actors_from_ids plugin hook and datasette.actors_from_ids() method (#2181)

* Prototype of actors_from_ids plugin hook, refs #2180
* datasette-remote-actors example plugin, refs #2180

tests/test_plugins.py

@@ -1215,3 +1215,65 @@ async def test_hook_register_permissions_allows_identical_duplicates():
     await ds.invoke_startup()
     # Check that ds.permissions has only one of each
     assert len([p for p in ds.permissions.values() if p.abbr == "abbr1"]) == 1
+
+
+@pytest.mark.asyncio
+async def test_hook_actors_from_ids():
+    # Without the hook should return default {"id": id} list
+    ds = Datasette()
+    await ds.invoke_startup()
+    db = ds.add_memory_database("actors_from_ids")
+    await db.execute_write(
+        "create table actors (id text primary key, name text, age int)"
+    )
+    await db.execute_write(
+        "insert into actors (id, name, age) values ('3', 'Cate Blanchett', 52)"
+    )
+    await db.execute_write(
+        "insert into actors (id, name, age) values ('5', 'Rooney Mara', 36)"
+    )
+    await db.execute_write(
+        "insert into actors (id, name, age) values ('7', 'Sarah Paulson', 46)"
+    )
+    await db.execute_write(
+        "insert into actors (id, name, age) values ('9', 'Helena Bonham Carter', 55)"
+    )
+    table_names = await db.table_names()
+    assert table_names == ["actors"]
+    actors1 = await ds.actors_from_ids(["3", "5", "7"])
+    assert actors1 == {
+        "3": {"id": "3"},
+        "5": {"id": "5"},
+        "7": {"id": "7"},
+    }
+
+    class ActorsFromIdsPlugin:
+        __name__ = "ActorsFromIdsPlugin"
+
+        @hookimpl
+        def actors_from_ids(self, datasette, actor_ids):
+            db = datasette.get_database("actors_from_ids")
+
+            async def inner():
+                sql = "select id, name from actors where id in ({})".format(
+                    ", ".join("?" for _ in actor_ids)
+                )
+                actors = {}
+                result = await db.execute(sql, actor_ids)
+                for row in result.rows:
+                    actor = dict(row)
+                    actors[actor["id"]] = actor
+                return actors
+
+            return inner
+
+    try:
+        pm.register(ActorsFromIdsPlugin(), name="ActorsFromIdsPlugin")
+        actors2 = await ds.actors_from_ids(["3", "5", "7"])
+        assert actors2 == {
+            "3": {"id": "3", "name": "Cate Blanchett"},
+            "5": {"id": "5", "name": "Rooney Mara"},
+            "7": {"id": "7", "name": "Sarah Paulson"},
+        }
+    finally:
+        pm.unregister(name="ReturnNothingPlugin")