Coverage for /Users/davegaeddert/Development/dropseed/plain/plain/plain/packages/registry.py: 79%
170 statements
« prev ^ index » next coverage.py v7.6.1, created at 2024-10-16 22:04 -0500
« prev ^ index » next coverage.py v7.6.1, created at 2024-10-16 22:04 -0500
1import functools
2import sys
3import threading
4import warnings
5from collections import Counter, defaultdict
6from functools import partial
8from plain.exceptions import ImproperlyConfigured, PackageRegistryNotReady
10from .config import PackageConfig
13class Packages:
14 """
15 A registry that stores the configuration of installed applications.
17 It also keeps track of models, e.g. to provide reverse relations.
18 """
20 def __init__(self, installed_packages=()):
21 # installed_packages is set to None when creating the main registry
22 # because it cannot be populated at that point. Other registries must
23 # provide a list of installed packages and are populated immediately.
24 if installed_packages is None and hasattr(sys.modules[__name__], "packages"):
25 raise RuntimeError("You must supply an installed_packages argument.")
27 # Mapping of app labels => model names => model classes. Every time a
28 # model is imported, ModelBase.__new__ calls packages.register_model which
29 # creates an entry in all_models. All imported models are registered,
30 # regardless of whether they're defined in an installed application
31 # and whether the registry has been populated. Since it isn't possible
32 # to reimport a module safely (it could reexecute initialization code)
33 # all_models is never overridden or reset.
34 self.all_models = defaultdict(dict)
36 # Mapping of labels to PackageConfig instances for installed packages.
37 self.package_configs = {}
39 # Stack of package_configs. Used to store the current state in
40 # set_available_packages and set_installed_packages.
41 self.stored_package_configs = []
43 # Whether the registry is populated.
44 self.packages_ready = self.models_ready = self.ready = False
46 # Lock for thread-safe population.
47 self._lock = threading.RLock()
48 self.loading = False
50 # Maps ("package_label", "modelname") tuples to lists of functions to be
51 # called when the corresponding model is ready. Used by this class's
52 # `lazy_model_operation()` and `do_pending_operations()` methods.
53 self._pending_operations = defaultdict(list)
55 # Populate packages and models, unless it's the main registry.
56 if installed_packages is not None:
57 self.populate(installed_packages)
59 def populate(self, installed_packages=None):
60 """
61 Load application configurations and models.
63 Import each application module and then each model module.
65 It is thread-safe and idempotent, but not reentrant.
66 """
67 if self.ready:
68 return
70 # populate() might be called by two threads in parallel on servers
71 # that create threads before initializing the WSGI callable.
72 with self._lock:
73 if self.ready:
74 return
76 # An RLock prevents other threads from entering this section. The
77 # compare and set operation below is atomic.
78 if self.loading:
79 # Prevent reentrant calls to avoid running PackageConfig.ready()
80 # methods twice.
81 raise RuntimeError("populate() isn't reentrant")
82 self.loading = True
84 # Phase 1: initialize app configs and import app modules.
85 for entry in installed_packages:
86 if isinstance(entry, PackageConfig):
87 package_config = entry
88 else:
89 package_config = PackageConfig.create(entry)
90 if package_config.label in self.package_configs:
91 raise ImproperlyConfigured(
92 "Package labels aren't unique, "
93 "duplicates: %s" % package_config.label
94 )
96 self.package_configs[package_config.label] = package_config
97 package_config.packages = self
99 # Check for duplicate app names.
100 counts = Counter(
101 package_config.name for package_config in self.package_configs.values()
102 )
103 duplicates = [name for name, count in counts.most_common() if count > 1]
104 if duplicates:
105 raise ImproperlyConfigured(
106 "Package names aren't unique, "
107 "duplicates: %s" % ", ".join(duplicates)
108 )
110 self.packages_ready = True
112 # Phase 2: import models modules.
113 for package_config in self.package_configs.values():
114 package_config.import_models()
116 self.clear_cache()
118 self.models_ready = True
120 # Phase 3: run ready() methods of app configs.
121 for package_config in self.get_package_configs():
122 package_config.ready()
124 self.ready = True
126 def check_packages_ready(self):
127 """Raise an exception if all packages haven't been imported yet."""
128 if not self.packages_ready:
129 from plain.runtime import settings
131 # If "not ready" is due to unconfigured settings, accessing
132 # INSTALLED_PACKAGES raises a more helpful ImproperlyConfigured
133 # exception.
134 settings.INSTALLED_PACKAGES
135 raise PackageRegistryNotReady("Packages aren't loaded yet.")
137 def check_models_ready(self):
138 """Raise an exception if all models haven't been imported yet."""
139 if not self.models_ready:
140 raise PackageRegistryNotReady("Models aren't loaded yet.")
142 def get_package_configs(self):
143 """Import applications and return an iterable of app configs."""
144 self.check_packages_ready()
145 return self.package_configs.values()
147 def get_package_config(self, package_label):
148 """
149 Import applications and returns an app config for the given label.
151 Raise LookupError if no application exists with this label.
152 """
153 self.check_packages_ready()
154 try:
155 return self.package_configs[package_label]
156 except KeyError:
157 message = "No installed app with label '%s'." % package_label
158 for package_config in self.get_package_configs():
159 if package_config.name == package_label:
160 message += " Did you mean '%s'?" % package_config.label
161 break
162 raise LookupError(message)
164 # This method is performance-critical at least for Plain's test suite.
165 @functools.cache
166 def get_models(self, include_auto_created=False, include_swapped=False):
167 """
168 Return a list of all installed models.
170 By default, the following models aren't included:
172 - auto-created models for many-to-many relations without
173 an explicit intermediate table,
174 - models that have been swapped out.
176 Set the corresponding keyword argument to True to include such models.
177 """
178 self.check_models_ready()
180 result = []
181 for package_config in self.package_configs.values():
182 result.extend(
183 package_config.get_models(include_auto_created, include_swapped)
184 )
185 return result
187 def get_model(self, package_label, model_name=None, require_ready=True):
188 """
189 Return the model matching the given package_label and model_name.
191 As a shortcut, package_label may be in the form <package_label>.<model_name>.
193 model_name is case-insensitive.
195 Raise LookupError if no application exists with this label, or no
196 model exists with this name in the application. Raise ValueError if
197 called with a single argument that doesn't contain exactly one dot.
198 """
199 if require_ready:
200 self.check_models_ready()
201 else:
202 self.check_packages_ready()
204 if model_name is None:
205 package_label, model_name = package_label.split(".")
207 package_config = self.get_package_config(package_label)
209 if not require_ready and package_config.models is None:
210 package_config.import_models()
212 return package_config.get_model(model_name, require_ready=require_ready)
214 def register_model(self, package_label, model):
215 # Since this method is called when models are imported, it cannot
216 # perform imports because of the risk of import loops. It mustn't
217 # call get_package_config().
218 model_name = model._meta.model_name
219 app_models = self.all_models[package_label]
220 if model_name in app_models:
221 if (
222 model.__name__ == app_models[model_name].__name__
223 and model.__module__ == app_models[model_name].__module__
224 ):
225 warnings.warn(
226 "Model '{}.{}' was already registered. Reloading models is not "
227 "advised as it can lead to inconsistencies, most notably with "
228 "related models.".format(package_label, model_name),
229 RuntimeWarning,
230 stacklevel=2,
231 )
232 else:
233 raise RuntimeError(
234 "Conflicting '{}' models in application '{}': {} and {}.".format(
235 model_name, package_label, app_models[model_name], model
236 )
237 )
238 app_models[model_name] = model
239 self.do_pending_operations(model)
240 self.clear_cache()
242 def is_installed(self, package_name):
243 """
244 Check whether an application with this name exists in the registry.
246 package_name is the full name of the app e.g. 'plain.staff'.
247 """
248 self.check_packages_ready()
249 return any(ac.name == package_name for ac in self.package_configs.values())
251 def get_containing_package_config(self, object_name):
252 """
253 Look for an app config containing a given object.
255 object_name is the dotted Python path to the object.
257 Return the app config for the inner application in case of nesting.
258 Return None if the object isn't in any registered app config.
259 """
260 self.check_packages_ready()
261 candidates = []
262 for package_config in self.package_configs.values():
263 if object_name.startswith(package_config.name):
264 subpath = object_name.removeprefix(package_config.name)
265 if subpath == "" or subpath[0] == ".":
266 candidates.append(package_config)
267 if candidates:
268 return sorted(candidates, key=lambda ac: -len(ac.name))[0]
270 def get_registered_model(self, package_label, model_name):
271 """
272 Similar to get_model(), but doesn't require that an app exists with
273 the given package_label.
275 It's safe to call this method at import time, even while the registry
276 is being populated.
277 """
278 model = self.all_models[package_label].get(model_name.lower())
279 if model is None:
280 raise LookupError(f"Model '{package_label}.{model_name}' not registered.")
281 return model
283 @functools.cache
284 def get_swappable_settings_name(self, to_string):
285 """
286 For a given model string (e.g. "auth.User"), return the name of the
287 corresponding settings name if it refers to a swappable model. If the
288 referred model is not swappable, return None.
290 This method is decorated with @functools.cache because it's performance
291 critical when it comes to migrations. Since the swappable settings don't
292 change after Plain has loaded the settings, there is no reason to get
293 the respective settings attribute over and over again.
294 """
295 to_string = to_string.lower()
296 for model in self.get_models(include_swapped=True):
297 swapped = model._meta.swapped
298 # Is this model swapped out for the model given by to_string?
299 if swapped and swapped.lower() == to_string:
300 return model._meta.swappable
301 # Is this model swappable and the one given by to_string?
302 if model._meta.swappable and model._meta.label_lower == to_string:
303 return model._meta.swappable
304 return None
306 def set_available_packages(self, available):
307 """
308 Restrict the set of installed packages used by get_package_config[s].
310 available must be an iterable of application names.
312 set_available_packages() must be balanced with unset_available_packages().
314 Primarily used for performance optimization in TransactionTestCase.
316 This method is safe in the sense that it doesn't trigger any imports.
317 """
318 available = set(available)
319 installed = {
320 package_config.name for package_config in self.get_package_configs()
321 }
322 if not available.issubset(installed):
323 raise ValueError(
324 "Available packages isn't a subset of installed packages, extra packages: %s"
325 % ", ".join(available - installed)
326 )
328 self.stored_package_configs.append(self.package_configs)
329 self.package_configs = {
330 label: package_config
331 for label, package_config in self.package_configs.items()
332 if package_config.name in available
333 }
334 self.clear_cache()
336 def unset_available_packages(self):
337 """Cancel a previous call to set_available_packages()."""
338 self.package_configs = self.stored_package_configs.pop()
339 self.clear_cache()
341 def set_installed_packages(self, installed):
342 """
343 Enable a different set of installed packages for get_package_config[s].
345 installed must be an iterable in the same format as INSTALLED_PACKAGES.
347 set_installed_packages() must be balanced with unset_installed_packages(),
348 even if it exits with an exception.
350 Primarily used as a receiver of the setting_changed signal in tests.
352 This method may trigger new imports, which may add new models to the
353 registry of all imported models. They will stay in the registry even
354 after unset_installed_packages(). Since it isn't possible to replay
355 imports safely (e.g. that could lead to registering listeners twice),
356 models are registered when they're imported and never removed.
357 """
358 if not self.ready:
359 raise PackageRegistryNotReady("Package registry isn't ready yet.")
360 self.stored_package_configs.append(self.package_configs)
361 self.package_configs = {}
362 self.packages_ready = self.models_ready = self.loading = self.ready = False
363 self.clear_cache()
364 self.populate(installed)
366 def clear_cache(self):
367 """
368 Clear all internal caches, for methods that alter the app registry.
370 This is mostly used in tests.
371 """
372 # Call expire cache on each model. This will purge
373 # the relation tree and the fields cache.
374 self.get_models.cache_clear()
375 if self.ready:
376 # Circumvent self.get_models() to prevent that the cache is refilled.
377 # This particularly prevents that an empty value is cached while cloning.
378 for package_config in self.package_configs.values():
379 for model in package_config.get_models(include_auto_created=True):
380 model._meta._expire_cache()
382 def lazy_model_operation(self, function, *model_keys):
383 """
384 Take a function and a number of ("package_label", "modelname") tuples, and
385 when all the corresponding models have been imported and registered,
386 call the function with the model classes as its arguments.
388 The function passed to this method must accept exactly n models as
389 arguments, where n=len(model_keys).
390 """
391 # Base case: no arguments, just execute the function.
392 if not model_keys:
393 function()
394 # Recursive case: take the head of model_keys, wait for the
395 # corresponding model class to be imported and registered, then apply
396 # that argument to the supplied function. Pass the resulting partial
397 # to lazy_model_operation() along with the remaining model args and
398 # repeat until all models are loaded and all arguments are applied.
399 else:
400 next_model, *more_models = model_keys
402 # This will be executed after the class corresponding to next_model
403 # has been imported and registered. The `func` attribute provides
404 # duck-type compatibility with partials.
405 def apply_next_model(model):
406 next_function = partial(apply_next_model.func, model)
407 self.lazy_model_operation(next_function, *more_models)
409 apply_next_model.func = function
411 # If the model has already been imported and registered, partially
412 # apply it to the function now. If not, add it to the list of
413 # pending operations for the model, where it will be executed with
414 # the model class as its sole argument once the model is ready.
415 try:
416 model_class = self.get_registered_model(*next_model)
417 except LookupError:
418 self._pending_operations[next_model].append(apply_next_model)
419 else:
420 apply_next_model(model_class)
422 def do_pending_operations(self, model):
423 """
424 Take a newly-prepared model and pass it to each function waiting for
425 it. This is called at the very end of Packages.register_model().
426 """
427 key = model._meta.package_label, model._meta.model_name
428 for function in self._pending_operations.pop(key, []):
429 function(model)
432packages = Packages(installed_packages=None)