import typing as t from ast import literal_eval from ast import parse from itertools import chain from itertools import islice from . import nodes from .compiler import CodeGenerator from .compiler import Frame from .compiler import has_safe_repr from .environment import Environment from .environment import Template def native_concat(values: t.Iterable[t.Any]) -> t.Optional[t.Any]: """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. :param values: Iterable of outputs to concatenate. """ head = list(islice(values, 2)) if not head: return None if len(head) == 1: raw = head[0] if not isinstance(raw, str): return raw else: raw = "".join([str(v) for v in chain(head, values)]) try: return literal_eval( # In Python 3.10+ ast.literal_eval removes leading spaces/tabs # from the given string. For backwards compatibility we need to # parse the string ourselves without removing leading spaces/tabs. parse(raw, mode="eval") ) except (ValueError, SyntaxError, MemoryError): return raw class NativeCodeGenerator(CodeGenerator): """A code generator which renders Python types by not adding ``str()`` around output nodes. """ @staticmethod def _default_finalize(value: t.Any) -> t.Any: return value def _output_const_repr(self, group: t.Iterable[t.Any]) -> str: return repr("".join([str(v) for v in group])) def _output_child_to_const( self, node: nodes.Expr, frame: Frame, finalize: CodeGenerator._FinalizeInfo ) -> t.Any: const = node.as_const(frame.eval_ctx) if not has_safe_repr(const): raise nodes.Impossible() if isinstance(node, nodes.TemplateData): return const return finalize.const(const) # type: ignore def _output_child_pre( self, node: nodes.Expr, frame: Frame, finalize: CodeGenerator._FinalizeInfo ) -> None: if finalize.src is not None: self.write(finalize.src) def _output_child_post( self, node: nodes.Expr, frame: Frame, finalize: CodeGenerator._FinalizeInfo ) -> None: if finalize.src is not None: self.write(")") class NativeEnvironment(Environment): """An environment that renders templates to native Python types.""" code_generator_class = NativeCodeGenerator class NativeTemplate(Template): environment_class = NativeEnvironment def render(self, *args: t.Any, **kwargs: t.Any) -> t.Any: """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. """ ctx = self.new_context(dict(*args, **kwargs)) try: return native_concat(self.root_render_func(ctx)) # type: ignore except Exception: return self.environment.handle_exception() async def render_async(self, *args: t.Any, **kwargs: t.Any) -> t.Any: if not self.environment.is_async: raise RuntimeError( "The environment was not created with async mode enabled." ) ctx = self.new_context(dict(*args, **kwargs)) try: return native_concat( [n async for n in self.root_render_func(ctx)] # type: ignore ) except Exception: return self.environment.handle_exception() NativeEnvironment.template_class = NativeTemplate