dependency on typed_ast in 2.0.0 breaks installation on Python 3 when a compiler is not available

[michaelboulton]

Steps to reproduce

1. Go into a Python 3.3+ environment without a compiler (eg docker run -i -t python:3.6-alpine /bin/sh)
2. Try to install astroid (or Pylint) pip install astroid

Current behavior

Installation fails:

...
  unable to execute 'gcc': No such file or directory
  error: command 'gcc' failed with exit status 1

Expected behavior

Installs as normal, like with Python 2

I found this when trying to install Pylint in a docker container in CI.

I understand that 2.0.0 is a 'major' change so this might be expected behaviour, but it means that I either have to lock to a version astroid<2 or install a compiler into the docker container, both of which are not ideal. Is there some way to install this (and by extension Pylint) without using the typed_ast module?

[PCManticore]

This was already mentioned in https://github.com/PyCQA/pylint/issues/2291, where the culprit was also alpine. But you said an interesting thing in that we can make typed_ast optional. The thing is that we want typed_ast to be installed by default at all times, so need to look if this is actually feasible or not.

[brycepg]

Here's an alpine Dockerfile which works around this issue by telling pip that the typed_ast manylinux wheel is compatible with this system. It appears that their is no ABI issue:

FROM alpine:latest

RUN apk add --no-cache --update python3
RUN python3 -m ensurepip
RUN pip3 install --upgrade pip
RUN python3 -c 'import sys; f = open("/usr/lib/python3.6/site-packages/_manylinux.py", "w"); f.write("manylinux1_compatible = True"); f.close()'
RUN python3 -m pip install --upgrade astroid

---

It might help using a container that's based of off glibc instead of musl.

[hairyhenderson]

This seems to no longer be an issue with astroid v2.3.0+ and Python 3.8:

$ docker run -it --rm python:3.8-alpine /bin/sh
/ # pip install astroid
[...]
Installing collected packages: wrapt, six, lazy-object-proxy, astroid
Successfully installed astroid-2.3.2 lazy-object-proxy-1.4.3 six-1.12.0 wrapt-1.11.2
/ # 

Looks like maybe typed_ast isn't used by default now?

[hairyhenderson]

Ah, indeed, from reading https://github.com/PyCQA/astroid/issues/675 it seems typed_ast is not used on Python 3.8+. I guess this issue can be closed now?

[PCManticore]

@hairyhenderson typed_ast was merged in the standard library's ast module on Python 3.8, if I recall correctly. At this point, I think we need to make typed_ast optional for 3.5-3.7.

[DanielNoord]

Closing as we won't invest the time to fix this for a release we are no longer supporting in the somewhat near future.