Source code for launch.substitutions.find_executable

# Copyright 2018 Open Source Robotics Foundation, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Module for the FindExecutable substitution."""

from typing import Any
from typing import Dict
from typing import List
from typing import Sequence
from typing import Text
from typing import Tuple
from typing import Type

from osrf_pycommon.process_utils import which  # type: ignore


from .substitution_failure import SubstitutionFailure
from ..frontend import expose_substitution
from ..launch_context import LaunchContext
from ..some_substitutions_type import SomeSubstitutionsType
from ..substitution import Substitution




@expose_substitution('find-exec')
class FindExecutable(Substitution):
    """
    Substitution that tries to locate an executable on the PATH.

    :raise: SubstitutionFailure when executable not found
    """



    def __init__(self, *, name: SomeSubstitutionsType) -> None:
        """Create a FindExecutable substitution."""
        super().__init__()

        from ..utilities import normalize_to_list_of_substitutions  # import here to avoid loop
        self.__name = normalize_to_list_of_substitutions(name)




    @classmethod
    def parse(cls, data: Sequence[SomeSubstitutionsType]
              ) -> Tuple[Type['FindExecutable'], Dict[str, Any]]:
        """Parse `FindExecutable` substitution."""
        if len(data) != 1:
            raise AttributeError('find-exec substitution expects 1 argument')
        return cls, {'name': data[0]}


    @property
    def name(self) -> List[Substitution]:
        """Getter for name."""
        return self.__name



    def describe(self) -> Text:
        """Return a description of this substitution as a string."""
        return 'FindExec({})'.format(' + '.join([sub.describe() for sub in self.name]))




    def perform(self, context: LaunchContext) -> Text:
        """Perform the substitution by locating the executable on the PATH."""
        from ..utilities import perform_substitutions  # import here to avoid loop
        result = which(perform_substitutions(context, self.name))
        if result is None:
            raise SubstitutionFailure("executable '{}' not found on the PATH".format(self.name))
        return result