entry_points

Load plugins through entry points.

This module deals with handling all plugged in strategies through the entry points API and importlib metadata API.

Special functionality is put in place to handle the OTE-API-specific entry points.

Since the entry points are information complete in and of themselves, there is no need to import actual strategy classes until they are truly needed. This therefore implements lazy loading of all plugin strategies.

EntryPointNotFound

Bases: Exception

A given strategy implementation (class) cannot be found from the given entry point value.

Source code in oteapi/plugins/entry_points.py

class EntryPointNotFound(Exception):
    """A given strategy implementation (class) cannot be found from the given entry
    point value."""

EntryPointStrategy

A strategy realized from an entry point.

An entry point strategy is made unique by its "strategy", i.e., its (strategy type, strategy name)-tuple, e.g., ("download", "https"). This tuple can be retrieved from the strategy property, where the strategy type is represented by the StrategyType enumeration.

Note

It may be that in the future an entry points strategy is made unique by its "full name" instead, i.e., the entry point group + the entry points name, e.g., oteapi.download:oteapi.https. This value can be retrieved from the full_name property.

This is a condition for uniqueness that is considered to be a superset of the current condition for uniqueness. It adds an extra package-specific uniqueness trait, allowing for different packages to implement the same strategies (which is currently not allowed according to the condition of uniqueness explained above).

Currently there is no consensus on the API for handling this added strategy ambiguity.

Raises:

Type	Description
ValueError	If the entry point name is not properly defined.

Source code in oteapi/plugins/entry_points.py

class EntryPointStrategy:
    """A strategy realized from an entry point.

    An entry point strategy is made unique by its "strategy", i.e., its
    (strategy type, strategy name)-tuple, e.g., `("download", "https")`.
    This tuple can be retrieved from the
    [`strategy`][oteapi.plugins.entry_points.EntryPointStrategy.strategy] property,
    where the strategy type is represented by the
    [`StrategyType`][oteapi.plugins.entry_points.StrategyType] enumeration.

    Note:
        It may be that in the future an entry points strategy is made unique by
        its "full name" instead, i.e., the entry point group + the entry points name,
        e.g., `oteapi.download:oteapi.https`.
        This value can be retrieved from the
        [`full_name`][oteapi.plugins.entry_points.EntryPointStrategy.full_name]
        property.

        This is a condition for uniqueness that is considered to be a superset of the
        current condition for uniqueness.
        It adds an extra package-specific uniqueness trait, allowing for different
        packages to implement the same strategies (which is currently not allowed
        according to the condition of uniqueness explained above).

        Currently there is no consensus on the API for handling this added strategy
        ambiguity.

    Raises:
        ValueError: If the entry point name is not properly defined.

    """

    ENTRY_POINT_NAME_REGEX = re.compile(
        r"^(?P<package_name>[A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9._-]*[A-Za-z0-9])\.(?P<strategy_name>.+)$"
    )
    """Regex for entry point names.

    The package_name group is a valid non-normalized package name regex adapted from
    PEP 508.
    For more information, see: https://peps.python.org/pep-0508/#names.
    """

    ENTRY_POINT_NAME_SEPARATOR = ":"

    def __init__(self, entry_point: "EntryPoint") -> None:
        self._entry_point = entry_point

        match = self.ENTRY_POINT_NAME_REGEX.match(self._entry_point.name)
        if match is None:
            raise ValueError(
                "Could not determine package name and/or strategy name for entry "
                f"point: {self.full_name}"
            )

        self._match = match
        self._type = StrategyType(self._entry_point.group[len("oteapi.") :])
        self._implementation: "Optional[Type[IStrategy]]" = None

    @property
    def type(self) -> StrategyType:
        """The strategy type.

        One part of the (strategy type, strategy name)-tuple.
        """
        return self._type

    @property
    def name(self) -> str:
        """The strategy name.

        One part of the (strategy type, strategy name)-tuple.
        """
        return self._match.group("strategy_name")

    @property
    def strategy(self) -> "Tuple[StrategyType, str]":
        """The unique index identifier for the strategy."""
        return self.type, self.name

    @property
    def package(self) -> str:
        """The importable base package name for the strategy plugin."""
        return self._match.group("package_name")

    @property
    def module(self) -> str:
        """The fully resolved importable module path."""
        return self._entry_point.module  # type: ignore[attr-defined]

    @property
    def full_name(self) -> str:
        """The full entry point name."""
        return (
            f"{self._entry_point.group}{self.ENTRY_POINT_NAME_SEPARATOR}"
            f"{self._entry_point.name}"
        )

    def __str__(self) -> str:
        return self.full_name

    def __repr__(self) -> str:
        return f"{self.__class__.__name__}(entry_point={self._entry_point!r})"

    @property
    def implementation_name(self) -> str:
        """The EntryPoint attr, which should be the strategy implementation class
        name."""
        return self._entry_point.attr  # type: ignore[attr-defined]

    @property
    def implementation(self) -> "Type[IStrategy]":
        """The actual strategy implementation."""
        if self._implementation is None:
            self._implementation = self._load_implementation()
        return self._implementation

    def _load_implementation(self) -> "Type[IStrategy]":
        """Load the strategy implementation.

        Because the actual importing of the module does not happen until this method is
        called, we are lazily loading in the strategy implementation.

        There is no need to check through the `globals()` built-in for whether the
        module and class have already been imported, because this caching layer is
        already implemented in the `importlib` API.

        Raises:
            EntryPointNotFound: If the strategy implementation (class) the entry point
                is pointing to cannot be found in the module or if the module cannot be
                imported.

        Returns:
            The imported strategy implementation (class).

        """
        try:
            module = importlib.import_module(self.module)
        except ImportError as exc:
            raise EntryPointNotFound(
                f"{self.module} cannot be imported. Did you install the "
                f"{self.package!r} package?"
            ) from exc

        if hasattr(module, self.implementation_name):
            return getattr(module, self.implementation_name)
        raise EntryPointNotFound(
            f"{self.implementation_name} cannot be found in {self.module}"
        )

    def __eq__(self, other: "Any") -> bool:
        if isinstance(other, self.__class__):
            return hash(self) == hash(other)
        return False

    def __hash__(self) -> int:
        return hash(self.strategy)

    def __lt__(self, other: "Any") -> bool:
        """Whether or not `self` is less than (`<`) `other`.

        This is implemented to allow sorting (using `sorted()`).

        The inequality is determined on the basis of the following properties:

        1. [`type`][oteapi.plugins.entry_points.EntryPointStrategy.type]
        2. [`package`][oteapi.plugins.entry_points.EntryPointStrategy.package]
        3. [`name`][oteapi.plugins.entry_points.EntryPointStrategy.name]

        Going from highest priority to lowest and in alphabetical ascending order.
        """
        if isinstance(other, self.__class__):
            if self.type == other.type:
                if self.package == other.package:
                    if self.name == other.name:
                        # Considered equal, i.e., one can by definition not be unequal
                        # with the other.
                        return False
                    return sorted([self.name, other.name])[0] == self.name
                return sorted([self.package, other.package])[0] == self.package
            return sorted([self.type.value, other.type.value])[0] == self.type.value
        raise NotImplementedError(
            f"Less than comparison is not implemented for {type(other)} type objects."
        )

ENTRY_POINT_NAME_REGEX = re.compile('^(?P<package_name>[A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9._-]*[A-Za-z0-9])\\.(?P<strategy_name>.+)$') class-attribute instance-attribute

Regex for entry point names.

The package_name group is a valid non-normalized package name regex adapted from PEP 508. For more information, see: https://peps.python.org/pep-0508/#names.

full_name: str property

The full entry point name.

implementation: Type[IStrategy] property

The actual strategy implementation.

implementation_name: str property

The EntryPoint attr, which should be the strategy implementation class name.

module: str property

The fully resolved importable module path.

name: str property

The strategy name.

One part of the (strategy type, strategy name)-tuple.

package: str property

The importable base package name for the strategy plugin.

strategy: Tuple[StrategyType, str] property

The unique index identifier for the strategy.

type: StrategyType property

The strategy type.

One part of the (strategy type, strategy name)-tuple.

EntryPointStrategyCollection

Bases: Collection

A collection of EntryPointStrategys.

Source code in oteapi/plugins/entry_points.py

class EntryPointStrategyCollection(abc.Collection):
    """A collection of
    [`EntryPointStrategy`][oteapi.plugins.entry_points.EntryPointStrategy]s."""

    def __init__(self, *entry_points: "EntryPointStrategy") -> None:
        self._entry_points: "Set[EntryPointStrategy]" = (
            set(entry_points) if entry_points else set()
        )

    def add(self, *entry_points: EntryPointStrategy) -> None:
        """Add entry points to the collection.

        Parameters:
            *entry_points (Iterable[EntryPointStrategy]): Entry points to add to the
                collection.

        """
        self._entry_points |= set(entry_points)

    def remove(self, *entry_points: EntryPointStrategy) -> None:
        """Remove entry points from the collection.

        Parameters:
            *entry_points (Iterable[EntryPointStrategy]): Entry points to remove from
                the collection.

        """
        self._entry_points -= set(entry_points)

    def exclusive_add(self, *entry_points: EntryPointStrategy) -> None:
        """Exclusively add entry points to the collection.

        Parameters:
            *entry_points (Iterable[EntryPointStrategy]): Entry points to add to the
                collection.

        Raises:
            KeyError: If an entry point to be added already exists in the collection.

        """
        for entry_point in entry_points:
            if entry_point in self:
                raise KeyError(
                    f"{entry_point.strategy} already exists in {self}. "
                    f"(Tried adding {entry_point}.)"
                )
            self.add(entry_point)

    def __len__(self) -> int:
        return len(self._entry_points)

    def __contains__(self, item: "Any") -> bool:
        """Whether or not `item` is contained in the collection.

        One can test with an `EntryPointStrategy`, a string of an entry point
        strategy's full name, or a tuple of an entry point's strategy type and name.

        Parameters:
            item: Item to test whether it is contained in the collection.

        Returns:
            Whether or not `item` is contained in the collection.
            If the `item` is an unrecognized type, `False` will be returned.

        """
        if isinstance(item, EntryPointStrategy):
            return item in self._entry_points
        if isinstance(item, str):
            for entry_point in self._entry_points:
                if item == entry_point.full_name:
                    return True
        if isinstance(item, tuple):
            if len(item) != 2 or (
                not isinstance(item[0], (StrategyType, str))
                or not isinstance(item[1], str)
            ):
                # Only tuples of type (Union[StrategyType, str], str) are allowed.
                return False
            try:
                item_ = (StrategyType.init(item[0]), item[1])
            except ValueError:
                # We only want to return True or False
                return False
            for entry_point in self._entry_points:
                if item_ == entry_point.strategy:
                    return True
        # For any other type:
        return False

    def __iter__(self) -> "Iterator[EntryPointStrategy]":
        yield from self._entry_points

    def __getitem__(self, key: "Any") -> EntryPointStrategy:
        return self.get_entry_point(key)

    def get_entry_point(
        self,
        key: "Union[EntryPointStrategy, str, Tuple[Union[StrategyType, str], str]]",
    ) -> EntryPointStrategy:
        """Retrieve an entry point from the collection.

        Parameters:
            key: The key to check for in the collection.

        Raises:
            KeyError: If an entry point cannot be found in the collection.
            TypeError: If the `key` is not of an expected type. See the `key` parameter
                above for the expected types.

        Returns:
            An entry point in the collection representing the key.

        """
        if isinstance(key, (EntryPointStrategy, str, tuple)):
            if key not in self:
                raise KeyError(f"{key} not found in {self}")
            return self._get_entry_point(key)
        raise TypeError(
            "key should either be of type EntryPointStrategy, a string of the full "
            "name or a strategy tuple."
        )

    def _get_entry_point(
        self,
        key: "Union[EntryPointStrategy, str, Tuple[Union[StrategyType, str], str]]",
    ) -> EntryPointStrategy:
        """Helper method for retrieving an entry point from the collection.

        Important:
            It is expected that the entry point representing the key exists in the
            collection. For example through a `key in self` test.

        Parameters:
            key: The key to check for in the collection.

        Raises:
            RuntimeError: If an entry point cannot be found in the collection, since
                this is a requirement.

        Returns:
            An entry point in the collection representing the key.

        """
        if isinstance(key, EntryPointStrategy):
            return key
        if isinstance(key, str):
            for entry_point in self._entry_points:
                if key == entry_point.full_name:
                    return entry_point
        if isinstance(key, tuple):
            key_ = (StrategyType(key[0]), key[1])
            for entry_point in self._entry_points:
                if key_ == entry_point.strategy:
                    return entry_point
        raise RuntimeError(
            f"{key} not found in {self}, which is a requirement for the "
            "_get_entry_point method."
        )

    def __eq__(self, other: "Any") -> bool:
        if isinstance(other, self.__class__):
            return hash(self) == hash(other)
        return False

    def __hash__(self) -> int:
        return hash(tuple(_ for _ in sorted(self._entry_points)))

    def __str__(self) -> str:
        number_of_strategies: "Dict[str, int]" = {}
        for entry_point in self._entry_points:
            if entry_point.type.value in number_of_strategies:
                number_of_strategies[entry_point.type.value] += 1
            else:
                number_of_strategies[entry_point.type.value] = 1
        sorted_list = sorted(
            f"{key} ({value})" for key, value in number_of_strategies.items()
        )
        return f"<{self.__class__.__name__}: " f"Strategies={', '.join(sorted_list)}>"

    def __repr__(self) -> str:
        return f"{self.__class__.__name__}(*{tuple(sorted(self._entry_points))!r})"

add(*entry_points)

Add entry points to the collection.

Parameters:

Name	Type	Description	Default
*entry_points	Iterable[EntryPointStrategy]	Entry points to add to the collection.	()

Source code in oteapi/plugins/entry_points.py

def add(self, *entry_points: EntryPointStrategy) -> None:
    """Add entry points to the collection.

    Parameters:
        *entry_points (Iterable[EntryPointStrategy]): Entry points to add to the
            collection.

    """
    self._entry_points |= set(entry_points)

exclusive_add(*entry_points)

Exclusively add entry points to the collection.

Parameters:

Name	Type	Description	Default
*entry_points	Iterable[EntryPointStrategy]	Entry points to add to the collection.	()

Raises:

Type	Description
KeyError	If an entry point to be added already exists in the collection.

Source code in oteapi/plugins/entry_points.py

def exclusive_add(self, *entry_points: EntryPointStrategy) -> None:
    """Exclusively add entry points to the collection.

    Parameters:
        *entry_points (Iterable[EntryPointStrategy]): Entry points to add to the
            collection.

    Raises:
        KeyError: If an entry point to be added already exists in the collection.

    """
    for entry_point in entry_points:
        if entry_point in self:
            raise KeyError(
                f"{entry_point.strategy} already exists in {self}. "
                f"(Tried adding {entry_point}.)"
            )
        self.add(entry_point)

get_entry_point(key)

Retrieve an entry point from the collection.

Parameters:

Name	Type	Description	Default
key	Union[EntryPointStrategy, str, Tuple[Union[StrategyType, str], str]]	The key to check for in the collection.	required

Raises:

Type	Description
KeyError	If an entry point cannot be found in the collection.
TypeError	If the key is not of an expected type. See the key parameter above for the expected types.

Returns:

Type	Description
EntryPointStrategy	An entry point in the collection representing the key.

Source code in oteapi/plugins/entry_points.py

def get_entry_point(
    self,
    key: "Union[EntryPointStrategy, str, Tuple[Union[StrategyType, str], str]]",
) -> EntryPointStrategy:
    """Retrieve an entry point from the collection.

    Parameters:
        key: The key to check for in the collection.

    Raises:
        KeyError: If an entry point cannot be found in the collection.
        TypeError: If the `key` is not of an expected type. See the `key` parameter
            above for the expected types.

    Returns:
        An entry point in the collection representing the key.

    """
    if isinstance(key, (EntryPointStrategy, str, tuple)):
        if key not in self:
            raise KeyError(f"{key} not found in {self}")
        return self._get_entry_point(key)
    raise TypeError(
        "key should either be of type EntryPointStrategy, a string of the full "
        "name or a strategy tuple."
    )

remove(*entry_points)

Remove entry points from the collection.

Parameters:

Name	Type	Description	Default
*entry_points	Iterable[EntryPointStrategy]	Entry points to remove from the collection.	()

Source code in oteapi/plugins/entry_points.py

def remove(self, *entry_points: EntryPointStrategy) -> None:
    """Remove entry points from the collection.

    Parameters:
        *entry_points (Iterable[EntryPointStrategy]): Entry points to remove from
            the collection.

    """
    self._entry_points -= set(entry_points)

StrategyType

Bases: Enum

An enumeration of available strategy types.

Available strategy types:

• download
• filter
• function
• mapping
• parse
• resource
• transformation

Source code in oteapi/plugins/entry_points.py

class StrategyType(Enum):
    """An enumeration of available strategy types.

    Available strategy types:

    - download
    - filter
    - function
    - mapping
    - parse
    - resource
    - transformation

    """

    DOWNLOAD = "download"
    FILTER = "filter"
    FUNCTION = "function"
    MAPPING = "mapping"
    PARSE = "parse"
    RESOURCE = "resource"
    TRANSFORMATION = "transformation"

    def map_to_field(self) -> str:
        """Map enumeration value to the strategy type's field."""
        return {
            "download": "scheme",
            "filter": "filterType",
            "function": "functionType",
            "mapping": "mappingType",
            "parse": "parserType",
            "resource": "resourceType",
            "transformation": "transformationType",
        }[self.value]

    @classmethod
    def map_from_field(cls, strategy_type_field: str) -> "StrategyType":
        """Map the strategy type's field to enumeration.

        Parameters:
            strategy_type_field: The strategy type's field. E.g., `scheme` for
                `download`.

        Raises:
            KeyError: If the `strategy_type_field` is not valid.

        Returns:
            An enumeration instance representing the strategy type's field.

        """
        return {
            "scheme": cls.DOWNLOAD,
            "filterType": cls.FILTER,
            "functionType": cls.FUNCTION,
            "mappingType": cls.MAPPING,
            "parserType": cls.PARSE,
            "resourceType": cls.RESOURCE,
            "transformationType": cls.TRANSFORMATION,
        }[strategy_type_field]

    @classmethod
    def init(cls, value: "Union[str, StrategyType]") -> "StrategyType":
        """Initialize a StrategyType with more than just the enumeration value.

        This method allows one to also initialize a StrategyType with an actual
        strategy type string, e.g., `scheme`, `mediaType`, etc.

        Raises:
            ValueError: As normal if the enumeration value is not valid.

        """
        if isinstance(value, str):
            try:
                return cls.map_from_field(value)
            except KeyError:
                pass
        return cls(value)

    @classmethod
    def all_values(cls) -> "Tuple[str, ...]":
        """Return all values."""
        return tuple(strategy_type.value for strategy_type in cls)

    def __str__(self) -> str:
        return str(self.value)

    def __repr__(self) -> str:
        return repr(str(self))

    @property
    def config_cls(self) -> "Type[StrategyConfig]":
        """Return the strategy-specific `*Config` class."""
        return {  # type: ignore[return-value]
            "download": ResourceConfig,
            "filter": FilterConfig,
            "function": FunctionConfig,
            "mapping": MappingConfig,
            "parse": ParserConfig,
            "resource": ResourceConfig,
            "transformation": TransformationConfig,
        }[self.value]

config_cls: Type[StrategyConfig] property

Return the strategy-specific *Config class.

all_values() classmethod

Return all values.

Source code in oteapi/plugins/entry_points.py

@classmethod
def all_values(cls) -> "Tuple[str, ...]":
    """Return all values."""
    return tuple(strategy_type.value for strategy_type in cls)

init(value) classmethod

Initialize a StrategyType with more than just the enumeration value.

This method allows one to also initialize a StrategyType with an actual strategy type string, e.g., scheme, mediaType, etc.

Raises:

Type	Description
ValueError	As normal if the enumeration value is not valid.

Source code in oteapi/plugins/entry_points.py

@classmethod
def init(cls, value: "Union[str, StrategyType]") -> "StrategyType":
    """Initialize a StrategyType with more than just the enumeration value.

    This method allows one to also initialize a StrategyType with an actual
    strategy type string, e.g., `scheme`, `mediaType`, etc.

    Raises:
        ValueError: As normal if the enumeration value is not valid.

    """
    if isinstance(value, str):
        try:
            return cls.map_from_field(value)
        except KeyError:
            pass
    return cls(value)

map_from_field(strategy_type_field) classmethod

Map the strategy type's field to enumeration.

Parameters:

Name	Type	Description	Default
strategy_type_field	str	The strategy type's field. E.g., scheme for download.	required

Raises:

Type	Description
KeyError	If the strategy_type_field is not valid.

Returns:

Type	Description
StrategyType	An enumeration instance representing the strategy type's field.

Source code in oteapi/plugins/entry_points.py

@classmethod
def map_from_field(cls, strategy_type_field: str) -> "StrategyType":
    """Map the strategy type's field to enumeration.

    Parameters:
        strategy_type_field: The strategy type's field. E.g., `scheme` for
            `download`.

    Raises:
        KeyError: If the `strategy_type_field` is not valid.

    Returns:
        An enumeration instance representing the strategy type's field.

    """
    return {
        "scheme": cls.DOWNLOAD,
        "filterType": cls.FILTER,
        "functionType": cls.FUNCTION,
        "mappingType": cls.MAPPING,
        "parserType": cls.PARSE,
        "resourceType": cls.RESOURCE,
        "transformationType": cls.TRANSFORMATION,
    }[strategy_type_field]

map_to_field()

Map enumeration value to the strategy type's field.

Source code in oteapi/plugins/entry_points.py

def map_to_field(self) -> str:
    """Map enumeration value to the strategy type's field."""
    return {
        "download": "scheme",
        "filter": "filterType",
        "function": "functionType",
        "mapping": "mappingType",
        "parse": "parserType",
        "resource": "resourceType",
        "transformation": "transformationType",
    }[self.value]

get_strategy_entry_points(strategy_type, enforce_uniqueness=True)

Retrieve all entry points from a specific strategy type.

Raises:

Type	Description
ValueError	If the strategy type is not supported.
KeyError	If enforce_uniqueness is True and an entry point strategy is duplicated.

Parameters:

Name	Type	Description	Default
strategy_type	Union[StrategyType, str]	A strategy type for which the entry points will be retrieved.	required
enforce_uniqueness	bool	Whether or not duplicate entry point strategies are allowed. Defaults to True, meaning duplicates are not allowed.	True

Returns:

Type	Description
EntryPointStrategyCollection	A collection of entry points for the specific strategy type.

Source code in oteapi/plugins/entry_points.py

def get_strategy_entry_points(
    strategy_type: "Union[StrategyType, str]",
    enforce_uniqueness: bool = True,
) -> EntryPointStrategyCollection:
    """Retrieve all entry points from a specific strategy type.

    Raises:
        ValueError: If the strategy type is not supported.
        KeyError: If `enforce_uniqueness` is `True` and an entry point strategy is
            duplicated.

    Parameters:
        strategy_type: A strategy type for which the entry points will be retrieved.
        enforce_uniqueness: Whether or not duplicate entry point strategies are
            allowed. Defaults to `True`, meaning duplicates are *not* allowed.

    Returns:
        A collection of entry points for the specific strategy type.

    """
    try:
        strategy_type = StrategyType(strategy_type)
    except ValueError as exc:
        str_strategy_type = (
            strategy_type
            if isinstance(strategy_type, str)
            else str(strategy_type.value)
        )
        raise ValueError(
            f"Strategy type {str_strategy_type!r} is not supported."
        ) from exc

    collection = EntryPointStrategyCollection()
    oteapi_entry_points = sorted(
        set(get_entry_points(group=f"oteapi.{strategy_type.value}"))
    )

    if enforce_uniqueness:
        collection.exclusive_add(*(EntryPointStrategy(_) for _ in oteapi_entry_points))
    else:
        collection.add(*(EntryPointStrategy(_) for _ in oteapi_entry_points))

    return collection