Coverage for /Users/davegaeddert/Developer/dropseed/plain/plain/plain/packages/registry.py: 79%
170 statements
« prev ^ index » next coverage.py v7.6.9, created at 2024-12-23 11:16 -0600
« prev ^ index » next coverage.py v7.6.9, created at 2024-12-23 11:16 -0600
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 f"duplicates: {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, " "duplicates: {}".format(
107 ", ".join(duplicates)
108 )
109 )
111 self.packages_ready = True
113 # Phase 2: import models modules.
114 for package_config in self.package_configs.values():
115 package_config.import_models()
117 self.clear_cache()
119 self.models_ready = True
121 # Phase 3: run ready() methods of app configs.
122 for package_config in self.get_package_configs():
123 package_config.ready()
125 self.ready = True
127 def check_packages_ready(self):
128 """Raise an exception if all packages haven't been imported yet."""
129 if not self.packages_ready:
130 from plain.runtime import settings
132 # If "not ready" is due to unconfigured settings, accessing
133 # INSTALLED_PACKAGES raises a more helpful ImproperlyConfigured
134 # exception.
135 settings.INSTALLED_PACKAGES
136 raise PackageRegistryNotReady("Packages aren't loaded yet.")
138 def check_models_ready(self):
139 """Raise an exception if all models haven't been imported yet."""
140 if not self.models_ready:
141 raise PackageRegistryNotReady("Models aren't loaded yet.")
143 def get_package_configs(self):
144 """Import applications and return an iterable of app configs."""
145 self.check_packages_ready()
146 return self.package_configs.values()
148 def get_package_config(self, package_label):
149 """
150 Import applications and returns an app config for the given label.
152 Raise LookupError if no application exists with this label.
153 """
154 self.check_packages_ready()
155 try:
156 return self.package_configs[package_label]
157 except KeyError:
158 message = f"No installed app with label '{package_label}'."
159 for package_config in self.get_package_configs():
160 if package_config.name == package_label:
161 message += f" Did you mean '{package_config.label}'?"
162 break
163 raise LookupError(message)
165 # This method is performance-critical at least for Plain's test suite.
166 @functools.cache
167 def get_models(self, include_auto_created=False, include_swapped=False):
168 """
169 Return a list of all installed models.
171 By default, the following models aren't included:
173 - auto-created models for many-to-many relations without
174 an explicit intermediate table,
175 - models that have been swapped out.
177 Set the corresponding keyword argument to True to include such models.
178 """
179 self.check_models_ready()
181 result = []
182 for package_config in self.package_configs.values():
183 result.extend(
184 package_config.get_models(include_auto_created, include_swapped)
185 )
186 return result
188 def get_model(self, package_label, model_name=None, require_ready=True):
189 """
190 Return the model matching the given package_label and model_name.
192 As a shortcut, package_label may be in the form <package_label>.<model_name>.
194 model_name is case-insensitive.
196 Raise LookupError if no application exists with this label, or no
197 model exists with this name in the application. Raise ValueError if
198 called with a single argument that doesn't contain exactly one dot.
199 """
200 if require_ready:
201 self.check_models_ready()
202 else:
203 self.check_packages_ready()
205 if model_name is None:
206 package_label, model_name = package_label.split(".")
208 package_config = self.get_package_config(package_label)
210 if not require_ready and package_config.models is None:
211 package_config.import_models()
213 return package_config.get_model(model_name, require_ready=require_ready)
215 def register_model(self, package_label, model):
216 # Since this method is called when models are imported, it cannot
217 # perform imports because of the risk of import loops. It mustn't
218 # call get_package_config().
219 model_name = model._meta.model_name
220 app_models = self.all_models[package_label]
221 if model_name in app_models:
222 if (
223 model.__name__ == app_models[model_name].__name__
224 and model.__module__ == app_models[model_name].__module__
225 ):
226 warnings.warn(
227 f"Model '{package_label}.{model_name}' was already registered. Reloading models is not "
228 "advised as it can lead to inconsistencies, most notably with "
229 "related models.",
230 RuntimeWarning,
231 stacklevel=2,
232 )
233 else:
234 raise RuntimeError(
235 f"Conflicting '{model_name}' models in application '{package_label}': {app_models[model_name]} and {model}."
236 )
237 app_models[model_name] = model
238 self.do_pending_operations(model)
239 self.clear_cache()
241 def is_installed(self, package_name):
242 """
243 Check whether an application with this name exists in the registry.
245 package_name is the full name of the app e.g. 'plain.staff'.
246 """
247 self.check_packages_ready()
248 return any(ac.name == package_name for ac in self.package_configs.values())
250 def get_containing_package_config(self, object_name):
251 """
252 Look for an app config containing a given object.
254 object_name is the dotted Python path to the object.
256 Return the app config for the inner application in case of nesting.
257 Return None if the object isn't in any registered app config.
258 """
259 self.check_packages_ready()
260 candidates = []
261 for package_config in self.package_configs.values():
262 if object_name.startswith(package_config.name):
263 subpath = object_name.removeprefix(package_config.name)
264 if subpath == "" or subpath[0] == ".":
265 candidates.append(package_config)
266 if candidates:
267 return sorted(candidates, key=lambda ac: -len(ac.name))[0]
269 def get_registered_model(self, package_label, model_name):
270 """
271 Similar to get_model(), but doesn't require that an app exists with
272 the given package_label.
274 It's safe to call this method at import time, even while the registry
275 is being populated.
276 """
277 model = self.all_models[package_label].get(model_name.lower())
278 if model is None:
279 raise LookupError(f"Model '{package_label}.{model_name}' not registered.")
280 return model
282 @functools.cache
283 def get_swappable_settings_name(self, to_string):
284 """
285 For a given model string (e.g. "auth.User"), return the name of the
286 corresponding settings name if it refers to a swappable model. If the
287 referred model is not swappable, return None.
289 This method is decorated with @functools.cache because it's performance
290 critical when it comes to migrations. Since the swappable settings don't
291 change after Plain has loaded the settings, there is no reason to get
292 the respective settings attribute over and over again.
293 """
294 to_string = to_string.lower()
295 for model in self.get_models(include_swapped=True):
296 swapped = model._meta.swapped
297 # Is this model swapped out for the model given by to_string?
298 if swapped and swapped.lower() == to_string:
299 return model._meta.swappable
300 # Is this model swappable and the one given by to_string?
301 if model._meta.swappable and model._meta.label_lower == to_string:
302 return model._meta.swappable
303 return None
305 def set_available_packages(self, available):
306 """
307 Restrict the set of installed packages used by get_package_config[s].
309 available must be an iterable of application names.
311 set_available_packages() must be balanced with unset_available_packages().
313 Primarily used for performance optimization in TransactionTestCase.
315 This method is safe in the sense that it doesn't trigger any imports.
316 """
317 available = set(available)
318 installed = {
319 package_config.name for package_config in self.get_package_configs()
320 }
321 if not available.issubset(installed):
322 raise ValueError(
323 "Available packages isn't a subset of installed packages, extra packages: {}".format(
324 ", ".join(available - installed)
325 )
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)