Py3 mode renames "str" type to "unicode" in auto-embedded signature

Consider this:

$ cat mylib.pyx
#cython: embedsignature=True
def listdir(str path):
    '''Print out *path*'''

    print(path)

$ cython --version
Cython version 0.19

$ cython mylib.pyx; grep 'Print out' mylib.c | head -1
static char __pyx_doc_5mylib_listdir[= "listdir(str path)\nPrint out *path*";

$ cython -3 mylib.pyx; grep 'Print out' mylib.c | head -1
static char __pyx_doc_5mylib_listdir[](]) = "listdir(unicode path)\nPrint out *path*";

In other words, when running with -3, the str type in the function signature becomes unicode.

I guess the idea is that when compiled for Python 2, the extension will expect a unicode object. However, when compiled under Python 3 (which is probably the more likely case), the signature is just confusing as there is no unicode type.

Moreover, the guess that under Python 2.x the function expects an unicode object is not necessarily correct. In my case, the function truly expects str in both Python 2.x and 3.x. Therefore, I think it would be just not rename any types when generating the docstring signature.

Migrated from http://trac.cython.org/ticket/812

[dgrunwald]

This bug also affects the inspect.signature() result:

# cython: binding=True
def f(path: str, a: int = 0, b: bool = True) -> typing.List[str]:
    pass

>>> testmodule.f.__annotations__
{'path': 'unicode', 'a': 'int', 'b': 'bool', 'return': typing.List[str]}

[fahhem]

This seems to cause errors with py3 typing code that uses str as a type.

Original source code (some YAML handling code):

AnyValue = Union[float, str, int, Dict]

Error at runtime:

Traceback (most recent call last):
...snip...
    AnyValue = Union[float, str, int, Dict]
NameError: name 'unicode' is not defined

The code runs under CPython3, but fails due to this rewriting. I’d be happy to send a PR up, though I can’t find where the str->unicode translation is happening. I looked at AutoDocTransforms though I don’t see how that does the translation, nor how I would use it to avoid the translation.