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import sys
from ast import literal_eval
from itertools import islice, chain
from jinja2 import nodes
from jinja2._compat import text_type
from jinja2.compiler import CodeGenerator, has_safe_repr
from jinja2.environment import Environment, Template
from jinja2.utils import concat, escape
def native_concat(nodes):
"""Return a native Python type from the list of compiled nodes. If the
result is a single node, its value is returned. Otherwise, the nodes are
concatenated as strings. If the result can be parsed with
:func:`ast.literal_eval`, the parsed value is returned. Otherwise, the
string is returned.
"""
head = list(islice(nodes, 2))
if not head:
return None
if len(head) == 1:
out = head[0]
else:
out = u''.join([text_type(v) for v in chain(head, nodes)])
try:
return literal_eval(out)
except (ValueError, SyntaxError, MemoryError):
return out
class NativeCodeGenerator(CodeGenerator):
"""A code generator which avoids injecting ``to_string()`` calls around the
internal code Jinja uses to render templates.
"""
def visit_Output(self, node, frame):
"""Same as :meth:`CodeGenerator.visit_Output`, but do not call
``to_string`` on output nodes in generated code.
"""
if self.has_known_extends and frame.require_output_check:
return
finalize = self.environment.finalize
finalize_context = getattr(finalize, 'contextfunction', False)
finalize_eval = getattr(finalize, 'evalcontextfunction', False)
finalize_env = getattr(finalize, 'environmentfunction', False)
if finalize is not None:
if finalize_context or finalize_eval:
const_finalize = None
elif finalize_env:
def const_finalize(x):
return finalize(self.environment, x)
else:
const_finalize = finalize
else:
def const_finalize(x):
return x
# 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:
if const_finalize is None:
raise nodes.Impossible()
const = child.as_const(frame.eval_ctx)
if not has_safe_repr(const):
raise nodes.Impossible()
except nodes.Impossible:
body.append(child)
continue
# the frame can't be volatile here, because 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 = 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(native_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 = 0
if finalize is not None:
self.write('environment.finalize(')
if finalize_context:
self.write('context, ')
close += 1
self.visit(item, frame)
if close > 0:
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(native_concat(item).replace('%', '%%'))
else:
format.append('%s')
arguments.append(item)
self.writeline('yield ')
self.write(repr(concat(format)) + ' % (')
self.indent()
for argument in arguments:
self.newline(argument)
close = 0
if finalize is not None:
self.write('environment.finalize(')
if finalize_context:
self.write('context, ')
elif finalize_eval:
self.write('context.eval_ctx, ')
elif finalize_env:
self.write('environment, ')
close += 1
self.visit(argument, frame)
self.write(')' * close + ', ')
self.outdent()
self.writeline(')')
if outdent_later:
self.outdent()
class NativeTemplate(Template):
def render(self, *args, **kwargs):
"""Render the template to produce a native Python type. If the result
is a single node, its value is returned. Otherwise, the nodes are
concatenated as strings. If the result can be parsed with
:func:`ast.literal_eval`, the parsed value is returned. Otherwise, the
string is returned.
"""
vars = dict(*args, **kwargs)
try:
return native_concat(self.root_render_func(self.new_context(vars)))
except Exception:
exc_info = sys.exc_info()
return self.environment.handle_exception(exc_info, True)
class NativeEnvironment(Environment):
"""An environment that renders templates to native Python types."""
code_generator_class = NativeCodeGenerator
template_class = NativeTemplate
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