610 lines (514 sloc) 23.3 KB
# -*- coding: utf-8 -*-
Jinja extensions allow to add custom tags similar to the way django custom
tags work. By default two example extensions exist: an i18n and a cache
:copyright: (c) 2017 by the Jinja Team.
:license: BSD.
from jinja2 import nodes
from jinja2.defaults import BLOCK_START_STRING, \
from jinja2.environment import Environment
from jinja2.runtime import concat
from jinja2.exceptions import TemplateAssertionError, TemplateSyntaxError
from jinja2.utils import contextfunction, import_string, Markup
from jinja2._compat import with_metaclass, string_types, iteritems
# the only real useful gettext functions for a Jinja template. Note
# that ugettext must be assigned to gettext as Jinja doesn't support
# non unicode strings.
GETTEXT_FUNCTIONS = ('_', 'gettext', 'ngettext')
class ExtensionRegistry(type):
"""Gives the extension an unique identifier."""
def __new__(cls, name, bases, d):
rv = type.__new__(cls, name, bases, d)
rv.identifier = rv.__module__ + '.' + rv.__name__
return rv
class Extension(with_metaclass(ExtensionRegistry, object)):
"""Extensions can be used to add extra functionality to the Jinja template
system at the parser level. Custom extensions are bound to an environment
but may not store environment specific data on `self`. The reason for
this is that an extension can be bound to another environment (for
overlays) by creating a copy and reassigning the `environment` attribute.
As extensions are created by the environment they cannot accept any
arguments for configuration. One may want to work around that by using
a factory function, but that is not possible as extensions are identified
by their import name. The correct way to configure the extension is
storing the configuration values on the environment. Because this way the
environment ends up acting as central configuration storage the
attributes may clash which is why extensions have to ensure that the names
they choose for configuration are not too generic. ``prefix`` for example
is a terrible name, ``fragment_cache_prefix`` on the other hand is a good
name as includes the name of the extension (fragment cache).
#: if this extension parses this is the list of tags it's listening to.
tags = set()
#: the priority of that extension. This is especially useful for
#: extensions that preprocess values. A lower value means higher
#: priority.
#: .. versionadded:: 2.4
priority = 100
def __init__(self, environment):
self.environment = environment
def bind(self, environment):
"""Create a copy of this extension bound to another environment."""
rv = object.__new__(self.__class__)
rv.environment = environment
return rv
def preprocess(self, source, name, filename=None):
"""This method is called before the actual lexing and can be used to
preprocess the source. The `filename` is optional. The return value
must be the preprocessed source.
return source
def filter_stream(self, stream):
"""It's passed a :class:`~jinja2.lexer.TokenStream` that can be used
to filter tokens returned. This method has to return an iterable of
:class:`~jinja2.lexer.Token`\\s, but it doesn't have to return a
In the `ext` folder of the Jinja2 source distribution there is a file
called `` which implements a filter that utilizes this
return stream
def parse(self, parser):
"""If any of the :attr:`tags` matched this method is called with the
parser as first argument. The token the parser stream is pointing at
is the name token that matched. This method has to return one or a
list of multiple nodes.
raise NotImplementedError()
def attr(self, name, lineno=None):
"""Return an attribute node for the current extension. This is useful
to pass constants on extensions to generated template code.
self.attr('_my_attribute', lineno=lineno)
return nodes.ExtensionAttribute(self.identifier, name, lineno=lineno)
def call_method(self, name, args=None, kwargs=None, dyn_args=None,
dyn_kwargs=None, lineno=None):
"""Call a method of the extension. This is a shortcut for
:meth:`attr` + :class:`jinja2.nodes.Call`.
if args is None:
args = []
if kwargs is None:
kwargs = []
return nodes.Call(self.attr(name, lineno=lineno), args, kwargs,
dyn_args, dyn_kwargs, lineno=lineno)
def _gettext_alias(__context, *args, **kwargs):
return'gettext'), *args, **kwargs)
def _make_new_gettext(func):
def gettext(__context, __string, **variables):
rv =, __string)
if __context.eval_ctx.autoescape:
rv = Markup(rv)
return rv % variables
return gettext
def _make_new_ngettext(func):
def ngettext(__context, __singular, __plural, __num, **variables):
variables.setdefault('num', __num)
rv =, __singular, __plural, __num)
if __context.eval_ctx.autoescape:
rv = Markup(rv)
return rv % variables
return ngettext
class InternationalizationExtension(Extension):
"""This extension adds gettext support to Jinja2."""
tags = set(['trans'])
# TODO: the i18n extension is currently reevaluating values in a few
# situations. Take this example:
# {% trans count=something() %}{{ count }} foo{% pluralize
# %}{{ count }} fooss{% endtrans %}
# something is called twice here. One time for the gettext value and
# the other time for the n-parameter of the ngettext function.
def __init__(self, environment):
Extension.__init__(self, environment)
environment.globals['_'] = _gettext_alias
def _install(self, translations, newstyle=None):
gettext = getattr(translations, 'ugettext', None)
if gettext is None:
gettext = translations.gettext
ngettext = getattr(translations, 'ungettext', None)
if ngettext is None:
ngettext = translations.ngettext
self._install_callables(gettext, ngettext, newstyle)
def _install_null(self, newstyle=None):
lambda x: x,
lambda s, p, n: (n != 1 and (p,) or (s,))[0],
def _install_callables(self, gettext, ngettext, newstyle=None):
if newstyle is not None:
self.environment.newstyle_gettext = newstyle
if self.environment.newstyle_gettext:
gettext = _make_new_gettext(gettext)
ngettext = _make_new_ngettext(ngettext)
def _uninstall(self, translations):
for key in 'gettext', 'ngettext':
self.environment.globals.pop(key, None)
def _extract(self, source, gettext_functions=GETTEXT_FUNCTIONS):
if isinstance(source, string_types):
source = self.environment.parse(source)
return extract_from_ast(source, gettext_functions)
def parse(self, parser):
"""Parse a translatable tag."""
lineno = next(
num_called_num = False
# find all the variables referenced. Additionally a variable can be
# defined in the body of the trans block too, but this is checked at
# a later state.
plural_expr = None
plural_expr_assignment = None
variables = {}
while != 'block_end':
if variables:'comma')
# skip colon for python compatibility
name ='name')
if name.value in variables:'translatable variable %r defined twice.' %
name.value, name.lineno,
# expressions
if == 'assign':
variables[name.value] = var = parser.parse_expression()
variables[name.value] = var = nodes.Name(name.value, 'load')
if plural_expr is None:
if isinstance(var, nodes.Call):
plural_expr = nodes.Name('_trans', 'load')
variables[name.value] = plural_expr
plural_expr_assignment = nodes.Assign(
nodes.Name('_trans', 'store'), var)
plural_expr = var
num_called_num = name.value == 'num''block_end')
plural = plural_names = None
have_plural = False
referenced = set()
# now parse until endtrans or pluralize
singular_names, singular = self._parse_block(parser, True)
if singular_names:
if plural_expr is None:
plural_expr = nodes.Name(singular_names[0], 'load')
num_called_num = singular_names[0] == 'num'
# if we have a pluralize block, we parse that too
have_plural = True
if != 'block_end':
name ='name')
if name.value not in variables:'unknown variable %r for pluralization' %
name.value, name.lineno,
plural_expr = variables[name.value]
num_called_num = name.value == 'num''block_end')
plural_names, plural = self._parse_block(parser, False)
# register free names as simple name expressions
for var in referenced:
if var not in variables:
variables[var] = nodes.Name(var, 'load')
if not have_plural:
plural_expr = None
elif plural_expr is None:'pluralize without variables', lineno)
node = self._make_node(singular, plural, variables, plural_expr,
num_called_num and have_plural)
if plural_expr_assignment is not None:
return [plural_expr_assignment, node]
return node
def _parse_block(self, parser, allow_pluralize):
"""Parse until the next block tag with a given name."""
referenced = []
buf = []
while 1:
if == 'data':
buf.append('%', '%%'))
elif == 'variable_begin':
name ='name').value
buf.append('%%(%s)s' % name)'variable_end')
elif == 'block_begin':
if allow_pluralize:
break'a translatable section can have only one '
'pluralize section')'control structures in translatable sections are '
'not allowed')
elif'unclosed translation block')
assert False, 'internal parser error'
return referenced, concat(buf)
def _make_node(self, singular, plural, variables, plural_expr,
vars_referenced, num_called_num):
"""Generates a useful node from the data provided."""
# no variables referenced? no need to escape for old style
# gettext invocations only if there are vars.
if not vars_referenced and not self.environment.newstyle_gettext:
singular = singular.replace('%%', '%')
if plural:
plural = plural.replace('%%', '%')
# singular only:
if plural_expr is None:
gettext = nodes.Name('gettext', 'load')
node = nodes.Call(gettext, [nodes.Const(singular)],
[], None, None)
# singular and plural
ngettext = nodes.Name('ngettext', 'load')
node = nodes.Call(ngettext, [
], [], None, None)
# in case newstyle gettext is used, the method is powerful
# enough to handle the variable expansion and autoescape
# handling itself
if self.environment.newstyle_gettext:
for key, value in iteritems(variables):
# the function adds that later anyways in case num was
# called num, so just skip it.
if num_called_num and key == 'num':
node.kwargs.append(nodes.Keyword(key, value))
# otherwise do that here
# mark the return value as safe if we are in an
# environment with autoescaping turned on
node = nodes.MarkSafeIfAutoescape(node)
if variables:
node = nodes.Mod(node, nodes.Dict([
nodes.Pair(nodes.Const(key), value)
for key, value in variables.items()
return nodes.Output([node])
class ExprStmtExtension(Extension):
"""Adds a `do` tag to Jinja2 that works like the print statement just
that it doesn't print the return value.
tags = set(['do'])
def parse(self, parser):
node = nodes.ExprStmt(lineno=next(
node.node = parser.parse_tuple()
return node
class LoopControlExtension(Extension):
"""Adds break and continue to the template engine."""
tags = set(['break', 'continue'])
def parse(self, parser):
token = next(
if token.value == 'break':
return nodes.Break(lineno=token.lineno)
return nodes.Continue(lineno=token.lineno)
class WithExtension(Extension):
class AutoEscapeExtension(Extension):
def extract_from_ast(node, gettext_functions=GETTEXT_FUNCTIONS,
"""Extract localizable strings from the given template node. Per
default this function returns matches in babel style that means non string
parameters as well as keyword arguments are returned as `None`. This
allows Babel to figure out what you really meant if you are using
gettext functions that allow keyword arguments for placeholder expansion.
If you don't want that behavior set the `babel_style` parameter to `False`
which causes only strings to be returned and parameters are always stored
in tuples. As a consequence invalid gettext calls (calls without a single
string parameter or string parameters after non-string parameters) are
This example explains the behavior:
>>> from jinja2 import Environment
>>> env = Environment()
>>> node = env.parse('{{ (_("foo"), _(), ngettext("foo", "bar", 42)) }}')
>>> list(extract_from_ast(node))
[(1, '_', 'foo'), (1, '_', ()), (1, 'ngettext', ('foo', 'bar', None))]
>>> list(extract_from_ast(node, babel_style=False))
[(1, '_', ('foo',)), (1, 'ngettext', ('foo', 'bar'))]
For every string found this function yields a ``(lineno, function,
message)`` tuple, where:
* ``lineno`` is the number of the line on which the string was found,
* ``function`` is the name of the ``gettext`` function used (if the
string was extracted from embedded Python code), and
* ``message`` is the string itself (a ``unicode`` object, or a tuple
of ``unicode`` objects for functions with multiple string arguments).
This extraction function operates on the AST and is because of that unable
to extract any comments. For comment support you have to use the babel
extraction interface or extract comments yourself.
for node in node.find_all(nodes.Call):
if not isinstance(node.node, nodes.Name) or \ not in gettext_functions:
strings = []
for arg in node.args:
if isinstance(arg, nodes.Const) and \
isinstance(arg.value, string_types):
for arg in node.kwargs:
if node.dyn_args is not None:
if node.dyn_kwargs is not None:
if not babel_style:
strings = tuple(x for x in strings if x is not None)
if not strings:
if len(strings) == 1:
strings = strings[0]
strings = tuple(strings)
yield node.lineno,, strings
class _CommentFinder(object):
"""Helper class to find comments in a token stream. Can only
find comments for gettext calls forwards. Once the comment
from line 4 is found, a comment for line 1 will not return a
usable value.
def __init__(self, tokens, comment_tags):
self.tokens = tokens
self.comment_tags = comment_tags
self.offset = 0
self.last_lineno = 0
def find_backwards(self, offset):
for _, token_type, token_value in \
if token_type in ('comment', 'linecomment'):
prefix, comment = token_value.split(None, 1)
except ValueError:
if prefix in self.comment_tags:
return [comment.rstrip()]
return []
self.offset = offset
def find_comments(self, lineno):
if not self.comment_tags or self.last_lineno > lineno:
return []
for idx, (token_lineno, _, _) in enumerate(self.tokens[self.offset:]):
if token_lineno > lineno:
return self.find_backwards(self.offset + idx)
return self.find_backwards(len(self.tokens))
def babel_extract(fileobj, keywords, comment_tags, options):
"""Babel extraction method for Jinja templates.
.. versionchanged:: 2.3
Basic support for translation comments was added. If `comment_tags`
is now set to a list of keywords for extraction, the extractor will
try to find the best preceeding comment that begins with one of the
keywords. For best results, make sure to not have more than one
gettext call in one line of code and the matching comment in the
same line or the line before.
.. versionchanged:: 2.5.1
The `newstyle_gettext` flag can be set to `True` to enable newstyle
gettext calls.
.. versionchanged:: 2.7
A `silent` option can now be provided. If set to `False` template
syntax errors are propagated instead of being ignored.
:param fileobj: the file-like object the messages should be extracted from
:param keywords: a list of keywords (i.e. function names) that should be
recognized as translation functions
:param comment_tags: a list of translator tags to search for and include
in the results.
:param options: a dictionary of additional options (optional)
:return: an iterator over ``(lineno, funcname, message, comments)`` tuples.
(comments will be empty currently)
extensions = set()
for extension in options.get('extensions', '').split(','):
extension = extension.strip()
if not extension:
if InternationalizationExtension not in extensions:
def getbool(options, key, default=False):
return options.get(key, str(default)).lower() in \
('1', 'on', 'yes', 'true')
silent = getbool(options, 'silent', True)
environment = Environment(
options.get('block_start_string', BLOCK_START_STRING),
options.get('block_end_string', BLOCK_END_STRING),
options.get('variable_start_string', VARIABLE_START_STRING),
options.get('variable_end_string', VARIABLE_END_STRING),
options.get('comment_start_string', COMMENT_START_STRING),
options.get('comment_end_string', COMMENT_END_STRING),
options.get('line_statement_prefix') or LINE_STATEMENT_PREFIX,
options.get('line_comment_prefix') or LINE_COMMENT_PREFIX,
getbool(options, 'trim_blocks', TRIM_BLOCKS),
getbool(options, 'lstrip_blocks', LSTRIP_BLOCKS),
getbool(options, 'keep_trailing_newline', KEEP_TRAILING_NEWLINE),
if getbool(options, 'newstyle_gettext'):
environment.newstyle_gettext = True
source ='encoding', 'utf-8'))
node = environment.parse(source)
tokens = list(environment.lex(environment.preprocess(source)))
except TemplateSyntaxError as e:
if not silent:
# skip templates with syntax errors
finder = _CommentFinder(tokens, comment_tags)
for lineno, func, message in extract_from_ast(node, keywords):
yield lineno, func, message, finder.find_comments(lineno)
#: nicer import names
i18n = InternationalizationExtension
do = ExprStmtExtension
loopcontrols = LoopControlExtension
with_ = WithExtension
autoescape = AutoEscapeExtension