Craft-parts cannot parse advanced grammar in stage and prime fields

[mr-cal]

Bug Description

Craft-parts assumes prime and stage entries are strings. This is not true if advanced grammar is used.

Craft-parts needs to be able to unmarshal parts with advanced grammar. The problematic code is here).

To Reproduce

See a snapcraft reproducer in https://bugs.launchpad.net/snapcraft/+bug/2083964

part yaml

parts:
  my-part:
    plugin: nil
    prime:
    - on amd64:
      - usr/lib/*/libvpl.so.*

Relevant log output

2024-10-09 09:12:00.397 Starting snapcraft, version 8.4.2
2024-10-09 09:12:00.397 Log verbosity level set to BRIEF
2024-10-09 09:12:00.397 Preparing application...
2024-10-09 09:12:00.397 Configuring application...
2024-10-09 09:12:00.398 Setting up ConfigService
2024-10-09 09:12:00.507 Build plan: platform=None, build_for=None
2024-10-09 09:12:00.507 Running snapcraft expand-extensions on host
2024-10-09 09:12:00.521 snapcraft internal error: AttributeError("'dict' object has no attribute 'startswith'")
2024-10-09 09:12:00.522 Traceback (most recent call last):
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_application/application.py", line 568, in run
2024-10-09 09:12:00.522     return_code = self._run_inner()
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/snapcraft/application.py", line 215, in _run_inner
2024-10-09 09:12:00.522     return_code = super()._run_inner()
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_application/application.py", line 549, in _run_inner
2024-10-09 09:12:00.522     return_code = dispatcher.run() or os.EX_OK
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_cli/dispatcher.py", line 487, in run
2024-10-09 09:12:00.522     return self._loaded_command.run(self._parsed_command_args)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/snapcraft/commands/extensions.py", line 137, in run
2024-10-09 09:12:00.522     project_data = models.Project.unmarshal(yaml_data_for_arch)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_application/models/base.py", line 61, in unmarshal
2024-10-09 09:12:00.522     return cls.model_validate(data)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/pydantic/main.py", line 568, in model_validate
2024-10-09 09:12:00.522     return cls.__pydantic_validator__.validate_python(
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_application/models/project.py", line 250, in _validate_part
2024-10-09 09:12:00.522     craft_parts.validate_part(part)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_parts/parts.py", line 648, in validate_part
2024-10-09 09:12:00.522     _get_part_spec(data)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_parts/parts.py", line 679, in _get_part_spec
2024-10-09 09:12:00.522     return PartSpec(**part_spec)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/pydantic/main.py", line 193, in __init__
2024-10-09 09:12:00.522     self.__pydantic_validator__.validate_python(data, self_instance=self)
2024-10-09 09:12:00.522   File "/snap/snapcraft/12783/lib/python3.10/site-packages/craft_parts/constraints.py", line 44, in _validate_relative_path_str
2024-10-09 09:12:00.522     if path.startswith("/"):
2024-10-09 09:12:00.522 AttributeError: 'dict' object has no attribute 'startswith'
2024-10-09 09:12:00.522 Full execution log: '/home/developer/.local/state/snapcraft/log/snapcraft-20241009-091200.396666.log'

[syncronize-issues-to-jira]

Thank you for reporting us your feedback!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-3559.

This message was autogenerated

[lengau]

While the error message here is bad, craft-parts doesn't need to handle grammar. I believe the grammar isn't being properly processed in the expand-extensions command.

The following part definition:

parts:
  my-part:
    plugin: nil
    stage-packages:
      - on amd64:
        - sl
      - nano
    prime:
      - on amd64:
        - usr/lib/*/libvpl.so.*
      - usr/bin

results in this yaml_data_for_arch object in ExpandExtensionsCommand.run():

{
  "parts": {
    "my-part": {
      "plugin": "nil",
      "stage-packages": [
        "sl",
        "nano"
      ],
      "prime": [
        {
          "on amd64": [
            "usr/lib/*/libvpl.so.*"
          ]
        },
        "usr/bin"
      ]
    }
  }
}

We should probably keep this bug around though, since this YAML:

parts:
  my-part:
    plugin: nil
    # prime:
    # - on amd64:
    #   - usr/lib/*/libvpl.so.*
    stage-packages:
      - on amd64:
        - sl

outputs a good error message:

python -m craft_parts --dry-run
Error: invalid parts specification: Part 'my-part' validation failed.
- Input should be a valid string in field 'stage-packages[0]'
Review part 'my-part' and make sure it's correct.

while uncommenting the prime keyword gets us a traceback.