fix: change file type for graph file from pickle to JSON

.gitignore

@@ -138,3 +138,6 @@ dmypy.json
 
 # Cython debug symbols
 cython_debug/
+
+# Some files that might be generated in tests
+tests/graph.json

src/remake_migrations/management/commands/remakemigrations.py

@@ -1,8 +1,9 @@
 from __future__ import annotations
 
 import datetime as dt
-import pickle
+import json
 from collections import defaultdict
+from importlib import import_module
 from pathlib import Path
 
 from django.apps import AppConfig, apps
@@ -28,7 +29,7 @@ class Command(BaseCommand):
     - makemigrations: should not detect any differences
     """
 
-    graph_file = Path(settings.BASE_DIR) / "graph.pickle"
+    graph_file = Path(settings.BASE_DIR) / "graph.json"
 
     def add_arguments(self, parser: CommandParser) -> None:
         """Add the option to run a specific step of the process."""
@@ -38,8 +39,6 @@ def add_arguments(self, parser: CommandParser) -> None:
     def handle(self, step: int, *args: str, **options: str) -> None:
         """Execute one step after another to avoid side effects between steps."""
         if step == 1:
-            # First, make sure we have applied all migrations
-            call_command("migrate")
             # Remove old migration files
             self.clear_old_migrations()
         if step == 2:
@@ -53,14 +52,12 @@ def handle(self, step: int, *args: str, **options: str) -> None:
     @property
     def old_migrations(self) -> dict[str, list[str]]:
         """Load old migrations from a pickle file."""
-        with self.graph_file.open("rb") as fh:
-            return pickle.load(fh)  # noqa S301
+        return json.loads(self.graph_file.read_text())
 
     @old_migrations.setter
     def old_migrations(self, value: dict[str, list[str]]) -> None:
-        """Save old migrations in a pickle file."""
-        with self.graph_file.open("wb") as fh:
-            pickle.dump(value, fh)
+        """Save old migrations graph in a file."""
+        self.graph_file.write_text(json.dumps(value, indent=2))
 
     def clear_old_migrations(self) -> None:
         """Remove all pre-existing migration files in first party apps."""
@@ -84,8 +81,11 @@ def _is_first_party(app_config: AppConfig) -> bool:
     @staticmethod
     def remove_migration_file(app_label: str, migration_name: str) -> None:
         """Remove file from the disk for the specified migration."""
-        app_config = apps.get_app_config(app_label)
-        migration_file = Path(app_config.path) / "migrations" / f"{migration_name}.py"
+        app_migrations_module_name, _ = MigrationLoader.migrations_module(app_label)
+        migration_module = import_module(
+            f"{app_migrations_module_name}.{migration_name}"
+        )
+        migration_file = Path(migration_module.__file__)  # type: ignore[arg-type]
         migration_file.unlink()
 
     def update_new_migrations(self) -> None:

tests/test_remakemigrations.py

@@ -0,0 +1,58 @@
+from __future__ import annotations
+
+import sys
+import time
+from pathlib import Path
+from textwrap import dedent
+
+import pytest
+from django.test import TestCase, override_settings
+
+from tests.utils import EMPTY_MIGRATION, run_command
+
+
+class RemakeMigrationsTests(TestCase):
+    @pytest.fixture(autouse=True)
+    def tmp_path_fixture(self, tmp_path):
+        migrations_module_name = "migrations" + str(time.time()).replace(".", "")
+        self.migrations_dir = tmp_path / migrations_module_name
+        self.migrations_dir.mkdir()
+        sys.path.insert(0, str(tmp_path))
+        try:
+            with override_settings(
+                MIGRATION_MODULES={"testapp": migrations_module_name}
+            ):
+                yield
+        finally:
+            sys.path.pop(0)
+
+    def test_success_step_1(self):
+        (self.migrations_dir / "__init__.py").touch()
+        initial_0001 = self.migrations_dir / "0001_initial.py"
+        initial_0001.write_text(EMPTY_MIGRATION)
+        migration_0002 = self.migrations_dir / "0002_something.py"
+        migration_0002.write_text(
+            dedent(
+                """\
+            from django.db import migrations
+
+            class Migration(migrations.Migration):
+                dependencies = [
+                    ('testapp', '0001_initial'),
+                ]
+                operations = []
+            """
+            )
+        )
+
+        out, err, returncode = run_command("remakemigrations", "--step", "1")
+
+        assert out == ""
+        assert err == ""
+        assert returncode == 0
+
+        assert not initial_0001.exists()
+        assert not migration_0002.exists()
+
+        graph_json = Path(__file__).parent / "graph.json"
+        assert graph_json.exists()

tests/utils.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from io import StringIO
+from textwrap import dedent
+
+from django.core.management import call_command
+
+
+def run_command(*args, **kwargs):
+    out = StringIO()
+    err = StringIO()
+    return_code: int | str | None = 0
+    try:
+        call_command(*args, stdout=out, stderr=err, **kwargs)
+    except SystemExit as exc:  # pragma: no cover
+        return_code = exc.code
+    return out.getvalue(), err.getvalue(), return_code
+
+
+EMPTY_MIGRATION = dedent(
+    """\
+    from django.db import migrations
+    class Migration(migrations.Migration):
+        pass
+    """
+)