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Diffstat (limited to 'python/jinja2/nodes.py')
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diff --git a/python/jinja2/nodes.py b/python/jinja2/nodes.py new file mode 100644 index 0000000..4d9a01a --- /dev/null +++ b/python/jinja2/nodes.py @@ -0,0 +1,999 @@ +# -*- coding: utf-8 -*- +""" + jinja2.nodes + ~~~~~~~~~~~~ + + This module implements additional nodes derived from the ast base node. + + It also provides some node tree helper functions like `in_lineno` and + `get_nodes` used by the parser and translator in order to normalize + python and jinja nodes. + + :copyright: (c) 2017 by the Jinja Team. + :license: BSD, see LICENSE for more details. +""" +import types +import operator + +from collections import deque +from jinja2.utils import Markup +from jinja2._compat import izip, with_metaclass, text_type, PY2 + + +#: the types we support for context functions +_context_function_types = (types.FunctionType, types.MethodType) + + +_binop_to_func = { + '*': operator.mul, + '/': operator.truediv, + '//': operator.floordiv, + '**': operator.pow, + '%': operator.mod, + '+': operator.add, + '-': operator.sub +} + +_uaop_to_func = { + 'not': operator.not_, + '+': operator.pos, + '-': operator.neg +} + +_cmpop_to_func = { + 'eq': operator.eq, + 'ne': operator.ne, + 'gt': operator.gt, + 'gteq': operator.ge, + 'lt': operator.lt, + 'lteq': operator.le, + 'in': lambda a, b: a in b, + 'notin': lambda a, b: a not in b +} + + +class Impossible(Exception): + """Raised if the node could not perform a requested action.""" + + +class NodeType(type): + """A metaclass for nodes that handles the field and attribute + inheritance. fields and attributes from the parent class are + automatically forwarded to the child.""" + + def __new__(cls, name, bases, d): + for attr in 'fields', 'attributes': + storage = [] + storage.extend(getattr(bases[0], attr, ())) + storage.extend(d.get(attr, ())) + assert len(bases) == 1, 'multiple inheritance not allowed' + assert len(storage) == len(set(storage)), 'layout conflict' + d[attr] = tuple(storage) + d.setdefault('abstract', False) + return type.__new__(cls, name, bases, d) + + +class EvalContext(object): + """Holds evaluation time information. Custom attributes can be attached + to it in extensions. + """ + + def __init__(self, environment, template_name=None): + self.environment = environment + if callable(environment.autoescape): + self.autoescape = environment.autoescape(template_name) + else: + self.autoescape = environment.autoescape + self.volatile = False + + def save(self): + return self.__dict__.copy() + + def revert(self, old): + self.__dict__.clear() + self.__dict__.update(old) + + +def get_eval_context(node, ctx): + if ctx is None: + if node.environment is None: + raise RuntimeError('if no eval context is passed, the ' + 'node must have an attached ' + 'environment.') + return EvalContext(node.environment) + return ctx + + +class Node(with_metaclass(NodeType, object)): + """Baseclass for all Jinja2 nodes. There are a number of nodes available + of different types. There are four major types: + + - :class:`Stmt`: statements + - :class:`Expr`: expressions + - :class:`Helper`: helper nodes + - :class:`Template`: the outermost wrapper node + + All nodes have fields and attributes. Fields may be other nodes, lists, + or arbitrary values. Fields are passed to the constructor as regular + positional arguments, attributes as keyword arguments. Each node has + two attributes: `lineno` (the line number of the node) and `environment`. + The `environment` attribute is set at the end of the parsing process for + all nodes automatically. + """ + fields = () + attributes = ('lineno', 'environment') + abstract = True + + def __init__(self, *fields, **attributes): + if self.abstract: + raise TypeError('abstract nodes are not instanciable') + if fields: + if len(fields) != len(self.fields): + if not self.fields: + raise TypeError('%r takes 0 arguments' % + self.__class__.__name__) + raise TypeError('%r takes 0 or %d argument%s' % ( + self.__class__.__name__, + len(self.fields), + len(self.fields) != 1 and 's' or '' + )) + for name, arg in izip(self.fields, fields): + setattr(self, name, arg) + for attr in self.attributes: + setattr(self, attr, attributes.pop(attr, None)) + if attributes: + raise TypeError('unknown attribute %r' % + next(iter(attributes))) + + def iter_fields(self, exclude=None, only=None): + """This method iterates over all fields that are defined and yields + ``(key, value)`` tuples. Per default all fields are returned, but + it's possible to limit that to some fields by providing the `only` + parameter or to exclude some using the `exclude` parameter. Both + should be sets or tuples of field names. + """ + for name in self.fields: + if (exclude is only is None) or \ + (exclude is not None and name not in exclude) or \ + (only is not None and name in only): + try: + yield name, getattr(self, name) + except AttributeError: + pass + + def iter_child_nodes(self, exclude=None, only=None): + """Iterates over all direct child nodes of the node. This iterates + over all fields and yields the values of they are nodes. If the value + of a field is a list all the nodes in that list are returned. + """ + for field, item in self.iter_fields(exclude, only): + if isinstance(item, list): + for n in item: + if isinstance(n, Node): + yield n + elif isinstance(item, Node): + yield item + + def find(self, node_type): + """Find the first node of a given type. If no such node exists the + return value is `None`. + """ + for result in self.find_all(node_type): + return result + + def find_all(self, node_type): + """Find all the nodes of a given type. If the type is a tuple, + the check is performed for any of the tuple items. + """ + for child in self.iter_child_nodes(): + if isinstance(child, node_type): + yield child + for result in child.find_all(node_type): + yield result + + def set_ctx(self, ctx): + """Reset the context of a node and all child nodes. Per default the + parser will all generate nodes that have a 'load' context as it's the + most common one. This method is used in the parser to set assignment + targets and other nodes to a store context. + """ + todo = deque([self]) + while todo: + node = todo.popleft() + if 'ctx' in node.fields: + node.ctx = ctx + todo.extend(node.iter_child_nodes()) + return self + + def set_lineno(self, lineno, override=False): + """Set the line numbers of the node and children.""" + todo = deque([self]) + while todo: + node = todo.popleft() + if 'lineno' in node.attributes: + if node.lineno is None or override: + node.lineno = lineno + todo.extend(node.iter_child_nodes()) + return self + + def set_environment(self, environment): + """Set the environment for all nodes.""" + todo = deque([self]) + while todo: + node = todo.popleft() + node.environment = environment + todo.extend(node.iter_child_nodes()) + return self + + def __eq__(self, other): + return type(self) is type(other) and \ + tuple(self.iter_fields()) == tuple(other.iter_fields()) + + def __ne__(self, other): + return not self.__eq__(other) + + # Restore Python 2 hashing behavior on Python 3 + __hash__ = object.__hash__ + + def __repr__(self): + return '%s(%s)' % ( + self.__class__.__name__, + ', '.join('%s=%r' % (arg, getattr(self, arg, None)) for + arg in self.fields) + ) + + def dump(self): + def _dump(node): + if not isinstance(node, Node): + buf.append(repr(node)) + return + + buf.append('nodes.%s(' % node.__class__.__name__) + if not node.fields: + buf.append(')') + return + for idx, field in enumerate(node.fields): + if idx: + buf.append(', ') + value = getattr(node, field) + if isinstance(value, list): + buf.append('[') + for idx, item in enumerate(value): + if idx: + buf.append(', ') + _dump(item) + buf.append(']') + else: + _dump(value) + buf.append(')') + buf = [] + _dump(self) + return ''.join(buf) + + + +class Stmt(Node): + """Base node for all statements.""" + abstract = True + + +class Helper(Node): + """Nodes that exist in a specific context only.""" + abstract = True + + +class Template(Node): + """Node that represents a template. This must be the outermost node that + is passed to the compiler. + """ + fields = ('body',) + + +class Output(Stmt): + """A node that holds multiple expressions which are then printed out. + This is used both for the `print` statement and the regular template data. + """ + fields = ('nodes',) + + +class Extends(Stmt): + """Represents an extends statement.""" + fields = ('template',) + + +class For(Stmt): + """The for loop. `target` is the target for the iteration (usually a + :class:`Name` or :class:`Tuple`), `iter` the iterable. `body` is a list + of nodes that are used as loop-body, and `else_` a list of nodes for the + `else` block. If no else node exists it has to be an empty list. + + For filtered nodes an expression can be stored as `test`, otherwise `None`. + """ + fields = ('target', 'iter', 'body', 'else_', 'test', 'recursive') + + +class If(Stmt): + """If `test` is true, `body` is rendered, else `else_`.""" + fields = ('test', 'body', 'elif_', 'else_') + + +class Macro(Stmt): + """A macro definition. `name` is the name of the macro, `args` a list of + arguments and `defaults` a list of defaults if there are any. `body` is + a list of nodes for the macro body. + """ + fields = ('name', 'args', 'defaults', 'body') + + +class CallBlock(Stmt): + """Like a macro without a name but a call instead. `call` is called with + the unnamed macro as `caller` argument this node holds. + """ + fields = ('call', 'args', 'defaults', 'body') + + +class FilterBlock(Stmt): + """Node for filter sections.""" + fields = ('body', 'filter') + + +class With(Stmt): + """Specific node for with statements. In older versions of Jinja the + with statement was implemented on the base of the `Scope` node instead. + + .. versionadded:: 2.9.3 + """ + fields = ('targets', 'values', 'body') + + +class Block(Stmt): + """A node that represents a block.""" + fields = ('name', 'body', 'scoped') + + +class Include(Stmt): + """A node that represents the include tag.""" + fields = ('template', 'with_context', 'ignore_missing') + + +class Import(Stmt): + """A node that represents the import tag.""" + fields = ('template', 'target', 'with_context') + + +class FromImport(Stmt): + """A node that represents the from import tag. It's important to not + pass unsafe names to the name attribute. The compiler translates the + attribute lookups directly into getattr calls and does *not* use the + subscript callback of the interface. As exported variables may not + start with double underscores (which the parser asserts) this is not a + problem for regular Jinja code, but if this node is used in an extension + extra care must be taken. + + The list of names may contain tuples if aliases are wanted. + """ + fields = ('template', 'names', 'with_context') + + +class ExprStmt(Stmt): + """A statement that evaluates an expression and discards the result.""" + fields = ('node',) + + +class Assign(Stmt): + """Assigns an expression to a target.""" + fields = ('target', 'node') + + +class AssignBlock(Stmt): + """Assigns a block to a target.""" + fields = ('target', 'filter', 'body') + + +class Expr(Node): + """Baseclass for all expressions.""" + abstract = True + + def as_const(self, eval_ctx=None): + """Return the value of the expression as constant or raise + :exc:`Impossible` if this was not possible. + + An :class:`EvalContext` can be provided, if none is given + a default context is created which requires the nodes to have + an attached environment. + + .. versionchanged:: 2.4 + the `eval_ctx` parameter was added. + """ + raise Impossible() + + def can_assign(self): + """Check if it's possible to assign something to this node.""" + return False + + +class BinExpr(Expr): + """Baseclass for all binary expressions.""" + fields = ('left', 'right') + operator = None + abstract = True + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + # intercepted operators cannot be folded at compile time + if self.environment.sandboxed and \ + self.operator in self.environment.intercepted_binops: + raise Impossible() + f = _binop_to_func[self.operator] + try: + return f(self.left.as_const(eval_ctx), self.right.as_const(eval_ctx)) + except Exception: + raise Impossible() + + +class UnaryExpr(Expr): + """Baseclass for all unary expressions.""" + fields = ('node',) + operator = None + abstract = True + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + # intercepted operators cannot be folded at compile time + if self.environment.sandboxed and \ + self.operator in self.environment.intercepted_unops: + raise Impossible() + f = _uaop_to_func[self.operator] + try: + return f(self.node.as_const(eval_ctx)) + except Exception: + raise Impossible() + + +class Name(Expr): + """Looks up a name or stores a value in a name. + The `ctx` of the node can be one of the following values: + + - `store`: store a value in the name + - `load`: load that name + - `param`: like `store` but if the name was defined as function parameter. + """ + fields = ('name', 'ctx') + + def can_assign(self): + return self.name not in ('true', 'false', 'none', + 'True', 'False', 'None') + + +class NSRef(Expr): + """Reference to a namespace value assignment""" + fields = ('name', 'attr') + + def can_assign(self): + # We don't need any special checks here; NSRef assignments have a + # runtime check to ensure the target is a namespace object which will + # have been checked already as it is created using a normal assignment + # which goes through a `Name` node. + return True + + +class Literal(Expr): + """Baseclass for literals.""" + abstract = True + + +class Const(Literal): + """All constant values. The parser will return this node for simple + constants such as ``42`` or ``"foo"`` but it can be used to store more + complex values such as lists too. Only constants with a safe + representation (objects where ``eval(repr(x)) == x`` is true). + """ + fields = ('value',) + + def as_const(self, eval_ctx=None): + rv = self.value + if PY2 and type(rv) is text_type and \ + self.environment.policies['compiler.ascii_str']: + try: + rv = rv.encode('ascii') + except UnicodeError: + pass + return rv + + @classmethod + def from_untrusted(cls, value, lineno=None, environment=None): + """Return a const object if the value is representable as + constant value in the generated code, otherwise it will raise + an `Impossible` exception. + """ + from .compiler import has_safe_repr + if not has_safe_repr(value): + raise Impossible() + return cls(value, lineno=lineno, environment=environment) + + +class TemplateData(Literal): + """A constant template string.""" + fields = ('data',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + if eval_ctx.volatile: + raise Impossible() + if eval_ctx.autoescape: + return Markup(self.data) + return self.data + + +class Tuple(Literal): + """For loop unpacking and some other things like multiple arguments + for subscripts. Like for :class:`Name` `ctx` specifies if the tuple + is used for loading the names or storing. + """ + fields = ('items', 'ctx') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return tuple(x.as_const(eval_ctx) for x in self.items) + + def can_assign(self): + for item in self.items: + if not item.can_assign(): + return False + return True + + +class List(Literal): + """Any list literal such as ``[1, 2, 3]``""" + fields = ('items',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return [x.as_const(eval_ctx) for x in self.items] + + +class Dict(Literal): + """Any dict literal such as ``{1: 2, 3: 4}``. The items must be a list of + :class:`Pair` nodes. + """ + fields = ('items',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return dict(x.as_const(eval_ctx) for x in self.items) + + +class Pair(Helper): + """A key, value pair for dicts.""" + fields = ('key', 'value') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return self.key.as_const(eval_ctx), self.value.as_const(eval_ctx) + + +class Keyword(Helper): + """A key, value pair for keyword arguments where key is a string.""" + fields = ('key', 'value') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return self.key, self.value.as_const(eval_ctx) + + +class CondExpr(Expr): + """A conditional expression (inline if expression). (``{{ + foo if bar else baz }}``) + """ + fields = ('test', 'expr1', 'expr2') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + if self.test.as_const(eval_ctx): + return self.expr1.as_const(eval_ctx) + + # if we evaluate to an undefined object, we better do that at runtime + if self.expr2 is None: + raise Impossible() + + return self.expr2.as_const(eval_ctx) + + +def args_as_const(node, eval_ctx): + args = [x.as_const(eval_ctx) for x in node.args] + kwargs = dict(x.as_const(eval_ctx) for x in node.kwargs) + + if node.dyn_args is not None: + try: + args.extend(node.dyn_args.as_const(eval_ctx)) + except Exception: + raise Impossible() + + if node.dyn_kwargs is not None: + try: + kwargs.update(node.dyn_kwargs.as_const(eval_ctx)) + except Exception: + raise Impossible() + + return args, kwargs + + +class Filter(Expr): + """This node applies a filter on an expression. `name` is the name of + the filter, the rest of the fields are the same as for :class:`Call`. + + If the `node` of a filter is `None` the contents of the last buffer are + filtered. Buffers are created by macros and filter blocks. + """ + + fields = ('node', 'name', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + + if eval_ctx.volatile or self.node is None: + raise Impossible() + + # we have to be careful here because we call filter_ below. + # if this variable would be called filter, 2to3 would wrap the + # call in a list beause it is assuming we are talking about the + # builtin filter function here which no longer returns a list in + # python 3. because of that, do not rename filter_ to filter! + filter_ = self.environment.filters.get(self.name) + + if filter_ is None or getattr(filter_, 'contextfilter', False): + raise Impossible() + + # We cannot constant handle async filters, so we need to make sure + # to not go down this path. + if ( + eval_ctx.environment.is_async + and getattr(filter_, 'asyncfiltervariant', False) + ): + raise Impossible() + + args, kwargs = args_as_const(self, eval_ctx) + args.insert(0, self.node.as_const(eval_ctx)) + + if getattr(filter_, 'evalcontextfilter', False): + args.insert(0, eval_ctx) + elif getattr(filter_, 'environmentfilter', False): + args.insert(0, self.environment) + + try: + return filter_(*args, **kwargs) + except Exception: + raise Impossible() + + +class Test(Expr): + """Applies a test on an expression. `name` is the name of the test, the + rest of the fields are the same as for :class:`Call`. + """ + + fields = ('node', 'name', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs') + + def as_const(self, eval_ctx=None): + test = self.environment.tests.get(self.name) + + if test is None: + raise Impossible() + + eval_ctx = get_eval_context(self, eval_ctx) + args, kwargs = args_as_const(self, eval_ctx) + args.insert(0, self.node.as_const(eval_ctx)) + + try: + return test(*args, **kwargs) + except Exception: + raise Impossible() + + +class Call(Expr): + """Calls an expression. `args` is a list of arguments, `kwargs` a list + of keyword arguments (list of :class:`Keyword` nodes), and `dyn_args` + and `dyn_kwargs` has to be either `None` or a node that is used as + node for dynamic positional (``*args``) or keyword (``**kwargs``) + arguments. + """ + fields = ('node', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs') + + +class Getitem(Expr): + """Get an attribute or item from an expression and prefer the item.""" + fields = ('node', 'arg', 'ctx') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + if self.ctx != 'load': + raise Impossible() + try: + return self.environment.getitem(self.node.as_const(eval_ctx), + self.arg.as_const(eval_ctx)) + except Exception: + raise Impossible() + + def can_assign(self): + return False + + +class Getattr(Expr): + """Get an attribute or item from an expression that is a ascii-only + bytestring and prefer the attribute. + """ + fields = ('node', 'attr', 'ctx') + + def as_const(self, eval_ctx=None): + if self.ctx != 'load': + raise Impossible() + try: + eval_ctx = get_eval_context(self, eval_ctx) + return self.environment.getattr(self.node.as_const(eval_ctx), + self.attr) + except Exception: + raise Impossible() + + def can_assign(self): + return False + + +class Slice(Expr): + """Represents a slice object. This must only be used as argument for + :class:`Subscript`. + """ + fields = ('start', 'stop', 'step') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + def const(obj): + if obj is None: + return None + return obj.as_const(eval_ctx) + return slice(const(self.start), const(self.stop), const(self.step)) + + +class Concat(Expr): + """Concatenates the list of expressions provided after converting them to + unicode. + """ + fields = ('nodes',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return ''.join(text_type(x.as_const(eval_ctx)) for x in self.nodes) + + +class Compare(Expr): + """Compares an expression with some other expressions. `ops` must be a + list of :class:`Operand`\\s. + """ + fields = ('expr', 'ops') + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + result = value = self.expr.as_const(eval_ctx) + try: + for op in self.ops: + new_value = op.expr.as_const(eval_ctx) + result = _cmpop_to_func[op.op](value, new_value) + value = new_value + except Exception: + raise Impossible() + return result + + +class Operand(Helper): + """Holds an operator and an expression.""" + fields = ('op', 'expr') + +if __debug__: + Operand.__doc__ += '\nThe following operators are available: ' + \ + ', '.join(sorted('``%s``' % x for x in set(_binop_to_func) | + set(_uaop_to_func) | set(_cmpop_to_func))) + + +class Mul(BinExpr): + """Multiplies the left with the right node.""" + operator = '*' + + +class Div(BinExpr): + """Divides the left by the right node.""" + operator = '/' + + +class FloorDiv(BinExpr): + """Divides the left by the right node and truncates conver the + result into an integer by truncating. + """ + operator = '//' + + +class Add(BinExpr): + """Add the left to the right node.""" + operator = '+' + + +class Sub(BinExpr): + """Subtract the right from the left node.""" + operator = '-' + + +class Mod(BinExpr): + """Left modulo right.""" + operator = '%' + + +class Pow(BinExpr): + """Left to the power of right.""" + operator = '**' + + +class And(BinExpr): + """Short circuited AND.""" + operator = 'and' + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return self.left.as_const(eval_ctx) and self.right.as_const(eval_ctx) + + +class Or(BinExpr): + """Short circuited OR.""" + operator = 'or' + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return self.left.as_const(eval_ctx) or self.right.as_const(eval_ctx) + + +class Not(UnaryExpr): + """Negate the expression.""" + operator = 'not' + + +class Neg(UnaryExpr): + """Make the expression negative.""" + operator = '-' + + +class Pos(UnaryExpr): + """Make the expression positive (noop for most expressions)""" + operator = '+' + + +# Helpers for extensions + + +class EnvironmentAttribute(Expr): + """Loads an attribute from the environment object. This is useful for + extensions that want to call a callback stored on the environment. + """ + fields = ('name',) + + +class ExtensionAttribute(Expr): + """Returns the attribute of an extension bound to the environment. + The identifier is the identifier of the :class:`Extension`. + + This node is usually constructed by calling the + :meth:`~jinja2.ext.Extension.attr` method on an extension. + """ + fields = ('identifier', 'name') + + +class ImportedName(Expr): + """If created with an import name the import name is returned on node + access. For example ``ImportedName('cgi.escape')`` returns the `escape` + function from the cgi module on evaluation. Imports are optimized by the + compiler so there is no need to assign them to local variables. + """ + fields = ('importname',) + + +class InternalName(Expr): + """An internal name in the compiler. You cannot create these nodes + yourself but the parser provides a + :meth:`~jinja2.parser.Parser.free_identifier` method that creates + a new identifier for you. This identifier is not available from the + template and is not threated specially by the compiler. + """ + fields = ('name',) + + def __init__(self): + raise TypeError('Can\'t create internal names. Use the ' + '`free_identifier` method on a parser.') + + +class MarkSafe(Expr): + """Mark the wrapped expression as safe (wrap it as `Markup`).""" + fields = ('expr',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + return Markup(self.expr.as_const(eval_ctx)) + + +class MarkSafeIfAutoescape(Expr): + """Mark the wrapped expression as safe (wrap it as `Markup`) but + only if autoescaping is active. + + .. versionadded:: 2.5 + """ + fields = ('expr',) + + def as_const(self, eval_ctx=None): + eval_ctx = get_eval_context(self, eval_ctx) + if eval_ctx.volatile: + raise Impossible() + expr = self.expr.as_const(eval_ctx) + if eval_ctx.autoescape: + return Markup(expr) + return expr + + +class ContextReference(Expr): + """Returns the current template context. It can be used like a + :class:`Name` node, with a ``'load'`` ctx and will return the + current :class:`~jinja2.runtime.Context` object. + + Here an example that assigns the current template name to a + variable named `foo`:: + + Assign(Name('foo', ctx='store'), + Getattr(ContextReference(), 'name')) + """ + + +class Continue(Stmt): + """Continue a loop.""" + + +class Break(Stmt): + """Break a loop.""" + + +class Scope(Stmt): + """An artificial scope.""" + fields = ('body',) + + +class OverlayScope(Stmt): + """An overlay scope for extensions. This is a largely unoptimized scope + that however can be used to introduce completely arbitrary variables into + a sub scope from a dictionary or dictionary like object. The `context` + field has to evaluate to a dictionary object. + + Example usage:: + + OverlayScope(context=self.call_method('get_context'), + body=[...]) + + .. versionadded:: 2.10 + """ + fields = ('context', 'body') + + +class EvalContextModifier(Stmt): + """Modifies the eval context. For each option that should be modified, + a :class:`Keyword` has to be added to the :attr:`options` list. + + Example to change the `autoescape` setting:: + + EvalContextModifier(options=[Keyword('autoescape', Const(True))]) + """ + fields = ('options',) + + +class ScopedEvalContextModifier(EvalContextModifier): + """Modifies the eval context and reverts it later. Works exactly like + :class:`EvalContextModifier` but will only modify the + :class:`~jinja2.nodes.EvalContext` for nodes in the :attr:`body`. + """ + fields = ('body',) + + +# make sure nobody creates custom nodes +def _failing_new(*args, **kwargs): + raise TypeError('can\'t create custom node types') +NodeType.__new__ = staticmethod(_failing_new); del _failing_new |