Fixed #31700 -- Made makemigrations command display meaningful symbol…

…s for each operation.

django/contrib/postgres/operations.py

@@ -5,12 +5,13 @@
 )
 from django.db import NotSupportedError, router
 from django.db.migrations import AddConstraint, AddIndex, RemoveIndex
-from django.db.migrations.operations.base import Operation
+from django.db.migrations.operations.base import Operation, OperationCategory
 from django.db.models.constraints import CheckConstraint
 
 
 class CreateExtension(Operation):
     reversible = True
+    category = OperationCategory.ADDITION
 
     def __init__(self, name):
         self.name = name
@@ -120,6 +121,7 @@ class AddIndexConcurrently(NotInTransactionMixin, AddIndex):
     """Create an index using PostgreSQL's CREATE INDEX CONCURRENTLY syntax."""
 
     atomic = False
+    category = OperationCategory.ADDITION
 
     def describe(self):
         return "Concurrently create index %s on field(s) %s of model %s" % (
@@ -145,6 +147,7 @@ class RemoveIndexConcurrently(NotInTransactionMixin, RemoveIndex):
     """Remove an index using PostgreSQL's DROP INDEX CONCURRENTLY syntax."""
 
     atomic = False
+    category = OperationCategory.REMOVAL
 
     def describe(self):
         return "Concurrently remove index %s from %s" % (self.name, self.model_name)
@@ -213,6 +216,8 @@ def remove_collation(self, schema_editor):
 class CreateCollation(CollationOperation):
     """Create a collation."""
 
+    category = OperationCategory.ADDITION
+
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         if schema_editor.connection.vendor != "postgresql" or not router.allow_migrate(
             schema_editor.connection.alias, app_label
@@ -236,6 +241,8 @@ def migration_name_fragment(self):
 class RemoveCollation(CollationOperation):
     """Remove a collation."""
 
+    category = OperationCategory.REMOVAL
+
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         if schema_editor.connection.vendor != "postgresql" or not router.allow_migrate(
             schema_editor.connection.alias, app_label
@@ -262,6 +269,8 @@ class AddConstraintNotValid(AddConstraint):
     NOT VALID syntax.
     """
 
+    category = OperationCategory.ADDITION
+
     def __init__(self, model_name, constraint):
         if not isinstance(constraint, CheckConstraint):
             raise TypeError(
@@ -293,6 +302,8 @@ def migration_name_fragment(self):
 class ValidateConstraint(Operation):
     """Validate a table NOT VALID constraint."""
 
+    category = OperationCategory.ALTERATION
+
     def __init__(self, model_name, name):
         self.model_name = model_name
         self.name = name

django/core/management/commands/makemigrations.py

@@ -348,7 +348,7 @@ def write_migration_files(self, changes, update_previous_migration_paths=None):
                     migration_string = self.get_relative_path(writer.path)
                     self.log("  %s\n" % self.style.MIGRATE_LABEL(migration_string))
                     for operation in migration.operations:
-                        self.log("    - %s" % operation.describe())
+                        self.log("    %s" % operation.formatted_description())
                     if self.scriptable:
                         self.stdout.write(migration_string)
                 if not self.dry_run:
@@ -456,7 +456,7 @@ def all_items_equal(seq):
                 for migration in merge_migrations:
                     self.log(self.style.MIGRATE_LABEL("  Branch %s" % migration.name))
                     for operation in migration.merged_operations:
-                        self.log("    - %s" % operation.describe())
+                        self.log("    %s" % operation.formatted_description())
             if questioner.ask_merge(app_label):
                 # If they still want to merge it, then write out an empty
                 # file depending on the migrations needing merging.

django/db/migrations/operations/base.py

@@ -1,6 +1,17 @@
+import enum
+
 from django.db import router
 
 
+class OperationCategory(str, enum.Enum):
+    ADDITION = "+"
+    REMOVAL = "-"
+    ALTERATION = "~"
+    PYTHON = "p"
+    SQL = "s"
+    MIXED = "?"
+
+
 class Operation:
     """
     Base class for migration operations.
@@ -33,6 +44,8 @@ class Operation:
 
     serialization_expand_args = []
 
+    category = None
+
     def __new__(cls, *args, **kwargs):
         # We capture the arguments to make returning them trivial
         self = object.__new__(cls)
@@ -85,6 +98,13 @@ def describe(self):
         """
         return "%s: %s" % (self.__class__.__name__, self._constructor_args)
 
+    def formatted_description(self):
+        """Output a description prefixed by a category symbol."""
+        description = self.describe()
+        if self.category is None:
+            return f"{OperationCategory.MIXED.value} {description}"
+        return f"{self.category.value} {description}"
+
     @property
     def migration_name_fragment(self):
         """

django/db/migrations/operations/fields.py

@@ -2,7 +2,7 @@
 from django.db.models import NOT_PROVIDED
 from django.utils.functional import cached_property
 
-from .base import Operation
+from .base import Operation, OperationCategory
 
 
 class FieldOperation(Operation):
@@ -75,6 +75,8 @@ def reduce(self, operation, app_label):
 class AddField(FieldOperation):
     """Add a field to a model."""
 
+    category = OperationCategory.ADDITION
+
     def __init__(self, model_name, name, field, preserve_default=True):
         self.preserve_default = preserve_default
         super().__init__(model_name, name, field)
@@ -154,6 +156,8 @@ def reduce(self, operation, app_label):
 class RemoveField(FieldOperation):
     """Remove a field from a model."""
 
+    category = OperationCategory.REMOVAL
+
     def deconstruct(self):
         kwargs = {
             "model_name": self.model_name,
@@ -201,6 +205,8 @@ class AlterField(FieldOperation):
     new field.
     """
 
+    category = OperationCategory.ALTERATION
+
     def __init__(self, model_name, name, field, preserve_default=True):
         self.preserve_default = preserve_default
         super().__init__(model_name, name, field)
@@ -270,6 +276,8 @@ def reduce(self, operation, app_label):
 class RenameField(FieldOperation):
     """Rename a field on the model. Might affect db_column too."""
 
+    category = OperationCategory.ALTERATION
+
     def __init__(self, model_name, old_name, new_name):
         self.old_name = old_name
         self.new_name = new_name

django/db/migrations/operations/models.py

@@ -1,5 +1,5 @@
 from django.db import models
-from django.db.migrations.operations.base import Operation
+from django.db.migrations.operations.base import Operation, OperationCategory
 from django.db.migrations.state import ModelState
 from django.db.migrations.utils import field_references, resolve_relation
 from django.db.models.options import normalize_together
@@ -41,6 +41,7 @@ def can_reduce_through(self, operation, app_label):
 class CreateModel(ModelOperation):
     """Create a model's table."""
 
+    category = OperationCategory.ADDITION
     serialization_expand_args = ["fields", "options", "managers"]
 
     def __init__(self, name, fields, options=None, bases=None, managers=None):
@@ -347,6 +348,8 @@ def reduce(self, operation, app_label):
 class DeleteModel(ModelOperation):
     """Drop a model's table."""
 
+    category = OperationCategory.REMOVAL
+
     def deconstruct(self):
         kwargs = {
             "name": self.name,
@@ -382,6 +385,8 @@ def migration_name_fragment(self):
 class RenameModel(ModelOperation):
     """Rename a model."""
 
+    category = OperationCategory.ALTERATION
+
     def __init__(self, old_name, new_name):
         self.old_name = old_name
         self.new_name = new_name
@@ -499,6 +504,8 @@ def reduce(self, operation, app_label):
 
 
 class ModelOptionOperation(ModelOperation):
+    category = OperationCategory.ALTERATION
+
     def reduce(self, operation, app_label):
         if (
             isinstance(operation, (self.__class__, DeleteModel))
@@ -849,6 +856,8 @@ def model_name_lower(self):
 class AddIndex(IndexOperation):
     """Add an index on a model."""
 
+    category = OperationCategory.ADDITION
+
     def __init__(self, model_name, index):
         self.model_name = model_name
         if not index.name:
@@ -911,6 +920,8 @@ def reduce(self, operation, app_label):
 class RemoveIndex(IndexOperation):
     """Remove an index from a model."""
 
+    category = OperationCategory.REMOVAL
+
     def __init__(self, model_name, name):
         self.model_name = model_name
         self.name = name
@@ -954,6 +965,8 @@ def migration_name_fragment(self):
 class RenameIndex(IndexOperation):
     """Rename an index."""
 
+    category = OperationCategory.ALTERATION
+
     def __init__(self, model_name, new_name, old_name=None, old_fields=None):
         if not old_name and not old_fields:
             raise ValueError(
@@ -1104,6 +1117,7 @@ def reduce(self, operation, app_label):
 
 
 class AddConstraint(IndexOperation):
+    category = OperationCategory.ADDITION
     option_name = "constraints"
 
     def __init__(self, model_name, constraint):
@@ -1154,6 +1168,7 @@ def reduce(self, operation, app_label):
 
 
 class RemoveConstraint(IndexOperation):
+    category = OperationCategory.REMOVAL
     option_name = "constraints"
 
     def __init__(self, model_name, name):

django/db/migrations/operations/special.py

@@ -1,6 +1,6 @@
 from django.db import router
 
-from .base import Operation
+from .base import Operation, OperationCategory
 
 
 class SeparateDatabaseAndState(Operation):
@@ -11,6 +11,7 @@ class SeparateDatabaseAndState(Operation):
     that affect the state or not the database, or so on.
     """
 
+    category = OperationCategory.MIXED
     serialization_expand_args = ["database_operations", "state_operations"]
 
     def __init__(self, database_operations=None, state_operations=None):
@@ -68,6 +69,7 @@ class RunSQL(Operation):
     by this SQL change, in case it's custom column/table creation/deletion.
     """
 
+    category = OperationCategory.SQL
     noop = ""
 
     def __init__(
@@ -138,6 +140,7 @@ class RunPython(Operation):
     Run Python code in a context suitable for doing versioned ORM operations.
     """
 
+    category = OperationCategory.PYTHON
     reduces_to_sql = False
 
     def __init__(

docs/intro/tutorial02.txt

@@ -241,8 +241,8 @@ You should see something similar to the following:
 
     Migrations for 'polls':
       polls/migrations/0001_initial.py
-        - Create model Question
-        - Create model Choice
+        + Create model Question
+        + Create model Choice
 
 By running ``makemigrations``, you're telling Django that you've made
 some changes to your models (in this case, you've made new ones) and that

docs/ref/contrib/gis/tutorial.txt

@@ -241,7 +241,7 @@ create a database migration:
     $ python manage.py makemigrations
     Migrations for 'world':
       world/migrations/0001_initial.py:
-        - Create model WorldBorder
+        + Create model WorldBorder
 
 Let's look at the SQL that will generate the table for the ``WorldBorder``
 model:

docs/ref/migration-operations.txt

@@ -475,6 +475,42 @@ operations.
 For an example using ``SeparateDatabaseAndState``, see
 :ref:`changing-a-manytomanyfield-to-use-a-through-model`.
 
+Operation category
+==================
+
+.. versionadded:: 5.1
+
+.. currentmodule:: django.db.migrations.operations.base
+
+.. class:: OperationCategory
+
+    Categories of migration operation used by the :djadmin:`makemigrations`
+    command to display meaningful symbols.
+
+    .. attribute:: ADDITION
+
+        *Symbol*: ``+``
+
+    .. attribute:: REMOVAL
+
+        *Symbol*: ``-``
+
+    .. attribute:: ALTERATION
+
+        *Symbol*: ``~``
+
+    .. attribute:: PYTHON
+
+        *Symbol*: ``p``
+
+    .. attribute:: SQL
+
+        *Symbol*: ``s``
+
+    .. attribute:: MIXED
+
+        *Symbol*: ``?``
+
 .. _writing-your-own-migration-operation:
 
 Writing your own
@@ -495,6 +531,10 @@ structure of an ``Operation`` looks like this::
         # If this is False, Django will refuse to reverse past this operation.
         reversible = False
 
+        # This categorizes the operation. The corresponding symbol will be
+        # display by the makemigrations command.
+        category = OperationCategory.ADDITION
+
         def __init__(self, arg1, arg2):
             # Operations are usually instantiated with arguments in migration
             # files. Store the values of them on self for later use.
@@ -516,7 +556,7 @@ structure of an ``Operation`` looks like this::
             pass
 
         def describe(self):
-            # This is used to describe what the operation does in console output.
+            # This is used to describe what the operation does.
             return "Custom Operation"
 
         @property

docs/releases/5.1.txt

@@ -178,12 +178,17 @@ Logging
 Management Commands
 ~~~~~~~~~~~~~~~~~~~
 
-* ...
+* :djadmin:`makemigrations` command now displays meaningful symbols for each
+  operation to highlight :class:`operation categories
+  <django.db.migrations.operations.base.OperationCategory>`.
 
 Migrations
 ~~~~~~~~~~
 
-* ...
+* The new ``Operation.category`` attribute allows specifying an
+  :class:`operation category
+  <django.db.migrations.operations.base.OperationCategory>` used by the
+  :djadmin:`makemigrations` to display a meaningful symbol for the operation.
 
 Models
 ~~~~~~

docs/topics/migrations.txt

@@ -118,7 +118,7 @@ field and remove a model - and then run :djadmin:`makemigrations`:
     $ python manage.py makemigrations
     Migrations for 'books':
       books/migrations/0003_auto.py:
-        - Alter field author on book
+        ~ Alter field author on book
 
 Your models will be scanned and compared to the versions currently
 contained in your migration files, and then a new set of migrations