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Edit File: pyparse.py
from collections.abc import Mapping import re import sys # Reason last stmt is continued (or C_NONE if it's not). (C_NONE, C_BACKSLASH, C_STRING_FIRST_LINE, C_STRING_NEXT_LINES, C_BRACKET) = range(5) if 0: # for throwaway debugging output def dump(*stuff): sys.__stdout__.write(" ".join(map(str, stuff)) + "\n") # Find what looks like the start of a popular stmt. _synchre = re.compile(r""" ^ [ \t]* (?: while | else | def | return | assert | break | class | continue | elif | try | except | raise | import | yield ) \b """, re.VERBOSE | re.MULTILINE).search # Match blank line or non-indenting comment line. _junkre = re.compile(r""" [ \t]* (?: \# \S .* )? \n """, re.VERBOSE).match # Match any flavor of string; the terminating quote is optional # so that we're robust in the face of incomplete program text. _match_stringre = re.compile(r""" \""" [^"\\]* (?: (?: \\. | "(?!"") ) [^"\\]* )* (?: \""" )? | " [^"\\\n]* (?: \\. [^"\\\n]* )* "? | ''' [^'\\]* (?: (?: \\. | '(?!'') ) [^'\\]* )* (?: ''' )? | ' [^'\\\n]* (?: \\. [^'\\\n]* )* '? """, re.VERBOSE | re.DOTALL).match # Match a line that starts with something interesting; # used to find the first item of a bracket structure. _itemre = re.compile(r""" [ \t]* [^\s#\\] # if we match, m.end()-1 is the interesting char """, re.VERBOSE).match # Match start of stmts that should be followed by a dedent. _closere = re.compile(r""" \s* (?: return | break | continue | raise | pass ) \b """, re.VERBOSE).match # Chew up non-special chars as quickly as possible. If match is # successful, m.end() less 1 is the index of the last boring char # matched. If match is unsuccessful, the string starts with an # interesting char. _chew_ordinaryre = re.compile(r""" [^[\](){}#'"\\]+ """, re.VERBOSE).match class StringTranslatePseudoMapping(Mapping): r"""Utility class to be used with str.translate() This Mapping class wraps a given dict. When a value for a key is requested via __getitem__() or get(), the key is looked up in the given dict. If found there, the value from the dict is returned. Otherwise, the default value given upon initialization is returned. This allows using str.translate() to make some replacements, and to replace all characters for which no replacement was specified with a given character instead of leaving them as-is. For example, to replace everything except whitespace with 'x': >>> whitespace_chars = ' \t\n\r' >>> preserve_dict = {ord(c): ord(c) for c in whitespace_chars} >>> mapping = StringTranslatePseudoMapping(preserve_dict, ord('x')) >>> text = "a + b\tc\nd" >>> text.translate(mapping) 'x x x\tx\nx' """ def __init__(self, non_defaults, default_value): self._non_defaults = non_defaults self._default_value = default_value def _get(key, _get=non_defaults.get, _default=default_value): return _get(key, _default) self._get = _get def __getitem__(self, item): return self._get(item) def __len__(self): return len(self._non_defaults) def __iter__(self): return iter(self._non_defaults) def get(self, key, default=None): return self._get(key) class Parser: def __init__(self, indentwidth, tabwidth): self.indentwidth = indentwidth self.tabwidth = tabwidth def set_str(self, s): assert len(s) == 0 or s[-1] == '\n' self.str = s self.study_level = 0 # Return index of a good place to begin parsing, as close to the # end of the string as possible. This will be the start of some # popular stmt like "if" or "def". Return None if none found: # the caller should pass more prior context then, if possible, or # if not (the entire program text up until the point of interest # has already been tried) pass 0 to set_lo. # # This will be reliable iff given a reliable is_char_in_string # function, meaning that when it says "no", it's absolutely # guaranteed that the char is not in a string. def find_good_parse_start(self, is_char_in_string=None, _synchre=_synchre): str, pos = self.str, None if not is_char_in_string: # no clue -- make the caller pass everything return None # Peek back from the end for a good place to start, # but don't try too often; pos will be left None, or # bumped to a legitimate synch point. limit = len(str) for tries in range(5): i = str.rfind(":\n", 0, limit) if i < 0: break i = str.rfind('\n', 0, i) + 1 # start of colon line m = _synchre(str, i, limit) if m and not is_char_in_string(m.start()): pos = m.start() break limit = i if pos is None: # Nothing looks like a block-opener, or stuff does # but is_char_in_string keeps returning true; most likely # we're in or near a giant string, the colorizer hasn't # caught up enough to be helpful, or there simply *aren't* # any interesting stmts. In any of these cases we're # going to have to parse the whole thing to be sure, so # give it one last try from the start, but stop wasting # time here regardless of the outcome. m = _synchre(str) if m and not is_char_in_string(m.start()): pos = m.start() return pos # Peeking back worked; look forward until _synchre no longer # matches. i = pos + 1 while 1: m = _synchre(str, i) if m: s, i = m.span() if not is_char_in_string(s): pos = s else: break return pos # Throw away the start of the string. Intended to be called with # find_good_parse_start's result. def set_lo(self, lo): assert lo == 0 or self.str[lo-1] == '\n' if lo > 0: self.str = self.str[lo:] # Build a translation table to map uninteresting chars to 'x', open # brackets to '(', close brackets to ')' while preserving quotes, # backslashes, newlines and hashes. This is to be passed to # str.translate() in _study1(). _tran = {} _tran.update((ord(c), ord('(')) for c in "({[") _tran.update((ord(c), ord(')')) for c in ")}]") _tran.update((ord(c), ord(c)) for c in "\"'\\\n#") _tran = StringTranslatePseudoMapping(_tran, default_value=ord('x')) # As quickly as humanly possible <wink>, find the line numbers (0- # based) of the non-continuation lines. # Creates self.{goodlines, continuation}. def _study1(self): if self.study_level >= 1: return self.study_level = 1 # Map all uninteresting characters to "x", all open brackets # to "(", all close brackets to ")", then collapse runs of # uninteresting characters. This can cut the number of chars # by a factor of 10-40, and so greatly speed the following loop. str = self.str str = str.translate(self._tran) str = str.replace('xxxxxxxx', 'x') str = str.replace('xxxx', 'x') str = str.replace('xx', 'x') str = str.replace('xx', 'x') str = str.replace('\nx', '\n') # note that replacing x\n with \n would be incorrect, because # x may be preceded by a backslash # March over the squashed version of the program, accumulating # the line numbers of non-continued stmts, and determining # whether & why the last stmt is a continuation. continuation = C_NONE level = lno = 0 # level is nesting level; lno is line number self.goodlines = goodlines = [0] push_good = goodlines.append i, n = 0, len(str) while i < n: ch = str[i] i = i+1 # cases are checked in decreasing order of frequency if ch == 'x': continue if ch == '\n': lno = lno + 1 if level == 0: push_good(lno) # else we're in an unclosed bracket structure continue if ch == '(': level = level + 1 continue if ch == ')': if level: level = level - 1 # else the program is invalid, but we can't complain continue if ch == '"' or ch == "'": # consume the string quote = ch if str[i-1:i+2] == quote * 3: quote = quote * 3 firstlno = lno w = len(quote) - 1 i = i+w while i < n: ch = str[i] i = i+1 if ch == 'x': continue if str[i-1:i+w] == quote: i = i+w break if ch == '\n': lno = lno + 1 if w == 0: # unterminated single-quoted string if level == 0: push_good(lno) break continue if ch == '\\': assert i < n if str[i] == '\n': lno = lno + 1 i = i+1 continue # else comment char or paren inside string else: # didn't break out of the loop, so we're still # inside a string if (lno - 1) == firstlno: # before the previous \n in str, we were in the first # line of the string continuation = C_STRING_FIRST_LINE else: continuation = C_STRING_NEXT_LINES continue # with outer loop if ch == '#': # consume the comment i = str.find('\n', i) assert i >= 0 continue assert ch == '\\' assert i < n if str[i] == '\n': lno = lno + 1 if i+1 == n: continuation = C_BACKSLASH i = i+1 # The last stmt may be continued for all 3 reasons. # String continuation takes precedence over bracket # continuation, which beats backslash continuation. if (continuation != C_STRING_FIRST_LINE and continuation != C_STRING_NEXT_LINES and level > 0): continuation = C_BRACKET self.continuation = continuation # Push the final line number as a sentinel value, regardless of # whether it's continued. assert (continuation == C_NONE) == (goodlines[-1] == lno) if goodlines[-1] != lno: push_good(lno) def get_continuation_type(self): self._study1() return self.continuation # study1 was sufficient to determine the continuation status, # but doing more requires looking at every character. study2 # does this for the last interesting statement in the block. # Creates: # self.stmt_start, stmt_end # slice indices of last interesting stmt # self.stmt_bracketing # the bracketing structure of the last interesting stmt; # for example, for the statement "say(boo) or die", stmt_bracketing # will be [(0, 0), (3, 1), (8, 0)]. Strings and comments are # treated as brackets, for the matter. # self.lastch # last non-whitespace character before optional trailing # comment # self.lastopenbracketpos # if continuation is C_BRACKET, index of last open bracket def _study2(self): if self.study_level >= 2: return self._study1() self.study_level = 2 # Set p and q to slice indices of last interesting stmt. str, goodlines = self.str, self.goodlines i = len(goodlines) - 1 p = len(str) # index of newest line while i: assert p # p is the index of the stmt at line number goodlines[i]. # Move p back to the stmt at line number goodlines[i-1]. q = p for nothing in range(goodlines[i-1], goodlines[i]): # tricky: sets p to 0 if no preceding newline p = str.rfind('\n', 0, p-1) + 1 # The stmt str[p:q] isn't a continuation, but may be blank # or a non-indenting comment line. if _junkre(str, p): i = i-1 else: break if i == 0: # nothing but junk! assert p == 0 q = p self.stmt_start, self.stmt_end = p, q # Analyze this stmt, to find the last open bracket (if any) # and last interesting character (if any). lastch = "" stack = [] # stack of open bracket indices push_stack = stack.append bracketing = [(p, 0)] while p < q: # suck up all except ()[]{}'"#\\ m = _chew_ordinaryre(str, p, q) if m: # we skipped at least one boring char newp = m.end() # back up over totally boring whitespace i = newp - 1 # index of last boring char while i >= p and str[i] in " \t\n": i = i-1 if i >= p: lastch = str[i] p = newp if p >= q: break ch = str[p] if ch in "([{": push_stack(p) bracketing.append((p, len(stack))) lastch = ch p = p+1 continue if ch in ")]}": if stack: del stack[-1] lastch = ch p = p+1 bracketing.append((p, len(stack))) continue if ch == '"' or ch == "'": # consume string # Note that study1 did this with a Python loop, but # we use a regexp here; the reason is speed in both # cases; the string may be huge, but study1 pre-squashed # strings to a couple of characters per line. study1 # also needed to keep track of newlines, and we don't # have to. bracketing.append((p, len(stack)+1)) lastch = ch p = _match_stringre(str, p, q).end() bracketing.append((p, len(stack))) continue if ch == '#': # consume comment and trailing newline bracketing.append((p, len(stack)+1)) p = str.find('\n', p, q) + 1 assert p > 0 bracketing.append((p, len(stack))) continue assert ch == '\\' p = p+1 # beyond backslash assert p < q if str[p] != '\n': # the program is invalid, but can't complain lastch = ch + str[p] p = p+1 # beyond escaped char # end while p < q: self.lastch = lastch if stack: self.lastopenbracketpos = stack[-1] self.stmt_bracketing = tuple(bracketing) # Assuming continuation is C_BRACKET, return the number # of spaces the next line should be indented. def compute_bracket_indent(self): self._study2() assert self.continuation == C_BRACKET j = self.lastopenbracketpos str = self.str n = len(str) origi = i = str.rfind('\n', 0, j) + 1 j = j+1 # one beyond open bracket # find first list item; set i to start of its line while j < n: m = _itemre(str, j) if m: j = m.end() - 1 # index of first interesting char extra = 0 break else: # this line is junk; advance to next line i = j = str.find('\n', j) + 1 else: # nothing interesting follows the bracket; # reproduce the bracket line's indentation + a level j = i = origi while str[j] in " \t": j = j+1 extra = self.indentwidth return len(str[i:j].expandtabs(self.tabwidth)) + extra # Return number of physical lines in last stmt (whether or not # it's an interesting stmt! this is intended to be called when # continuation is C_BACKSLASH). def get_num_lines_in_stmt(self): self._study1() goodlines = self.goodlines return goodlines[-1] - goodlines[-2] # Assuming continuation is C_BACKSLASH, return the number of spaces # the next line should be indented. Also assuming the new line is # the first one following the initial line of the stmt. def compute_backslash_indent(self): self._study2() assert self.continuation == C_BACKSLASH str = self.str i = self.stmt_start while str[i] in " \t": i = i+1 startpos = i # See whether the initial line starts an assignment stmt; i.e., # look for an = operator endpos = str.find('\n', startpos) + 1 found = level = 0 while i < endpos: ch = str[i] if ch in "([{": level = level + 1 i = i+1 elif ch in ")]}": if level: level = level - 1 i = i+1 elif ch == '"' or ch == "'": i = _match_stringre(str, i, endpos).end() elif ch == '#': break elif level == 0 and ch == '=' and \ (i == 0 or str[i-1] not in "=<>!") and \ str[i+1] != '=': found = 1 break else: i = i+1 if found: # found a legit =, but it may be the last interesting # thing on the line i = i+1 # move beyond the = found = re.match(r"\s*\\", str[i:endpos]) is None if not found: # oh well ... settle for moving beyond the first chunk # of non-whitespace chars i = startpos while str[i] not in " \t\n": i = i+1 return len(str[self.stmt_start:i].expandtabs(\ self.tabwidth)) + 1 # Return the leading whitespace on the initial line of the last # interesting stmt. def get_base_indent_string(self): self._study2() i, n = self.stmt_start, self.stmt_end j = i str = self.str while j < n and str[j] in " \t": j = j + 1 return str[i:j] # Did the last interesting stmt open a block? def is_block_opener(self): self._study2() return self.lastch == ':' # Did the last interesting stmt close a block? def is_block_closer(self): self._study2() return _closere(self.str, self.stmt_start) is not None # index of last open bracket ({[, or None if none lastopenbracketpos = None def get_last_open_bracket_pos(self): self._study2() return self.lastopenbracketpos # the structure of the bracketing of the last interesting statement, # in the format defined in _study2, or None if the text didn't contain # anything stmt_bracketing = None def get_last_stmt_bracketing(self): self._study2() return self.stmt_bracketing