Refs #33476 -- Added warning to optimizemigration/squashmigrations commands when black cannot be applied.

3 files changed, 37 insertions, 8 deletions

diff --git a/django/core/management/commands/optimizemigration.py b/django/core/management/commands/optimizemigration.py
index 7651c39866..2064dfbf3c 100644
--- a/django/core/management/commands/optimizemigration.py
+++ b/django/core/management/commands/optimizemigration.py
@@ -1,3 +1,4 @@
+import shutil
 import sys
 
 from django.apps import apps
@@ -111,6 +112,13 @@ class Command(BaseCommand):
                     "  See the comment at the top of the optimized migration for "
                     "details."
                 )
+                if shutil.which("black"):
+                    self.stdout.write(
+                        self.style.WARNING(
+                            "Optimized migration couldn't be formatted using the "
+                            '"black" command. You can call it manually.'
+                        )
+                    )
         with open(writer.path, "w", encoding="utf-8") as fh:
             fh.write(migration_file_string)
         run_formatters([writer.path])
diff --git a/django/core/management/commands/squashmigrations.py b/django/core/management/commands/squashmigrations.py
index 2d6e0ebfa3..a46edb3b7b 100644
--- a/django/core/management/commands/squashmigrations.py
+++ b/django/core/management/commands/squashmigrations.py
@@ -1,4 +1,5 @@
 import os
+import shutil
 
 from django.apps import apps
 from django.conf import settings
@@ -244,6 +245,13 @@ class Command(BaseCommand):
                     "  See the comment at the top of the squashed migration for "
                     "details."
                 )
+                if shutil.which("black"):
+                    self.stdout.write(
+                        self.style.WARNING(
+                            "Squashed migration couldn't be formatted using the "
+                            '"black" command. You can call it manually.'
+                        )
+                    )
 
     def find_migration(self, loader, app_label, name):
         try:
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 27a1ff6519..30136aab6b 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -2729,6 +2729,12 @@ class SquashMigrationsTests(MigrationTestBase):
                 "0001_squashed_0002_second.py",
             )
             self.assertTrue(os.path.exists(squashed_migration_file))
+        black_warning = ""
+        if HAS_BLACK:
+            black_warning = (
+                "Squashed migration couldn't be formatted using the "
+                '"black" command. You can call it manually.\n'
+            )
         self.assertEqual(
             out.getvalue(),
             f"Will squash the following migrations:\n"
@@ -2746,7 +2752,8 @@ class SquashMigrationsTests(MigrationTestBase):
             f"  Your migrations contained functions that must be manually copied "
             f"over,\n"
             f"  as we could not safely copy their implementation.\n"
-            f"  See the comment at the top of the squashed migration for details.\n",
+            f"  See the comment at the top of the squashed migration for details.\n"
+            + black_warning,
         )
 
 
@@ -2905,15 +2912,21 @@ class OptimizeMigrationTests(MigrationTestBase):
             with open(optimized_migration_file) as fp:
                 content = fp.read()
                 self.assertIn("replaces = [", content)
+        black_warning = ""
+        if HAS_BLACK:
+            black_warning = (
+                "Optimized migration couldn't be formatted using the "
+                '"black" command. You can call it manually.\n'
+            )
         self.assertEqual(
             out.getvalue(),
-            f"Optimizing from 3 operations to 2 operations.\n"
-            f"Manual porting required\n"
-            f"  Your migrations contained functions that must be manually copied over,"
-            f"\n"
-            f"  as we could not safely copy their implementation.\n"
-            f"  See the comment at the top of the optimized migration for details.\n"
-            f"Optimized migration {optimized_migration_file}\n",
+            "Optimizing from 3 operations to 2 operations.\n"
+            "Manual porting required\n"
+            "  Your migrations contained functions that must be manually copied over,\n"
+            "  as we could not safely copy their implementation.\n"
+            "  See the comment at the top of the optimized migration for details.\n"
+            + black_warning
+            + f"Optimized migration {optimized_migration_file}\n",
         )
 
     def test_fails_squash_migration_manual_porting(self):