Add Python templating engine Jinja2 to third_party

third_party/jinja2/compiler.py

+# -*- coding: utf-8 -*-
+"""
+    jinja2.compiler
+    ~~~~~~~~~~~~~~~
+
+    Compiles nodes into python code.
+
+    :copyright: (c) 2010 by the Jinja Team.
+    :license: BSD, see LICENSE for more details.
+"""
+from cStringIO import StringIO
+from itertools import chain
+from copy import deepcopy
+from jinja2 import nodes
+from jinja2.nodes import EvalContext
+from jinja2.visitor import NodeVisitor
+from jinja2.exceptions import TemplateAssertionError
+from jinja2.utils import Markup, concat, escape, is_python_keyword, next
+
+
+operators = {
+    'eq':       '==',
+    'ne':       '!=',
+    'gt':       '>',
+    'gteq':     '>=',
+    'lt':       '<',
+    'lteq':     '<=',
+    'in':       'in',
+    'notin':    'not in'
+}
+
+try:
+    exec '(0 if 0 else 0)'
+except SyntaxError:
+    have_condexpr = False
+else:
+    have_condexpr = True
+
+
+# what method to iterate over items do we want to use for dict iteration
+# in generated code?  on 2.x let's go with iteritems, on 3.x with items
+if hasattr(dict, 'iteritems'):
+    dict_item_iter = 'iteritems'
+else:
+    dict_item_iter = 'items'
+
+
+# does if 0: dummy(x) get us x into the scope?
+def unoptimize_before_dead_code():
+    x = 42
+    def f():
+        if 0: dummy(x)
+    return f
+unoptimize_before_dead_code = bool(unoptimize_before_dead_code().func_closure)
+
+
+def generate(node, environment, name, filename, stream=None,
+             defer_init=False):
+    """Generate the python source for a node tree."""
+    if not isinstance(node, nodes.Template):
+        raise TypeError('Can\'t compile non template nodes')
+    generator = CodeGenerator(environment, name, filename, stream, defer_init)
+    generator.visit(node)
+    if stream is None:
+        return generator.stream.getvalue()
+
+
+def has_safe_repr(value):
+    """Does the node have a safe representation?"""
+    if value is None or value is NotImplemented or value is Ellipsis:
+        return True
+    if isinstance(value, (bool, int, long, float, complex, basestring,
+                          xrange, Markup)):
+        return True
+    if isinstance(value, (tuple, list, set, frozenset)):
+        for item in value:
+            if not has_safe_repr(item):
+                return False
+        return True
+    elif isinstance(value, dict):
+        for key, value in value.iteritems():
+            if not has_safe_repr(key):
+                return False
+            if not has_safe_repr(value):
+                return False
+        return True
+    return False
+
+
+def find_undeclared(nodes, names):
+    """Check if the names passed are accessed undeclared.  The return value
+    is a set of all the undeclared names from the sequence of names found.
+    """
+    visitor = UndeclaredNameVisitor(names)
+    try:
+        for node in nodes:
+            visitor.visit(node)
+    except VisitorExit:
+        pass
+    return visitor.undeclared
+
+
+class Identifiers(object):
+    """Tracks the status of identifiers in frames."""
+
+    def __init__(self):
+        # variables that are known to be declared (probably from outer
+        # frames or because they are special for the frame)
+        self.declared = set()
+
+        # undeclared variables from outer scopes
+        self.outer_undeclared = set()
+
+        # names that are accessed without being explicitly declared by
+        # this one or any of the outer scopes.  Names can appear both in
+        # declared and undeclared.
+        self.undeclared = set()
+
+        # names that are declared locally
+        self.declared_locally = set()
+
+        # names that are declared by parameters
+        self.declared_parameter = set()
+
+    def add_special(self, name):
+        """Register a special name like `loop`."""
+        self.undeclared.discard(name)
+        self.declared.add(name)
+
+    def is_declared(self, name):
+        """Check if a name is declared in this or an outer scope."""
+        if name in self.declared_locally or name in self.declared_parameter:
+            return True
+        return name in self.declared
+
+    def copy(self):
+        return deepcopy(self)
+
+
+class Frame(object):
+    """Holds compile time information for us."""
+
+    def __init__(self, eval_ctx, parent=None):
+        self.eval_ctx = eval_ctx
+        self.identifiers = Identifiers()
+
+        # a toplevel frame is the root + soft frames such as if conditions.
+        self.toplevel = False
+
+        # the root frame is basically just the outermost frame, so no if
+        # conditions.  This information is used to optimize inheritance
+        # situations.
+        self.rootlevel = False
+
+        # in some dynamic inheritance situations the compiler needs to add
+        # write tests around output statements.
+        self.require_output_check = parent and parent.require_output_check
+
+        # inside some tags we are using a buffer rather than yield statements.
+        # this for example affects {% filter %} or {% macro %}.  If a frame
+        # is buffered this variable points to the name of the list used as
+        # buffer.
+        self.buffer = None
+
+        # the name of the block we're in, otherwise None.
+        self.block = parent and parent.block or None
+
+        # a set of actually assigned names
+        self.assigned_names = set()
+
+        # the parent of this frame
+        self.parent = parent
+
+        if parent is not None:
+            self.identifiers.declared.update(
+                parent.identifiers.declared |
+                parent.identifiers.declared_parameter |
+                parent.assigned_names
+            )
+            self.identifiers.outer_undeclared.update(
+                parent.identifiers.undeclared -
+                self.identifiers.declared
+            )
+            self.buffer = parent.buffer
+
+    def copy(self):
+        """Create a copy of the current one."""
+        rv = object.__new__(self.__class__)
+        rv.__dict__.update(self.__dict__)
+        rv.identifiers = object.__new__(self.identifiers.__class__)
+        rv.identifiers.__dict__.update(self.identifiers.__dict__)
+        return rv
+
+    def inspect(self, nodes):
+        """Walk the node and check for identifiers.  If the scope is hard (eg:
+        enforce on a python level) overrides from outer scopes are tracked
+        differently.
+        """
+        visitor = FrameIdentifierVisitor(self.identifiers)
+        for node in nodes:
+            visitor.visit(node)
+
+    def find_shadowed(self, extra=()):
+        """Find all the shadowed names.  extra is an iterable of variables
+        that may be defined with `add_special` which may occour scoped.
+        """
+        i = self.identifiers
+        return (i.declared | i.outer_undeclared) & \
+               (i.declared_locally | i.declared_parameter) | \
+               set(x for x in extra if i.is_declared(x))
+
+    def inner(self):
+        """Return an inner frame."""
+        return Frame(self.eval_ctx, self)
+
+    def soft(self):
+        """Return a soft frame.  A soft frame may not be modified as
+        standalone thing as it shares the resources with the frame it
+        was created of, but it's not a rootlevel frame any longer.
+        """
+        rv = self.copy()
+        rv.rootlevel = False
+        return rv
+
+    __copy__ = copy
+
+
+class VisitorExit(RuntimeError):
+    """Exception used by the `UndeclaredNameVisitor` to signal a stop."""
+
+
+class DependencyFinderVisitor(NodeVisitor):
+    """A visitor that collects filter and test calls."""
+
+    def __init__(self):
+        self.filters = set()
+        self.tests = set()
+
+    def visit_Filter(self, node):
+        self.generic_visit(node)
+        self.filters.add(node.name)
+
+    def visit_Test(self, node):
+        self.generic_visit(node)
+        self.tests.add(node.name)
+
+    def visit_Block(self, node):
+        """Stop visiting at blocks."""
+
+
+class UndeclaredNameVisitor(NodeVisitor):
+    """A visitor that checks if a name is accessed without being
+    declared.  This is different from the frame visitor as it will
+    not stop at closure frames.
+    """
+
+    def __init__(self, names):
+        self.names = set(names)
+        self.undeclared = set()
+
+    def visit_Name(self, node):
+        if node.ctx == 'load' and node.name in self.names:
+            self.undeclared.add(node.name)
+            if self.undeclared == self.names:
+                raise VisitorExit()
+        else:
+            self.names.discard(node.name)
+
+    def visit_Block(self, node):
+        """Stop visiting a blocks."""
+
+
+class FrameIdentifierVisitor(NodeVisitor):
+    """A visitor for `Frame.inspect`."""
+
+    def __init__(self, identifiers):
+        self.identifiers = identifiers
+
+    def visit_Name(self, node):
+        """All assignments to names go through this function."""
+        if node.ctx == 'store':
+            self.identifiers.declared_locally.add(node.name)
+        elif node.ctx == 'param':
+            self.identifiers.declared_parameter.add(node.name)
+        elif node.ctx == 'load' and not \
+             self.identifiers.is_declared(node.name):
+            self.identifiers.undeclared.add(node.name)
+
+    def visit_If(self, node):
+        self.visit(node.test)
+        real_identifiers = self.identifiers
+
+        old_names = real_identifiers.declared_locally | \
+                    real_identifiers.declared_parameter
+
+        def inner_visit(nodes):
+            if not nodes:
+                return set()
+            self.identifiers = real_identifiers.copy()
+            for subnode in nodes:
+                self.visit(subnode)
+            rv = self.identifiers.declared_locally - old_names
+            # we have to remember the undeclared variables of this branch
+            # because we will have to pull them.
+            real_identifiers.undeclared.update(self.identifiers.undeclared)
+            self.identifiers = real_identifiers
+            return rv
+
+        body = inner_visit(node.body)
+        else_ = inner_visit(node.else_ or ())
+
+        # the differences between the two branches are also pulled as
+        # undeclared variables
+        real_identifiers.undeclared.update(body.symmetric_difference(else_) -
+                                           real_identifiers.declared)
+
+        # remember those that are declared.
+        real_identifiers.declared_locally.update(body | else_)
+
+    def visit_Macro(self, node):
+        self.identifiers.declared_locally.add(node.name)
+
+    def visit_Import(self, node):
+        self.generic_visit(node)
+        self.identifiers.declared_locally.add(node.target)
+
+    def visit_FromImport(self, node):
+        self.generic_visit(node)
+        for name in node.names:
+            if isinstance(name, tuple):
+                self.identifiers.declared_locally.add(name[1])
+            else:
+                self.identifiers.declared_locally.add(name)
+
+    def visit_Assign(self, node):
+        """Visit assignments in the correct order."""
+        self.visit(node.node)
+        self.visit(node.target)
+
+    def visit_For(self, node):
+        """Visiting stops at for blocks.  However the block sequence
+        is visited as part of the outer scope.
+        """
+        self.visit(node.iter)
+
+    def visit_CallBlock(self, node):
+        self.visit(node.call)
+
+    def visit_FilterBlock(self, node):
+        self.visit(node.filter)
+
+    def visit_Scope(self, node):
+        """Stop visiting at scopes."""
+
+    def visit_Block(self, node):
+        """Stop visiting at blocks."""
+
+
+class CompilerExit(Exception):
+    """Raised if the compiler encountered a situation where it just
+    doesn't make sense to further process the code.  Any block that
+    raises such an exception is not further processed.
+    """
+
+
+class CodeGenerator(NodeVisitor):
+
+    def __init__(self, environment, name, filename, stream=None,
+                 defer_init=False):
+        if stream is None:
+            stream = StringIO()
+        self.environment = environment
+        self.name = name
+        self.filename = filename
+        self.stream = stream
+        self.created_block_context = False
+        self.defer_init = defer_init
+
+        # aliases for imports
+        self.import_aliases = {}
+
+        # a registry for all blocks.  Because blocks are moved out
+        # into the global python scope they are registered here
+        self.blocks = {}
+
+        # the number of extends statements so far
+        self.extends_so_far = 0
+
+        # some templates have a rootlevel extends.  In this case we
+        # can safely assume that we're a child template and do some
+        # more optimizations.
+        self.has_known_extends = False
+
+        # the current line number
+        self.code_lineno = 1
+
+        # registry of all filters and tests (global, not block local)
+        self.tests = {}
+        self.filters = {}
+
+        # the debug information
+        self.debug_info = []
+        self._write_debug_info = None
+
+        # the number of new lines before the next write()
+        self._new_lines = 0
+
+        # the line number of the last written statement
+        self._last_line = 0
+
+        # true if nothing was written so far.
+        self._first_write = True
+
+        # used by the `temporary_identifier` method to get new
+        # unique, temporary identifier
+        self._last_identifier = 0
+
+        # the current indentation
+        self._indentation = 0
+
+    # -- Various compilation helpers
+
+    def fail(self, msg, lineno):
+        """Fail with a :exc:`TemplateAssertionError`."""
+        raise TemplateAssertionError(msg, lineno, self.name, self.filename)
+
+    def temporary_identifier(self):
+        """Get a new unique identifier."""
+        self._last_identifier += 1
+        return 't_%d' % self._last_identifier
+
+    def buffer(self, frame):
+        """Enable buffering for the frame from that point onwards."""
+        frame.buffer = self.temporary_identifier()
+        self.writeline('%s = []' % frame.buffer)
+
+    def return_buffer_contents(self, frame):
+        """Return the buffer contents of the frame."""
+        if frame.eval_ctx.volatile:
+            self.writeline('if context.eval_ctx.autoescape:')
+            self.indent()
+            self.writeline('return Markup(concat(%s))' % frame.buffer)
+            self.outdent()
+            self.writeline('else:')
+            self.indent()
+            self.writeline('return concat(%s)' % frame.buffer)
+            self.outdent()
+        elif frame.eval_ctx.autoescape:
+            self.writeline('return Markup(concat(%s))' % frame.buffer)
+        else:
+            self.writeline('return concat(%s)' % frame.buffer)
+
+    def indent(self):
+        """Indent by one."""
+        self._indentation += 1
+
+    def outdent(self, step=1):
+        """Outdent by step."""
+        self._indentation -= step
+
+    def start_write(self, frame, node=None):
+        """Yield or write into the frame buffer."""
+        if frame.buffer is None:
+            self.writeline('yield ', node)
+        else:
+            self.writeline('%s.append(' % frame.buffer, node)
+
+    def end_write(self, frame):
+        """End the writing process started by `start_write`."""
+        if frame.buffer is not None:
+            self.write(')')
+
+    def simple_write(self, s, frame, node=None):
+        """Simple shortcut for start_write + write + end_write."""
+        self.start_write(frame, node)
+        self.write(s)
+        self.end_write(frame)
+
+    def blockvisit(self, nodes, frame):
+        """Visit a list of nodes as block in a frame.  If the current frame
+        is no buffer a dummy ``if 0: yield None`` is written automatically
+        unless the force_generator parameter is set to False.
+        """
+        if frame.buffer is None:
+            self.writeline('if 0: yield None')
+        else:
+            self.writeline('pass')
+        try:
+            for node in nodes:
+                self.visit(node, frame)
+        except CompilerExit:
+            pass
+
+    def write(self, x):
+        """Write a string into the output stream."""
+        if self._new_lines:
+            if not self._first_write:
+                self.stream.write('\n' * self._new_lines)
+                self.code_lineno += self._new_lines
+                if self._write_debug_info is not None:
+                    self.debug_info.append((self._write_debug_info,
+                                            self.code_lineno))
+                    self._write_debug_info = None
+            self._first_write = False
+            self.stream.write('    ' * self._indentation)
+            self._new_lines = 0
+        self.stream.write(x)
+
+    def writeline(self, x, node=None, extra=0):
+        """Combination of newline and write."""
+        self.newline(node, extra)
+        self.write(x)
+
+    def newline(self, node=None, extra=0):
+        """Add one or more newlines before the next write."""
+        self._new_lines = max(self._new_lines, 1 + extra)
+        if node is not None and node.lineno != self._last_line:
+            self._write_debug_info = node.lineno
+            self._last_line = node.lineno
+
+    def signature(self, node, frame, extra_kwargs=None):
+        """Writes a function call to the stream for the current node.
+        A leading comma is added automatically.  The extra keyword
+        arguments may not include python keywords otherwise a syntax
+        error could occour.  The extra keyword arguments should be given
+        as python dict.
+        """
+        # if any of the given keyword arguments is a python keyword
+        # we have to make sure that no invalid call is created.
+        kwarg_workaround = False
+        for kwarg in chain((x.key for x in node.kwargs), extra_kwargs or ()):
+            if is_python_keyword(kwarg):
+                kwarg_workaround = True
+                break
+
+        for arg in node.args:
+            self.write(', ')
+            self.visit(arg, frame)
+
+        if not kwarg_workaround:
+            for kwarg in node.kwargs:
+                self.write(', ')
+                self.visit(kwarg, frame)
+            if extra_kwargs is not None:
+                for key, value in extra_kwargs.iteritems():
+                    self.write(', %s=%s' % (key, value))
+        if node.dyn_args:
+            self.write(', *')
+            self.visit(node.dyn_args, frame)
+
+        if kwarg_workaround:
+            if node.dyn_kwargs is not None:
+                self.write(', **dict({')
+            else:
+                self.write(', **{')
+            for kwarg in node.kwargs:
+                self.write('%r: ' % kwarg.key)
+                self.visit(kwarg.value, frame)
+                self.write(', ')
+            if extra_kwargs is not None:
+                for key, value in extra_kwargs.iteritems():
+                    self.write('%r: %s, ' % (key, value))
+            if node.dyn_kwargs is not None:
+                self.write('}, **')
+                self.visit(node.dyn_kwargs, frame)
+                self.write(')')
+            else:
+                self.write('}')
+
+        elif node.dyn_kwargs is not None:
+            self.write(', **')
+            self.visit(node.dyn_kwargs, frame)
+
+    def pull_locals(self, frame):
+        """Pull all the references identifiers into the local scope."""
+        for name in frame.identifiers.undeclared:
+            self.writeline('l_%s = context.resolve(%r)' % (name, name))
+
+    def pull_dependencies(self, nodes):
+        """Pull all the dependencies."""
+        visitor = DependencyFinderVisitor()
+        for node in nodes:
+            visitor.visit(node)
+        for dependency in 'filters', 'tests':
+            mapping = getattr(self, dependency)
+            for name in getattr(visitor, dependency):
+                if name not in mapping:
+                    mapping[name] = self.temporary_identifier()
+                self.writeline('%s = environment.%s[%r]' %
+                               (mapping[name], dependency, name))
+
+    def unoptimize_scope(self, frame):
+        """Disable Python optimizations for the frame."""
+        # XXX: this is not that nice but it has no real overhead.  It
+        # mainly works because python finds the locals before dead code
+        # is removed.  If that breaks we have to add a dummy function
+        # that just accepts the arguments and does nothing.
+        if frame.identifiers.declared:
+            self.writeline('%sdummy(%s)' % (
+                unoptimize_before_dead_code and 'if 0: ' or '',
+                ', '.join('l_' + name for name in frame.identifiers.declared)
+            ))
+
+    def push_scope(self, frame, extra_vars=()):
+        """This function returns all the shadowed variables in a dict
+        in the form name: alias and will write the required assignments
+        into the current scope.  No indentation takes place.
+
+        This also predefines locally declared variables from the loop
+        body because under some circumstances it may be the case that
+
+        `extra_vars` is passed to `Frame.find_shadowed`.
+        """
+        aliases = {}
+        for name in frame.find_shadowed(extra_vars):
+            aliases[name] = ident = self.temporary_identifier()
+            self.writeline('%s = l_%s' % (ident, name))
+        to_declare = set()
+        for name in frame.identifiers.declared_locally:
+            if name not in aliases:
+                to_declare.add('l_' + name)
+        if to_declare:
+            self.writeline(' = '.join(to_declare) + ' = missing')
+        return aliases
+
+    def pop_scope(self, aliases, frame):
+        """Restore all aliases and delete unused variables."""
+        for name, alias in aliases.iteritems():
+            self.writeline('l_%s = %s' % (name, alias))
+        to_delete = set()
+        for name in frame.identifiers.declared_locally:
+            if name not in aliases:
+                to_delete.add('l_' + name)
+        if to_delete:
+            # we cannot use the del statement here because enclosed
+            # scopes can trigger a SyntaxError:
+            #   a = 42; b = lambda: a; del a
+            self.writeline(' = '.join(to_delete) + ' = missing')
+
+    def function_scoping(self, node, frame, children=None,
+                         find_special=True):
+        """In Jinja a few statements require the help of anonymous
+        functions.  Those are currently macros and call blocks and in
+        the future also recursive loops.  As there is currently
+        technical limitation that doesn't allow reading and writing a
+        variable in a scope where the initial value is coming from an
+        outer scope, this function tries to fall back with a common
+        error message.  Additionally the frame passed is modified so
+        that the argumetns are collected and callers are looked up.
+
+        This will return the modified frame.
+        """
+        # we have to iterate twice over it, make sure that works
+        if children is None:
+            children = node.iter_child_nodes()
+        children = list(children)
+        func_frame = frame.inner()
+        func_frame.inspect(children)
+
+        # variables that are undeclared (accessed before declaration) and
+        # declared locally *and* part of an outside scope raise a template
+        # assertion error. Reason: we can't generate reasonable code from
+        # it without aliasing all the variables.
+        # this could be fixed in Python 3 where we have the nonlocal
+        # keyword or if we switch to bytecode generation
+        overriden_closure_vars = (
+            func_frame.identifiers.undeclared &
+            func_frame.identifiers.declared &
+            (func_frame.identifiers.declared_locally |
+             func_frame.identifiers.declared_parameter)
+        )
+        if overriden_closure_vars:
+            self.fail('It\'s not possible to set and access variables '
+                      'derived from an outer scope! (affects: %s)' %
+                      ', '.join(sorted(overriden_closure_vars)), node.lineno)
+
+        # remove variables from a closure from the frame's undeclared
+        # identifiers.
+        func_frame.identifiers.undeclared -= (
+            func_frame.identifiers.undeclared &
+            func_frame.identifiers.declared
+        )
+
+        # no special variables for this scope, abort early
+        if not find_special:
+            return func_frame
+
+        func_frame.accesses_kwargs = False
+        func_frame.accesses_varargs = False
+        func_frame.accesses_caller = False
+        func_frame.arguments = args = ['l_' + x.name for x in node.args]
+
+        undeclared = find_undeclared(children, ('caller', 'kwargs', 'varargs'))
+
+        if 'caller' in undeclared:
+            func_frame.accesses_caller = True
+            func_frame.identifiers.add_special('caller')
+            args.append('l_caller')
+        if 'kwargs' in undeclared:
+            func_frame.accesses_kwargs = True
+            func_frame.identifiers.add_special('kwargs')
+            args.append('l_kwargs')
+        if 'varargs' in undeclared:
+            func_frame.accesses_varargs = True
+            func_frame.identifiers.add_special('varargs')
+            args.append('l_varargs')
+        return func_frame
+
+    def macro_body(self, node, frame, children=None):
+        """Dump the function def of a macro or call block."""
+        frame = self.function_scoping(node, frame, children)
+        # macros are delayed, they never require output checks
+        frame.require_output_check = False
+        args = frame.arguments
+        # XXX: this is an ugly fix for the loop nesting bug
+        # (tests.test_old_bugs.test_loop_call_bug).  This works around
+        # a identifier nesting problem we have in general.  It's just more
+        # likely to happen in loops which is why we work around it.  The
+        # real solution would be "nonlocal" all the identifiers that are
+        # leaking into a new python frame and might be used both unassigned
+        # and assigned.
+        if 'loop' in frame.identifiers.declared:
+            args = args + ['l_loop=l_loop']
+        self.writeline('def macro(%s):' % ', '.join(args), node)
+        self.indent()
+        self.buffer(frame)
+        self.pull_locals(frame)
+        self.blockvisit(node.body, frame)
+        self.return_buffer_contents(frame)
+        self.outdent()
+        return frame
+
+    def macro_def(self, node, frame):
+        """Dump the macro definition for the def created by macro_body."""
+        arg_tuple = ', '.join(repr(x.name) for x in node.args)
+        name = getattr(node, 'name', None)
+        if len(node.args) == 1:
+            arg_tuple += ','
+        self.write('Macro(environment, macro, %r, (%s), (' %
+                   (name, arg_tuple))
+        for arg in node.defaults:
+            self.visit(arg, frame)
+            self.write(', ')
+        self.write('), %r, %r, %r)' % (
+            bool(frame.accesses_kwargs),
+            bool(frame.accesses_varargs),
+            bool(frame.accesses_caller)
+        ))
+
+    def position(self, node):
+        """Return a human readable position for the node."""
+        rv = 'line %d' % node.lineno
+        if self.name is not None:
+            rv += ' in ' + repr(self.name)
+        return rv
+
+    # -- Statement Visitors
+
+    def visit_Template(self, node, frame=None):
+        assert frame is None, 'no root frame allowed'
+        eval_ctx = EvalContext(self.environment, self.name)
+
+        from jinja2.runtime import __all__ as exported
+        self.writeline('from __future__ import division')
+        self.writeline('from jinja2.runtime import ' + ', '.join(exported))
+        if not unoptimize_before_dead_code:
+            self.writeline('dummy = lambda *x: None')
+
+        # if we want a deferred initialization we cannot move the
+        # environment into a local name
+        envenv = not self.defer_init and ', environment=environment' or ''
+
+        # do we have an extends tag at all?  If not, we can save some
+        # overhead by just not processing any inheritance code.
+        have_extends = node.find(nodes.Extends) is not None
+
+        # find all blocks
+        for block in node.find_all(nodes.Block):
+            if block.name in self.blocks:
+                self.fail('block %r defined twice' % block.name, block.lineno)
+            self.blocks[block.name] = block
+
+        # find all imports and import them
+        for import_ in node.find_all(nodes.ImportedName):
+            if import_.importname not in self.import_aliases:
+                imp = import_.importname
+                self.import_aliases[imp] = alias = self.temporary_identifier()
+                if '.' in imp:
+                    module, obj = imp.rsplit('.', 1)
+                    self.writeline('from %s import %s as %s' %
+                                   (module, obj, alias))
+                else:
+                    self.writeline('import %s as %s' % (imp, alias))
+
+        # add the load name
+        self.writeline('name = %r' % self.name)
+
+        # generate the root render function.
+        self.writeline('def root(context%s):' % envenv, extra=1)
+
+        # process the root
+        frame = Frame(eval_ctx)
+        frame.inspect(node.body)
+        frame.toplevel = frame.rootlevel = True
+        frame.require_output_check = have_extends and not self.has_known_extends
+        self.indent()
+        if have_extends:
+            self.writeline('parent_template = None')
+        if 'self' in find_undeclared(node.body, ('self',)):
+            frame.identifiers.add_special('self')
+            self.writeline('l_self = TemplateReference(context)')
+        self.pull_locals(frame)
+        self.pull_dependencies(node.body)
+        self.blockvisit(node.body, frame)
+        self.outdent()
+
+        # make sure that the parent root is called.
+        if have_extends:
+            if not self.has_known_extends:
+                self.indent()
+                self.writeline('if parent_template is not None:')
+            self.indent()
+            self.writeline('for event in parent_template.'
+                           'root_render_func(context):')
+            self.indent()
+            self.writeline('yield event')
+            self.outdent(2 + (not self.has_known_extends))
+
+        # at this point we now have the blocks collected and can visit them too.
+        for name, block in self.blocks.iteritems():
+            block_frame = Frame(eval_ctx)
+            block_frame.inspect(block.body)
+            block_frame.block = name
+            self.writeline('def block_%s(context%s):' % (name, envenv),
+                           block, 1)
+            self.indent()
+            undeclared = find_undeclared(block.body, ('self', 'super'))
+            if 'self' in undeclared:
+                block_frame.identifiers.add_special('self')
+                self.writeline('l_self = TemplateReference(context)')
+            if 'super' in undeclared:
+                block_frame.identifiers.add_special('super')
+                self.writeline('l_super = context.super(%r, '
+                               'block_%s)' % (name, name))
+            self.pull_locals(block_frame)
+            self.pull_dependencies(block.body)
+            self.blockvisit(block.body, block_frame)
+            self.outdent()
+
+        self.writeline('blocks = {%s}' % ', '.join('%r: block_%s' % (x, x)
+                                                   for x in self.blocks),
+                       extra=1)
+
+        # add a function that returns the debug info
+        self.writeline('debug_info = %r' % '&'.join('%s=%s' % x for x
+                                                    in self.debug_info))
+
+    def visit_Block(self, node, frame):
+        """Call a block and register it for the template."""
+        level = 1
+        if frame.toplevel:
+            # if we know that we are a child template, there is no need to
+            # check if we are one
+            if self.has_known_extends:
+                return
+            if self.extends_so_far > 0:
+                self.writeline('if parent_template is None:')
+                self.indent()
+                level += 1
+        context = node.scoped and 'context.derived(locals())' or 'context'
+        self.writeline('for event in context.blocks[%r][0](%s):' % (
+                       node.name, context), node)
+        self.indent()
+        self.simple_write('event', frame)
+        self.outdent(level)
+
+    def visit_Extends(self, node, frame):
+        """Calls the extender."""
+        if not frame.toplevel:
+            self.fail('cannot use extend from a non top-level scope',
+                      node.lineno)
+
+        # if the number of extends statements in general is zero so
+        # far, we don't have to add a check if something extended
+        # the template before this one.
+        if self.extends_so_far > 0:
+
+            # if we have a known extends we just add a template runtime
+            # error into the generated code.  We could catch that at compile
+            # time too, but i welcome it not to confuse users by throwing the
+            # same error at different times just "because we can".
+            if not self.has_known_extends:
+                self.writeline('if parent_template is not None:')
+                self.indent()
+            self.writeline('raise TemplateRuntimeError(%r)' %
+                           'extended multiple times')
+            self.outdent()
+
+            # if we have a known extends already we don't need that code here
+            # as we know that the template execution will end here.
+            if self.has_known_extends:
+                raise CompilerExit()
+
+        self.writeline('parent_template = environment.get_template(', node)
+        self.visit(node.template, frame)
+        self.write(', %r)' % self.name)
+        self.writeline('for name, parent_block in parent_template.'
+                       'blocks.%s():' % dict_item_iter)
+        self.indent()
+        self.writeline('context.blocks.setdefault(name, []).'
+                       'append(parent_block)')
+        self.outdent()
+
+        # if this extends statement was in the root level we can take
+        # advantage of that information and simplify the generated code
+        # in the top level from this point onwards
+        if frame.rootlevel:
+            self.has_known_extends = True
+
+        # and now we have one more
+        self.extends_so_far += 1
+
+    def visit_Include(self, node, frame):
+        """Handles includes."""
+        if node.with_context:
+            self.unoptimize_scope(frame)
+        if node.ignore_missing:
+            self.writeline('try:')
+            self.indent()
+
+        func_name = 'get_or_select_template'
+        if isinstance(node.template, nodes.Const):
+            if isinstance(node.template.value, basestring):
+                func_name = 'get_template'
+            elif isinstance(node.template.value, (tuple, list)):
+                func_name = 'select_template'
+        elif isinstance(node.template, (nodes.Tuple, nodes.List)):
+            func_name = 'select_template'
+
+        self.writeline('template = environment.%s(' % func_name, node)
+        self.visit(node.template, frame)
+        self.write(', %r)' % self.name)
+        if node.ignore_missing:
+            self.outdent()
+            self.writeline('except TemplateNotFound:')
+            self.indent()
+            self.writeline('pass')
+            self.outdent()
+            self.writeline('else:')
+            self.indent()
+
+        if node.with_context:
+            self.writeline('for event in template.root_render_func('
+                           'template.new_context(context.parent, True, '
+                           'locals())):')
+        else:
+            self.writeline('for event in template.module._body_stream:')
+
+        self.indent()
+        self.simple_write('event', frame)
+        self.outdent()
+
+        if node.ignore_missing:
+            self.outdent()
+
+    def visit_Import(self, node, frame):
+        """Visit regular imports."""
+        if node.with_context:
+            self.unoptimize_scope(frame)
+        self.writeline('l_%s = ' % node.target, node)
+        if frame.toplevel:
+            self.write('context.vars[%r] = ' % node.target)
+        self.write('environment.get_template(')
+        self.visit(node.template, frame)
+        self.write(', %r).' % self.name)
+        if node.with_context:
+            self.write('make_module(context.parent, True, locals())')
+        else:
+            self.write('module')
+        if frame.toplevel and not node.target.startswith('_'):
+            self.writeline('context.exported_vars.discard(%r)' % node.target)
+        frame.assigned_names.add(node.target)
+
+    def visit_FromImport(self, node, frame):
+        """Visit named imports."""
+        self.newline(node)
+        self.write('included_template = environment.get_template(')
+        self.visit(node.template, frame)
+        self.write(', %r).' % self.name)
+        if node.with_context:
+            self.write('make_module(context.parent, True)')
+        else:
+            self.write('module')
+
+        var_names = []
+        discarded_names = []
+        for name in node.names:
+            if isinstance(name, tuple):
+                name, alias = name
+            else:
+                alias = name
+            self.writeline('l_%s = getattr(included_template, '
+                           '%r, missing)' % (alias, name))
+            self.writeline('if l_%s is missing:' % alias)
+            self.indent()
+            self.writeline('l_%s = environment.undefined(%r %% '
+                           'included_template.__name__, '
+                           'name=%r)' %
+                           (alias, 'the template %%r (imported on %s) does '
+                           'not export the requested name %s' % (
+                                self.position(node),
+                                repr(name)
+                           ), name))
+            self.outdent()
+            if frame.toplevel:
+                var_names.append(alias)
+                if not alias.startswith('_'):
+                    discarded_names.append(alias)
+            frame.assigned_names.add(alias)
+
+        if var_names:
+            if len(var_names) == 1:
+                name = var_names[0]
+                self.writeline('context.vars[%r] = l_%s' % (name, name))
+            else:
+                self.writeline('context.vars.update({%s})' % ', '.join(
+                    '%r: l_%s' % (name, name) for name in var_names
+                ))
+        if discarded_names:
+            if len(discarded_names) == 1:
+                self.writeline('context.exported_vars.discard(%r)' %
+                               discarded_names[0])
+            else:
+                self.writeline('context.exported_vars.difference_'
+                               'update((%s))' % ', '.join(map(repr, discarded_names)))
+
+    def visit_For(self, node, frame):
+        # when calculating the nodes for the inner frame we have to exclude
+        # the iterator contents from it
+        children = node.iter_child_nodes(exclude=('iter',))
+        if node.recursive:
+            loop_frame = self.function_scoping(node, frame, children,
+                                               find_special=False)
+        else:
+            loop_frame = frame.inner()
+            loop_frame.inspect(children)
+
+        # try to figure out if we have an extended loop.  An extended loop
+        # is necessary if the loop is in recursive mode if the special loop
+        # variable is accessed in the body.
+        extended_loop = node.recursive or 'loop' in \
+                        find_undeclared(node.iter_child_nodes(
+                            only=('body',)), ('loop',))
+
+        # if we don't have an recursive loop we have to find the shadowed
+        # variables at that point.  Because loops can be nested but the loop
+        # variable is a special one we have to enforce aliasing for it.
+        if not node.recursive:
+            aliases = self.push_scope(loop_frame, ('loop',))
+
+        # otherwise we set up a buffer and add a function def
+        else:
+            self.writeline('def loop(reciter, loop_render_func):', node)
+            self.indent()
+            self.buffer(loop_frame)
+            aliases = {}
+
+        # make sure the loop variable is a special one and raise a template
+        # assertion error if a loop tries to write to loop
+        if extended_loop:
+            loop_frame.identifiers.add_special('loop')
+        for name in node.find_all(nodes.Name):
+            if name.ctx == 'store' and name.name == 'loop':
+                self.fail('Can\'t assign to special loop variable '
+                          'in for-loop target', name.lineno)
+
+        self.pull_locals(loop_frame)
+        if node.else_:
+            iteration_indicator = self.temporary_identifier()
+            self.writeline('%s = 1' % iteration_indicator)
+
+        # Create a fake parent loop if the else or test section of a
+        # loop is accessing the special loop variable and no parent loop
+        # exists.
+        if 'loop' not in aliases and 'loop' in find_undeclared(
+           node.iter_child_nodes(only=('else_', 'test')), ('loop',)):
+            self.writeline("l_loop = environment.undefined(%r, name='loop')" %
+                ("'loop' is undefined. the filter section of a loop as well "
+                 "as the else block don't have access to the special 'loop'"
+                 " variable of the current loop.  Because there is no parent "
+                 "loop it's undefined.  Happened in loop on %s" %
+                 self.position(node)))
+
+        self.writeline('for ', node)
+        self.visit(node.target, loop_frame)
+        self.write(extended_loop and ', l_loop in LoopContext(' or ' in ')
+
+        # if we have an extened loop and a node test, we filter in the
+        # "outer frame".
+        if extended_loop and node.test is not None:
+            self.write('(')
+            self.visit(node.target, loop_frame)
+            self.write(' for ')
+            self.visit(node.target, loop_frame)
+            self.write(' in ')
+            if node.recursive:
+                self.write('reciter')
+            else:
+                self.visit(node.iter, loop_frame)
+            self.write(' if (')
+            test_frame = loop_frame.copy()
+            self.visit(node.test, test_frame)
+            self.write('))')
+
+        elif node.recursive:
+            self.write('reciter')
+        else:
+            self.visit(node.iter, loop_frame)
+
+        if node.recursive:
+            self.write(', recurse=loop_render_func):')
+        else:
+            self.write(extended_loop and '):' or ':')
+
+        # tests in not extended loops become a continue
+        if not extended_loop and node.test is not None:
+            self.indent()
+            self.writeline('if not ')
+            self.visit(node.test, loop_frame)
+            self.write(':')
+            self.indent()
+            self.writeline('continue')
+            self.outdent(2)
+
+        self.indent()
+        self.blockvisit(node.body, loop_frame)
+        if node.else_:
+            self.writeline('%s = 0' % iteration_indicator)
+        self.outdent()
+
+        if node.else_:
+            self.writeline('if %s:' % iteration_indicator)
+            self.indent()
+            self.blockvisit(node.else_, loop_frame)
+            self.outdent()
+
+        # reset the aliases if there are any.
+        if not node.recursive:
+            self.pop_scope(aliases, loop_frame)
+
+        # if the node was recursive we have to return the buffer contents
+        # and start the iteration code
+        if node.recursive:
+            self.return_buffer_contents(loop_frame)
+            self.outdent()
+            self.start_write(frame, node)
+            self.write('loop(')
+            self.visit(node.iter, frame)
+            self.write(', loop)')
+            self.end_write(frame)
+
+    def visit_If(self, node, frame):
+        if_frame = frame.soft()
+        self.writeline('if ', node)
+        self.visit(node.test, if_frame)
+        self.write(':')
+        self.indent()
+        self.blockvisit(node.body, if_frame)
+        self.outdent()
+        if node.else_:
+            self.writeline('else:')
+            self.indent()
+            self.blockvisit(node.else_, if_frame)
+            self.outdent()
+
+    def visit_Macro(self, node, frame):
+        macro_frame = self.macro_body(node, frame)
+        self.newline()
+        if frame.toplevel:
+            if not node.name.startswith('_'):
+                self.write('context.exported_vars.add(%r)' % node.name)
+            self.writeline('context.vars[%r] = ' % node.name)
+        self.write('l_%s = ' % node.name)
+        self.macro_def(node, macro_frame)
+        frame.assigned_names.add(node.name)
+
+    def visit_CallBlock(self, node, frame):
+        children = node.iter_child_nodes(exclude=('call',))
+        call_frame = self.macro_body(node, frame, children)
+        self.writeline('caller = ')
+        self.macro_def(node, call_frame)
+        self.start_write(frame, node)
+        self.visit_Call(node.call, call_frame, forward_caller=True)
+        self.end_write(frame)
+
+    def visit_FilterBlock(self, node, frame):
+        filter_frame = frame.inner()
+        filter_frame.inspect(node.iter_child_nodes())
+        aliases = self.push_scope(filter_frame)
+        self.pull_locals(filter_frame)
+        self.buffer(filter_frame)
+        self.blockvisit(node.body, filter_frame)
+        self.start_write(frame, node)
+        self.visit_Filter(node.filter, filter_frame)
+        self.end_write(frame)
+        self.pop_scope(aliases, filter_frame)
+
+    def visit_ExprStmt(self, node, frame):
+        self.newline(node)
+        self.visit(node.node, frame)
+
+    def visit_Output(self, node, frame):
+        # if we have a known extends statement, we don't output anything
+        # if we are in a require_output_check section
+        if self.has_known_extends and frame.require_output_check:
+            return
+
+        if self.environment.finalize:
+            finalize = lambda x: unicode(self.environment.finalize(x))
+        else:
+            finalize = unicode
+
+        # if we are inside a frame that requires output checking, we do so
+        outdent_later = False
+        if frame.require_output_check:
+            self.writeline('if parent_template is None:')
+            self.indent()
+            outdent_later = True
+
+        # try to evaluate as many chunks as possible into a static
+        # string at compile time.
+        body = []
+        for child in node.nodes:
+            try:
+                const = child.as_const(frame.eval_ctx)
+            except nodes.Impossible:
+                body.append(child)
+                continue
+            # the frame can't be volatile here, becaus otherwise the
+            # as_const() function would raise an Impossible exception
+            # at that point.
+            try:
+                if frame.eval_ctx.autoescape:
+                    if hasattr(const, '__html__'):
+                        const = const.__html__()
+                    else:
+                        const = escape(const)
+                const = finalize(const)
+            except Exception:
+                # if something goes wrong here we evaluate the node
+                # at runtime for easier debugging
+                body.append(child)
+                continue
+            if body and isinstance(body[-1], list):
+                body[-1].append(const)
+            else:
+                body.append([const])
+
+        # if we have less than 3 nodes or a buffer we yield or extend/append
+        if len(body) < 3 or frame.buffer is not None:
+            if frame.buffer is not None:
+                # for one item we append, for more we extend
+                if len(body) == 1:
+                    self.writeline('%s.append(' % frame.buffer)
+                else:
+                    self.writeline('%s.extend((' % frame.buffer)
+                self.indent()
+            for item in body:
+                if isinstance(item, list):
+                    val = repr(concat(item))
+                    if frame.buffer is None:
+                        self.writeline('yield ' + val)
+                    else:
+                        self.writeline(val + ', ')
+                else:
+                    if frame.buffer is None:
+                        self.writeline('yield ', item)
+                    else:
+                        self.newline(item)
+                    close = 1
+                    if frame.eval_ctx.volatile:
+                        self.write('(context.eval_ctx.autoescape and'
+                                   ' escape or to_string)(')
+                    elif frame.eval_ctx.autoescape:
+                        self.write('escape(')
+                    else:
+                        self.write('to_string(')
+                    if self.environment.finalize is not None:
+                        self.write('environment.finalize(')
+                        close += 1
+                    self.visit(item, frame)
+                    self.write(')' * close)
+                    if frame.buffer is not None:
+                        self.write(', ')
+            if frame.buffer is not None:
+                # close the open parentheses
+                self.outdent()
+                self.writeline(len(body) == 1 and ')' or '))')
+
+        # otherwise we create a format string as this is faster in that case
+        else:
+            format = []
+            arguments = []
+            for item in body:
+                if isinstance(item, list):
+                    format.append(concat(item).replace('%', '%%'))
+                else:
+                    format.append('%s')
+                    arguments.append(item)
+            self.writeline('yield ')
+            self.write(repr(concat(format)) + ' % (')
+            idx = -1
+            self.indent()
+            for argument in arguments:
+                self.newline(argument)
+                close = 0
+                if frame.eval_ctx.volatile:
+                    self.write('(context.eval_ctx.autoescape and'
+                               ' escape or to_string)(')
+                    close += 1
+                elif frame.eval_ctx.autoescape:
+                    self.write('escape(')
+                    close += 1
+                if self.environment.finalize is not None:
+                    self.write('environment.finalize(')
+                    close += 1
+                self.visit(argument, frame)
+                self.write(')' * close + ', ')
+            self.outdent()
+            self.writeline(')')
+
+        if outdent_later:
+            self.outdent()
+
+    def visit_Assign(self, node, frame):
+        self.newline(node)
+        # toplevel assignments however go into the local namespace and
+        # the current template's context.  We create a copy of the frame
+        # here and add a set so that the Name visitor can add the assigned
+        # names here.
+        if frame.toplevel:
+            assignment_frame = frame.copy()
+            assignment_frame.toplevel_assignments = set()
+        else:
+            assignment_frame = frame
+        self.visit(node.target, assignment_frame)
+        self.write(' = ')
+        self.visit(node.node, frame)
+
+        # make sure toplevel assignments are added to the context.
+        if frame.toplevel:
+            public_names = [x for x in assignment_frame.toplevel_assignments
+                            if not x.startswith('_')]
+            if len(assignment_frame.toplevel_assignments) == 1:
+                name = next(iter(assignment_frame.toplevel_assignments))
+                self.writeline('context.vars[%r] = l_%s' % (name, name))
+            else:
+                self.writeline('context.vars.update({')
+                for idx, name in enumerate(assignment_frame.toplevel_assignments):
+                    if idx:
+                        self.write(', ')
+                    self.write('%r: l_%s' % (name, name))
+                self.write('})')
+            if public_names:
+                if len(public_names) == 1:
+                    self.writeline('context.exported_vars.add(%r)' %
+                                   public_names[0])
+                else:
+                    self.writeline('context.exported_vars.update((%s))' %
+                                   ', '.join(map(repr, public_names)))
+
+    # -- Expression Visitors
+
+    def visit_Name(self, node, frame):
+        if node.ctx == 'store' and frame.toplevel:
+            frame.toplevel_assignments.add(node.name)
+        self.write('l_' + node.name)
+        frame.assigned_names.add(node.name)
+
+    def visit_Const(self, node, frame):
+        val = node.value
+        if isinstance(val, float):
+            self.write(str(val))
+        else:
+            self.write(repr(val))
+
+    def visit_TemplateData(self, node, frame):
+        try:
+            self.write(repr(node.as_const(frame.eval_ctx)))
+        except nodes.Impossible:
+            self.write('(context.eval_ctx.autoescape and Markup or identity)(%r)'
+                       % node.data)
+
+    def visit_Tuple(self, node, frame):
+        self.write('(')
+        idx = -1
+        for idx, item in enumerate(node.items):
+            if idx:
+                self.write(', ')
+            self.visit(item, frame)
+        self.write(idx == 0 and ',)' or ')')
+
+    def visit_List(self, node, frame):
+        self.write('[')
+        for idx, item in enumerate(node.items):
+            if idx:
+                self.write(', ')
+            self.visit(item, frame)
+        self.write(']')
+
+    def visit_Dict(self, node, frame):
+        self.write('{')
+        for idx, item in enumerate(node.items):
+            if idx:
+                self.write(', ')
+            self.visit(item.key, frame)
+            self.write(': ')
+            self.visit(item.value, frame)
+        self.write('}')
+
+    def binop(operator, interceptable=True):
+        def visitor(self, node, frame):
+            if self.environment.sandboxed and \
+               operator in self.environment.intercepted_binops:
+                self.write('environment.call_binop(context, %r, ' % operator)
+                self.visit(node.left, frame)
+                self.write(', ')
+                self.visit(node.right, frame)
+            else:
+                self.write('(')
+                self.visit(node.left, frame)
+                self.write(' %s ' % operator)
+                self.visit(node.right, frame)
+            self.write(')')
+        return visitor
+
+    def uaop(operator, interceptable=True):
+        def visitor(self, node, frame):
+            if self.environment.sandboxed and \
+               operator in self.environment.intercepted_unops:
+                self.write('environment.call_unop(context, %r, ' % operator)
+                self.visit(node.node, frame)
+            else:
+                self.write('(' + operator)
+                self.visit(node.node, frame)
+            self.write(')')
+        return visitor
+
+    visit_Add = binop('+')
+    visit_Sub = binop('-')
+    visit_Mul = binop('*')
+    visit_Div = binop('/')
+    visit_FloorDiv = binop('//')
+    visit_Pow = binop('**')
+    visit_Mod = binop('%')
+    visit_And = binop('and', interceptable=False)
+    visit_Or = binop('or', interceptable=False)
+    visit_Pos = uaop('+')
+    visit_Neg = uaop('-')
+    visit_Not = uaop('not ', interceptable=False)
+    del binop, uaop
+
+    def visit_Concat(self, node, frame):
+        if frame.eval_ctx.volatile:
+            func_name = '(context.eval_ctx.volatile and' \
+                        ' markup_join or unicode_join)'
+        elif frame.eval_ctx.autoescape:
+            func_name = 'markup_join'
+        else:
+            func_name = 'unicode_join'
+        self.write('%s((' % func_name)
+        for arg in node.nodes:
+            self.visit(arg, frame)
+            self.write(', ')
+        self.write('))')
+
+    def visit_Compare(self, node, frame):
+        self.visit(node.expr, frame)
+        for op in node.ops:
+            self.visit(op, frame)
+
+    def visit_Operand(self, node, frame):
+        self.write(' %s ' % operators[node.op])
+        self.visit(node.expr, frame)
+
+    def visit_Getattr(self, node, frame):
+        self.write('environment.getattr(')
+        self.visit(node.node, frame)
+        self.write(', %r)' % node.attr)
+
+    def visit_Getitem(self, node, frame):
+        # slices bypass the environment getitem method.
+        if isinstance(node.arg, nodes.Slice):
+            self.visit(node.node, frame)
+            self.write('[')
+            self.visit(node.arg, frame)
+            self.write(']')
+        else:
+            self.write('environment.getitem(')
+            self.visit(node.node, frame)
+            self.write(', ')
+            self.visit(node.arg, frame)
+            self.write(')')
+
+    def visit_Slice(self, node, frame):
+        if node.start is not None:
+            self.visit(node.start, frame)
+        self.write(':')
+        if node.stop is not None:
+            self.visit(node.stop, frame)
+        if node.step is not None:
+            self.write(':')
+            self.visit(node.step, frame)
+
+    def visit_Filter(self, node, frame):
+        self.write(self.filters[node.name] + '(')
+        func = self.environment.filters.get(node.name)
+        if func is None:
+            self.fail('no filter named %r' % node.name, node.lineno)
+        if getattr(func, 'contextfilter', False):
+            self.write('context, ')
+        elif getattr(func, 'evalcontextfilter', False):
+            self.write('context.eval_ctx, ')
+        elif getattr(func, 'environmentfilter', False):
+            self.write('environment, ')
+
+        # if the filter node is None we are inside a filter block
+        # and want to write to the current buffer
+        if node.node is not None:
+            self.visit(node.node, frame)
+        elif frame.eval_ctx.volatile:
+            self.write('(context.eval_ctx.autoescape and'
+                       ' Markup(concat(%s)) or concat(%s))' %
+                       (frame.buffer, frame.buffer))
+        elif frame.eval_ctx.autoescape:
+            self.write('Markup(concat(%s))' % frame.buffer)
+        else:
+            self.write('concat(%s)' % frame.buffer)
+        self.signature(node, frame)
+        self.write(')')
+
+    def visit_Test(self, node, frame):
+        self.write(self.tests[node.name] + '(')
+        if node.name not in self.environment.tests:
+            self.fail('no test named %r' % node.name, node.lineno)
+        self.visit(node.node, frame)
+        self.signature(node, frame)
+        self.write(')')
+
+    def visit_CondExpr(self, node, frame):
+        def write_expr2():
+            if node.expr2 is not None:
+                return self.visit(node.expr2, frame)
+            self.write('environment.undefined(%r)' % ('the inline if-'
+                       'expression on %s evaluated to false and '
+                       'no else section was defined.' % self.position(node)))
+
+        if not have_condexpr:
+            self.write('((')
+            self.visit(node.test, frame)
+            self.write(') and (')
+            self.visit(node.expr1, frame)
+            self.write(',) or (')
+            write_expr2()
+            self.write(',))[0]')
+        else:
+            self.write('(')
+            self.visit(node.expr1, frame)
+            self.write(' if ')
+            self.visit(node.test, frame)
+            self.write(' else ')
+            write_expr2()
+            self.write(')')
+
+    def visit_Call(self, node, frame, forward_caller=False):
+        if self.environment.sandboxed:
+            self.write('environment.call(context, ')
+        else:
+            self.write('context.call(')
+        self.visit(node.node, frame)
+        extra_kwargs = forward_caller and {'caller': 'caller'} or None
+        self.signature(node, frame, extra_kwargs)
+        self.write(')')
+
+    def visit_Keyword(self, node, frame):
+        self.write(node.key + '=')
+        self.visit(node.value, frame)
+
+    # -- Unused nodes for extensions
+
+    def visit_MarkSafe(self, node, frame):
+        self.write('Markup(')
+        self.visit(node.expr, frame)
+        self.write(')')
+
+    def visit_MarkSafeIfAutoescape(self, node, frame):
+        self.write('(context.eval_ctx.autoescape and Markup or identity)(')
+        self.visit(node.expr, frame)
+        self.write(')')
+
+    def visit_EnvironmentAttribute(self, node, frame):
+        self.write('environment.' + node.name)
+
+    def visit_ExtensionAttribute(self, node, frame):
+        self.write('environment.extensions[%r].%s' % (node.identifier, node.name))
+
+    def visit_ImportedName(self, node, frame):
+        self.write(self.import_aliases[node.importname])
+
+    def visit_InternalName(self, node, frame):
+        self.write(node.name)
+
+    def visit_ContextReference(self, node, frame):
+        self.write('context')
+
+    def visit_Continue(self, node, frame):
+        self.writeline('continue', node)
+
+    def visit_Break(self, node, frame):
+        self.writeline('break', node)
+
+    def visit_Scope(self, node, frame):
+        scope_frame = frame.inner()
+        scope_frame.inspect(node.iter_child_nodes())
+        aliases = self.push_scope(scope_frame)
+        self.pull_locals(scope_frame)
+        self.blockvisit(node.body, scope_frame)
+        self.pop_scope(aliases, scope_frame)
+
+    def visit_EvalContextModifier(self, node, frame):
+        for keyword in node.options:
+            self.writeline('context.eval_ctx.%s = ' % keyword.key)
+            self.visit(keyword.value, frame)
+            try:
+                val = keyword.value.as_const(frame.eval_ctx)
+            except nodes.Impossible:
+                frame.eval_ctx.volatile = True
+            else:
+                setattr(frame.eval_ctx, keyword.key, val)
+
+    def visit_ScopedEvalContextModifier(self, node, frame):
+        old_ctx_name = self.temporary_identifier()
+        safed_ctx = frame.eval_ctx.save()
+        self.writeline('%s = context.eval_ctx.save()' % old_ctx_name)
+        self.visit_EvalContextModifier(node, frame)
+        for child in node.body:
+            self.visit(child, frame)
+        frame.eval_ctx.revert(safed_ctx)
+        self.writeline('context.eval_ctx.revert(%s)' % old_ctx_name)