Made check for whether migrations exist consistent

Fixes #20

HISTORY.rst

@@ -2,6 +2,12 @@
 History
 =======
 
+* Made check for whether migrations exist consistent between the system checks
+  and ``create-max-migration-files``.
+
+  Thanks to @ahumeau for the report in `Issue #20
+  <https://github.com/adamchainz/django-linear-migrations/issues/20>`__.
+
 * Also assume modules in ``dist-packages`` are third-party apps.
 
   Thanks to Serkan Hosca for `Pull Request #21

src/django_linear_migrations/apps.py

@@ -55,6 +55,7 @@ def has_migrations(self):
             and not is_namespace_module(self.migrations_module)
             # Django ignores non-package migrations modules
             and hasattr(self.migrations_module, "__path__")
+            and len(self.names) > 0
         )
 
     @cached_property

src/django_linear_migrations/management/commands/create-max-migration-files.py

@@ -47,7 +47,7 @@ def handle(self, *app_labels, **options):
                 continue
 
             max_migration_txt = migration_details.dir / "max_migration.txt"
-            if not max_migration_txt.exists() and len(migration_details.names) > 0:
+            if not max_migration_txt.exists():
                 max_migration_name = max(migration_details.names)
                 max_migration_txt.write_text(max_migration_name + "\n")
                 self.stdout.write(

tests/test_checks.py

@@ -51,6 +51,7 @@ def test_skipped_unspecified_app(self):
 
     def test_dlm_E001(self):
         (self.migrations_dir / "__init__.py").touch()
+        (self.migrations_dir / "0001_initial.py").touch()
 
         result = check_max_migration_files()
 
@@ -60,6 +61,7 @@ def test_dlm_E001(self):
 
     def test_dlm_E002(self):
         (self.migrations_dir / "__init__.py").touch()
+        (self.migrations_dir / "0001_initial.py").touch()
         (self.migrations_dir / "max_migration.txt").write_text("line1\nline2\n")
 
         result = check_max_migration_files()