Remove use of storage wrappers

Use a dynamic subclass instead that always deconstructs to a fake
subclass with a __eq__ method that always returns True. This should
trick makemigrations into never creating a new migrations for
changes to the storage class or the arguments.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/common/classes.py

@@ -72,6 +72,16 @@ class ErrorLogNamespace(object):
         return ErrorLogEntry.objects.filter(namespace=self.name)
 
 
+class FakeStorageSubclass(object):
+    """
+    Placeholder class to allow serializing the real storage subclass to
+    support migrations.
+    """
+
+    def __eq__(self, other):
+        return True
+
+
 class MissingItem(object):
     _registry = []
 

mayan/apps/common/migrations/0011_auto_20181229_0738.py

@@ -1,10 +1,10 @@
 # -*- coding: utf-8 -*-
-# Generated by Django 1.11.16 on 2018-12-28 04:22
+# Generated by Django 1.11.16 on 2018-12-29 07:38
 from __future__ import unicode_literals
 
 from django.db import migrations, models
+import mayan.apps.common.classes
 import mayan.apps.common.models
-import mayan.apps.common.storages
 
 
 class Migration(migrations.Migration):
@@ -17,6 +17,6 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='shareduploadedfile',
             name='file',
-            field=models.FileField(storage=mayan.apps.common.storages.storage_sharedupload_wrapper, upload_to=mayan.apps.common.models.upload_to, verbose_name='File'),
+            field=models.FileField(storage=mayan.apps.common.classes.FakeStorageSubclass(), upload_to=mayan.apps.common.models.upload_to, verbose_name='File'),
         ),
     ]

mayan/apps/common/models.py

@@ -13,7 +13,7 @@ from django.utils.encoding import force_text, python_2_unicode_compatible
 from django.utils.translation import ugettext_lazy as _
 
 from .managers import ErrorLogEntryManager, UserLocaleProfileManager
-from .storages import storage_sharedupload_wrapper
+from .storages import storage_sharedupload
 
 logger = logging.getLogger(__name__)
 
@@ -58,7 +58,7 @@ class SharedUploadedFile(models.Model):
     that runs out of process.
     """
     file = models.FileField(
-        storage=storage_sharedupload_wrapper, upload_to=upload_to,
+        storage=storage_sharedupload, upload_to=upload_to,
         verbose_name=_('File')
     )
     filename = models.CharField(max_length=255, verbose_name=_('Filename'))

mayan/apps/common/storages.py

@@ -1,13 +1,8 @@
 from __future__ import unicode_literals
 
-from django.utils.module_loading import import_string
-
 from .settings import setting_shared_storage, setting_shared_storage_arguments
+from .utils import get_storage_subclass
 
-storage_sharedupload = import_string(
+storage_sharedupload = get_storage_subclass(
     dotted_path=setting_shared_storage.value
 )(**setting_shared_storage_arguments.value)
-
-
-def storage_sharedupload_wrapper():
-    return storage_sharedupload

mayan/apps/common/utils.py

@@ -12,6 +12,7 @@ from django.urls.base import get_script_prefix
 from django.utils.datastructures import MultiValueDict
 from django.utils.http import urlencode as django_urlencode
 from django.utils.http import urlquote as django_urlquote
+from django.utils.module_loading import import_string
 from django.utils.six.moves import reduce as reduce_function
 from django.utils.six.moves import xmlrpc_client
 
@@ -100,6 +101,28 @@ def get_descriptor(file_input, read=True):
         return file_input
 
 
+def get_storage_subclass(dotted_path):
+    """
+    Import a storage class and return a subclass that will always return eq
+    True to avoid creating a new migration when for runtime storage class
+    changes.
+    """
+    imported_storage_class = import_string(dotted_path=dotted_path)
+
+    class StorageSubclass(imported_storage_class):
+        def __init__(self, *args, **kwargs):
+            return super(StorageSubclass, self).__init__(*args, **kwargs)
+
+        def __eq__(self, other):
+            return True
+
+        def deconstruct(self):
+            return ('mayan.apps.common.classes.FakeStorageSubclass', (), {})
+
+
+    return StorageSubclass
+
+
 def TemporaryFile(*args, **kwargs):
     kwargs.update({'dir': setting_temporary_directory.value})
     return tempfile.TemporaryFile(*args, **kwargs)

mayan/apps/document_signatures/migrations/0009_auto_20181229_0737.py

@@ -1,10 +1,10 @@
 # -*- coding: utf-8 -*-
-# Generated by Django 1.11.16 on 2018-12-28 04:22
+# Generated by Django 1.11.16 on 2018-12-29 07:37
 from __future__ import unicode_literals
 
 from django.db import migrations, models
+import mayan.apps.common.classes
 import mayan.apps.document_signatures.models
-import mayan.apps.document_signatures.storages
 
 
 class Migration(migrations.Migration):
@@ -17,6 +17,6 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='detachedsignature',
             name='signature_file',
-            field=models.FileField(blank=True, null=True, storage=mayan.apps.document_signatures.storages.storage_detachedsignature_wrapper, upload_to=mayan.apps.document_signatures.models.upload_to, verbose_name='Signature file'),
+            field=models.FileField(blank=True, null=True, storage=mayan.apps.common.classes.FakeStorageSubclass(), upload_to=mayan.apps.document_signatures.models.upload_to, verbose_name='Signature file'),
         ),
     ]

mayan/apps/document_signatures/models.py

@@ -15,7 +15,7 @@ from mayan.apps.django_gpg.models import Key
 from mayan.apps.documents.models import DocumentVersion
 
 from .managers import EmbeddedSignatureManager
-from .storages import storage_detachedsignature_wrapper
+from .storages import storage_detachedsignature
 
 logger = logging.getLogger(__name__)
 
@@ -127,7 +127,7 @@ class EmbeddedSignature(SignatureBaseModel):
 @python_2_unicode_compatible
 class DetachedSignature(SignatureBaseModel):
     signature_file = models.FileField(
-        blank=True, null=True, storage=storage_detachedsignature_wrapper,
+        blank=True, null=True, storage=storage_detachedsignature,
         upload_to=upload_to, verbose_name=_('Signature file')
     )
 
@@ -143,7 +143,7 @@ class DetachedSignature(SignatureBaseModel):
 
     def delete(self, *args, **kwargs):
         if self.signature_file.name:
-            self.signature_file.storage().delete(name=self.signature_file.name)
+            self.signature_file.storage.delete(name=self.signature_file.name)
         super(DetachedSignature, self).delete(*args, **kwargs)
 
     def save(self, *args, **kwargs):

mayan/apps/document_signatures/storages.py

@@ -2,14 +2,12 @@ from __future__ import unicode_literals
 
 from django.utils.module_loading import import_string
 
+from mayan.apps.common.utils import get_storage_subclass
+
 from .settings import (
     setting_storage_backend, setting_storage_backend_arguments
 )
 
-storage_detachedsignature = import_string(
+storage_detachedsignature = get_storage_subclass(
     dotted_path=setting_storage_backend.value
 )(**setting_storage_backend_arguments.value)
-
-
-def storage_detachedsignature_wrapper():
-    return

mayan/apps/documents/migrations/0051_auto_20181229_0745.py

@@ -1,9 +1,9 @@
 # -*- coding: utf-8 -*-
-# Generated by Django 1.11.16 on 2018-12-28 04:22
+# Generated by Django 1.11.16 on 2018-12-29 07:45
 from __future__ import unicode_literals
 
 from django.db import migrations, models
-import mayan.apps.documents.storages
+import mayan.apps.common.classes
 import mayan.apps.documents.utils
 
 
@@ -17,6 +17,6 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='documentversion',
             name='file',
-            field=models.FileField(storage=mayan.apps.documents.storages.storage_documentversion_wrapper, upload_to=mayan.apps.documents.utils.document_uuid_function, verbose_name='File'),
+            field=models.FileField(storage=mayan.apps.common.classes.FakeStorageSubclass(), upload_to=mayan.apps.documents.utils.document_uuid_function, verbose_name='File'),
         ),
     ]

mayan/apps/documents/models/document_version_models.py

@@ -21,7 +21,7 @@ from ..literals import DOCUMENT_IMAGES_CACHE_NAME
 from ..managers import DocumentVersionManager
 from ..settings import setting_fix_orientation
 from ..signals import post_document_created, post_version_upload
-from ..storages import storage_documentversion_wrapper
+from ..storages import storage_documentversion
 from ..utils import document_hash_function, document_uuid_function
 
 from .document_models import Document
@@ -67,7 +67,7 @@ class DocumentVersion(models.Model):
 
     # File related fields
     file = models.FileField(
-        storage=storage_documentversion_wrapper, upload_to=document_uuid_function,
+        storage=storage_documentversion, upload_to=document_uuid_function,
         verbose_name=_('File')
     )
     mimetype = models.CharField(
@@ -137,7 +137,7 @@ class DocumentVersion(models.Model):
         be in the document storage. This is a diagnostic flag to help users
         detect if the storage has desynchronized (ie: Amazon's S3).
         """
-        return self.file.storage().exists(self.file.name)
+        return self.file.storage.exists(self.file.name)
 
     def fix_orientation(self):
         for page in self.pages.all():
@@ -329,7 +329,7 @@ class DocumentVersion(models.Model):
     @property
     def size(self):
         if self.exists():
-            return self.file.storage().size(self.file.name)
+            return self.file.storage.size(self.file.name)
         else:
             return None
 

mayan/apps/documents/storages.py

@@ -2,20 +2,18 @@ from __future__ import unicode_literals
 
 from django.utils.module_loading import import_string
 
+from mayan.apps.common.utils import get_storage_subclass
+
 from .settings import (
     setting_documentimagecache_storage,
     setting_documentimagecache_storage_arguments, setting_storage_backend,
     setting_storage_backend_arguments
 )
 
-storage_documentversion = import_string(
+storage_documentversion = get_storage_subclass(
     dotted_path=setting_storage_backend.value
 )(**setting_storage_backend_arguments.value)
 
 storage_documentimagecache = import_string(
     dotted_path=setting_documentimagecache_storage.value
 )(**setting_documentimagecache_storage_arguments.value)
-
-
-def storage_documentversion_wrapper():
-    return storage_documentversion