Source code for plaster.loaders
try:
from importlib import metadata
except ImportError: # pragma: no cover < py38
import importlib_metadata as metadata
from .exceptions import LoaderNotFound, MultipleLoadersFound
from .interfaces import ILoaderInfo
from .uri import parse_uri
def get_sections(config_uri):
"""
Load the list of named sections.
.. code-block:: python
sections = plaster.get_sections('development.ini')
full_config = {
section: plaster.get_settings('development.ini', section)
for section in sections
}
:param config_uri: Anything that can be parsed by
:func:`plaster.parse_uri`.
:returns: A list of section names in the config file.
"""
loader = get_loader(config_uri)
return loader.get_sections()
[docs]
def get_settings(config_uri, section=None, defaults=None):
"""
Load the settings from a named section.
.. code-block:: python
settings = plaster.get_settings(...)
print(settings['foo'])
:param config_uri: Anything that can be parsed by
:func:`plaster.parse_uri`.
:param section: The name of the section in the config file. If this is
``None`` then it is up to the loader to determine a sensible default
usually derived from the fragment in the ``path#name`` syntax of the
``config_uri``.
:param defaults: A ``dict`` of default values used to populate the
settings and support variable interpolation. Any values in ``defaults``
may be overridden by the loader prior to returning the final
configuration dictionary.
:returns: A ``dict`` of settings. This should return a dictionary object
even if no data is available.
"""
loader = get_loader(config_uri)
return loader.get_settings(section, defaults)
[docs]
def setup_logging(config_uri, defaults=None):
"""
Execute the logging configuration defined in the config file.
This function should, at least, configure the Python standard logging
module. However, it may also be used to configure any other logging
subsystems that serve a similar purpose.
:param config_uri: Anything that can be parsed by
:func:`plaster.parse_uri`.
:param defaults: A ``dict`` of default values used to populate the
settings and support variable interpolation. Any values in ``defaults``
may be overridden by the loader prior to returning the final
configuration dictionary.
"""
loader = get_loader(config_uri)
return loader.setup_logging(defaults)
[docs]
def get_loader(config_uri, protocols=None):
"""
Find a :class:`plaster.ILoader` object capable of handling ``config_uri``.
:param config_uri: Anything that can be parsed by
:func:`plaster.parse_uri`.
:param protocols: Zero or more :term:`loader protocol` identifiers that
the loader must implement to match the desired ``config_uri``.
:returns: A :class:`plaster.ILoader` object.
:raises plaster.LoaderNotFound: If no loader could be found.
:raises plaster.MultipleLoadersFound: If multiple loaders match the
requested criteria. If this happens, you can disambiguate the lookup
by appending the package name to the scheme for the loader you wish
to use. For example if ``ini`` is ambiguous then specify
``ini+myapp`` to use the ini loader from the ``myapp`` package.
"""
config_uri = parse_uri(config_uri)
requested_scheme = config_uri.scheme
matched_loaders = find_loaders(requested_scheme, protocols=protocols)
if len(matched_loaders) < 1:
raise LoaderNotFound(requested_scheme, protocols=protocols)
if len(matched_loaders) > 1:
raise MultipleLoadersFound(
requested_scheme, matched_loaders, protocols=protocols
)
loader_info = matched_loaders[0]
loader = loader_info.load(config_uri)
return loader
[docs]
def find_loaders(scheme, protocols=None):
"""
Find all loaders that match the requested scheme and protocols.
:param scheme: Any valid scheme. Examples would be something like ``ini``
or ``pastedeploy+ini``.
:param protocols: Zero or more :term:`loader protocol` identifiers that
the loader must implement. If ``None`` then only generic loaders will
be returned.
:returns: A list containing zero or more :class:`plaster.ILoaderInfo`
objects.
"""
# build a list of all required entry points
matching_groups = ["plaster.loader_factory"]
if protocols:
matching_groups += [f"plaster.{proto}_loader_factory" for proto in protocols]
scheme = scheme.lower()
# if a distribution is specified then it overrides the default search
parts = scheme.split("+", 1)
if len(parts) == 2:
try:
dist = metadata.distribution(parts[0])
except metadata.PackageNotFoundError:
pass
else:
ep = _find_ep_in_dist(dist, parts[1], matching_groups)
# if we got one or more loaders from a specific distribution
# then they override everything else so we'll just return them
if ep:
return [EntryPointLoaderInfo(dist, ep, protocols)]
return [
EntryPointLoaderInfo(dist, ep, protocols=protocols)
for (dist, ep) in _iter_ep_in_dists(scheme, matching_groups)
]
def _iter_ep_in_dists(scheme, groups):
# XXX this is a hack to deduplicate distributions because importlib.metadata
# does not do this for us by default, at least up to Python 3.11.
# Specifically, if ``lib`` is symlinked to ``lib64`` then a Distribution
# object will be returned for each path, causing duplicate entry points
# to be found.
#
# See https://github.com/Pylons/plaster/issues/25
dups = set()
for dist in metadata.distributions():
name = dist.metadata["Name"]
if name in dups: # pragma: no cover
continue
dups.add(name)
ep = _find_ep_in_dist(dist, scheme, groups)
if ep:
yield (dist, ep)
def _find_ep_in_dist(dist, scheme, groups):
entry_points = [
entry_point
for entry_point in dist.entry_points
if entry_point.group in groups
and (scheme is None or scheme == entry_point.name.lower())
]
# verify that the entry point from each group points to the same factory
if len({ep.value for ep in entry_points}) == 1:
return entry_points[0]
class EntryPointLoaderInfo(ILoaderInfo):
def __init__(self, dist, ep, protocols=None):
self.entry_point = ep
self.scheme = "{}+{}".format(
dist.metadata["name"] if "name" in dist.metadata else "Unknown", ep.name
)
self.protocols = protocols
self._factory = None
@property
def factory(self):
if self._factory is None:
self._factory = self.entry_point.load()
return self._factory
def load(self, config_uri):
config_uri = parse_uri(config_uri)
return self.factory(config_uri)
