Refs #29898 -- Moved state_forwards()'s logic from migration operations to ProjectState.

Thanks Simon Charette and Markus Holtermann for reviews.

3 files changed, 189 insertions, 138 deletions

diff --git a/django/db/migrations/operations/fields.py b/django/db/migrations/operations/fields.py
index b303f70465..641c142191 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -1,7 +1,4 @@
-from django.core.exceptions import FieldDoesNotExist
-from django.db.migrations.utils import (
-    field_is_referenced, field_references, get_references,
-)
+from django.db.migrations.utils import field_references
 from django.db.models import NOT_PROVIDED
 from django.utils.functional import cached_property
 
@@ -85,16 +82,13 @@ class AddField(FieldOperation):
         )
 
     def state_forwards(self, app_label, state):
-        # If preserve default is off, don't use the default for future state
-        if not self.preserve_default:
-            field = self.field.clone()
-            field.default = NOT_PROVIDED
-        else:
-            field = self.field
-        state.models[app_label, self.model_name_lower].fields[self.name] = field
-        # Delay rendering of relationships if it's not a relational field
-        delay = not field.is_relation
-        state.reload_model(app_label, self.model_name_lower, delay=delay)
+        state.add_field(
+            app_label,
+            self.model_name_lower,
+            self.name,
+            self.field,
+            self.preserve_default,
+        )
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
@@ -160,11 +154,7 @@ class RemoveField(FieldOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        old_field = model_state.fields.pop(self.name)
-        # Delay rendering of relationships if it's not a relational field
-        delay = not old_field.is_relation
-        state.reload_model(app_label, self.model_name_lower, delay=delay)
+        state.remove_field(app_label, self.model_name_lower, self.name)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         from_model = from_state.apps.get_model(app_label, self.model_name)
@@ -216,24 +206,13 @@ class AlterField(FieldOperation):
         )
 
     def state_forwards(self, app_label, state):
-        if not self.preserve_default:
-            field = self.field.clone()
-            field.default = NOT_PROVIDED
-        else:
-            field = self.field
-        model_state = state.models[app_label, self.model_name_lower]
-        model_state.fields[self.name] = field
-        # TODO: investigate if old relational fields must be reloaded or if it's
-        # sufficient if the new field is (#27737).
-        # Delay rendering of relationships if it's not a relational field and
-        # not referenced by a foreign key.
-        delay = (
-            not field.is_relation and
-            not field_is_referenced(
-                state, (app_label, self.model_name_lower), (self.name, field),
-            )
+        state.alter_field(
+            app_label,
+            self.model_name_lower,
+            self.name,
+            self.field,
+            self.preserve_default,
         )
-        state.reload_model(app_label, self.model_name_lower, delay=delay)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
@@ -301,49 +280,7 @@ class RenameField(FieldOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        # Rename the field
-        fields = model_state.fields
-        try:
-            found = fields.pop(self.old_name)
-        except KeyError:
-            raise FieldDoesNotExist(
-                "%s.%s has no field named '%s'" % (app_label, self.model_name, self.old_name)
-            )
-        fields[self.new_name] = found
-        for field in fields.values():
-            # Fix from_fields to refer to the new field.
-            from_fields = getattr(field, 'from_fields', None)
-            if from_fields:
-                field.from_fields = tuple([
-                    self.new_name if from_field_name == self.old_name else from_field_name
-                    for from_field_name in from_fields
-                ])
-        # Fix index/unique_together to refer to the new field
-        options = model_state.options
-        for option in ('index_together', 'unique_together'):
-            if option in options:
-                options[option] = [
-                    [self.new_name if n == self.old_name else n for n in together]
-                    for together in options[option]
-                ]
-        # Fix to_fields to refer to the new field.
-        delay = True
-        references = get_references(
-            state, (app_label, self.model_name_lower), (self.old_name, found),
-        )
-        for *_, field, reference in references:
-            delay = False
-            if reference.to:
-                remote_field, to_fields = reference.to
-                if getattr(remote_field, 'field_name', None) == self.old_name:
-                    remote_field.field_name = self.new_name
-                if to_fields:
-                    field.to_fields = tuple([
-                        self.new_name if to_field_name == self.old_name else to_field_name
-                        for to_field_name in to_fields
-                    ])
-        state.reload_model(app_label, self.model_name_lower, delay=delay)
+        state.rename_field(app_label, self.model_name_lower, self.old_name, self.new_name)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 10f2686dc6..982816be3a 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -1,9 +1,7 @@
 from django.db import models
 from django.db.migrations.operations.base import Operation
 from django.db.migrations.state import ModelState
-from django.db.migrations.utils import (
-    field_references, get_references, resolve_relation,
-)
+from django.db.migrations.utils import field_references, resolve_relation
 from django.db.models.options import normalize_together
 from django.utils.functional import cached_property
 
@@ -316,31 +314,7 @@ class RenameModel(ModelOperation):
         )
 
     def state_forwards(self, app_label, state):
-        # Add a new model.
-        renamed_model = state.models[app_label, self.old_name_lower].clone()
-        renamed_model.name = self.new_name
-        state.models[app_label, self.new_name_lower] = renamed_model
-        # Repoint all fields pointing to the old model to the new one.
-        old_model_tuple = (app_label, self.old_name_lower)
-        new_remote_model = '%s.%s' % (app_label, self.new_name)
-        to_reload = set()
-        for model_state, name, field, reference in get_references(state, old_model_tuple):
-            changed_field = None
-            if reference.to:
-                changed_field = field.clone()
-                changed_field.remote_field.model = new_remote_model
-            if reference.through:
-                if changed_field is None:
-                    changed_field = field.clone()
-                changed_field.remote_field.through = new_remote_model
-            if changed_field:
-                model_state.fields[name] = changed_field
-                to_reload.add((model_state.app_label, model_state.name_lower))
-        # Reload models related to old model before removing the old model.
-        state.reload_models(to_reload, delay=True)
-        # Remove the old model.
-        state.remove_model(app_label, self.old_name_lower)
-        state.reload_model(app_label, self.new_name_lower, delay=True)
+        state.rename_model(app_label, self.old_name, self.new_name)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.new_name)
@@ -458,8 +432,7 @@ class AlterModelTable(ModelOptionOperation):
         )
 
     def state_forwards(self, app_label, state):
-        state.models[app_label, self.name_lower].options["db_table"] = self.table
-        state.reload_model(app_label, self.name_lower, delay=True)
+        state.alter_model_options(app_label, self.name_lower, {'db_table': self.table})
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
@@ -518,9 +491,11 @@ class AlterTogetherOptionOperation(ModelOptionOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name_lower]
-        model_state.options[self.option_name] = self.option_value
-        state.reload_model(app_label, self.name_lower, delay=True)
+        state.alter_model_options(
+            app_label,
+            self.name_lower,
+            {self.option_name: self.option_value},
+        )
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
@@ -596,9 +571,11 @@ class AlterOrderWithRespectTo(ModelOptionOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name_lower]
-        model_state.options['order_with_respect_to'] = self.order_with_respect_to
-        state.reload_model(app_label, self.name_lower, delay=True)
+        state.alter_model_options(
+            app_label,
+            self.name_lower,
+            {self.option_name: self.order_with_respect_to},
+        )
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.name)
@@ -676,12 +653,12 @@ class AlterModelOptions(ModelOptionOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name_lower]
-        model_state.options = {**model_state.options, **self.options}
-        for key in self.ALTER_OPTION_KEYS:
-            if key not in self.options:
-                model_state.options.pop(key, False)
-        state.reload_model(app_label, self.name_lower, delay=True)
+        state.alter_model_options(
+            app_label,
+            self.name_lower,
+            self.options,
+            self.ALTER_OPTION_KEYS,
+        )
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         pass
@@ -714,9 +691,7 @@ class AlterModelManagers(ModelOptionOperation):
         )
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.name_lower]
-        model_state.managers = list(self.managers)
-        state.reload_model(app_label, self.name_lower, delay=True)
+        state.alter_model_managers(app_label, self.name_lower, self.managers)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         pass
@@ -753,9 +728,7 @@ class AddIndex(IndexOperation):
         self.index = index
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        model_state.options[self.option_name] = [*model_state.options[self.option_name], self.index.clone()]
-        state.reload_model(app_label, self.model_name_lower, delay=True)
+        state.add_index(app_label, self.model_name_lower, self.index)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = to_state.apps.get_model(app_label, self.model_name)
@@ -804,10 +777,7 @@ class RemoveIndex(IndexOperation):
         self.name = name
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        indexes = model_state.options[self.option_name]
-        model_state.options[self.option_name] = [idx for idx in indexes if idx.name != self.name]
-        state.reload_model(app_label, self.model_name_lower, delay=True)
+        state.remove_index(app_label, self.model_name_lower, self.name)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = from_state.apps.get_model(app_label, self.model_name)
@@ -850,9 +820,7 @@ class AddConstraint(IndexOperation):
         self.constraint = constraint
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        model_state.options[self.option_name] = [*model_state.options[self.option_name], self.constraint]
-        state.reload_model(app_label, self.model_name_lower, delay=True)
+        state.add_constraint(app_label, self.model_name_lower, self.constraint)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = to_state.apps.get_model(app_label, self.model_name)
@@ -886,10 +854,7 @@ class RemoveConstraint(IndexOperation):
         self.name = name
 
     def state_forwards(self, app_label, state):
-        model_state = state.models[app_label, self.model_name_lower]
-        constraints = model_state.options[self.option_name]
-        model_state.options[self.option_name] = [c for c in constraints if c.name != self.name]
-        state.reload_model(app_label, self.model_name_lower, delay=True)
+        state.remove_constraint(app_label, self.model_name_lower, self.name)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = to_state.apps.get_model(app_label, self.model_name)
diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 38ec72dd72..af9093c4e8 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -6,7 +6,10 @@ from functools import partial
 from django.apps import AppConfig
 from django.apps.registry import Apps, apps as global_apps
 from django.conf import settings
+from django.core.exceptions import FieldDoesNotExist
 from django.db import models
+from django.db.migrations.utils import field_is_referenced, get_references
+from django.db.models import NOT_PROVIDED
 from django.db.models.fields.related import RECURSIVE_RELATIONSHIP_CONSTANT
 from django.db.models.options import DEFAULT_NAMES, normalize_together
 from django.db.models.utils import make_model_tuple
@@ -107,6 +110,152 @@ class ProjectState:
             # the cache automatically (#24513)
             self.apps.clear_cache()
 
+    def rename_model(self, app_label, old_name, new_name):
+        # Add a new model.
+        old_name_lower = old_name.lower()
+        new_name_lower = new_name.lower()
+        renamed_model = self.models[app_label, old_name_lower].clone()
+        renamed_model.name = new_name
+        self.models[app_label, new_name_lower] = renamed_model
+        # Repoint all fields pointing to the old model to the new one.
+        old_model_tuple = (app_label, old_name_lower)
+        new_remote_model = f'{app_label}.{new_name}'
+        to_reload = set()
+        for model_state, name, field, reference in get_references(self, old_model_tuple):
+            changed_field = None
+            if reference.to:
+                changed_field = field.clone()
+                changed_field.remote_field.model = new_remote_model
+            if reference.through:
+                if changed_field is None:
+                    changed_field = field.clone()
+                changed_field.remote_field.through = new_remote_model
+            if changed_field:
+                model_state.fields[name] = changed_field
+                to_reload.add((model_state.app_label, model_state.name_lower))
+        # Reload models related to old model before removing the old model.
+        self.reload_models(to_reload, delay=True)
+        # Remove the old model.
+        self.remove_model(app_label, old_name_lower)
+        self.reload_model(app_label, new_name_lower, delay=True)
+
+    def alter_model_options(self, app_label, model_name, options, option_keys=None):
+        model_state = self.models[app_label, model_name]
+        model_state.options = {**model_state.options, **options}
+        if option_keys:
+            for key in option_keys:
+                if key not in options:
+                    model_state.options.pop(key, False)
+        self.reload_model(app_label, model_name, delay=True)
+
+    def alter_model_managers(self, app_label, model_name, managers):
+        model_state = self.models[app_label, model_name]
+        model_state.managers = list(managers)
+        self.reload_model(app_label, model_name, delay=True)
+
+    def _append_option(self, app_label, model_name, option_name, obj):
+        model_state = self.models[app_label, model_name]
+        model_state.options[option_name] = [*model_state.options[option_name], obj]
+        self.reload_model(app_label, model_name, delay=True)
+
+    def _remove_option(self, app_label, model_name, option_name, obj_name):
+        model_state = self.models[app_label, model_name]
+        objs = model_state.options[option_name]
+        model_state.options[option_name] = [obj for obj in objs if obj.name != obj_name]
+        self.reload_model(app_label, model_name, delay=True)
+
+    def add_index(self, app_label, model_name, index):
+        self._append_option(app_label, model_name, 'indexes', index)
+
+    def remove_index(self, app_label, model_name, index_name):
+        self._remove_option(app_label, model_name, 'indexes', index_name)
+
+    def add_constraint(self, app_label, model_name, constraint):
+        self._append_option(app_label, model_name, 'constraints', constraint)
+
+    def remove_constraint(self, app_label, model_name, constraint_name):
+        self._remove_option(app_label, model_name, 'constraints', constraint_name)
+
+    def add_field(self, app_label, model_name, name, field, preserve_default):
+        # If preserve default is off, don't use the default for future state.
+        if not preserve_default:
+            field = field.clone()
+            field.default = NOT_PROVIDED
+        else:
+            field = field
+        self.models[app_label, model_name].fields[name] = field
+        # Delay rendering of relationships if it's not a relational field.
+        delay = not field.is_relation
+        self.reload_model(app_label, model_name, delay=delay)
+
+    def remove_field(self, app_label, model_name, name):
+        model_state = self.models[app_label, model_name]
+        old_field = model_state.fields.pop(name)
+        # Delay rendering of relationships if it's not a relational field.
+        delay = not old_field.is_relation
+        self.reload_model(app_label, model_name, delay=delay)
+
+    def alter_field(self, app_label, model_name, name, field, preserve_default):
+        if not preserve_default:
+            field = field.clone()
+            field.default = NOT_PROVIDED
+        else:
+            field = field
+        model_state = self.models[app_label, model_name]
+        model_state.fields[name] = field
+        # TODO: investigate if old relational fields must be reloaded or if
+        # it's sufficient if the new field is (#27737).
+        # Delay rendering of relationships if it's not a relational field and
+        # not referenced by a foreign key.
+        delay = (
+            not field.is_relation and
+            not field_is_referenced(self, (app_label, model_name), (name, field))
+        )
+        self.reload_model(app_label, model_name, delay=delay)
+
+    def rename_field(self, app_label, model_name, old_name, new_name):
+        model_state = self.models[app_label, model_name]
+        # Rename the field.
+        fields = model_state.fields
+        try:
+            found = fields.pop(old_name)
+        except KeyError:
+            raise FieldDoesNotExist(
+                f"{app_label}.{model_name} has no field named '{old_name}'"
+            )
+        fields[new_name] = found
+        for field in fields.values():
+            # Fix from_fields to refer to the new field.
+            from_fields = getattr(field, 'from_fields', None)
+            if from_fields:
+                field.from_fields = tuple([
+                    new_name if from_field_name == old_name else from_field_name
+                    for from_field_name in from_fields
+                ])
+        # Fix index/unique_together to refer to the new field.
+        options = model_state.options
+        for option in ('index_together', 'unique_together'):
+            if option in options:
+                options[option] = [
+                    [new_name if n == old_name else n for n in together]
+                    for together in options[option]
+                ]
+        # Fix to_fields to refer to the new field.
+        delay = True
+        references = get_references(self, (app_label, model_name), (old_name, found))
+        for *_, field, reference in references:
+            delay = False
+            if reference.to:
+                remote_field, to_fields = reference.to
+                if getattr(remote_field, 'field_name', None) == old_name:
+                    remote_field.field_name = new_name
+                if to_fields:
+                    field.to_fields = tuple([
+                        new_name if to_field_name == old_name else to_field_name
+                        for to_field_name in to_fields
+                    ])
+        self.reload_model(app_label, model_name, delay=delay)
+
     def _find_reload_model(self, app_label, model_name, delay=False):
         if delay:
             self.is_delayed = True