Fix #209 - Raise when getting SQL statements fail.

CHANGELOG.md

@@ -1,5 +1,9 @@
-## 4.1.1 (unreleased)
+## 5.0.0 (unreleased)
 
+- **Breaking change**: stop silently ignoring when the internal `sqlmigrate` call fails and the linter cannot analyse the migration.
+Instead, the linter crashes and lets the `sqlmigrate` error raise, in order to avoid letting a problematic migration pass.
+One common reason for such an error is the SQL generation which requires the database to be actually migrated in order to fetch actual constraint names from it.
+The crash is a sign to double-check the migration. But if you are certain the migration is safe, you can ignore it (issue #209)
 - Fixed `RunPython` model import check when using a `through` object like `MyModel.many_to_many.through.objects.filter(...)` (issue #218)
 
 ## 4.1.0

django_migration_linter/migration_linter.py

@@ -315,14 +315,11 @@ class MigrationLinter(object):
             )
         except (ValueError, ProgrammingError):
             logger.warning(
-                (
-                    "Error while executing sqlmigrate on (%s, %s). "
-                    "Continuing execution with empty SQL."
-                ),
+                "Error while executing sqlmigrate on (%s, %s).",
                 app_label,
                 migration_name,
             )
-            sql_statement = ""
+            raise
         return sql_statement.splitlines()
 
     @staticmethod

tests/functional/test_lintmigrations_command.py

@@ -8,6 +8,11 @@ from django.test.utils import override_settings
 class LintMigrationsCommandTestCase(TransactionTestCase):
     databases = {"default", "sqlite"}
 
+    def setUp(self):
+        call_command("migrate", "app_unique_together", "0002")
+        self.addCleanup(call_command, "migrate", "app_unique_together")
+        super().setUp()
+
     def test_plain(self):
         with self.assertRaises(SystemExit):
             call_command("lintmigrations")

tests/functional/test_migration_linter.py

@@ -2,6 +2,7 @@ import os
 import unittest
 
 from django.conf import settings
+from django.core.management import call_command
 
 from django_migration_linter import MigrationLinter
 from tests import fixtures
@@ -9,7 +10,20 @@ from tests import fixtures
 
 class BaseBackwardCompatibilityDetection(object):
     def setUp(self, *args, **kwargs):
+        self.database = next(iter(self.databases))
         self.test_project_path = os.path.dirname(settings.BASE_DIR)
+        call_command(
+            "migrate",
+            "app_unique_together",
+            "0002",
+            database=self.database,
+        )
+        self.addCleanup(
+            call_command,
+            "migrate",
+            "app_unique_together",
+            database=self.database,
+        )
         return super(BaseBackwardCompatibilityDetection, self).setUp(*args, **kwargs)
 
     def _test_linter_finds_errors(self, app=None, commit_id=None):
@@ -25,7 +39,7 @@ class BaseBackwardCompatibilityDetection(object):
     def _launch_linter(self, app=None, commit_id=None):
         linter = MigrationLinter(
             self.test_project_path,
-            database=next(iter(self.databases)),
+            database=self.database,
             no_cache=True,
         )
         linter.lint_all_migrations(app_label=app, git_commit_id=commit_id)
@@ -91,6 +105,13 @@ class BaseBackwardCompatibilityDetection(object):
     def test_with_git_ref(self):
         self._test_linter_finds_errors(commit_id="v0.1.4")
 
+    def test_failing_get_sql(self):
+        call_command("migrate", "app_unique_together", database=self.database)
+
+        linter = MigrationLinter(database=self.database)
+        with self.assertRaises(ValueError):
+            linter.get_sql("app_unique_together", "0003")
+
 
 class SqliteBackwardCompatibilityDetectionTestCase(
     BaseBackwardCompatibilityDetection, unittest.TestCase