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Diffstat (limited to 'src/jinja/nodes.py')
| -rw-r--r-- | src/jinja/nodes.py | 1087 |
1 files changed, 1087 insertions, 0 deletions
diff --git a/src/jinja/nodes.py b/src/jinja/nodes.py new file mode 100644 index 0000000..f0e9e03 --- /dev/null +++ b/src/jinja/nodes.py @@ -0,0 +1,1087 @@ +# -*- coding: utf-8 -*- +"""AST nodes generated by the parser for the compiler. Also provides +some node tree helper functions used by the parser and compiler in order +to normalize nodes. +""" +import operator +from collections import deque + +from ._compat import izip +from ._compat import PY2 +from ._compat import text_type +from ._compat import with_metaclass +from .utils import Markup + +_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__(mcs, 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__(mcs, 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 Jinja 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 instantiable") + 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 _, 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 because 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) + + if not result: + return False + + 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')) + + This is basically equivalent to using the + :func:`~jinja2.contextfunction` decorator when using the + high-level API, which causes a reference to the context to be passed + as the first argument to a function. + """ + + +class DerivedContextReference(Expr): + """Return the current template context including locals. Behaves + exactly like :class:`ContextReference`, but includes local + variables, such as from a ``for`` loop. + + .. versionadded:: 2.11 + """ + + +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 |