Hatchling v1.26.1 not allow string-value to license key in pyproject.toml

[digitronik]

I am encountering an error when setting the license field to an string-value (license = "something") in the pyproject.toml file, using Hatchling v1.26.1.

[project]
name = "foo-bar"
readme = "README.rst"
license = "MIT OR GPL-2.0-or-later OR (FSFUL AND BSD-2-Clause)"

I think as per PEP 639, setting the license field to an string is completely valid. However, Hatchling is throwing the following error during the build process:

  Preparing editable metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error
  
  × Preparing editable metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [21 lines of output]
      Traceback (most recent call last):
        File "/home/ndhandre/RedHat/iqe/.iqe_env/lib64/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
          main()
        File "/home/ndhandre/RedHat/iqe/.iqe_env/lib64/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/home/ndhandre/RedHat/iqe/.iqe_env/lib64/python3.11/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 176, in prepare_metadata_for_build_editable
          whl_basename = build_hook(metadata_directory, config_settings)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-exmmg97_/overlay/lib/python3.11/site-packages/hatchling/build.py", line 83, in build_editable
          return os.path.basename(next(builder.build(directory=wheel_directory, versions=['editable'])))
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-exmmg97_/overlay/lib/python3.11/site-packages/hatchling/builders/plugin/interface.py", line 90, in build
          self.metadata.validate_fields()
        File "/tmp/pip-build-env-exmmg97_/overlay/lib/python3.11/site-packages/hatchling/metadata/core.py", line 266, in validate_fields
          self.core.validate_fields()
        File "/tmp/pip-build-env-exmmg97_/overlay/lib/python3.11/site-packages/hatchling/metadata/core.py", line 1366, in validate_fields
          getattr(self, attribute)
        File "/tmp/pip-build-env-exmmg97_/overlay/lib/python3.11/site-packages/hatchling/metadata/core.py", line 683, in license
          raise ValueError(message) from None
      ValueError: Error parsing field `project.license` - Invalid license expression: ''
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

[ofek]

Please show me something so that I can reproduce, I can't from your example.

[GregoryLand]

I am also seeing this behavior with a project that previously worked. I am currently trying to track down the issue.

[ofek]

Please upgrade Hatchling

[GregoryLand]

So I am doing this inside a docker container using ubuntu:24.04. The project gets built using

pipx run hatch build
pipx run hatch run projectName

Manually running pipx run hatch --version returns Hatch, verison 1.13.0. I believe that hatchling is also current. Bashing into the docker container and running pipx install hatch results in a site packages directory for hatch using hatchling-1.26.3

Here is a ls of the site packages directory after a pipx install hatch

_cffi_backend.cpython-312-x86_64-linux-gnu.so
anyio
anyio-4.6.2.post1.dist-info
certifi
certifi-2024.8.30.dist-info
cffi
cffi-1.17.1.dist-info
click
click-8.1.7.dist-info
cryptography
cryptography-43.0.3.dist-info
distlib
distlib-0.3.9.dist-info
filelock
filelock-3.16.1.dist-info
h11
h11-0.14.0.dist-info
hatch
hatch-1.13.0.dist-info
hatchling
hatchling-1.26.3.dist-info
httpcore
httpcore-1.0.7.dist-info
httpx
httpx-0.27.2.dist-info
hyperlink
hyperlink-21.0.0.dist-info
idna
idna-3.10.dist-info
jaraco
jaraco.classes-3.4.0.dist-info
jaraco.context-6.0.1.dist-info
jaraco.functools-4.1.0.dist-info
jeepney
jeepney-0.8.0.dist-info
keyring
keyring-25.5.0.dist-info
markdown_it
markdown_it_py-3.0.0.dist-info
mdurl
mdurl-0.1.2.dist-info
more_itertools
more_itertools-10.5.0.dist-info
packaging
packaging-24.2.dist-info
pathspec
pathspec-0.12.1.dist-info
pexpect
pexpect-4.9.0.dist-info
pipx_shared.pth
platformdirs
platformdirs-4.3.6.dist-info
pluggy
pluggy-1.5.0.dist-info
ptyprocess
ptyprocess-0.7.0.dist-info
pycparser
pycparser-2.22.dist-info
pygments
pygments-2.18.0.dist-info
rich
rich-13.9.4.dist-info
secretstorage
shellingham
shellingham-1.5.4.dist-info
sniffio
sniffio-1.3.1.dist-info
tomli_w
tomli_w-1.1.0.dist-info
tomlkit
tomlkit-0.13.2.dist-info
trove_classifiers
trove_classifiers-2024.10.21.16.dist-info
userpath
userpath-1.9.2.dist-info
uv
uv-0.5.4.dist-info
virtualenv
virtualenv-20.27.1.dist-info
zstandard
zstandard-0.23.0.dist-info```