pip tries to parse PEP 508 URLs in pyproject.toml's [build-system] requires as file path

[ghost]

Environment

• pip version: tox doesn't tell me 😨
• Python version: 3.7
• OS: Fedora GNU/Linux

Description
This is what happens when attempting to specify "wobblui @ https://github.com/wobblui/wobblui/archive/master.zip":

  Requirement 'wobblui @ https://github.com/wobblui/wobblui/archive/master.zip' looks like a filename, but the file does not exist
  Processing ./wobblui @ https:/github.com/wobblui/wobblui/archive/master.zip
  Could not install packages due to an EnvironmentError: [Errno 2] No such file or directory: '/home/jonas/Develop/myproj/wobblui @ https:/github.com/wobblui/wobblui/archive/master.zip'

Expected behavior
That it works, because it also works in seutp_requires and this is the recommended replacement, right?

How to Reproduce
Use this pyproject.toml:

[build-system]
requires = ["setuptools", "wheel", "wobblui @ https://github.com/wobblui/wobblui/archive/master.zip"]
build-backend = "setuptools.build_meta"

Output

  Requirement 'wobblui @ https://github.com/wobblui/wobblui/archive/master.zip' looks like a filename, but the file does not exist
  Processing ./wobblui @ https:/github.com/wobblui/wobblui/archive/master.zip
  Could not install packages due to an EnvironmentError: [Errno 2] No such file or directory: '/home/jonas/Develop/myproj/wobblui @ https:/github.com/wobblui/wobblui/archive/master.zip'

[cjerdonek]

I believe this is a duplicate of #6202?

[ghost]

Hmm that one seems to mention requirements.txt and I wouldn't know if internally uses the same mechanism. If it does uses the same one, then it's probably a duplicate 👍

[cjerdonek]

I'm pretty sure it uses the same mechanism, but I guess it can't hurt to keep this open until we're sure it's fixed.

[chrahunt]

For what it's worth, pip from the PR associated with that issue (#6203) was able to install the pyproject.toml provided here without issue.

[chrahunt]

#6203 was merged and I was able to confirm the fix against master:

fixed.sh

#!/bin/sh
cd "$(mktemp -d)"
python -m venv .venv
. .venv/bin/activate

set -ex
pip install --upgrade git+https://github.com/pypa/pip.git
cat <<EOF > pyproject.toml
[build-system]
requires = ["setuptools", "wheel", "wobblui @ https://github.com/wobblui/wobblui/archive/master.zip"]
build-backend = "setuptools.build_meta"
EOF
echo "from setuptools import setup; setup(name='hello')" > setup.py
pip install .

Output

+ pip install --upgrade git+https://github.com/pypa/pip.git
Collecting git+https://github.com/pypa/pip.git
  Cloning https://github.com/pypa/pip.git to /tmp/user/1000/pip-req-build-vj85ywtn
  Installing build dependencies ... done
Installing collected packages: pip
  Found existing installation: pip 18.1
    Uninstalling pip-18.1:
      Successfully uninstalled pip-18.1
  Running setup.py install for pip ... done
Successfully installed pip-19.3.dev0
+ cat
+ echo from setuptools import setup; setup(name='hello')
+ pip install .
Processing /tmp/user/1000/tmp.xAtiVhhzb7
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Building wheels for collected packages: hello
  Building wheel for hello (PEP 517) ... done
  Created wheel for hello: filename=hello-0.0.0-cp37-none-any.whl size=971 sha256=777a97a967e962ad9ae4d085b5eb369b8ead6340b4c1faae4cc42707a170bd1b
  Stored in directory: /tmp/user/1000/pip-ephem-wheel-cache-rvibo0ng/wheels/15/31/64/f6d8e3210b2f9a59fb104fc18d2651440f5e6d328adeca6341
Successfully built hello
Installing collected packages: hello
Successfully installed hello-0.0.0

so I will close this issue as a duplicate. Please let me know if you see something different!