#16978 Parametrize with only one arg broken Issue created by kaos Describe the bug You can not parametrize a regular (non-generator) target with a single value (i.e. it is not parametrized at all) Pants version

main

Additional info The parametrization correctly deduces that there is no parametrization going on, but fails to unwrap the parametrization object on the field value. The log lines added below are from: pants/src/python/pants/engine/internals/graph.py Lines 306 to 309 in </pantsbuild/pants/commit/f5de7c4e2538376bede255be27ef32afae56ccf0|f5de7c4> as:

else:
        <http://logger.info|logger.info>(f"ADAPTOR: {target_adaptor}, kwargs: {target_adaptor.kwargs}")
        first, *rest = Parametrize.expand(address, target_adaptor.kwargs)
        <http://logger.info|logger.info>(f"first, rest: {first} : {rest}")
        if rest:
            # The target was parametrized, and so the original Target does not exist.

10:52:54.40 [INFO] ADAPTOR: TargetAdaptor(type_alias=python_requirement, name=pydevd-pycharm), kwargs: {'resolve': parametrize(python-default), 'requirements': ['pydevd-pycharm==203.5419.8']}
10:52:54.40 [INFO] first, rest: (Address(3rdparty/python:pydevd-pycharm@resolve=python-default), {'requirements': ['pydevd-pycharm==203.5419.8'], 'resolve': 'python-default'}) : []
10:52:54.40 [ERROR] 1 Exception encountered:

Engine traceback:
  in select
  in pants.backend.project_info.peek.peek (default_env)
  in pants.engine.internals.graph.resolve_unexpanded_targets (default_env)
  in pants.engine.internals.specs_rules.resolve_addresses_from_specs (default_env)
  in pants.engine.internals.specs_rules.resolve_addresses_from_raw_specs (default_env)
  in pants.engine.internals.specs_rules.addresses_from_raw_specs_without_file_owners (default_env)
  in pants.engine.internals.graph.resolve_target_parametrizations (3rdparty/python:pydevd-pycharm, default_env)
Traceback (most recent call last):
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/internals/selectors.py", line 593, in native_engine_generator_send
    res = func.send(arg)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/internals/graph.py", line 327, in resolve_target_parametrizations
    target = target_type(
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/util/meta.py", line 164, in new_init
    prev_init(self, *args, **kwargs)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 414, in __init__
    self.field_values = self._calculate_field_values(
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 449, in _calculate_field_values
    field_values[field_type] = field_type(value, address)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 239, in __init__
    super().__init__(raw_value, address)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/util/meta.py", line 164, in new_init
    prev_init(self, *args, **kwargs)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 139, in __init__
    self.value: Optional[ImmutableValue] = self.compute_value(raw_value, address)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 1740, in compute_value
    value_or_default = super().compute_value(raw_value, address)
  File "/Users/andreas.stenius/src/github/kaos/pants/src/python/pants/engine/target.py", line 1639, in compute_value
    raise InvalidFieldTypeException(
pants.engine.target.InvalidFieldTypeException: The 'resolve' field in target 3rdparty/python:pydevd-pycharm must be a string, but was `parametrize(python-default)` with type `Parametrize`.

pantsbuild/pants