"""ANTLR3 runtime package""" # begin[licence] # # [The "BSD licence"] # Copyright (c) 2005-2012 Terence Parr # All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions # are met: # 1. Redistributions of source code must retain the above copyright # notice, this list of conditions and the following disclaimer. # 2. Redistributions in binary form must reproduce the above copyright # notice, this list of conditions and the following disclaimer in the # documentation and/or other materials provided with the distribution. # 3. The name of the author may not be used to endorse or promote products # derived from this software without specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. # # end[licence] import sys import inspect from .constants import compatible_api_versions, DEFAULT_CHANNEL, \ HIDDEN_CHANNEL, EOF, EOR_TOKEN_TYPE, INVALID_TOKEN_TYPE from .exceptions import RecognitionException, MismatchedTokenException, \ MismatchedRangeException, MismatchedTreeNodeException, \ NoViableAltException, EarlyExitException, MismatchedSetException, \ MismatchedNotSetException, FailedPredicateException, \ BacktrackingFailed, UnwantedTokenException, MissingTokenException from .tokens import CommonToken, SKIP_TOKEN class RecognizerSharedState(object): """ The set of fields needed by an abstract recognizer to recognize input and recover from errors etc... As a separate state object, it can be shared among multiple grammars; e.g., when one grammar imports another. These fields are publically visible but the actual state pointer per parser is protected. """ def __init__(self): # Track the set of token types that can follow any rule invocation. # Stack grows upwards. self.following = [] # This is true when we see an error and before having successfully # matched a token. Prevents generation of more than one error message # per error. self.errorRecovery = False # The index into the input stream where the last error occurred. # This is used to prevent infinite loops where an error is found # but no token is consumed during recovery...another error is found, # ad naseum. This is a failsafe mechanism to guarantee that at least # one token/tree node is consumed for two errors. self.lastErrorIndex = -1 # If 0, no backtracking is going on. Safe to exec actions etc... # If >0 then it's the level of backtracking. self.backtracking = 0 # An array[size num rules] of (int -> int) dicts that tracks # the stop token index for each rule. ruleMemo[ruleIndex] is # the memoization table for ruleIndex. For key ruleStartIndex, you # get back the stop token for associated rule or MEMO_RULE_FAILED. # # This is only used if rule memoization is on (which it is by default). self.ruleMemo = None ## Did the recognizer encounter a syntax error? Track how many. self.syntaxErrors = 0 # LEXER FIELDS (must be in same state object to avoid casting # constantly in generated code and Lexer object) :( ## The goal of all lexer rules/methods is to create a token object. # This is an instance variable as multiple rules may collaborate to # create a single token. nextToken will return this object after # matching lexer rule(s). If you subclass to allow multiple token # emissions, then set this to the last token to be matched or # something nonnull so that the auto token emit mechanism will not # emit another token. self.token = None ## What character index in the stream did the current token start at? # Needed, for example, to get the text for current token. Set at # the start of nextToken. self.tokenStartCharIndex = -1 ## The line on which the first character of the token resides self.tokenStartLine = None ## The character position of first character within the line self.tokenStartCharPositionInLine = None ## The channel number for the current token self.channel = None ## The token type for the current token self.type = None ## You can set the text for the current token to override what is in # the input char buffer. Use setText() or can set this instance var. self.text = None class BaseRecognizer(object): """ @brief Common recognizer functionality. A generic recognizer that can handle recognizers generated from lexer, parser, and tree grammars. This is all the parsing support code essentially; most of it is error recovery stuff and backtracking. """ MEMO_RULE_FAILED = -2 MEMO_RULE_UNKNOWN = -1 # copies from Token object for convenience in actions DEFAULT_TOKEN_CHANNEL = DEFAULT_CHANNEL # for convenience in actions HIDDEN = HIDDEN_CHANNEL # overridden by generated subclasses grammarFileName = None tokenNames = None # The api_version attribute has been introduced in 3.3. If it is not # overwritten in the generated recognizer, we assume a default of v0. api_version = 0 def __init__(self, state=None): # Input stream of the recognizer. Must be initialized by a subclass. self.input = None ## State of a lexer, parser, or tree parser are collected into a state # object so the state can be shared. This sharing is needed to # have one grammar import others and share same error variables # and other state variables. It's a kind of explicit multiple # inheritance via delegation of methods and shared state. if state is None: state = RecognizerSharedState() self._state = state if self.api_version not in compatible_api_versions: raise RuntimeError( "ANTLR version mismatch: " "The recognizer has been generated with API V{}, " "but this runtime does not support this." .format(self.api_version)) # this one only exists to shut up pylint :( def setInput(self, input): self.input = input def reset(self): """ reset the parser's state; subclasses must rewind the input stream """ # wack everything related to error recovery if self._state is None: # no shared state work to do return self._state.following = [] self._state.errorRecovery = False self._state.lastErrorIndex = -1 self._state.syntaxErrors = 0 # wack everything related to backtracking and memoization self._state.backtracking = 0 if self._state.ruleMemo is not None: self._state.ruleMemo = {} def match(self, input, ttype, follow): """ Match current input symbol against ttype. Attempt single token insertion or deletion error recovery. If that fails, throw MismatchedTokenException. To turn off single token insertion or deletion error recovery, override recoverFromMismatchedToken() and have it throw an exception. See TreeParser.recoverFromMismatchedToken(). This way any error in a rule will cause an exception and immediate exit from rule. Rule would recover by resynchronizing to the set of symbols that can follow rule ref. """ matchedSymbol = self.getCurrentInputSymbol(input) if self.input.LA(1) == ttype: self.input.consume() self._state.errorRecovery = False return matchedSymbol if self._state.backtracking > 0: # FIXME: need to return matchedSymbol here as well. damn!! raise BacktrackingFailed matchedSymbol = self.recoverFromMismatchedToken(input, ttype, follow) return matchedSymbol def matchAny(self): """Match the wildcard: in a symbol""" self._state.errorRecovery = False self.input.consume() def mismatchIsUnwantedToken(self, input, ttype): return input.LA(2) == ttype def mismatchIsMissingToken(self, input, follow): if follow is None: # we have no information about the follow; we can only consume # a single token and hope for the best return False # compute what can follow this grammar element reference if EOR_TOKEN_TYPE in follow: viableTokensFollowingThisRule = self.computeContextSensitiveRuleFOLLOW() follow |= viableTokensFollowingThisRule if len(self._state.following) > 0: # remove EOR if we're not the start symbol follow -= {EOR_TOKEN_TYPE} # if current token is consistent with what could come after set # then we know we're missing a token; error recovery is free to # "insert" the missing token if input.LA(1) in follow or EOR_TOKEN_TYPE in follow: return True return False def reportError(self, e): """Report a recognition problem. This method sets errorRecovery to indicate the parser is recovering not parsing. Once in recovery mode, no errors are generated. To get out of recovery mode, the parser must successfully match a token (after a resync). So it will go: 1. error occurs 2. enter recovery mode, report error 3. consume until token found in resync set 4. try to resume parsing 5. next match() will reset errorRecovery mode If you override, make sure to update syntaxErrors if you care about that. """ # if we've already reported an error and have not matched a token # yet successfully, don't report any errors. if self._state.errorRecovery: return self._state.syntaxErrors += 1 # don't count spurious self._state.errorRecovery = True self.displayRecognitionError(e) def displayRecognitionError(self, e): hdr = self.getErrorHeader(e) msg = self.getErrorMessage(e) self.emitErrorMessage(hdr + " " + msg) def getErrorMessage(self, e): """ What error message should be generated for the various exception types? Not very object-oriented code, but I like having all error message generation within one method rather than spread among all of the exception classes. This also makes it much easier for the exception handling because the exception classes do not have to have pointers back to this object to access utility routines and so on. Also, changing the message for an exception type would be difficult because you would have to subclassing exception, but then somehow get ANTLR to make those kinds of exception objects instead of the default. This looks weird, but trust me--it makes the most sense in terms of flexibility. For grammar debugging, you will want to override this to add more information such as the stack frame with getRuleInvocationStack(e, this.getClass().getName()) and, for no viable alts, the decision description and state etc... Override this to change the message generated for one or more exception types. """ if isinstance(e, UnwantedTokenException): if e.expecting == EOF: tokenName = "EOF" else: tokenName = self.tokenNames[e.expecting] msg = "extraneous input {} expecting {}".format( self.getTokenErrorDisplay(e.getUnexpectedToken()), tokenName ) elif isinstance(e, MissingTokenException): if e.expecting == EOF: tokenName = "EOF" else: tokenName = self.tokenNames[e.expecting] msg = "missing {} at {}".format( tokenName, self.getTokenErrorDisplay(e.token) ) elif isinstance(e, MismatchedTokenException): if e.expecting == EOF: tokenName = "EOF" else: tokenName = self.tokenNames[e.expecting] msg = "mismatched input {} expecting {}".format( self.getTokenErrorDisplay(e.token), tokenName ) elif isinstance(e, MismatchedTreeNodeException): if e.expecting == EOF: tokenName = "EOF" else: tokenName = self.tokenNames[e.expecting] msg = "mismatched tree node: {} expecting {}".format( e.node, tokenName) elif isinstance(e, NoViableAltException): msg = "no viable alternative at input {}".format( self.getTokenErrorDisplay(e.token)) elif isinstance(e, EarlyExitException): msg = "required (...)+ loop did not match anything at input {}".format( self.getTokenErrorDisplay(e.token)) elif isinstance(e, MismatchedSetException): msg = "mismatched input {} expecting set {!r}".format( self.getTokenErrorDisplay(e.token), e.expecting ) elif isinstance(e, MismatchedNotSetException): msg = "mismatched input {} expecting set {!r}".format( self.getTokenErrorDisplay(e.token), e.expecting ) elif isinstance(e, FailedPredicateException): msg = "rule {} failed predicate: {{{}}}?".format( e.ruleName, e.predicateText ) else: msg = str(e) return msg def getNumberOfSyntaxErrors(self): """ Get number of recognition errors (lexer, parser, tree parser). Each recognizer tracks its own number. So parser and lexer each have separate count. Does not count the spurious errors found between an error and next valid token match. See also reportError(). """ return self._state.syntaxErrors def getErrorHeader(self, e): """ What is the error header, normally line/character position information? """ source_name = self.getSourceName() if source_name is not None: return "{} line {}:{}".format(source_name, e.line, e.charPositionInLine) return "line {}:{}".format(e.line, e.charPositionInLine) def getTokenErrorDisplay(self, t): """ How should a token be displayed in an error message? The default is to display just the text, but during development you might want to have a lot of information spit out. Override in that case to use t.toString() (which, for CommonToken, dumps everything about the token). This is better than forcing you to override a method in your token objects because you don't have to go modify your lexer so that it creates a new Java type. """ s = t.text if s is None: if t.type == EOF: s = "" else: s = "<{}>".format(t.typeName) return repr(s) def emitErrorMessage(self, msg): """Override this method to change where error messages go""" sys.stderr.write(msg + '\n') def recover(self, input, re): """ Recover from an error found on the input stream. This is for NoViableAlt and mismatched symbol exceptions. If you enable single token insertion and deletion, this will usually not handle mismatched symbol exceptions but there could be a mismatched token that the match() routine could not recover from. """ # PROBLEM? what if input stream is not the same as last time # perhaps make lastErrorIndex a member of input if self._state.lastErrorIndex == input.index(): # uh oh, another error at same token index; must be a case # where LT(1) is in the recovery token set so nothing is # consumed; consume a single token so at least to prevent # an infinite loop; this is a failsafe. input.consume() self._state.lastErrorIndex = input.index() followSet = self.computeErrorRecoverySet() self.beginResync() self.consumeUntil(input, followSet) self.endResync() def beginResync(self): """ A hook to listen in on the token consumption during error recovery. The DebugParser subclasses this to fire events to the listenter. """ pass def endResync(self): """ A hook to listen in on the token consumption during error recovery. The DebugParser subclasses this to fire events to the listenter. """ pass def computeErrorRecoverySet(self): """ Compute the error recovery set for the current rule. During rule invocation, the parser pushes the set of tokens that can follow that rule reference on the stack; this amounts to computing FIRST of what follows the rule reference in the enclosing rule. This local follow set only includes tokens from within the rule; i.e., the FIRST computation done by ANTLR stops at the end of a rule. EXAMPLE When you find a "no viable alt exception", the input is not consistent with any of the alternatives for rule r. The best thing to do is to consume tokens until you see something that can legally follow a call to r *or* any rule that called r. You don't want the exact set of viable next tokens because the input might just be missing a token--you might consume the rest of the input looking for one of the missing tokens. Consider grammar: a : '[' b ']' | '(' b ')' ; b : c '^' INT ; c : ID | INT ; At each rule invocation, the set of tokens that could follow that rule is pushed on a stack. Here are the various "local" follow sets: FOLLOW(b1_in_a) = FIRST(']') = ']' FOLLOW(b2_in_a) = FIRST(')') = ')' FOLLOW(c_in_b) = FIRST('^') = '^' Upon erroneous input "[]", the call chain is a -> b -> c and, hence, the follow context stack is: depth local follow set after call to rule 0 \ a (from main()) 1 ']' b 3 '^' c Notice that ')' is not included, because b would have to have been called from a different context in rule a for ')' to be included. For error recovery, we cannot consider FOLLOW(c) (context-sensitive or otherwise). We need the combined set of all context-sensitive FOLLOW sets--the set of all tokens that could follow any reference in the call chain. We need to resync to one of those tokens. Note that FOLLOW(c)='^' and if we resync'd to that token, we'd consume until EOF. We need to sync to context-sensitive FOLLOWs for a, b, and c: {']','^'}. In this case, for input "[]", LA(1) is in this set so we would not consume anything and after printing an error rule c would return normally. It would not find the required '^' though. At this point, it gets a mismatched token error and throws an exception (since LA(1) is not in the viable following token set). The rule exception handler tries to recover, but finds the same recovery set and doesn't consume anything. Rule b exits normally returning to rule a. Now it finds the ']' (and with the successful match exits errorRecovery mode). So, you cna see that the parser walks up call chain looking for the token that was a member of the recovery set. Errors are not generated in errorRecovery mode. ANTLR's error recovery mechanism is based upon original ideas: "Algorithms + Data Structures = Programs" by Niklaus Wirth and "A note on error recovery in recursive descent parsers": http://portal.acm.org/citation.cfm?id=947902.947905 Later, Josef Grosch had some good ideas: "Efficient and Comfortable Error Recovery in Recursive Descent Parsers": ftp://www.cocolab.com/products/cocktail/doca4.ps/ell.ps.zip Like Grosch I implemented local FOLLOW sets that are combined at run-time upon error to avoid overhead during parsing. """ return self.combineFollows(False) def computeContextSensitiveRuleFOLLOW(self): """ Compute the context-sensitive FOLLOW set for current rule. This is set of token types that can follow a specific rule reference given a specific call chain. You get the set of viable tokens that can possibly come next (lookahead depth 1) given the current call chain. Contrast this with the definition of plain FOLLOW for rule r: FOLLOW(r)={x | S=>*alpha r beta in G and x in FIRST(beta)} where x in T* and alpha, beta in V*; T is set of terminals and V is the set of terminals and nonterminals. In other words, FOLLOW(r) is the set of all tokens that can possibly follow references to r in *any* sentential form (context). At runtime, however, we know precisely which context applies as we have the call chain. We may compute the exact (rather than covering superset) set of following tokens. For example, consider grammar: stat : ID '=' expr ';' // FOLLOW(stat)=={EOF} | "return" expr '.' ; expr : atom ('+' atom)* ; // FOLLOW(expr)=={';','.',')'} atom : INT // FOLLOW(atom)=={'+',')',';','.'} | '(' expr ')' ; The FOLLOW sets are all inclusive whereas context-sensitive FOLLOW sets are precisely what could follow a rule reference. For input "i=(3);", here is the derivation: stat => ID '=' expr ';' => ID '=' atom ('+' atom)* ';' => ID '=' '(' expr ')' ('+' atom)* ';' => ID '=' '(' atom ')' ('+' atom)* ';' => ID '=' '(' INT ')' ('+' atom)* ';' => ID '=' '(' INT ')' ';' At the "3" token, you'd have a call chain of stat -> expr -> atom -> expr -> atom What can follow that specific nested ref to atom? Exactly ')' as you can see by looking at the derivation of this specific input. Contrast this with the FOLLOW(atom)={'+',')',';','.'}. You want the exact viable token set when recovering from a token mismatch. Upon token mismatch, if LA(1) is member of the viable next token set, then you know there is most likely a missing token in the input stream. "Insert" one by just not throwing an exception. """ return self.combineFollows(True) def combineFollows(self, exact): followSet = set() for idx, localFollowSet in reversed(list(enumerate(self._state.following))): followSet |= localFollowSet if exact: # can we see end of rule? if EOR_TOKEN_TYPE in localFollowSet: # Only leave EOR in set if at top (start rule); this lets # us know if have to include follow(start rule); i.e., EOF if idx > 0: followSet.remove(EOR_TOKEN_TYPE) else: # can't see end of rule, quit break return followSet def recoverFromMismatchedToken(self, input, ttype, follow): """Attempt to recover from a single missing or extra token. EXTRA TOKEN LA(1) is not what we are looking for. If LA(2) has the right token, however, then assume LA(1) is some extra spurious token. Delete it and LA(2) as if we were doing a normal match(), which advances the input. MISSING TOKEN If current token is consistent with what could come after ttype then it is ok to 'insert' the missing token, else throw exception For example, Input 'i=(3;' is clearly missing the ')'. When the parser returns from the nested call to expr, it will have call chain: stat -> expr -> atom and it will be trying to match the ')' at this point in the derivation: => ID '=' '(' INT ')' ('+' atom)* ';' ^ match() will see that ';' doesn't match ')' and report a mismatched token error. To recover, it sees that LA(1)==';' is in the set of tokens that can follow the ')' token reference in rule atom. It can assume that you forgot the ')'. """ e = None # if next token is what we are looking for then "delete" this token if self.mismatchIsUnwantedToken(input, ttype): e = UnwantedTokenException(ttype, input) self.beginResync() input.consume() # simply delete extra token self.endResync() # report after consuming so AW sees the token in the exception self.reportError(e) # we want to return the token we're actually matching matchedSymbol = self.getCurrentInputSymbol(input) # move past ttype token as if all were ok input.consume() return matchedSymbol # can't recover with single token deletion, try insertion if self.mismatchIsMissingToken(input, follow): inserted = self.getMissingSymbol(input, e, ttype, follow) e = MissingTokenException(ttype, input, inserted) # report after inserting so AW sees the token in the exception self.reportError(e) return inserted # even that didn't work; must throw the exception e = MismatchedTokenException(ttype, input) raise e def recoverFromMismatchedSet(self, input, e, follow): """Not currently used""" if self.mismatchIsMissingToken(input, follow): self.reportError(e) # we don't know how to conjure up a token for sets yet return self.getMissingSymbol(input, e, INVALID_TOKEN_TYPE, follow) # TODO do single token deletion like above for Token mismatch raise e def getCurrentInputSymbol(self, input): """ Match needs to return the current input symbol, which gets put into the label for the associated token ref; e.g., x=ID. Token and tree parsers need to return different objects. Rather than test for input stream type or change the IntStream interface, I use a simple method to ask the recognizer to tell me what the current input symbol is. This is ignored for lexers. """ return None def getMissingSymbol(self, input, e, expectedTokenType, follow): """Conjure up a missing token during error recovery. The recognizer attempts to recover from single missing symbols. But, actions might refer to that missing symbol. For example, x=ID {f($x);}. The action clearly assumes that there has been an identifier matched previously and that $x points at that token. If that token is missing, but the next token in the stream is what we want we assume that this token is missing and we keep going. Because we have to return some token to replace the missing token, we have to conjure one up. This method gives the user control over the tokens returned for missing tokens. Mostly, you will want to create something special for identifier tokens. For literals such as '{' and ',', the default action in the parser or tree parser works. It simply creates a CommonToken of the appropriate type. The text will be the token. If you change what tokens must be created by the lexer, override this method to create the appropriate tokens. """ return None def consumeUntil(self, input, tokenTypes): """ Consume tokens until one matches the given token or token set tokenTypes can be a single token type or a set of token types """ if not isinstance(tokenTypes, (set, frozenset)): tokenTypes = frozenset([tokenTypes]) ttype = input.LA(1) while ttype != EOF and ttype not in tokenTypes: input.consume() ttype = input.LA(1) def getRuleInvocationStack(self): """ Return List of the rules in your parser instance leading up to a call to this method. You could override if you want more details such as the file/line info of where in the parser java code a rule is invoked. This is very useful for error messages and for context-sensitive error recovery. You must be careful, if you subclass a generated recognizers. The default implementation will only search the module of self for rules, but the subclass will not contain any rules. You probably want to override this method to look like def getRuleInvocationStack(self): return self._getRuleInvocationStack(.__module__) where is the class of the generated recognizer, e.g. the superclass of self. """ return self._getRuleInvocationStack(self.__module__) @classmethod def _getRuleInvocationStack(cls, module): """ A more general version of getRuleInvocationStack where you can pass in, for example, a RecognitionException to get it's rule stack trace. This routine is shared with all recognizers, hence, static. TODO: move to a utility class or something; weird having lexer call this """ # mmmhhh,... perhaps look at the first argument # (f_locals[co_varnames[0]]?) and test if it's a (sub)class of # requested recognizer... rules = [] for frame in reversed(inspect.stack()): code = frame[0].f_code codeMod = inspect.getmodule(code) if codeMod is None: continue # skip frames not in requested module if codeMod.__name__ != module: continue # skip some unwanted names if code.co_name in ('nextToken', ''): continue rules.append(code.co_name) return rules def getBacktrackingLevel(self): return self._state.backtracking def setBacktrackingLevel(self, n): self._state.backtracking = n def getGrammarFileName(self): """For debugging and other purposes, might want the grammar name. Have ANTLR generate an implementation for this method. """ return self.grammarFileName def getSourceName(self): raise NotImplementedError def toStrings(self, tokens): """A convenience method for use most often with template rewrites. Convert a Token list to a str list. """ if tokens is None: return None return [token.text for token in tokens] def getRuleMemoization(self, ruleIndex, ruleStartIndex): """ Given a rule number and a start token index number, return MEMO_RULE_UNKNOWN if the rule has not parsed input starting from start index. If this rule has parsed input starting from the start index before, then return where the rule stopped parsing. It returns the index of the last token matched by the rule. """ if ruleIndex not in self._state.ruleMemo: self._state.ruleMemo[ruleIndex] = {} return self._state.ruleMemo[ruleIndex].get( ruleStartIndex, self.MEMO_RULE_UNKNOWN ) def alreadyParsedRule(self, input, ruleIndex): """ Has this rule already parsed input at the current index in the input stream? Return the stop token index or MEMO_RULE_UNKNOWN. If we attempted but failed to parse properly before, return MEMO_RULE_FAILED. This method has a side-effect: if we have seen this input for this rule and successfully parsed before, then seek ahead to 1 past the stop token matched for this rule last time. """ stopIndex = self.getRuleMemoization(ruleIndex, input.index()) if stopIndex == self.MEMO_RULE_UNKNOWN: return False if stopIndex == self.MEMO_RULE_FAILED: raise BacktrackingFailed else: input.seek(stopIndex + 1) return True def memoize(self, input, ruleIndex, ruleStartIndex, success): """ Record whether or not this rule parsed the input at this position successfully. """ if success: stopTokenIndex = input.index() - 1 else: stopTokenIndex = self.MEMO_RULE_FAILED if ruleIndex in self._state.ruleMemo: self._state.ruleMemo[ruleIndex][ruleStartIndex] = stopTokenIndex def traceIn(self, ruleName, ruleIndex, inputSymbol): sys.stdout.write("enter {} {}".format(ruleName, inputSymbol)) if self._state.backtracking > 0: sys.stdout.write(" backtracking={}".format(self._state.backtracking)) sys.stdout.write('\n') def traceOut(self, ruleName, ruleIndex, inputSymbol): sys.stdout.write("exit {} {}".format(ruleName, inputSymbol)) if self._state.backtracking > 0: sys.stdout.write(" backtracking={}".format(self._state.backtracking)) # mmmm... we use BacktrackingFailed exceptions now. So how could we # get that information here? #if self._state.failed: # sys.stdout.write(" failed") #else: # sys.stdout.write(" succeeded") sys.stdout.write('\n') class TokenSource(object): """ @brief Abstract baseclass for token producers. A source of tokens must provide a sequence of tokens via nextToken() and also must reveal it's source of characters; CommonToken's text is computed from a CharStream; it only store indices into the char stream. Errors from the lexer are never passed to the parser. Either you want to keep going or you do not upon token recognition error. If you do not want to continue lexing then you do not want to continue parsing. Just throw an exception not under RecognitionException and Java will naturally toss you all the way out of the recognizers. If you want to continue lexing then you should not throw an exception to the parser--it has already requested a token. Keep lexing until you get a valid one. Just report errors and keep going, looking for a valid token. """ def nextToken(self): """Return a Token object from your input stream (usually a CharStream). Do not fail/return upon lexing error; keep chewing on the characters until you get a good one; errors are not passed through to the parser. """ raise NotImplementedError def __iter__(self): """The TokenSource is an interator. The iteration will not include the final EOF token, see also the note for the __next__() method. """ return self def __next__(self): """Return next token or raise StopIteration. Note that this will raise StopIteration when hitting the EOF token, so EOF will not be part of the iteration. """ token = self.nextToken() if token is None or token.type == EOF: raise StopIteration return token class Lexer(BaseRecognizer, TokenSource): """ @brief Baseclass for generated lexer classes. A lexer is recognizer that draws input symbols from a character stream. lexer grammars result in a subclass of this object. A Lexer object uses simplified match() and error recovery mechanisms in the interest of speed. """ def __init__(self, input, state=None): BaseRecognizer.__init__(self, state) TokenSource.__init__(self) # Where is the lexer drawing characters from? self.input = input def reset(self): super().reset() # reset all recognizer state variables if self.input is not None: # rewind the input self.input.seek(0) if self._state is None: # no shared state work to do return # wack Lexer state variables self._state.token = None self._state.type = INVALID_TOKEN_TYPE self._state.channel = DEFAULT_CHANNEL self._state.tokenStartCharIndex = -1 self._state.tokenStartLine = -1 self._state.tokenStartCharPositionInLine = -1 self._state.text = None def makeEOFToken(self): eof = CommonToken( type=EOF, channel=DEFAULT_CHANNEL, input=self.input, start=self.input.index(), stop=self.input.index()) eof.line = self.input.line eof.charPositionInLine = self.input.charPositionInLine return eof def nextToken(self): """ Return a token from this source; i.e., match a token on the char stream. """ while 1: self._state.token = None self._state.channel = DEFAULT_CHANNEL self._state.tokenStartCharIndex = self.input.index() self._state.tokenStartCharPositionInLine = self.input.charPositionInLine self._state.tokenStartLine = self.input.line self._state.text = None if self.input.LA(1) == EOF: return self.makeEOFToken() try: self.mTokens() if self._state.token is None: self.emit() elif self._state.token == SKIP_TOKEN: continue return self._state.token except NoViableAltException as re: self.reportError(re) self.recover(re) # throw out current char and try again except RecognitionException as re: self.reportError(re) # match() routine has already called recover() def skip(self): """ Instruct the lexer to skip creating a token for current lexer rule and look for another token. nextToken() knows to keep looking when a lexer rule finishes with token set to SKIP_TOKEN. Recall that if token==null at end of any token rule, it creates one for you and emits it. """ self._state.token = SKIP_TOKEN def mTokens(self): """This is the lexer entry point that sets instance var 'token'""" # abstract method raise NotImplementedError def setCharStream(self, input): """Set the char stream and reset the lexer""" self.input = None self.reset() self.input = input def getSourceName(self): return self.input.getSourceName() def emit(self, token=None): """ The standard method called to automatically emit a token at the outermost lexical rule. The token object should point into the char buffer start..stop. If there is a text override in 'text', use that to set the token's text. Override this method to emit custom Token objects. If you are building trees, then you should also override Parser or TreeParser.getMissingSymbol(). """ if token is None: token = CommonToken( input=self.input, type=self._state.type, channel=self._state.channel, start=self._state.tokenStartCharIndex, stop=self.getCharIndex()-1 ) token.line = self._state.tokenStartLine token.text = self._state.text token.charPositionInLine = self._state.tokenStartCharPositionInLine self._state.token = token return token def match(self, s): if isinstance(s, str): for c in s: if self.input.LA(1) != ord(c): if self._state.backtracking > 0: raise BacktrackingFailed mte = MismatchedTokenException(c, self.input) self.recover(mte) raise mte self.input.consume() else: if self.input.LA(1) != s: if self._state.backtracking > 0: raise BacktrackingFailed mte = MismatchedTokenException(chr(s), self.input) self.recover(mte) # don't really recover; just consume in lexer raise mte self.input.consume() def matchAny(self): self.input.consume() def matchRange(self, a, b): if self.input.LA(1) < a or self.input.LA(1) > b: if self._state.backtracking > 0: raise BacktrackingFailed mre = MismatchedRangeException(chr(a), chr(b), self.input) self.recover(mre) raise mre self.input.consume() def getLine(self): return self.input.line def getCharPositionInLine(self): return self.input.charPositionInLine def getCharIndex(self): """What is the index of the current character of lookahead?""" return self.input.index() def getText(self): """ Return the text matched so far for the current token or any text override. """ if self._state.text is not None: return self._state.text return self.input.substring( self._state.tokenStartCharIndex, self.getCharIndex()-1 ) def setText(self, text): """ Set the complete text of this token; it wipes any previous changes to the text. """ self._state.text = text text = property(getText, setText) def reportError(self, e): ## TODO: not thought about recovery in lexer yet. ## # if we've already reported an error and have not matched a token ## # yet successfully, don't report any errors. ## if self.errorRecovery: ## return ## ## self.errorRecovery = True self.displayRecognitionError(e) def getErrorMessage(self, e): msg = None if isinstance(e, MismatchedTokenException): msg = "mismatched character {} expecting {}".format( self.getCharErrorDisplay(e.c), self.getCharErrorDisplay(e.expecting)) elif isinstance(e, NoViableAltException): msg = "no viable alternative at character {}".format( self.getCharErrorDisplay(e.c)) elif isinstance(e, EarlyExitException): msg = "required (...)+ loop did not match anything at character {}".format( self.getCharErrorDisplay(e.c)) elif isinstance(e, MismatchedNotSetException): msg = "mismatched character {} expecting set {!r}".format( self.getCharErrorDisplay(e.c), e.expecting) elif isinstance(e, MismatchedSetException): msg = "mismatched character {} expecting set {!r}".format( self.getCharErrorDisplay(e.c), e.expecting) elif isinstance(e, MismatchedRangeException): msg = "mismatched character {} expecting set {}..{}".format( self.getCharErrorDisplay(e.c), self.getCharErrorDisplay(e.a), self.getCharErrorDisplay(e.b)) else: msg = super().getErrorMessage(e) return msg def getCharErrorDisplay(self, c): if c == EOF: c = '' return repr(c) def recover(self, re): """ Lexers can normally match any char in it's vocabulary after matching a token, so do the easy thing and just kill a character and hope it all works out. You can instead use the rule invocation stack to do sophisticated error recovery if you are in a fragment rule. """ self.input.consume() def traceIn(self, ruleName, ruleIndex): inputSymbol = "{} line={}:{}".format(self.input.LT(1), self.getLine(), self.getCharPositionInLine() ) super().traceIn(ruleName, ruleIndex, inputSymbol) def traceOut(self, ruleName, ruleIndex): inputSymbol = "{} line={}:{}".format(self.input.LT(1), self.getLine(), self.getCharPositionInLine() ) super().traceOut(ruleName, ruleIndex, inputSymbol) class Parser(BaseRecognizer): """ @brief Baseclass for generated parser classes. """ def __init__(self, lexer, state=None): super().__init__(state) self.input = lexer def reset(self): super().reset() # reset all recognizer state variables if self.input is not None: self.input.seek(0) # rewind the input def getCurrentInputSymbol(self, input): return input.LT(1) def getMissingSymbol(self, input, e, expectedTokenType, follow): if expectedTokenType == EOF: tokenText = "" else: tokenText = "".format(self.tokenNames[expectedTokenType]) t = CommonToken(type=expectedTokenType, text=tokenText) current = input.LT(1) if current.type == EOF: current = input.LT(-1) if current is not None: t.line = current.line t.charPositionInLine = current.charPositionInLine t.channel = DEFAULT_CHANNEL return t def setTokenStream(self, input): """Set the token stream and reset the parser""" self.input = None self.reset() self.input = input def getTokenStream(self): return self.input def getSourceName(self): return self.input.getSourceName() def traceIn(self, ruleName, ruleIndex): super().traceIn(ruleName, ruleIndex, self.input.LT(1)) def traceOut(self, ruleName, ruleIndex): super().traceOut(ruleName, ruleIndex, self.input.LT(1)) class RuleReturnScope(object): """ Rules can return start/stop info as well as possible trees and templates. """ def getStart(self): """Return the start token or tree.""" return None def getStop(self): """Return the stop token or tree.""" return None def getTree(self): """Has a value potentially if output=AST.""" return None def getTemplate(self): """Has a value potentially if output=template.""" return None class ParserRuleReturnScope(RuleReturnScope): """ Rules that return more than a single value must return an object containing all the values. Besides the properties defined in RuleLabelScope.predefinedRulePropertiesScope there may be user-defined return values. This class simply defines the minimum properties that are always defined and methods to access the others that might be available depending on output option such as template and tree. Note text is not an actual property of the return value, it is computed from start and stop using the input stream's toString() method. I could add a ctor to this so that we can pass in and store the input stream, but I'm not sure we want to do that. It would seem to be undefined to get the .text property anyway if the rule matches tokens from multiple input streams. I do not use getters for fields of objects that are used simply to group values such as this aggregate. The getters/setters are there to satisfy the superclass interface. """ def __init__(self): super().__init__() self.start = None self.stop = None self.tree = None # only used when output=AST def getStart(self): return self.start def getStop(self): return self.stop def getTree(self): return self.tree