Coverage for python/lsst/daf/butler/core/storageClassDelegate.py: 17%
117 statements
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1# This file is part of daf_butler.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <http://www.gnu.org/licenses/>.
22"""Support for reading and writing composite objects."""
24from __future__ import annotations
26__all__ = ("DatasetComponent", "StorageClassDelegate")
28import collections.abc
29import logging
30from dataclasses import dataclass
31from typing import TYPE_CHECKING, Any, Dict, Iterable, Mapping, Optional, Set, Tuple, Type
33if TYPE_CHECKING:
34 from .storageClass import StorageClass
36log = logging.getLogger(__name__)
39@dataclass
40class DatasetComponent:
41 """Component of a dataset and associated information."""
43 name: str
44 """Name of the component.
45 """
47 storageClass: StorageClass
48 """StorageClass to be used when reading or writing this component.
49 """
51 component: Any
52 """Component extracted from the composite object.
53 """
56class StorageClassDelegate:
57 """Delegate class for StorageClass components and parameters.
59 This class delegates the handling of components and parameters for the
60 python type associated with a particular `StorageClass`.
62 A delegate is required for any storage class that defines components
63 (derived or otherwise) or support read parameters. It is used for
64 composite disassembly and assembly.
66 Attributes
67 ----------
68 storageClass : `StorageClass`
70 Parameters
71 ----------
72 storageClass : `StorageClass`
73 `StorageClass` to be used with this delegate.
74 """
76 def __init__(self, storageClass: StorageClass):
77 assert storageClass is not None
78 self.storageClass = storageClass
80 @staticmethod
81 def _attrNames(componentName: str, getter: bool = True) -> Tuple[str, ...]:
82 """Return list of suitable attribute names to attempt to use.
84 Parameters
85 ----------
86 componentName : `str`
87 Name of component/attribute to look for.
88 getter : `bool`
89 If true, return getters, else return setters.
91 Returns
92 -------
93 attrs : `tuple(str)`
94 Tuple of strings to attempt.
95 """
96 root = "get" if getter else "set"
98 # Capitalized name for getXxx must only capitalize first letter and not
99 # downcase the rest. getVisitInfo and not getVisitinfo
100 first = componentName[0].upper()
101 if len(componentName) > 1:
102 tail = componentName[1:]
103 else:
104 tail = ""
105 capitalized = f"{root}{first}{tail}"
106 return (componentName, f"{root}_{componentName}", capitalized)
108 def assemble(self, components: Dict[str, Any], pytype: Optional[Type] = None) -> Any:
109 """Construct an object from components based on storageClass.
111 This generic implementation assumes that instances of objects
112 can be created either by passing all the components to a constructor
113 or by calling setter methods with the name.
115 Parameters
116 ----------
117 components : `dict`
118 Collection of components from which to assemble a new composite
119 object. Keys correspond to composite names in the `StorageClass`.
120 pytype : `type`, optional
121 Override the type from the
122 :attr:`StorageClassDelegate.storageClass`
123 to use when assembling the final object.
125 Returns
126 -------
127 composite : `object`
128 New composite object assembled from components.
130 Raises
131 ------
132 ValueError
133 Some components could not be used to create the object or,
134 alternatively, some components were not defined in the associated
135 StorageClass.
136 """
137 if pytype is not None:
138 cls = pytype
139 else:
140 cls = self.storageClass.pytype
142 # Check that the storage class components are consistent
143 understood = set(self.storageClass.components)
144 requested = set(components.keys())
145 unknown = requested - understood
146 if unknown:
147 raise ValueError(f"Requested component(s) not known to StorageClass: {unknown}")
149 # First try to create an instance directly using keyword args
150 try:
151 obj = cls(**components)
152 except TypeError:
153 obj = None
155 # Now try to use setters if direct instantiation didn't work
156 if not obj:
157 obj = cls()
159 failed = []
160 for name, component in components.items():
161 if component is None:
162 continue
163 for attr in self._attrNames(name, getter=False):
164 if hasattr(obj, attr):
165 if attr == name: # Real attribute
166 setattr(obj, attr, component)
167 else:
168 setter = getattr(obj, attr)
169 setter(component)
170 break
171 else:
172 failed.append(name)
174 if failed:
175 raise ValueError(f"Unhandled components during assembly ({failed})")
177 return obj
179 def getValidComponents(self, composite: Any) -> Dict[str, Any]:
180 """Extract all non-None components from a composite.
182 Parameters
183 ----------
184 composite : `object`
185 Composite from which to extract components.
187 Returns
188 -------
189 comps : `dict`
190 Non-None components extracted from the composite, indexed by the
191 component name as derived from the
192 `StorageClassDelegate.storageClass`.
193 """
194 components = {}
195 if self.storageClass.isComposite():
196 for c in self.storageClass.components:
197 if isinstance(composite, collections.abc.Mapping):
198 comp = composite[c]
199 else:
200 try:
201 comp = self.getComponent(composite, c)
202 except AttributeError:
203 pass
204 else:
205 if comp is not None:
206 components[c] = comp
207 return components
209 def getComponent(self, composite: Any, componentName: str) -> Any:
210 """Attempt to retrieve component from composite object by heuristic.
212 Will attempt a direct attribute retrieval, or else getter methods of
213 the form "get_componentName" and "getComponentName".
215 Parameters
216 ----------
217 composite : `object`
218 Item to query for the component.
219 componentName : `str`
220 Name of component to retrieve.
222 Returns
223 -------
224 component : `object`
225 Component extracted from composite.
227 Raises
228 ------
229 AttributeError
230 The attribute could not be read from the composite.
231 """
232 component = None
234 if hasattr(composite, "__contains__") and componentName in composite:
235 component = composite[componentName]
236 return component
238 for attr in self._attrNames(componentName, getter=True):
239 if hasattr(composite, attr):
240 component = getattr(composite, attr)
241 if attr != componentName: # We have a method
242 component = component()
243 break
244 else:
245 raise AttributeError(f"Unable to get component {componentName}")
246 return component
248 def disassemble(
249 self, composite: Any, subset: Optional[Iterable] = None, override: Optional[Any] = None
250 ) -> Dict[str, DatasetComponent]:
251 """Disassembler a composite.
253 This is a generic implementation of a disassembler.
254 This implementation attempts to extract components from the parent
255 by looking for attributes of the same name or getter methods derived
256 from the component name.
258 Parameters
259 ----------
260 composite : `object`
261 Parent composite object consisting of components to be extracted.
262 subset : iterable, optional
263 Iterable containing subset of components to extract from composite.
264 Must be a subset of those defined in
265 `StorageClassDelegate.storageClass`.
266 override : `object`, optional
267 Object to use for disassembly instead of parent. This can be useful
268 when called from subclasses that have composites in a hierarchy.
270 Returns
271 -------
272 components : `dict`
273 `dict` with keys matching the components defined in
274 `StorageClassDelegate.storageClass`
275 and values being `DatasetComponent` instances describing the
276 component.
278 Raises
279 ------
280 ValueError
281 A requested component can not be found in the parent using generic
282 lookups.
283 TypeError
284 The parent object does not match the supplied
285 `StorageClassDelegate.storageClass`.
286 """
287 if not self.storageClass.isComposite():
288 raise TypeError(
289 f"Can not disassemble something that is not a composite (storage class={self.storageClass})"
290 )
292 if not self.storageClass.validateInstance(composite):
293 raise TypeError(
294 "Unexpected type mismatch between parent and StorageClass "
295 f"({type(composite)} != {self.storageClass.pytype})"
296 )
298 requested = set(self.storageClass.components)
300 if subset is not None:
301 subset = set(subset)
302 diff = subset - requested
303 if diff:
304 raise ValueError(f"Requested subset is not a subset of supported components: {diff}")
305 requested = subset
307 if override is not None:
308 composite = override
310 components = {}
311 for c in list(requested):
312 # Try three different ways to get a value associated with the
313 # component name.
314 try:
315 component = self.getComponent(composite, c)
316 except AttributeError:
317 # Defer complaining so we get an idea of how many problems
318 # we have
319 pass
320 else:
321 # If we found a match store it in the results dict and remove
322 # it from the list of components we are still looking for.
323 if component is not None:
324 components[c] = DatasetComponent(c, self.storageClass.components[c], component)
325 requested.remove(c)
327 if requested:
328 raise ValueError(f"Unhandled components during disassembly ({requested})")
330 return components
332 def handleParameters(self, inMemoryDataset: Any, parameters: Optional[Mapping[str, Any]] = None) -> Any:
333 """Modify the in-memory dataset using the supplied parameters.
335 Can return a possibly new object.
337 For safety, if any parameters are given to this method an
338 exception will be raised. This is to protect the user from
339 thinking that parameters have been applied when they have not been
340 applied.
342 Parameters
343 ----------
344 inMemoryDataset : `object`
345 Object to modify based on the parameters.
346 parameters : `dict`
347 Parameters to apply. Values are specific to the parameter.
348 Supported parameters are defined in the associated
349 `StorageClass`. If no relevant parameters are specified the
350 inMemoryDataset will be return unchanged.
352 Returns
353 -------
354 inMemoryDataset : `object`
355 Updated form of supplied in-memory dataset, after parameters
356 have been used.
358 Raises
359 ------
360 ValueError
361 Parameters have been provided to this default implementation.
362 """
363 if parameters:
364 raise ValueError(f"Parameters ({parameters}) provided to default implementation.")
366 return inMemoryDataset
368 @classmethod
369 def selectResponsibleComponent(cls, derivedComponent: str, fromComponents: Set[Optional[str]]) -> str:
370 """Select the best component for calculating a derived component.
372 Given a possible set of components to choose from, return the
373 component that should be used to calculate the requested derived
374 component.
376 Parameters
377 ----------
378 derivedComponent : `str`
379 The derived component that is being requested.
380 fromComponents : `set` of `str`
381 The available set of component options from which that derived
382 component can be computed. `None` can be included but should
383 be ignored.
385 Returns
386 -------
387 required : `str`
388 The component that should be used.
390 Raises
391 ------
392 NotImplementedError
393 Raised if this delegate refuses to answer the question.
394 ValueError
395 Raised if this delegate can not determine a relevant component
396 from the supplied options.
397 """
398 raise NotImplementedError("This delegate does not support derived components")