule must be properly unwound. If no viable alt occurs it is within an enter/exit decision, which also must be rewound. Even the rewind for each mark must be unwount. In the Java target this is pretty easy using try/finally, if a bit ugly in the generated code. The rewind is generated in DFA.predict() actually so no code needs to be generated for that. For languages w/o this “finally” feature (C++?), the target implementor will have to build an event stack or something. Across a socket for remote debugging, only the RecognitionError data fields are transmitted. The token object or whatever that caused the problem was the last object referenced by look. The immediately preceding look event should hold the unexpected Token or char. Here is a sample event trace for grammar: b : C ({;}A|B) // {;} is there to prevent A|B becoming a set | D ; The sequence for this rule (with no viable alt in the subrule) for input ‘c c’ (there are 3 tokens) is: commence look enterRule b location 7 1 enter decision 3 look exit decision 3 enterAlt1 location 7 5 look consumeToken [c/<4>,1:0] location 7 7 enterSubRule 2 enter decision 2 look look recognitionError NoViableAltError 2 1 2 exit decision 2 exitSubRule 2 beginResync look consumeToken [c/<4>,1:1] look endResync look(-1) exitRule b terminate

# File lib/antlr3/debug.rb, line 546
def recognition_exception( exception )
  # do nothing
end
resync() { |self| ... } click to toggle source
# File lib/antlr3/debug.rb, line 570
def resync
  begin_resync
  yield( self )
  end_resync
end
rewind( marker = nil ) click to toggle source

After an arbitrairly long look as with a cyclic DFA (or with any backtrack), this informs the debugger that stream should be rewound to the position associated with marker.

# File lib/antlr3/debug.rb, line 467
def rewind( marker = nil )
  # do nothing
end
semantic_predicate( result, predicate ) click to toggle source

A semantic predicate was evaluate with this result and action text

# File lib/antlr3/debug.rb, line 578
def semantic_predicate( result, predicate )
  # do nothing
end
set_token_boundaries( tree, token_start_index, token_stop_index ) click to toggle source

Set the token start/stop token index for a subtree root or node. If you are receiving this event over a socket via RemoteDebugEventSocketListener then only tree.ID is set.

# File lib/antlr3/debug.rb, line 671
def set_token_boundaries( tree, token_start_index, token_stop_index )
  # do nothing
end
terminate( ) click to toggle source

Parsing is over; successfully or not. Mostly useful for telling remote debugging listeners that it’s time to quit. When the rule invocation level goes to zero at the end of a rule, we are done parsing.

# File lib/antlr3/debug.rb, line 598
def terminate(  )
  # do nothing
end