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Editing: lexer.py
"""Implements a Jinja / Python combination lexer. The ``Lexer`` class is used to do some preprocessing. It filters out invalid operators like the bitshift operators we don't allow in templates. It separates template code and python code in expressions. """ import re import typing as t from ast import literal_eval from collections import deque from sys import intern from ._identifier import pattern as name_re from .exceptions import TemplateSyntaxError from .utils import LRUCache if t.TYPE_CHECKING: import typing_extensions as te from .environment import Environment # cache for the lexers. Exists in order to be able to have multiple # environments with the same lexer _lexer_cache: t.MutableMapping[t.Tuple, "Lexer"] = LRUCache(50) # type: ignore # static regular expressions whitespace_re = re.compile(r"\s+") newline_re = re.compile(r"(\r\n|\r|\n)") string_re = re.compile( r"('([^'\\]*(?:\\.[^'\\]*)*)'" r'|"([^"\\]*(?:\\.[^"\\]*)*)")', re.S ) integer_re = re.compile( r""" ( 0b(_?[0-1])+ # binary | 0o(_?[0-7])+ # octal | 0x(_?[\da-f])+ # hex | [1-9](_?\d)* # decimal | 0(_?0)* # decimal zero ) """, re.IGNORECASE | re.VERBOSE, ) float_re = re.compile( r""" (?<!\.) # doesn't start with a . (\d+_)*\d+ # digits, possibly _ separated ( (\.(\d+_)*\d+)? # optional fractional part e[+\-]?(\d+_)*\d+ # exponent part | \.(\d+_)*\d+ # required fractional part ) """, re.IGNORECASE | re.VERBOSE, ) # internal the tokens and keep references to them TOKEN_ADD = intern("add") TOKEN_ASSIGN = intern("assign") TOKEN_COLON = intern("colon") TOKEN_COMMA = intern("comma") TOKEN_DIV = intern("div") TOKEN_DOT = intern("dot") TOKEN_EQ = intern("eq") TOKEN_FLOORDIV = intern("floordiv") TOKEN_GT = intern("gt") TOKEN_GTEQ = intern("gteq") TOKEN_LBRACE = intern("lbrace") TOKEN_LBRACKET = intern("lbracket") TOKEN_LPAREN = intern("lparen") TOKEN_LT = intern("lt") TOKEN_LTEQ = intern("lteq") TOKEN_MOD = intern("mod") TOKEN_MUL = intern("mul") TOKEN_NE = intern("ne") TOKEN_PIPE = intern("pipe") TOKEN_POW = intern("pow") TOKEN_RBRACE = intern("rbrace") TOKEN_RBRACKET = intern("rbracket") TOKEN_RPAREN = intern("rparen") TOKEN_SEMICOLON = intern("semicolon") TOKEN_SUB = intern("sub") TOKEN_TILDE = intern("tilde") TOKEN_WHITESPACE = intern("whitespace") TOKEN_FLOAT = intern("float") TOKEN_INTEGER = intern("integer") TOKEN_NAME = intern("name") TOKEN_STRING = intern("string") TOKEN_OPERATOR = intern("operator") TOKEN_BLOCK_BEGIN = intern("block_begin") TOKEN_BLOCK_END = intern("block_end") TOKEN_VARIABLE_BEGIN = intern("variable_begin") TOKEN_VARIABLE_END = intern("variable_end") TOKEN_RAW_BEGIN = intern("raw_begin") TOKEN_RAW_END = intern("raw_end") TOKEN_COMMENT_BEGIN = intern("comment_begin") TOKEN_COMMENT_END = intern("comment_end") TOKEN_COMMENT = intern("comment") TOKEN_LINESTATEMENT_BEGIN = intern("linestatement_begin") TOKEN_LINESTATEMENT_END = intern("linestatement_end") TOKEN_LINECOMMENT_BEGIN = intern("linecomment_begin") TOKEN_LINECOMMENT_END = intern("linecomment_end") TOKEN_LINECOMMENT = intern("linecomment") TOKEN_DATA = intern("data") TOKEN_INITIAL = intern("initial") TOKEN_EOF = intern("eof") # bind operators to token types operators = { "+": TOKEN_ADD, "-": TOKEN_SUB, "/": TOKEN_DIV, "//": TOKEN_FLOORDIV, "*": TOKEN_MUL, "%": TOKEN_MOD, "**": TOKEN_POW, "~": TOKEN_TILDE, "[": TOKEN_LBRACKET, "]": TOKEN_RBRACKET, "(": TOKEN_LPAREN, ")": TOKEN_RPAREN, "{": TOKEN_LBRACE, "}": TOKEN_RBRACE, "==": TOKEN_EQ, "!=": TOKEN_NE, ">": TOKEN_GT, ">=": TOKEN_GTEQ, "<": TOKEN_LT, "<=": TOKEN_LTEQ, "=": TOKEN_ASSIGN, ".": TOKEN_DOT, ":": TOKEN_COLON, "|": TOKEN_PIPE, ",": TOKEN_COMMA, ";": TOKEN_SEMICOLON, } reverse_operators = {v: k for k, v in operators.items()} assert len(operators) == len(reverse_operators), "operators dropped" operator_re = re.compile( f"({'|'.join(re.escape(x) for x in sorted(operators, key=lambda x: -len(x)))})" ) ignored_tokens = frozenset( [ TOKEN_COMMENT_BEGIN, TOKEN_COMMENT, TOKEN_COMMENT_END, TOKEN_WHITESPACE, TOKEN_LINECOMMENT_BEGIN, TOKEN_LINECOMMENT_END, TOKEN_LINECOMMENT, ] ) ignore_if_empty = frozenset( [TOKEN_WHITESPACE, TOKEN_DATA, TOKEN_COMMENT, TOKEN_LINECOMMENT] ) def _describe_token_type(token_type: str) -> str: if token_type in reverse_operators: return reverse_operators[token_type] return { TOKEN_COMMENT_BEGIN: "begin of comment", TOKEN_COMMENT_END: "end of comment", TOKEN_COMMENT: "comment", TOKEN_LINECOMMENT: "comment", TOKEN_BLOCK_BEGIN: "begin of statement block", TOKEN_BLOCK_END: "end of statement block", TOKEN_VARIABLE_BEGIN: "begin of print statement", TOKEN_VARIABLE_END: "end of print statement", TOKEN_LINESTATEMENT_BEGIN: "begin of line statement", TOKEN_LINESTATEMENT_END: "end of line statement", TOKEN_DATA: "template data / text", TOKEN_EOF: "end of template", }.get(token_type, token_type) def describe_token(token: "Token") -> str: """Returns a description of the token.""" if token.type == TOKEN_NAME: return token.value return _describe_token_type(token.type) def describe_token_expr(expr: str) -> str: """Like `describe_token` but for token expressions.""" if ":" in expr: type, value = expr.split(":", 1) if type == TOKEN_NAME: return value else: type = expr return _describe_token_type(type) def count_newlines(value: str) -> int: """Count the number of newline characters in the string. This is useful for extensions that filter a stream. """ return len(newline_re.findall(value)) def compile_rules(environment: "Environment") -> t.List[t.Tuple[str, str]]: """Compiles all the rules from the environment into a list of rules.""" e = re.escape rules = [ ( len(environment.comment_start_string), TOKEN_COMMENT_BEGIN, e(environment.comment_start_string), ), ( len(environment.block_start_string), TOKEN_BLOCK_BEGIN, e(environment.block_start_string), ), ( len(environment.variable_start_string), TOKEN_VARIABLE_BEGIN, e(environment.variable_start_string), ), ] if environment.line_statement_prefix is not None: rules.append( ( len(environment.line_statement_prefix), TOKEN_LINESTATEMENT_BEGIN, r"^[ \t\v]*" + e(environment.line_statement_prefix), ) ) if environment.line_comment_prefix is not None: rules.append( ( len(environment.line_comment_prefix), TOKEN_LINECOMMENT_BEGIN, r"(?:^|(?<=\S))[^\S\r\n]*" + e(environment.line_comment_prefix), ) ) return [x[1:] for x in sorted(rules, reverse=True)] class Failure: """Class that raises a `TemplateSyntaxError` if called. Used by the `Lexer` to specify known errors. """ def __init__( self, message: str, cls: t.Type[TemplateSyntaxError] = TemplateSyntaxError ) -> None: self.message = message self.error_class = cls def __call__(self, lineno: int, filename: str) -> "te.NoReturn": raise self.error_class(self.message, lineno, filename) class Token(t.NamedTuple): lineno: int type: str value: str def __str__(self) -> str: return describe_token(self) def test(self, expr: str) -> bool: """Test a token against a token expression. This can either be a token type or ``'token_type:token_value'``. This can only test against string values and types. """ # here we do a regular string equality check as test_any is usually # passed an iterable of not interned strings. if self.type == expr: return True if ":" in expr: return expr.split(":", 1) == [self.type, self.value] return False def test_any(self, *iterable: str) -> bool: """Test against multiple token expressions.""" return any(self.test(expr) for expr in iterable) class TokenStreamIterator: """The iterator for tokenstreams. Iterate over the stream until the eof token is reached. """ def __init__(self, stream: "TokenStream") -> None: self.stream = stream def __iter__(self) -> "TokenStreamIterator": return self def __next__(self) -> Token: token = self.stream.current if token.type is TOKEN_EOF: self.stream.close() raise StopIteration next(self.stream) return token class TokenStream: """A token stream is an iterable that yields :class:`Token`\\s. The parser however does not iterate over it but calls :meth:`next` to go one token ahead. The current active token is stored as :attr:`current`. """ def __init__( self, generator: t.Iterable[Token], name: t.Optional[str], filename: t.Optional[str], ): self._iter = iter(generator) self._pushed: "te.Deque[Token]" = deque() self.name = name self.filename = filename self.closed = False self.current = Token(1, TOKEN_INITIAL, "") next(self) def __iter__(self) -> TokenStreamIterator: return TokenStreamIterator(self) def __bool__(self) -> bool: return bool(self._pushed) or self.current.type is not TOKEN_EOF @property def eos(self) -> bool: """Are we at the end of the stream?""" return not self def push(self, token: Token) -> None: """Push a token back to the stream.""" self._pushed.append(token) def look(self) -> Token: """Look at the next token.""" old_token = next(self) result = self.current self.push(result) self.current = old_token return result def skip(self, n: int = 1) -> None: """Got n tokens ahead.""" for _ in range(n): next(self) def next_if(self, expr: str) -> t.Optional[Token]: """Perform the token test and return the token if it matched. Otherwise the return value is `None`. """ if self.current.test(expr): return next(self) return None def skip_if(self, expr: str) -> bool: """Like :meth:`next_if` but only returns `True` or `False`.""" return self.next_if(expr) is not None def __next__(self) -> Token: """Go one token ahead and return the old one. Use the built-in :func:`next` instead of calling this directly. """ rv = self.current if self._pushed: self.current = self._pushed.popleft() elif self.current.type is not TOKEN_EOF: try: self.current = next(self._iter) except StopIteration: self.close() return rv def close(self) -> None: """Close the stream.""" self.current = Token(self.current.lineno, TOKEN_EOF, "") self._iter = iter(()) self.closed = True def expect(self, expr: str) -> Token: """Expect a given token type and return it. This accepts the same argument as :meth:`jinja2.lexer.Token.test`. """ if not self.current.test(expr): expr = describe_token_expr(expr) if self.current.type is TOKEN_EOF: raise TemplateSyntaxError( f"unexpected end of template, expected {expr!r}.", self.current.lineno, self.name, self.filename, ) raise TemplateSyntaxError( f"expected token {expr!r}, got {describe_token(self.current)!r}", self.current.lineno, self.name, self.filename, ) return next(self) def get_lexer(environment: "Environment") -> "Lexer": """Return a lexer which is probably cached.""" key = ( environment.block_start_string, environment.block_end_string, environment.variable_start_string, environment.variable_end_string, environment.comment_start_string, environment.comment_end_string, environment.line_statement_prefix, environment.line_comment_prefix, environment.trim_blocks, environment.lstrip_blocks, environment.newline_sequence, environment.keep_trailing_newline, ) lexer = _lexer_cache.get(key) if lexer is None: _lexer_cache[key] = lexer = Lexer(environment) return lexer class OptionalLStrip(tuple): """A special tuple for marking a point in the state that can have lstrip applied. """ __slots__ = () # Even though it looks like a no-op, creating instances fails # without this. def __new__(cls, *members, **kwargs): # type: ignore return super().__new__(cls, members) class _Rule(t.NamedTuple): pattern: t.Pattern[str] tokens: t.Union[str, t.Tuple[str, ...], t.Tuple[Failure]] command: t.Optional[str] class Lexer: """Class that implements a lexer for a given environment. Automatically created by the environment class, usually you don't have to do that. Note that the lexer is not automatically bound to an environment. Multiple environments can share the same lexer. """ def __init__(self, environment: "Environment") -> None: # shortcuts e = re.escape def c(x: str) -> t.Pattern[str]: return re.compile(x, re.M | re.S) # lexing rules for tags tag_rules: t.List[_Rule] = [ _Rule(whitespace_re, TOKEN_WHITESPACE, None), _Rule(float_re, TOKEN_FLOAT, None), _Rule(integer_re, TOKEN_INTEGER, None), _Rule(name_re, TOKEN_NAME, None), _Rule(string_re, TOKEN_STRING, None), _Rule(operator_re, TOKEN_OPERATOR, None), ] # assemble the root lexing rule. because "|" is ungreedy # we have to sort by length so that the lexer continues working # as expected when we have parsing rules like <% for block and # <%= for variables. (if someone wants asp like syntax) # variables are just part of the rules if variable processing # is required. root_tag_rules = compile_rules(environment) block_start_re = e(environment.block_start_string) block_end_re = e(environment.block_end_string) comment_end_re = e(environment.comment_end_string) variable_end_re = e(environment.variable_end_string) # block suffix if trimming is enabled block_suffix_re = "\\n?" if environment.trim_blocks else "" # If lstrip is enabled, it should not be applied if there is any # non-whitespace between the newline and block. self.lstrip_unless_re = c(r"[^ \t]") if environment.lstrip_blocks else None self.newline_sequence = environment.newline_sequence self.keep_trailing_newline = environment.keep_trailing_newline root_raw_re = ( fr"(?P<raw_begin>{block_start_re}(\-|\+|)\s*raw\s*" fr"(?:\-{block_end_re}\s*|{block_end_re}))" ) root_parts_re = "|".join( [root_raw_re] + [fr"(?P<{n}>{r}(\-|\+|))" for n, r in root_tag_rules] ) # global lexing rules self.rules: t.Dict[str, t.List[_Rule]] = { "root": [ # directives _Rule( c(fr"(.*?)(?:{root_parts_re})"), OptionalLStrip(TOKEN_DATA, "#bygroup"), # type: ignore "#bygroup", ), # data _Rule(c(".+"), TOKEN_DATA, None), ], # comments TOKEN_COMMENT_BEGIN: [ _Rule( c( fr"(.*?)((?:\+{comment_end_re}|\-{comment_end_re}\s*" fr"|{comment_end_re}{block_suffix_re}))" ), (TOKEN_COMMENT, TOKEN_COMMENT_END), "#pop", ), _Rule(c(r"(.)"), (Failure("Missing end of comment tag"),), None), ], # blocks TOKEN_BLOCK_BEGIN: [ _Rule( c( fr"(?:\+{block_end_re}|\-{block_end_re}\s*" fr"|{block_end_re}{block_suffix_re})" ), TOKEN_BLOCK_END, "#pop", ), ] + tag_rules, # variables TOKEN_VARIABLE_BEGIN: [ _Rule( c(fr"\-{variable_end_re}\s*|{variable_end_re}"), TOKEN_VARIABLE_END, "#pop", ) ] + tag_rules, # raw block TOKEN_RAW_BEGIN: [ _Rule( c( fr"(.*?)((?:{block_start_re}(\-|\+|))\s*endraw\s*" fr"(?:\+{block_end_re}|\-{block_end_re}\s*" fr"|{block_end_re}{block_suffix_re}))" ), OptionalLStrip(TOKEN_DATA, TOKEN_RAW_END), # type: ignore "#pop", ), _Rule(c(r"(.)"), (Failure("Missing end of raw directive"),), None), ], # line statements TOKEN_LINESTATEMENT_BEGIN: [ _Rule(c(r"\s*(\n|$)"), TOKEN_LINESTATEMENT_END, "#pop") ] + tag_rules, # line comments TOKEN_LINECOMMENT_BEGIN: [ _Rule( c(r"(.*?)()(?=\n|$)"), (TOKEN_LINECOMMENT, TOKEN_LINECOMMENT_END), "#pop", ) ], } def _normalize_newlines(self, value: str) -> str: """Replace all newlines with the configured sequence in strings and template data. """ return newline_re.sub(self.newline_sequence, value) def tokenize( self, source: str, name: t.Optional[str] = None, filename: t.Optional[str] = None, state: t.Optional[str] = None, ) -> TokenStream: """Calls tokeniter + tokenize and wraps it in a token stream.""" stream = self.tokeniter(source, name, filename, state) return TokenStream(self.wrap(stream, name, filename), name, filename) def wrap( self, stream: t.Iterable[t.Tuple[int, str, str]], name: t.Optional[str] = None, filename: t.Optional[str] = None, ) -> t.Iterator[Token]: """This is called with the stream as returned by `tokenize` and wraps every token in a :class:`Token` and converts the value. """ for lineno, token, value_str in stream: if token in ignored_tokens: continue value: t.Any = value_str if token == TOKEN_LINESTATEMENT_BEGIN: token = TOKEN_BLOCK_BEGIN elif token == TOKEN_LINESTATEMENT_END: token = TOKEN_BLOCK_END # we are not interested in those tokens in the parser elif token in (TOKEN_RAW_BEGIN, TOKEN_RAW_END): continue elif token == TOKEN_DATA: value = self._normalize_newlines(value_str) elif token == "keyword": token = value_str elif token == TOKEN_NAME: value = value_str if not value.isidentifier(): raise TemplateSyntaxError( "Invalid character in identifier", lineno, name, filename ) elif token == TOKEN_STRING: # try to unescape string try: value = ( self._normalize_newlines(value_str[1:-1]) .encode("ascii", "backslashreplace") .decode("unicode-escape") ) except Exception as e: msg = str(e).split(":")[-1].strip() raise TemplateSyntaxError(msg, lineno, name, filename) from e elif token == TOKEN_INTEGER: value = int(value_str.replace("_", ""), 0) elif token == TOKEN_FLOAT: # remove all "_" first to support more Python versions value = literal_eval(value_str.replace("_", "")) elif token == TOKEN_OPERATOR: token = operators[value_str] yield Token(lineno, token, value) def tokeniter( self, source: str, name: t.Optional[str], filename: t.Optional[str] = None, state: t.Optional[str] = None, ) -> t.Iterator[t.Tuple[int, str, str]]: """This method tokenizes the text and returns the tokens in a generator. Use this method if you just want to tokenize a template. .. versionchanged:: 3.0 Only ``\\n``, ``\\r\\n`` and ``\\r`` are treated as line breaks. """ lines = newline_re.split(source)[::2] if not self.keep_trailing_newline and lines[-1] == "": del lines[-1] source = "\n".join(lines) pos = 0 lineno = 1 stack = ["root"] if state is not None and state != "root": assert state in ("variable", "block"), "invalid state" stack.append(state + "_begin") statetokens = self.rules[stack[-1]] source_length = len(source) balancing_stack: t.List[str] = [] lstrip_unless_re = self.lstrip_unless_re newlines_stripped = 0 line_starting = True while True: # tokenizer loop for regex, tokens, new_state in statetokens: m = regex.match(source, pos) # if no match we try again with the next rule if m is None: continue # we only match blocks and variables if braces / parentheses # are balanced. continue parsing with the lower rule which # is the operator rule. do this only if the end tags look # like operators if balancing_stack and tokens in ( TOKEN_VARIABLE_END, TOKEN_BLOCK_END, TOKEN_LINESTATEMENT_END, ): continue # tuples support more options if isinstance(tokens, tuple): groups = m.groups() if isinstance(tokens, OptionalLStrip): # Rule supports lstrip. Match will look like # text, block type, whitespace control, type, control, ... text = groups[0] # Skipping the text and first type, every other group is the # whitespace control for each type. One of the groups will be # -, +, or empty string instead of None. strip_sign = next(g for g in groups[2::2] if g is not None) if strip_sign == "-": # Strip all whitespace between the text and the tag. stripped = text.rstrip() newlines_stripped = text[len(stripped) :].count("\n") groups = [stripped, *groups[1:]] elif ( # Not marked for preserving whitespace. strip_sign != "+" # lstrip is enabled. and lstrip_unless_re is not None # Not a variable expression. and not m.groupdict().get(TOKEN_VARIABLE_BEGIN) ): # The start of text between the last newline and the tag. l_pos = text.rfind("\n") + 1 if l_pos > 0 or line_starting: # If there's only whitespace between the newline and the # tag, strip it. if not lstrip_unless_re.search(text, l_pos): groups = [text[:l_pos], *groups[1:]] for idx, token in enumerate(tokens): # failure group if token.__class__ is Failure: raise token(lineno, filename) # bygroup is a bit more complex, in that case we # yield for the current token the first named # group that matched elif token == "#bygroup": for key, value in m.groupdict().items(): if value is not None: yield lineno, key, value lineno += value.count("\n") break else: raise RuntimeError( f"{regex!r} wanted to resolve the token dynamically" " but no group matched" ) # normal group else: data = groups[idx] if data or token not in ignore_if_empty: yield lineno, token, data lineno += data.count("\n") + newlines_stripped newlines_stripped = 0 # strings as token just are yielded as it. else: data = m.group() # update brace/parentheses balance if tokens == TOKEN_OPERATOR: if data == "{": balancing_stack.append("}") elif data == "(": balancing_stack.append(")") elif data == "[": balancing_stack.append("]") elif data in ("}", ")", "]"): if not balancing_stack: raise TemplateSyntaxError( f"unexpected '{data}'", lineno, name, filename ) expected_op = balancing_stack.pop() if expected_op != data: raise TemplateSyntaxError( f"unexpected '{data}', expected '{expected_op}'", lineno, name, filename, ) # yield items if data or tokens not in ignore_if_empty: yield lineno, tokens, data lineno += data.count("\n") line_starting = m.group()[-1:] == "\n" # fetch new position into new variable so that we can check # if there is a internal parsing error which would result # in an infinite loop pos2 = m.end() # handle state changes if new_state is not None: # remove the uppermost state if new_state == "#pop": stack.pop() # resolve the new state by group checking elif new_state == "#bygroup": for key, value in m.groupdict().items(): if value is not None: stack.append(key) break else: raise RuntimeError( f"{regex!r} wanted to resolve the new state dynamically" f" but no group matched" ) # direct state name given else: stack.append(new_state) statetokens = self.rules[stack[-1]] # we are still at the same position and no stack change. # this means a loop without break condition, avoid that and # raise error elif pos2 == pos: raise RuntimeError( f"{regex!r} yielded empty string without stack change" ) # publish new function and start again pos = pos2 break # if loop terminated without break we haven't found a single match # either we are at the end of the file or we have a problem else: # end of text if pos >= source_length: return # something went wrong raise TemplateSyntaxError( f"unexpected char {source[pos]!r} at {pos}", lineno, name, filename )
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