jinja2/parser.py

# -*- coding: utf-8 -*-
"""
    jinja2.parser
    ~~~~~~~~~~~~~

    Implements the template parser.

    :copyright: 2008 by Armin Ronacher.
    :license: BSD, see LICENSE for more details.
"""
from jinja2 import nodes
from jinja2.exceptions import TemplateSyntaxError, TemplateAssertionError


_statement_keywords = frozenset(['for', 'if', 'block', 'extends', 'print',
                                 'macro', 'include', 'from', 'import',
                                 'set'])
_compare_operators = frozenset(['eq', 'ne', 'lt', 'lteq', 'gt', 'gteq'])


class Parser(object):
    """This is the central parsing class Jinja2 uses.  It's passed to
    extensions and can be used to parse expressions or statements.
    """

    def __init__(self, environment, source, name=None, filename=None):
        self.environment = environment
        self.source = unicode(source)
        self.name = name
        self.filename = filename
        self.closed = False
        self.stream = environment.lexer.tokenize(self.source, name, filename)
        self.extensions = {}
        for extension in environment.extensions.itervalues():
            for tag in extension.tags:
                self.extensions[tag] = extension.parse
        self._last_identifier = 0

    def fail(self, msg, lineno=None, exc=TemplateSyntaxError):
        """Convenience method that raises `exc` with the message, passed
        line number or last line number as well as the current name and
        filename.
        """
        if lineno is None:
            lineno = self.stream.current.lineno
        raise exc(msg, lineno, self.name, self.filename)

    def is_tuple_end(self, extra_end_rules=None):
        """Are we at the end of a tuple?"""
        if self.stream.current.type in ('variable_end', 'block_end', 'rparen'):
            return True
        elif extra_end_rules is not None:
            return self.stream.current.test_any(extra_end_rules)
        return False

    def free_identifier(self, lineno=None):
        """Return a new free identifier as :class:`~jinja2.nodes.InternalName`."""
        self._last_identifier += 1
        rv = object.__new__(nodes.InternalName)
        nodes.Node.__init__(rv, 'fi%d' % self._last_identifier, lineno=lineno)
        return rv

    def parse_statement(self):
        """Parse a single statement."""
        token = self.stream.current
        if token.type is not 'name':
            self.fail('tag name expected', token.lineno)
        if token.value in _statement_keywords:
            return getattr(self, 'parse_' + self.stream.current.value)()
        if token.value == 'call':
            return self.parse_call_block()
        if token.value == 'filter':
            return self.parse_filter_block()
        ext = self.extensions.get(token.value)
        if ext is not None:
            return ext(self)
        self.fail('unknown tag %r' % token.value, token.lineno)

    def parse_statements(self, end_tokens, drop_needle=False):
        """Parse multiple statements into a list until one of the end tokens
        is reached.  This is used to parse the body of statements as it also
        parses template data if appropriate.  The parser checks first if the
        current token is a colon and skips it if there is one.  Then it checks
        for the block end and parses until if one of the `end_tokens` is
        reached.  Per default the active token in the stream at the end of
        the call is the matched end token.  If this is not wanted `drop_needle`
        can be set to `True` and the end token is removed.
        """
        # the first token may be a colon for python compatibility
        self.stream.skip_if('colon')

        # in the future it would be possible to add whole code sections
        # by adding some sort of end of statement token and parsing those here.
        self.stream.expect('block_end')
        result = self.subparse(end_tokens)

        if drop_needle:
            self.stream.next()
        return result

    def parse_set(self):
        """Parse an assign statement."""
        lineno = self.stream.next().lineno
        target = self.parse_assign_target()
        self.stream.expect('assign')
        expr = self.parse_tuple()
        return nodes.Assign(target, expr, lineno=lineno)

    def parse_for(self):
        """Parse a for loop."""
        lineno = self.stream.expect('name:for').lineno
        target = self.parse_assign_target(extra_end_rules=('name:in',))
        self.stream.expect('name:in')
        iter = self.parse_tuple(with_condexpr=False,
                                extra_end_rules=('name:recursive',))
        test = None
        if self.stream.skip_if('name:if'):
            test = self.parse_expression()
        recursive = self.stream.skip_if('name:recursive')
        body = self.parse_statements(('name:endfor', 'name:else'))
        if self.stream.next().value == 'endfor':
            else_ = []
        else:
            else_ = self.parse_statements(('name:endfor',), drop_needle=True)
        return nodes.For(target, iter, body, else_, test,
                         recursive, lineno=lineno)

    def parse_if(self):
        """Parse an if construct."""
        node = result = nodes.If(lineno=self.stream.expect('name:if').lineno)
        while 1:
            node.test = self.parse_tuple(with_condexpr=False)
            node.body = self.parse_statements(('name:elif', 'name:else',
                                               'name:endif'))
            token = self.stream.next()
            if token.test('name:elif'):
                new_node = nodes.If(lineno=self.stream.current.lineno)
                node.else_ = [new_node]
                node = new_node
                continue
            elif token.test('name:else'):
                node.else_ = self.parse_statements(('name:endif',),
                                                   drop_needle=True)
            else:
                node.else_ = []
            break
        return result

    def parse_block(self):
        node = nodes.Block(lineno=self.stream.next().lineno)
        node.name = self.stream.expect('name').value
        node.body = self.parse_statements(('name:endblock',), drop_needle=True)
        self.stream.skip_if('name:' + node.name)
        return node

    def parse_extends(self):
        node = nodes.Extends(lineno=self.stream.next().lineno)
        node.template = self.parse_expression()
        return node

    def parse_import_context(self, node, default):
        if self.stream.current.test_any('name:with', 'name:without') and \
           self.stream.look().test('name:context'):
            node.with_context = self.stream.next().value == 'with'
            self.stream.skip()
        else:
            node.with_context = default
        return node

    def parse_include(self):
        node = nodes.Include(lineno=self.stream.next().lineno)
        node.template = self.parse_expression()
        return self.parse_import_context(node, True)

    def parse_import(self):
        node = nodes.Import(lineno=self.stream.next().lineno)
        node.template = self.parse_expression()
        self.stream.expect('name:as')
        node.target = self.parse_assign_target(name_only=True).name
        return self.parse_import_context(node, False)

    def parse_from(self):
        node = nodes.FromImport(lineno=self.stream.next().lineno)
        node.template = self.parse_expression()
        self.stream.expect('name:import')
        node.names = []

        def parse_context():
            if self.stream.current.value in ('with', 'without') and \
               self.stream.look().test('name:context'):
                node.with_context = self.stream.next().value == 'with'
                self.stream.skip()
                return True
            return False

        while 1:
            if node.names:
                self.stream.expect('comma')
            if self.stream.current.type is 'name':
                if parse_context():
                    break
                target = self.parse_assign_target(name_only=True)
                if target.name.startswith('_'):
                    self.fail('names starting with an underline can not '
                              'be imported', target.lineno,
                              exc=TemplateAssertionError)
                if self.stream.skip_if('name:as'):
                    alias = self.parse_assign_target(name_only=True)
                    node.names.append((target.name, alias.name))
                else:
                    node.names.append(target.name)
                if parse_context() or self.stream.current.type is not 'comma':
                    break
            else:
                break
        if not hasattr(node, 'with_context'):
            node.with_context = False
            self.stream.skip_if('comma')
        return node

    def parse_signature(self, node):
        node.args = args = []
        node.defaults = defaults = []
        self.stream.expect('lparen')
        while self.stream.current.type is not 'rparen':
            if args:
                self.stream.expect('comma')
            arg = self.parse_assign_target(name_only=True)
            arg.set_ctx('param')
            if self.stream.skip_if('assign'):
                defaults.append(self.parse_expression())
            args.append(arg)
        self.stream.expect('rparen')

    def parse_call_block(self):
        node = nodes.CallBlock(lineno=self.stream.next().lineno)
        if self.stream.current.type is 'lparen':
            self.parse_signature(node)
        else:
            node.args = []
            node.defaults = []

        node.call = self.parse_expression()
        if not isinstance(node.call, nodes.Call):
            self.fail('expected call', node.lineno)
        node.body = self.parse_statements(('name:endcall',), drop_needle=True)
        return node

    def parse_filter_block(self):
        node = nodes.FilterBlock(lineno=self.stream.next().lineno)
        node.filter = self.parse_filter(None, start_inline=True)
        node.body = self.parse_statements(('name:endfilter',),
                                          drop_needle=True)
        return node

    def parse_macro(self):
        node = nodes.Macro(lineno=self.stream.next().lineno)
        node.name = self.parse_assign_target(name_only=True).name
        self.parse_signature(node)
        node.body = self.parse_statements(('name:endmacro',),
                                          drop_needle=True)
        return node

    def parse_print(self):
        node = nodes.Output(lineno=self.stream.next().lineno)
        node.nodes = []
        while self.stream.current.type is not 'block_end':
            if node.nodes:
                self.stream.expect('comma')
            node.nodes.append(self.parse_expression())
        return node

    def parse_assign_target(self, with_tuple=True, name_only=False,
                            extra_end_rules=None):
        """Parse an assignment target.  As Jinja2 allows assignments to
        tuples, this function can parse all allowed assignment targets.  Per
        default assignments to tuples are parsed, that can be disable however
        by setting `with_tuple` to `False`.  If only assignments to names are
        wanted `name_only` can be set to `True`.  The `extra_end_rules`
        parameter is forwarded to the tuple parsing function.
        """
        if name_only:
            token = self.stream.expect('name')
            target = nodes.Name(token.value, 'store', lineno=token.lineno)
        else:
            if with_tuple:
                target = self.parse_tuple(simplified=True,
                                          extra_end_rules=extra_end_rules)
            else:
                target = self.parse_primary(with_postfix=False)
            target.set_ctx('store')
        if not target.can_assign():
            self.fail('can\'t assign to %r' % target.__class__.
                      __name__.lower(), target.lineno)
        return target

    def parse_expression(self, with_condexpr=True):
        """Parse an expression.  Per default all expressions are parsed, if
        the optional `with_condexpr` parameter is set to `False` conditional
        expressions are not parsed.
        """
        if with_condexpr:
            return self.parse_condexpr()
        return self.parse_or()

    def parse_condexpr(self):
        lineno = self.stream.current.lineno
        expr1 = self.parse_or()
        while self.stream.skip_if('name:if'):
            expr2 = self.parse_or()
            self.stream.expect('name:else')
            expr3 = self.parse_condexpr()
            expr1 = nodes.CondExpr(expr2, expr1, expr3, lineno=lineno)
            lineno = self.stream.current.lineno
        return expr1

    def parse_or(self):
        lineno = self.stream.current.lineno
        left = self.parse_and()
        while self.stream.skip_if('name:or'):
            right = self.parse_and()
            left = nodes.Or(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_and(self):
        lineno = self.stream.current.lineno
        left = self.parse_compare()
        while self.stream.skip_if('name:and'):
            right = self.parse_compare()
            left = nodes.And(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_compare(self):
        lineno = self.stream.current.lineno
        expr = self.parse_add()
        ops = []
        while 1:
            token_type = self.stream.current.type
            if token_type in _compare_operators:
                self.stream.next()
                ops.append(nodes.Operand(token_type, self.parse_add()))
            elif self.stream.skip_if('name:in'):
                ops.append(nodes.Operand('in', self.parse_add()))
            elif self.stream.current.test('name:not') and \
                 self.stream.look().test('name:in'):
                self.stream.skip(2)
                ops.append(nodes.Operand('notin', self.parse_add()))
            else:
                break
            lineno = self.stream.current.lineno
        if not ops:
            return expr
        return nodes.Compare(expr, ops, lineno=lineno)

    def parse_add(self):
        lineno = self.stream.current.lineno
        left = self.parse_sub()
        while self.stream.current.type is 'add':
            self.stream.next()
            right = self.parse_sub()
            left = nodes.Add(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_sub(self):
        lineno = self.stream.current.lineno
        left = self.parse_concat()
        while self.stream.current.type is 'sub':
            self.stream.next()
            right = self.parse_concat()
            left = nodes.Sub(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_concat(self):
        lineno = self.stream.current.lineno
        args = [self.parse_mul()]
        while self.stream.current.type is 'tilde':
            self.stream.next()
            args.append(self.parse_mul())
        if len(args) == 1:
            return args[0]
        return nodes.Concat(args, lineno=lineno)

    def parse_mul(self):
        lineno = self.stream.current.lineno
        left = self.parse_div()
        while self.stream.current.type is 'mul':
            self.stream.next()
            right = self.parse_div()
            left = nodes.Mul(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_div(self):
        lineno = self.stream.current.lineno
        left = self.parse_floordiv()
        while self.stream.current.type is 'div':
            self.stream.next()
            right = self.parse_floordiv()
            left = nodes.Div(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_floordiv(self):
        lineno = self.stream.current.lineno
        left = self.parse_mod()
        while self.stream.current.type is 'floordiv':
            self.stream.next()
            right = self.parse_mod()
            left = nodes.FloorDiv(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_mod(self):
        lineno = self.stream.current.lineno
        left = self.parse_pow()
        while self.stream.current.type is 'mod':
            self.stream.next()
            right = self.parse_pow()
            left = nodes.Mod(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_pow(self):
        lineno = self.stream.current.lineno
        left = self.parse_unary()
        while self.stream.current.type is 'pow':
            self.stream.next()
            right = self.parse_unary()
            left = nodes.Pow(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left

    def parse_unary(self):
        token_type = self.stream.current.type
        lineno = self.stream.current.lineno
        if token_type is 'name' and self.stream.current.value == 'not':
            self.stream.next()
            node = self.parse_unary()
            return nodes.Not(node, lineno=lineno)
        if token_type is 'sub':
            self.stream.next()
            node = self.parse_unary()
            return nodes.Neg(node, lineno=lineno)
        if token_type is 'add':
            self.stream.next()
            node = self.parse_unary()
            return nodes.Pos(node, lineno=lineno)
        return self.parse_primary()

    def parse_primary(self, with_postfix=True):
        token = self.stream.current
        if token.type is 'name':
            if token.value in ('true', 'false', 'True', 'False'):
                node = nodes.Const(token.value in ('true', 'True'),
                                   lineno=token.lineno)
            elif token.value in ('none', 'None'):
                node = nodes.Const(None, lineno=token.lineno)
            else:
                node = nodes.Name(token.value, 'load', lineno=token.lineno)
            self.stream.next()
        elif token.type in ('integer', 'float', 'string'):
            self.stream.next()
            node = nodes.Const(token.value, lineno=token.lineno)
        elif token.type is 'lparen':
            self.stream.next()
            node = self.parse_tuple()
            self.stream.expect('rparen')
        elif token.type is 'lbracket':
            node = self.parse_list()
        elif token.type is 'lbrace':
            node = self.parse_dict()
        else:
            self.fail("unexpected token '%s'" % (token,), token.lineno)
        if with_postfix:
            node = self.parse_postfix(node)
        return node

    def parse_tuple(self, simplified=False, with_condexpr=True,
                    extra_end_rules=None):
        """Works like `parse_expression` but if multiple expressions are
        delimited by a comma a :class:`~jinja2.nodes.Tuple` node is created.
        This method could also return a regular expression instead of a tuple
        if no commas where found.

        The default parsing mode is a full tuple.  If `simplified` is `True`
        only names and literals are parsed.  The `no_condexpr` parameter is
        forwarded to :meth:`parse_expression`.

        Because tuples do not require delimiters and may end in a bogus comma
        an extra hint is needed that marks the end of a tuple.  For example
        for loops support tuples between `for` and `in`.  In that case the
        `extra_end_rules` is set to ``['name:in']``.
        """
        lineno = self.stream.current.lineno
        if simplified:
            parse = lambda: self.parse_primary(with_postfix=False)
        elif with_condexpr:
            parse = self.parse_expression
        else:
            parse = lambda: self.parse_expression(with_condexpr=False)
        args = []
        is_tuple = False
        while 1:
            if args:
                self.stream.expect('comma')
            if self.is_tuple_end(extra_end_rules):
                break
            args.append(parse())
            if self.stream.current.type is 'comma':
                is_tuple = True
            else:
                break
            lineno = self.stream.current.lineno
        if not is_tuple and args:
            return args[0]
        return nodes.Tuple(args, 'load', lineno=lineno)

    def parse_list(self):
        token = self.stream.expect('lbracket')
        items = []
        while self.stream.current.type is not 'rbracket':
            if items:
                self.stream.expect('comma')
            if self.stream.current.type == 'rbracket':
                break
            items.append(self.parse_expression())
        self.stream.expect('rbracket')
        return nodes.List(items, lineno=token.lineno)

    def parse_dict(self):
        token = self.stream.expect('lbrace')
        items = []
        while self.stream.current.type is not 'rbrace':
            if items:
                self.stream.expect('comma')
            if self.stream.current.type == 'rbrace':
                break
            key = self.parse_expression()
            self.stream.expect('colon')
            value = self.parse_expression()
            items.append(nodes.Pair(key, value, lineno=key.lineno))
        self.stream.expect('rbrace')
        return nodes.Dict(items, lineno=token.lineno)

    def parse_postfix(self, node):
        while 1:
            token_type = self.stream.current.type
            if token_type is 'dot' or token_type is 'lbracket':
                node = self.parse_subscript(node)
            elif token_type is 'lparen':
                node = self.parse_call(node)
            elif token_type is 'pipe':
                node = self.parse_filter(node)
            elif token_type is 'name' and self.stream.current.value == 'is':
                node = self.parse_test(node)
            else:
                break
        return node

    def parse_subscript(self, node):
        token = self.stream.next()
        if token.type is 'dot':
            attr_token = self.stream.current
            self.stream.next()
            if attr_token.type is 'name':
                return nodes.Getattr(node, attr_token.value, 'load',
                                     lineno=token.lineno)
            elif attr_token.type is not 'integer':
                self.fail('expected name or number', attr_token.lineno)
            arg = nodes.Const(attr_token.value, lineno=attr_token.lineno)
            return nodes.Getitem(node, arg, 'load', lineno=token.lineno)
        if token.type is 'lbracket':
            priority_on_attribute = False
            args = []
            while self.stream.current.type is not 'rbracket':
                if args:
                    self.stream.expect('comma')
                args.append(self.parse_subscribed())
            self.stream.expect('rbracket')
            if len(args) == 1:
                arg = args[0]
            else:
                arg = nodes.Tuple(args, self.lineno, self.filename)
            return nodes.Getitem(node, arg, 'load', lineno=token.lineno)
        self.fail('expected subscript expression', self.lineno)

    def parse_subscribed(self):
        lineno = self.stream.current.lineno

        if self.stream.current.type is 'colon':
            self.stream.next()
            args = [None]
        else:
            node = self.parse_expression()
            if self.stream.current.type is not 'colon':
                return node
            self.stream.next()
            args = [node]

        if self.stream.current.type is 'colon':
            args.append(None)
        elif self.stream.current.type not in ('rbracket', 'comma'):
            args.append(self.parse_expression())
        else:
            args.append(None)

        if self.stream.current.type is 'colon':
            self.stream.next()
            if self.stream.current.type not in ('rbracket', 'comma'):
                args.append(self.parse_expression())
            else:
                args.append(None)
        else:
            args.append(None)

        return nodes.Slice(lineno=lineno, *args)

    def parse_call(self, node):
        token = self.stream.expect('lparen')
        args = []
        kwargs = []
        dyn_args = dyn_kwargs = None
        require_comma = False

        def ensure(expr):
            if not expr:
                self.fail('invalid syntax for function call expression',
                          token.lineno)

        while self.stream.current.type is not 'rparen':
            if require_comma:
                self.stream.expect('comma')
                # support for trailing comma
                if self.stream.current.type is 'rparen':
                    break
            if self.stream.current.type is 'mul':
                ensure(dyn_args is None and dyn_kwargs is None)
                self.stream.next()
                dyn_args = self.parse_expression()
            elif self.stream.current.type is 'pow':
                ensure(dyn_kwargs is None)
                self.stream.next()
                dyn_kwargs = self.parse_expression()
            else:
                ensure(dyn_args is None and dyn_kwargs is None)
                if self.stream.current.type is 'name' and \
                    self.stream.look().type is 'assign':
                    key = self.stream.current.value
                    self.stream.skip(2)
                    value = self.parse_expression()
                    kwargs.append(nodes.Keyword(key, value,
                                                lineno=value.lineno))
                else:
                    ensure(not kwargs)
                    args.append(self.parse_expression())

            require_comma = True
        self.stream.expect('rparen')

        if node is None:
            return args, kwargs, dyn_args, dyn_kwargs
        return nodes.Call(node, args, kwargs, dyn_args, dyn_kwargs,
                          lineno=token.lineno)

    def parse_filter(self, node, start_inline=False):
        while self.stream.current.type == 'pipe' or start_inline:
            if not start_inline:
                self.stream.next()
            token = self.stream.expect('name')
            name = token.value
            while self.stream.current.type is 'dot':
                self.stream.next()
                name += '.' + self.stream.expect('name').value
            if self.stream.current.type is 'lparen':
                args, kwargs, dyn_args, dyn_kwargs = self.parse_call(None)
            else:
                args = []
                kwargs = []
                dyn_args = dyn_kwargs = None
            node = nodes.Filter(node, name, args, kwargs, dyn_args,
                                dyn_kwargs, lineno=token.lineno)
            start_inline = False
        return node

    def parse_test(self, node):
        token = self.stream.next()
        if self.stream.current.test('name:not'):
            self.stream.next()
            negated = True
        else:
            negated = False
        name = self.stream.expect('name').value
        while self.stream.current.type is 'dot':
            self.stream.next()
            name += '.' + self.stream.expect('name').value
        dyn_args = dyn_kwargs = None
        kwargs = []
        if self.stream.current.type is 'lparen':
            args, kwargs, dyn_args, dyn_kwargs = self.parse_call(None)
        elif self.stream.current.type in ('name', 'string', 'integer',
                                          'float', 'lparen', 'lbracket',
                                          'lbrace') and not \
             self.stream.current.test_any('name:else', 'name:or',
                                          'name:and'):
            if self.stream.current.test('name:is'):
                self.fail('You cannot chain multiple tests with is')
            args = [self.parse_expression()]
        else:
            args = []
        node = nodes.Test(node, name, args, kwargs, dyn_args,
                          dyn_kwargs, lineno=token.lineno)
        if negated:
            node = nodes.Not(node, lineno=token.lineno)
        return node

    def subparse(self, end_tokens=None):
        body = []
        data_buffer = []
        add_data = data_buffer.append

        def flush_data():
            if data_buffer:
                lineno = data_buffer[0].lineno
                body.append(nodes.Output(data_buffer[:], lineno=lineno))
                del data_buffer[:]

        while self.stream:
            token = self.stream.current
            if token.type is 'data':
                if token.value:
                    add_data(nodes.TemplateData(token.value,
                                                lineno=token.lineno))
                self.stream.next()
            elif token.type is 'variable_begin':
                self.stream.next()
                add_data(self.parse_tuple(with_condexpr=True))
                self.stream.expect('variable_end')
            elif token.type is 'block_begin':
                flush_data()
                self.stream.next()
                if end_tokens is not None and \
                   self.stream.current.test_any(*end_tokens):
                    return body
                rv = self.parse_statement()
                if isinstance(rv, list):
                    body.extend(rv)
                else:
                    body.append(rv)
                self.stream.expect('block_end')
            else:
                raise AssertionError('internal parsing error')

        flush_data()
        return body

    def parse(self):
        """Parse the whole template into a `Template` node."""
        result = nodes.Template(self.subparse(), lineno=1)
        result.set_environment(self.environment)
        return result