Command "pdm show" fails when using PEP-621 license field

[mferriz]

Command pdm show seems to be enforcing draft PEP-639 and expects field license-expression to exist. The command cannot process standard PEP-621 license field.

This may be related to pdm-project/pdm-backend#78

• I have searched the issue tracker and believe that this is not a duplicate.

Steps to reproduce

Create a project with a pyproject.toml and a license field containing:

license = {file = "LICENSE"}

Do pdm install and then pdm show

Actual behavior

When using pdm show -v:

/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/models/project_info.py:48: PDMWarning: 'license-expression' is missing
  license_expression = getattr(metadata, "license_expression", None)
Traceback (most recent call last):
  File "/usr/local/bin/pdm", line 8, in <module>
    sys.exit(main())
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/core.py", line 233, in main
    return Core().main(args)
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/core.py", line 168, in main
    raise cast(Exception, err).with_traceback(traceback)
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/core.py", line 163, in main
    f(options.project, options)
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/cli/commands/show.py", line 72, in handle
    project.core.ui.display_columns(list(project_info.generate_rows()))
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/termui.py", line 139, in display_columns
    sizes = list(
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/termui.py", line 141, in <lambda>
    lambda column: max(map(lambda x: len(strip_ansi(x)), column)),
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/termui.py", line 141, in <lambda>
    lambda column: max(map(lambda x: len(strip_ansi(x)), column)),
  File "/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/click/_compat.py", line 494, in strip_ansi
    return _ansi_re.sub("", value)
TypeError: expected string or bytes-like object

When using pdm show --license -v:

/usr/local/Cellar/pdm/1.13.4/libexec/lib/python3.10/site-packages/pdm/models/project_info.py:48: PDMWarning: 'license-expression' is missing
  license_expression = getattr(metadata, "license_expression", None)
None

Expected behavior

Command pdm show should display the package information, including the license.

Environment Information

PDM version:        1.13.4
Python Interpreter: /usr/local/opt/python@3.9/bin/python3.9 (3.9)
Project Root:       /Users/mariof/Development/Project
Project Packages:   /Users/mariof/Development/Project/__pypackages__/3.9
{
  "implementation_name": "cpython",
  "implementation_version": "3.9.10",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "21.2.0",
  "platform_system": "Darwin",
  "platform_version": "Darwin Kernel Version 21.2.0: Sun Nov 28 20:28:54 PST 2021; root:xnu-8019.61.5~1/RELEASE_X86_64",
  "python_full_version": "3.9.10",
  "platform_python_implementation": "CPython",
  "python_version": "3.9",
  "sys_platform": "darwin"
}