Fixed #24375 -- Added Migration.initial attribute

The new attribute is checked when the `migrate --fake-initial` option
is used. initial will be set to True for all initial migrations (this
is particularly useful when initial migrations are split) as well as
for squashed migrations.

5 files changed, 47 insertions, 10 deletions

diff --git a/django/core/management/commands/squashmigrations.py b/django/core/management/commands/squashmigrations.py
index 74e5ce78c3..db55195187 100644
--- a/django/core/management/commands/squashmigrations.py
+++ b/django/core/management/commands/squashmigrations.py
@@ -131,6 +131,7 @@ class Command(BaseCommand):
             "dependencies": dependencies,
             "operations": new_operations,
             "replaces": replaces,
+            "initial": True,
         })
         new_migration = subclass("0001_squashed_%s" % migration.name, app_label)
 
diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index ddf8e36b83..b20946999f 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -33,6 +33,7 @@ class MigrationAutodetector(object):
         self.from_state = from_state
         self.to_state = to_state
         self.questioner = questioner or MigrationQuestioner()
+        self.existing_apps = {app for app, model in from_state.models}
 
     def changes(self, graph, trim_to_apps=None, convert_apps=None, migration_name=None):
         """
@@ -297,6 +298,7 @@ class MigrationAutodetector(object):
                         instance = subclass("auto_%i" % (len(self.migrations.get(app_label, [])) + 1), app_label)
                         instance.dependencies = list(dependencies)
                         instance.operations = chopped
+                        instance.initial = app_label not in self.existing_apps
                         self.migrations.setdefault(app_label, []).append(instance)
                         chop_mode = False
                     else:
diff --git a/django/db/migrations/executor.py b/django/db/migrations/executor.py
index aeb021e33c..c25aee6193 100644
--- a/django/db/migrations/executor.py
+++ b/django/db/migrations/executor.py
@@ -197,19 +197,25 @@ class MigrationExecutor(object):
     def detect_soft_applied(self, project_state, migration):
         """
         Tests whether a migration has been implicitly applied - that the
-        tables it would create exist. This is intended only for use
-        on initial migrations (as it only looks for CreateModel).
+        tables or columns it would create exist. This is intended only for use
+        on initial migrations (as it only looks for CreateModel and AddField).
         """
-        # Bail if the migration isn't the first one in its app
-        if [name for app, name in migration.dependencies if app == migration.app_label]:
+        if migration.initial is None:
+            # Bail if the migration isn't the first one in its app
+            if any(app == migration.app_label for app, name in migration.dependencies):
+                return False, project_state
+        elif migration.initial is False:
+            # Bail if it's NOT an initial migration
             return False, project_state
+
         if project_state is None:
             after_state = self.loader.project_state((migration.app_label, migration.name), at_end=True)
         else:
             after_state = migration.mutate_state(project_state)
         apps = after_state.apps
-        found_create_migration = False
-        # Make sure all create model are done
+        found_create_model_migration = False
+        found_add_field_migration = False
+        # Make sure all create model and add field operations are done
         for operation in migration.operations:
             if isinstance(operation, migrations.CreateModel):
                 model = apps.get_model(migration.app_label, operation.name)
@@ -217,9 +223,26 @@ class MigrationExecutor(object):
                     # We have to fetch the model to test with from the
                     # main app cache, as it's not a direct dependency.
                     model = global_apps.get_model(model._meta.swapped)
+                if model._meta.proxy or not model._meta.managed:
+                    continue
                 if model._meta.db_table not in self.connection.introspection.table_names(self.connection.cursor()):
                     return False, project_state
-                found_create_migration = True
-        # If we get this far and we found at least one CreateModel migration,
+                found_create_model_migration = True
+            elif isinstance(operation, migrations.AddField):
+                model = apps.get_model(migration.app_label, operation.model_name)
+                if model._meta.swapped:
+                    # We have to fetch the model to test with from the
+                    # main app cache, as it's not a direct dependency.
+                    model = global_apps.get_model(model._meta.swapped)
+                if model._meta.proxy or not model._meta.managed:
+                    continue
+
+                table = model._meta.db_table
+                db_field = model._meta.get_field(operation.name).column
+                fields = self.connection.introspection.get_table_description(self.connection.cursor(), table)
+                if db_field not in (f.name for f in fields):
+                    return False, project_state
+                found_add_field_migration = True
+        # If we get this far and we found at least one CreateModel or AddField migration,
         # the migration is considered implicitly applied.
-        return found_create_migration, after_state
+        return (found_create_model_migration or found_add_field_migration), after_state
diff --git a/django/db/migrations/migration.py b/django/db/migrations/migration.py
index 59edf599f6..7641eb45bc 100644
--- a/django/db/migrations/migration.py
+++ b/django/db/migrations/migration.py
@@ -41,6 +41,13 @@ class Migration(object):
     # are not applied.
     replaces = []
 
+    # Is this an initial migration? Initial migrations are skipped on
+    # --fake-initial if the table or fields already exist. If None, check if
+    # the migration has any dependencies to determine if there are dependencies
+    # to tell if db introspection needs to be done. If True, always perform
+    # introspection. If False, never perform introspection.
+    initial = None
+
     def __init__(self, name, app_label):
         self.name = name
         self.app_label = app_label
diff --git a/django/db/migrations/writer.py b/django/db/migrations/writer.py
index a7848d744f..11ecb6ed2b 100644
--- a/django/db/migrations/writer.py
+++ b/django/db/migrations/writer.py
@@ -155,6 +155,7 @@ class MigrationWriter(object):
         """
         items = {
             "replaces_str": "",
+            "initial_str": "",
         }
 
         imports = set()
@@ -211,6 +212,9 @@ class MigrationWriter(object):
         if self.migration.replaces:
             items['replaces_str'] = "\n    replaces = %s\n" % self.serialize(self.migration.replaces)[0]
 
+        if self.migration.initial:
+            items['initial_str'] = "\n    initial = True\n"
+
         return (MIGRATION_TEMPLATE % items).encode("utf8")
 
     @staticmethod
@@ -508,7 +512,7 @@ from __future__ import unicode_literals
 %(imports)s
 
 class Migration(migrations.Migration):
-%(replaces_str)s
+%(replaces_str)s%(initial_str)s
     dependencies = [
 %(dependencies)s\
     ]