storage_checker: Add more complete typing

swh/scrubber/storage_checker.py

@@ -11,7 +11,7 @@ import dataclasses
 import datetime
 import json
 import logging
-from typing import Iterable, Optional, Tuple, Union
+from typing import Any, Iterable, NoReturn, Optional, Tuple, Union
 
 import psycopg2
 import tenacity
@@ -31,7 +31,7 @@ from swh.model.model import (
 from swh.storage.algos.directory import directory_get_many
 from swh.storage.algos.snapshot import snapshot_get_all_branches
 from swh.storage.cassandra.storage import CassandraStorage
-from swh.storage.interface import StorageInterface
+from swh.storage.interface import PagedResult, StorageInterface
 from swh.storage.postgresql.storage import Storage as PostgresqlStorage
 
 from .db import Datastore, ScrubberDb
@@ -41,6 +41,16 @@ logger = logging.getLogger(__name__)
 ScrubbableObject = Union[Revision, Release, Snapshot, Directory, Content]
 
 
+def assert_never(value: NoReturn, msg) -> NoReturn:
+    """mypy makes sure this function is never called, through exhaustive checking
+    of ``value`` in the parent function.
+
+    See https://mypy.readthedocs.io/en/latest/literal_types.html#exhaustive-checks
+    for details.
+    """
+    assert False, msg
+
+
 @contextlib.contextmanager
 def postgresql_storage_db(storage):
     db = storage.get_db()
@@ -204,27 +214,41 @@ class StorageChecker:
     ) -> None:
         page_token = None
         while True:
-            if object_type in (swhids.ObjectType.RELEASE, swhids.ObjectType.REVISION):
-                method = getattr(self.storage, f"{self.object_type}_get_partition")
-                page = method(partition_id, self.nb_partitions, page_token=page_token)
+            page: PagedResult[Any]
+            objects: Iterable[ScrubbableObject]
+            if object_type is swhids.ObjectType.REVISION:
+                page = self.storage.revision_get_partition(
+                    partition_id, self.nb_partitions, page_token=page_token
+                )
+                objects = page.results
+            elif object_type is swhids.ObjectType.RELEASE:
+                page = self.storage.release_get_partition(
+                    partition_id, self.nb_partitions, page_token=page_token
+                )
                 objects = page.results
-            elif object_type == swhids.ObjectType.DIRECTORY:
+            elif object_type is swhids.ObjectType.DIRECTORY:
                 page = self.storage.directory_get_id_partition(
                     partition_id, self.nb_partitions, page_token=page_token
                 )
                 directory_ids = page.results
-                objects = list(directory_get_many(self.storage, directory_ids))
-            elif object_type == swhids.ObjectType.SNAPSHOT:
+                objects = []
+                for dir_ in directory_get_many(self.storage, directory_ids):
+                    assert dir_ is not None, directory_ids
+                    objects.append(dir_)
+            elif object_type is swhids.ObjectType.SNAPSHOT:
                 page = self.storage.snapshot_get_id_partition(
                     partition_id, self.nb_partitions, page_token=page_token
                 )
                 snapshot_ids = page.results
-                objects = [
-                    snapshot_get_all_branches(self.storage, snapshot_id)
-                    for snapshot_id in snapshot_ids
-                ]
+                objects = []
+                for snapshot_id in snapshot_ids:
+                    snp = snapshot_get_all_branches(self.storage, snapshot_id)
+                    assert snp is not None
+                    objects.append(snp)
+            elif object_type is swhids.ObjectType.CONTENT:
+                assert False, "storage_checker does not support content objects yet"
             else:
-                assert False, f"Unexpected object type: {object_type}"
+                assert_never(object_type, f"Unexpected object type: {object_type}")
 
             with self.statsd().timed(
                 "batch_duration_seconds", tags={"operation": "check_hashes"}