Sub-dependencies of platform-specific dependencies are not added to the lockfile

[Systemcluster]

Issue description

When a Pipfile.lock is created (with pipenv lock or pipenv update), sub-dependencies of platform specific dependencies for other platforms (e.g. those with a sys_platform="!='win32'" marker) aren't added.

Users installing the project will then be missing the sub-dependency.

A similar issue was reported under #3902, but the then-proposed solution of pipenv lock --keep-outdated does not change this behavior.

Expected result

I would expect sub-dependencies to be added with the same marker as the main dependency.

Actual result

The sub-dependencies are missing from Pipfile.lock.

Steps to replicate

Create a project with the following Pipfile (adjust the platform marker to exclude your current platform):

[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true
[dev-packages]
[packages]
pyunpack = { version=">=0.2.1", sys_platform="!='win32'" }

Then run pipenv lock. Pipfile.lock now contains pyunpack, but not its dependency easyprocess.

---

$ pipenv --support

Pipenv version: '2020.8.13'

Pipenv location: 'c:\\users\\chris\\appdata\\local\\programs\\python\\python38\\lib\\site-packages\\pipenv'

Python location: 'c:\\users\\chris\\appdata\\local\\programs\\python\\python38\\python.exe'

Python installations found:

Traceback (most recent call last):
  File "c:\users\chris\appdata\local\programs\python\python38\lib\runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "c:\users\chris\appdata\local\programs\python\python38\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Scripts\pipenv.exe\__main__.py", line 7, in <module>
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 782, in main
    rv = self.invoke(ctx)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 1236, in invoke
    return Command.invoke(self, ctx)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\decorators.py", line 73, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "C:\Users\Chris\AppData\Local\Programs\Python\Python38\Lib\site-packages\pipenv\vendor\click\decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "c:\users\chris\appdata\local\programs\python\python38\lib\site-packages\pipenv\cli\command.py", line 139, in cli    get_pipenv_diagnostics()
  File "c:\users\chris\appdata\local\programs\python\python38\lib\site-packages\pipenv\help.py", line 33, in get_pipenv_diagnostics
    python_paths = finder.find_all_python_versions()
  File "c:\users\chris\appdata\local\programs\python\python38\lib\site-packages\pipenv\vendor\pythonfinder\pythonfinder.py", line 328, in find_all_python_versions
    path_list = sorted(versions, key=version_sort, reverse=True)
AttributeError: 'NoneType' object has no attribute 'version_sort'

It seems like pipenv --support still crashes while trying to enumerate the python installations, but I'm reporting this from Python 3.8.5.

[frostming]

Lock the dependencies on non-windows platforms.

--keep-outdated exists so that the transient dependencies won't get removed if the lock file is regenerated on Windows.

[Systemcluster]

That's a workaround but not a great solution. If you have windows-only and linux-only dependencies, you would always have to run pipenv update on two different systems to get an up-to-date lockfile.

Also, in my case, I develop a cross-platform application but currently only have access to a Windows system. I only noticed this behavior when a user notified me that a dependency was missing. I worked around this by specifying the sub-dependency directly in the Pipfile, but that's not a great solution either.

[frostming]

See my explanation in #4451 #4451 (comment)

Basically, it is hard to make cross-platform dependency resolution work without failures.

[frostming]

Also I would like to close this due to the duplication

[Systemcluster]

Ah, I completely missed that existing issue, apologies!