Unexpected exception: "Unknown license key(s): MPL-2.0+"

[hhoffstaette]

I wanted to create an ebuild for https://github.com/rustic-rs/rustic, so I downloaded the tarball and decided to give pycargoebuild a try. It didn't go well:

[WARNING] Crate owo-colors-3.5.0.crate uses license-file='LICENSE', please inspect the license manually and add it *separately* from crate licenses
[WARNING] Crate ring-0.16.20.crate uses license-file='LICENSE', please inspect the license manually and add it *separately* from crate licenses
[WARNING] Crate webpki-0.22.0.crate uses license-file='LICENSE', please inspect the license manually and add it *separately* from crate licenses
Traceback (most recent call last):
  File "/usr/lib/python-exec/python3.11/pycargoebuild", line 8, in <module>
    sys.exit(entry_point())
             ^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pycargoebuild/__main__.py", line 205, in entry_point
    sys.exit(main(*sys.argv))
             ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pycargoebuild/__main__.py", line 161, in main
    ebuild = get_ebuild(pkg_meta,
             ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pycargoebuild/ebuild.py", line 163, in get_ebuild
    crate_licenses=get_crate_LICENSE(crate_files),
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/pycargoebuild/ebuild.py", line 115, in get_crate_LICENSE
    parsed_license = spdx.parse(combined_license, validate=True, strict=True)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/license_expression/__init__.py", line 560, in parse
    self.validate_license_keys(expression)
  File "/usr/lib/python3.11/site-packages/license_expression/__init__.py", line 467, in validate_license_keys
    raise ExpressionError(msg)
license_expression.ExpressionError: Unknown license key(s): MPL-2.0+

I understand the LICENSE-related warnings (e.g. owo-colors has both license: and license-file: in its Cargo.toml), but don't know what to do about them.
Neither do I understand what to do about the exception.

cargo-ebuild emits the same warnings, but at least creates a usable ebuild:

holger>cargo-ebuild ebuild
WARNING: unknown license "MIT-0" at package "dunce", please correct manually
WARNING: owo-colors uses a license-file, not handled
WARNING: ring uses a license-file, not handled
WARNING: unknown license "MPL-2.0+" at package "smartstring", please correct manually
WARNING: unknown license "Unicode-DFS-2016" at package "unicode-ident", please correct manually
WARNING: webpki uses a license-file, not handled
Wrote: rustic-rs-0.5.0.ebuild

Am I holding it wrong? In any case it would be useful to say what and where the problem is and - if possible - suggest how to fix it.
I also tried to "update" an empty ebuild skeleton with the required CRATE and LICENSE entries, but that ended in the same exception.

[mgorny]

The error comes from license_expression Python package. I need to figure out whether it's a bug in that package or in the license string of smartstring. Then, figure out how to workaround it.

[mgorny]

Ok, so apparently it's by design, sigh. I'm going to see if we can just disable the license validation there.

[mgorny]

See: aboutcode-org/license-expression#9

[mgorny]

I've pushed 0.6.3 with the fix. Thanks for the report!