Python build is failing with Pipfile.lock and null markers

Issue

When try to build a Python serverless project on Vercel, the build is sometimes failing with the following error:

[20:15:35.199] Retrieving list of deployment files...
[20:15:35.473] Previous build caches not available
[20:15:37.624] Downloading 13 deployment files...
[20:15:38.535] Running "vercel build"
[20:15:39.191] Vercel CLI 28.5.3
[20:15:39.361] WARN! Due to `builds` existing in your configuration file, the Build and Development Settings defined in your Project Settings will not apply. Learn More: https://vercel.link/unused-build-settings
[20:15:39.460] Installing required dependencies...
[20:15:41.462] Failed to run "pipfile2req"
[20:15:41.522] Error: Command failed: /tmp/1d640a54/bin/pipfile2req
[20:15:41.523] Traceback (most recent call last):
[20:15:41.523]   File "/tmp/1d640a54/bin/pipfile2req", line 8, in <module>
[20:15:41.523]     sys.exit(main())
[20:15:41.523]   File "/tmp/1d640a54/pipfile2req/__init__.py", line 112, in main
[20:15:41.523]     lines = convert_pipfile_or_lock(
[20:15:41.523]   File "/tmp/1d640a54/pipfile2req/__init__.py", line 96, in convert_pipfile_or_lock
[20:15:41.524]     lines = [
[20:15:41.524]   File "/tmp/1d640a54/pipfile2req/__init__.py", line 97, in <listcomp>
[20:15:41.524]     requirement_from_pipfile(name, package, hashes)
[20:15:41.524]   File "/tmp/1d640a54/pipfile2req/requirements.py", line 10, in requirement_from_pipfile
[20:15:41.524]     return Requirement.parse(name, package).as_line(include_hashes)
[20:15:41.524]   File "/tmp/1d640a54/pipfile2req/requirements.py", line 97, in parse
[20:15:41.524]     kwargs["markers"] = _merge_markers(markers)
[20:15:41.525]   File "/tmp/1d640a54/pipfile2req/requirements.py", line 14, in _merge_markers
[20:15:41.525]     result = Marker(markers[0])
[20:15:41.525]   File "/tmp/1d640a54/packaging/markers.py", line 278, in __init__
[20:15:41.525]     self._markers = _coerce_parse_result(MARKER.parseString(marker))
[20:15:41.525]   File "/tmp/1d640a54/pyparsing/core.py", line 1129, in parse_string
[20:15:41.525]     instring = instring.expandtabs()
[20:15:41.525] AttributeError: 'NoneType' object has no attribute 'expandtabs'
[20:15:41.525] 
[20:15:41.526] 

Investigations

Investigation on my part across multiple project with the same error showed the following:

• Pipfile.lock (generated by pipenv) is containing "markers": null for some packages
• pipfile2req (used by Vercel Python runtime) is trying to parse markers without checking for null values thus failing

Potential solutions

• Submit a PR to pipfile2req to fix the behavior
• Instead of pipfile2req, use pipenv requirements within Vercel Python runtime to generate the requirements.txt file

[rclement]

Issue is fixed starting with pipenv version 2022.12.17: https://github.com/pypa/pipenv/releases/tag/v2022.12.17

FYI: Renovatebot seems to have picked up the latest version of pipenv as null markers are not appearing in Pipfile.lock anymore

[andymckay]

Oops, thanks for spotting that.