211 lines
8.0 KiB
Python
211 lines
8.0 KiB
Python
from django.db import models
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from django.db.models.loading import BaseAppCache
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from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
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from django.utils import six
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from django.utils.module_loading import import_by_path
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class InvalidBasesError(ValueError):
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pass
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class ProjectState(object):
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"""
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Represents the entire project's overall state.
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This is the item that is passed around - we do it here rather than at the
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app level so that cross-app FKs/etc. resolve properly.
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"""
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def __init__(self, models=None):
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self.models = models or {}
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self.app_cache = None
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def add_model_state(self, model_state):
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self.models[(model_state.app_label, model_state.name.lower())] = model_state
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def clone(self):
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"Returns an exact copy of this ProjectState"
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return ProjectState(
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models=dict((k, v.clone()) for k, v in self.models.items())
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)
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def render(self):
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"Turns the project state into actual models in a new AppCache"
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if self.app_cache is None:
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self.app_cache = BaseAppCache()
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# We keep trying to render the models in a loop, ignoring invalid
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# base errors, until the size of the unrendered models doesn't
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# decrease by at least one, meaning there's a base dependency loop/
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# missing base.
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unrendered_models = list(self.models.values())
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while unrendered_models:
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new_unrendered_models = []
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for model in unrendered_models:
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try:
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model.render(self.app_cache)
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except InvalidBasesError:
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new_unrendered_models.append(model)
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if len(new_unrendered_models) == len(unrendered_models):
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raise InvalidBasesError("Cannot resolve bases for %r" % new_unrendered_models)
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unrendered_models = new_unrendered_models
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return self.app_cache
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@classmethod
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def from_app_cache(cls, app_cache):
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"Takes in an AppCache and returns a ProjectState matching it"
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app_models = {}
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for model in app_cache.get_models():
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model_state = ModelState.from_model(model)
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app_models[(model_state.app_label, model_state.name.lower())] = model_state
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return cls(app_models)
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def __eq__(self, other):
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if set(self.models.keys()) != set(other.models.keys()):
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return False
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return all(model == other.models[key] for key, model in self.models.items())
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def __ne__(self, other):
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return not (self == other)
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class ModelState(object):
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"""
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Represents a Django Model. We don't use the actual Model class
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as it's not designed to have its options changed - instead, we
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mutate this one and then render it into a Model as required.
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Note that while you are allowed to mutate .fields, you are not allowed
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to mutate the Field instances inside there themselves - you must instead
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assign new ones, as these are not detached during a clone.
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"""
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def __init__(self, app_label, name, fields, options=None, bases=None):
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self.app_label = app_label
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self.name = name
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self.fields = fields
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self.options = options or {}
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self.bases = bases or (models.Model, )
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# Sanity-check that fields is NOT a dict. It must be ordered.
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if isinstance(self.fields, dict):
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raise ValueError("ModelState.fields cannot be a dict - it must be a list of 2-tuples.")
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@classmethod
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def from_model(cls, model):
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"""
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Feed me a model, get a ModelState representing it out.
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"""
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# Deconstruct the fields
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fields = []
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for field in model._meta.local_fields:
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name, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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try:
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fields.append((name, field_class(*args, **kwargs)))
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except TypeError as e:
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raise TypeError("Couldn't reconstruct field %s on %s.%s: %s" % (
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name,
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model._meta.app_label,
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model._meta.object_name,
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e,
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))
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for field in model._meta.local_many_to_many:
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name, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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try:
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fields.append((name, field_class(*args, **kwargs)))
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except TypeError as e:
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raise TypeError("Couldn't reconstruct m2m field %s on %s: %s" % (
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name,
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model._meta.object_name,
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e,
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))
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# Extract the options
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options = {}
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for name in DEFAULT_NAMES:
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# Ignore some special options
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if name in ["app_cache", "app_label"]:
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continue
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elif name in model._meta.original_attrs:
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if name == "unique_together":
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ut = model._meta.original_attrs["unique_together"]
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options[name] = set(normalize_unique_together(ut))
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else:
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options[name] = model._meta.original_attrs[name]
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# Make our record
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bases = tuple(
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("%s.%s" % (base._meta.app_label, base._meta.object_name.lower()) if hasattr(base, "_meta") else base)
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for base in model.__bases__
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if (not hasattr(base, "_meta") or not base._meta.abstract)
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)
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if not bases:
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bases = (models.Model, )
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return cls(
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model._meta.app_label,
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model._meta.object_name,
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fields,
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options,
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bases,
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)
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def clone(self):
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"Returns an exact copy of this ModelState"
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# We deep-clone the fields using deconstruction
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fields = []
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for name, field in self.fields:
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_, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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fields.append((name, field_class(*args, **kwargs)))
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# Now make a copy
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return self.__class__(
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app_label=self.app_label,
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name=self.name,
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fields=fields,
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options=dict(self.options),
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bases=self.bases,
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)
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def render(self, app_cache):
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"Creates a Model object from our current state into the given app_cache"
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# First, make a Meta object
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meta_contents = {'app_label': self.app_label, "app_cache": app_cache}
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meta_contents.update(self.options)
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if "unique_together" in meta_contents:
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meta_contents["unique_together"] = list(meta_contents["unique_together"])
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meta = type("Meta", tuple(), meta_contents)
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# Then, work out our bases
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bases = tuple(
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(app_cache.get_model(*base.split(".", 1)) if isinstance(base, six.string_types) else base)
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for base in self.bases
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)
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if None in bases:
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raise InvalidBasesError("Cannot resolve one or more bases from %r" % (self.bases,))
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# Turn fields into a dict for the body, add other bits
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body = dict(self.fields)
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body['Meta'] = meta
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body['__module__'] = "__fake__"
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# Then, make a Model object
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return type(
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self.name,
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bases,
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body,
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)
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def get_field_by_name(self, name):
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for fname, field in self.fields:
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if fname == name:
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return field
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raise ValueError("No field called %s on model %s" % (name, self.name))
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def __eq__(self, other):
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return (
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(self.app_label == other.app_label) and
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(self.name == other.name) and
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(len(self.fields) == len(other.fields)) and
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all((k1 == k2 and (f1.deconstruct()[1:] == f2.deconstruct()[1:])) for (k1, f1), (k2, f2) in zip(self.fields, other.fields)) and
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(self.options == other.options) and
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(self.bases == other.bases)
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)
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def __ne__(self, other):
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return not (self == other)
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