Independent unused flag preflight check

Author: davegaeddert

plain-flags/plain/flags/models.py

@@ -2,12 +2,6 @@
 
 from plain import models
 from plain.exceptions import ValidationError
-from plain.models import OperationalError, ProgrammingError
-from plain.preflight import PreflightResult
-from plain.runtime import settings
-
-from .bridge import get_flag_class
-from .exceptions import FlagImportError
 
 
 def validate_flag_name(value: str) -> None:
@@ -61,37 +55,3 @@ class Flag(models.Model):
 
     def __str__(self) -> str:
         return self.name
-
-    @classmethod
-    def preflight(cls) -> list[PreflightResult]:
-        """
-        Check for flags that are in the database, but no longer defined in code.
-
-        Only returns Info errors because it is valid to leave them if you're worried about
-        putting the flag back, but they should probably be deleted eventually.
-        """
-        errors = super().preflight()
-
-        flag_names = cls.query.all().values_list("name", flat=True)
-
-        try:
-            flag_names = set(flag_names)
-        except (ProgrammingError, OperationalError):
-            # The table doesn't exist yet
-            # (migrations probably haven't run yet),
-            # so we can't check it.
-            return errors
-
-        for flag_name in flag_names:
-            try:
-                get_flag_class(flag_name)
-            except FlagImportError:
-                errors.append(
-                    PreflightResult(
-                        fix=f"Flag {flag_name} is not used. Remove the flag from the database or define it in the {settings.FLAGS_MODULE} module.",
-                        warning=True,
-                        id="flags.unused_flags",
-                    )
-                )
-
-        return errors

plain-flags/plain/flags/preflight.py

@@ -0,0 +1,46 @@
+from plain.models import OperationalError, ProgrammingError
+from plain.preflight import PreflightCheck, PreflightResult, register_check
+from plain.runtime import settings
+
+from .bridge import get_flag_class
+from .exceptions import FlagImportError
+
+
+@register_check(name="flags.unused_flags")
+class CheckUnusedFlags(PreflightCheck):
+    """
+    Check for flags that are in the database, but no longer defined in code.
+
+    Only returns Info errors because it is valid to leave them if you're worried about
+    putting the flag back, but they should probably be deleted eventually.
+    """
+
+    def run(self) -> list[PreflightResult]:
+        # Import here to avoid circular import
+        from .models import Flag
+
+        errors = []
+
+        flag_names = Flag.query.all().values_list("name", flat=True)
+
+        try:
+            flag_names = set(flag_names)
+        except (ProgrammingError, OperationalError):
+            # The table doesn't exist yet
+            # (migrations probably haven't run yet),
+            # so we can't check it.
+            return errors
+
+        for flag_name in flag_names:
+            try:
+                get_flag_class(flag_name)
+            except FlagImportError:
+                errors.append(
+                    PreflightResult(
+                        fix=f"Flag {flag_name} is not used. Remove the flag from the database or define it in the {settings.FLAGS_MODULE} module.",
+                        warning=True,
+                        id="flags.unused_flags",
+                    )
+                )
+
+        return errors