djblets.registries.registry¶

Djblets registries.

Registries are collections that keep track of unique objects.

For information on writing registries, see the guide on writing registries.

DEFAULT_ERRORS = {'already_registered': 'Could not register %(item)s: it is already registered.', 'attribute_registered': 'Could not register %(item)s: another item (%(duplicate)s) is already registered with %(attr_name)s = %(attr_value)s.', 'invalid_attribute': '"%(attr_name)s" is not a registered lookup attribute.', 'load_entry_point': 'Could not load entry point %(entry_point)s: %(error)s.', 'missing_attribute': 'Could not register %(item)s: it does not have a "%(attr_name)s" attribute.', 'not_registered': 'No item registered with %(attr_name)s = %(attr_value)s.', 'unregister': 'Could not unregister %(item)s: it is not registered.'}[source]¶

Default error messages for registries.

RegistryItemType[source]¶

A generic type for items stored in a registry.

This can be used for subclasses of Registry, mixins, or other utility code that need to stay generic. In normal usage, an explicit type will be provided when subclassing instead.

New in version 3.1.

alias of TypeVar(‘RegistryItemType’)

class Registry[source]¶

Bases: Generic[djblets.registries.registry.RegistryItemType]

An item registry.

Item registries hold a set of objects that can be looked up by attributes. Each item is guaranteed to be unique and not share these attributes with any other item in the registry.

Registries default to holding arbitrary objects. To limit objects to a specific type, specify a type when subclassing. For example:

class MyRegistry(Registry[MyItemType]):
    ...

Changed in version 3.1: Added support for specifying a registry item type when subclassing this registry.

item_name: Optional[str] = None¶

The name of the items being registered.

Type

str

lookup_attrs: Sequence[str] = []¶

A list of attributes that items can be looked up by.

Type

list of str

errors: Dict[str, str] = {}¶

Error formatting strings for exceptions.

Entries here override the global DEFAULT_ERRORS dictionary for error messages.

Type

dict

default_errors: Dict[str, str] = {'already_registered': 'Could not register %(item)s: it is already registered.', 'attribute_registered': 'Could not register %(item)s: another item (%(duplicate)s) is already registered with %(attr_name)s = %(attr_value)s.', 'invalid_attribute': '"%(attr_name)s" is not a registered lookup attribute.', 'load_entry_point': 'Could not load entry point %(entry_point)s: %(error)s.', 'missing_attribute': 'Could not register %(item)s: it does not have a "%(attr_name)s" attribute.', 'not_registered': 'No item registered with %(attr_name)s = %(attr_value)s.', 'unregister': 'Could not unregister %(item)s: it is not registered.'}¶

The default error formatting strings.

If subclasses need to provide additional errors that can be overridden, they should copy DEFAULT_ERRORS and set their copy on the subclass as this attribute.

Type

dict

already_registered_error_class¶

The error class indicating an already registered item.

This must be a subclass of AlreadyRegisteredError.

Type

type

alias of djblets.registries.errors.AlreadyRegisteredError

lookup_error_class¶

The lookup error exception class.

This must be a subclass of ItemLookupError.

Type

type

alias of djblets.registries.errors.ItemLookupError

__init__() → None[source]¶

Initialize the registry.

property populated: bool[source]¶

Whether or not the registry is populated.

Returns

Whether or not the registry is populated.

Return type

bool

format_error(error_name: str, **error_kwargs) → str[source]¶

Format an error message.

Parameters

• error_name (str) – A symbolic name for the error, such as ALREADY_REGISTERED.

• **error_kwargs (dict) – The keyword arguments to provide to the error-specific formatting string.

Returns

The formatted error message.

Return type

str

Raises

ValueError – A registered error message for error_name could not be found.

get(attr_name: str, attr_value: object) → djblets.registries.registry.RegistryItemType[source]¶

Return an item by its attribute value.

Parameters

• attr_name (str) – The attribute name to look up an item by.

• attr_value (object) – The corresponding attribute value.

Returns

The registered item.

Return type

object

Raises

djblets.registries.errors.ItemLookupError – When a lookup is attempted with an unsupported attribute, or the item cannot be found, this exception is raised.

get_or_none(attr_name: str, attr_value: object) → Optional[djblets.registries.registry.RegistryItemType][source]¶

Return the requested registered item, or None if not found.

New in version 3.1.

Parameters

• attr_name (str) – The attribute name.

• attr_value (object) – The attribute value.

Returns

The matching registered item, if found. Otherwise, None is returned.

Return type

object

register(item: djblets.registries.registry.RegistryItemType) → None[source]¶

Register an item.

Parameters

item (object) – The item to register with the class.

Raises

• djblets.registries.errors.RegistrationError – Raised if the item is missing one of the required attributes.

• djblets.registries.errors.AlreadyRegisteredError – Raised if the item is already registered or if the item shares an attribute name, attribute value pair with another item in the registry.

unregister_by_attr(attr_name: str, attr_value: object) → None[source]¶

Unregister an item from the registry by an attribute.

Parameters

• attr_name (str) – The name of the attribute.

• attr_value (object) – The attribute value.

Raises

djblets.registries.errors.ItemLookupError – Raised if the attribute value is not found in the registry.

unregister(item: djblets.registries.registry.RegistryItemType) → None[source]¶

Unregister an item from the registry.

Parameters

item (object) – The item to unregister. This must be present in the registry.

Raises

djblets.registries.errors.ItemLookupError – Raised if the item is not found in the registry.

populate() → None[source]¶

Ensure the registry is populated.

Calling this method when the registry is populated will have no effect.

get_defaults() → Iterable[djblets.registries.registry.RegistryItemType][source]¶

Return the default items for the registry.

This method should be overridden by a subclass.

Returns

The default items for the registry.

Return type

list

reset() → None[source]¶

Unregister all items and mark the registry unpopulated.

This will result in the registry containing no entries. Any call to a method that would populate the registry will repopulate it.

__iter__() → Iterator[djblets.registries.registry.RegistryItemType][source]¶

Iterate through all items in the registry.

This method does not provide a stable ordering.

Yields

object – The items registered in this registry.

__len__() → int[source]¶

Return the number of items in the registry.

Returns

The number of items in the registry.

Return type

int

__contains__(item: djblets.registries.registry.RegistryItemType) → bool[source]¶

Return whether or not the item is contained in the registry.

Parameters

item (object) – The item to look for.

Returns

Whether or not the item is contained in the registry.

Return type

bool

__annotations__ = {'_items': 'Set[RegistryItemType]', '_populated': 'bool', '_registry': 'Dict[str, Dict[object, RegistryItemType]]', 'already_registered_error_class': typing.Type[djblets.registries.errors.AlreadyRegisteredError], 'default_errors': typing.Dict[str, str], 'errors': typing.Dict[str, str], 'item_name': typing.Optional[str], 'lookup_attrs': typing.Sequence[str], 'lookup_error_class': typing.Type[djblets.registries.errors.ItemLookupError]}¶

__orig_bases__ = (typing.Generic[~RegistryItemType],)¶

__parameters__ = (~RegistryItemType,)¶

class EntryPointRegistry[source]¶

Bases: djblets.registries.registry.Registry[djblets.registries.registry.RegistryItemType]

A registry that auto-populates from an entry-point.

entry_point: Optional[str] = None¶

The entry point name.

Type

str

get_defaults() → Iterable[djblets.registries.registry.RegistryItemType][source]¶

Yield the values from the entry point.

Yields

object – The object from the entry point.

process_value_from_entry_point(entry_point: pkg_resources.EntryPoint) → djblets.registries.registry.RegistryItemType[source]¶

Return the item to register from the entry point.

By default, this returns the loaded entry point.

Parameters

entry_point (pkg_resources.EntryPoint) – The entry point.

Returns

The processed entry point value.

Return type

object

__annotations__ = {'_items': 'Set[RegistryItemType]', '_populated': 'bool', '_registry': 'Dict[str, Dict[object, RegistryItemType]]', 'already_registered_error_class': 'Type[AlreadyRegisteredError]', 'default_errors': 'Dict[str, str]', 'entry_point': typing.Optional[str], 'errors': 'Dict[str, str]', 'item_name': 'Optional[str]', 'lookup_attrs': 'Sequence[str]', 'lookup_error_class': 'Type[ItemLookupError]'}¶

__orig_bases__ = (djblets.registries.registry.Registry[~RegistryItemType],)¶

__parameters__ = (~RegistryItemType,)¶

class OrderedRegistry[source]¶

Bases: djblets.registries.registry.Registry[djblets.registries.registry.RegistryItemType]

A registry that keeps track of registration order.

__init__() → None[source]¶

Initialize the OrderedRegistry

register(item: djblets.registries.registry.RegistryItemType) → None[source]¶

Register an item.

Parameters

item (object) – The item to register with the class.

Raises

• djblets.registries.errors.RegistrationError – Raised if the item is missing one of the required attributes.

• djblets.registries.errors.AlreadyRegisteredError – Raised if the item is already registered or if the item shares an attribute name, attribute value pair with another item in the registry.

unregister(item: djblets.registries.registry.RegistryItemType) → None[source]¶

Unregister an item from the registry.

Parameters

item (object) – The item to unregister. This must be present in the registry.

Raises

djblets.registries.errors.ItemLookupError – Raised if the item is not found in the registry.

__iter__() → Iterator[djblets.registries.registry.RegistryItemType][source]¶

Yield the items in the order they were registered.

Yields

object – The registered items.

__getitem__(index: int) → djblets.registries.registry.RegistryItemType[source]¶

Return an item by its registered index.

Parameters

index (int) – The position at which the item was registered. This is 0-based and negative indices are supported.

Returns

The requested item.

Return type

object

Raises

• IndexError – This exception is raised if the requested index is out of range.

• TypeError – This exception is raised if the requested index is not an integer.

__annotations__ = {}¶

__orig_bases__ = (djblets.registries.registry.Registry[~RegistryItemType],)¶

__parameters__ = (~RegistryItemType,)¶