122 lines
4.2 KiB
Python
122 lines
4.2 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
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from django.utils.module_loading import import_by_path
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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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for model in self.models.values():
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model.render(self.app_cache)
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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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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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models[(model_state.app_label, model_state.name.lower())] = model_state
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return cls(models)
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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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fields.append((name, field_class(*args, **kwargs)))
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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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if name in model._meta.original_attrs:
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options[name] = model._meta.original_attrs[name]
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# Make our record
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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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model.__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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return self.__class__(
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app_label = self.app_label,
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name = self.name,
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fields = list(self.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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meta = type("Meta", tuple(), meta_contents)
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# Then, work out our bases
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# TODO: Use the actual 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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tuple(self.bases),
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body,
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)
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