pip mangles relative file:// URLs in contraints.txt

[brianthelion]

Environment

• pip version: 19.0.1
• Python version: 3.6
• OS: Ubuntu 18.04

Description

# requirements.txt
myfoo

# constraints.txt
file://myfoo/#egg=myfoo

$ pip install -r requirements.txt -c constraints.txt
Processing ./\\myfoo
Could not install packages due to an EnvironmentError: [Errno 2] No such file or directory: '/some/absolute/path/\\\\myfoo'
$ ls myfoo
setup.py

Note the mangling of the path string.

Expected behavior
myfoo installed successfully.

How to Reproduce
As above.

Output
As above.

[brianthelion]

@cjerdonek This looks like it should be type: bug. The output above exhibits a pretty evident pathology. pip is trying to do the right thing, but failing due to some misplaced escapes or something.

[cjerdonek]

@brianthelion You might want to take a look at PR #5892, which I believe impacts this issue. I don't know yet what behavior we want here.

[cjerdonek]

Marking as a bug per @brianthelion's comment. At the least there should be a better error message.

[froli-code]

i just reproduced this issue, and the current output is the following:

ERROR: Exception:
Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/pip/_internal/cli/base_command.py", line 160, in exc_logging_wrapper
    status = run_func(*args)
  File "/usr/lib/python3.10/site-packages/pip/_internal/cli/req_command.py", line 247, in wrapper
    return func(self, options, args)
  File "/usr/lib/python3.10/site-packages/pip/_internal/commands/install.py", line 344, in run
    reqs = self.get_requirements(args, options, finder, session)
  File "/usr/lib/python3.10/site-packages/pip/_internal/cli/req_command.py", line 403, in get_requirements
    req_to_add = install_req_from_parsed_requirement(
  File "/usr/lib/python3.10/site-packages/pip/_internal/req/constructors.py", line 471, in install_req_from_parsed_requirement
    req = install_req_from_line(
  File "/usr/lib/python3.10/site-packages/pip/_internal/req/constructors.py", line 395, in install_req_from_line
    return InstallRequirement(
  File "/usr/lib/python3.10/site-packages/pip/_internal/req/req_install.py", line 127, in __init__
    self.local_file_path = self.link.file_path
  File "/usr/lib/python3.10/site-packages/pip/_internal/models/link.py", line 330, in file_path
    return url_to_path(self.url)
  File "/usr/lib/python3.10/site-packages/pip/_internal/utils/urls.py", line 43, in url_to_path
    raise ValueError(
ValueError: non-local file URIs are not supported on this platform: 'file://myfoo/#egg=myfoo'

System: Manjaro 22.0.0
Python: 3.10
Pip: 22.3

I think we could close this issue, since the error message looks way better now and explains the issue.

[uranusjr]

In the original report, file://myfoo/ was supposed to mean the relative path ./myfoo/. However, that is not the correct interpretation; according to standards, this means a directory / under domain myfoo instead (as the current exception indicates).

We could possibly show an even better error message for this (which explains the above context), but that can be a separate issue. Feel free to contribute.

[froli-code]

created #11577 as a successor to this issue.