Implement soft delete for zip store

src/zarr/storage/_zip.py

@@ -241,11 +241,19 @@ async def delete_dir(self, prefix: str) -> None:
 
     async def delete(self, key: str) -> None:
         # docstring inherited
-        # we choose to only raise NotImplementedError here if the key exists
-        # this allows the array/group APIs to avoid the overhead of existence checks
+        # If key is present it is replaced by an empty byte literal as a way of representing it as deleted
         self._check_writable()
         if await self.exists(key):
-            raise NotImplementedError
+            keyinfo = zipfile.ZipInfo(filename=key, date_time=time.localtime(time.time())[:6])
+            keyinfo.compress_type = self.compression
+            if keyinfo.filename[-1] == os.sep:
+                keyinfo.external_attr = 0o40775 << 16  # drwxrwxr-x
+                keyinfo.external_attr |= 0x10
+            else:
+                keyinfo.external_attr = 0o644 << 16  # ?rw-r--r--
+
+            with self._lock:
+                self._zf.writestr(keyinfo, b"")
 
     async def exists(self, key: str) -> bool:
         # docstring inherited

src/zarr/testing/store.py

@@ -5,7 +5,7 @@
 from abc import abstractmethod
 from typing import TYPE_CHECKING, Generic, TypeVar
 
-from zarr.storage import WrapperStore
+from zarr.storage import WrapperStore, ZipStore
 
 if TYPE_CHECKING:
     from typing import Any
@@ -340,6 +340,15 @@ async def test_delete(self, store: S) -> None:
         await store.delete("foo/zarr.json")
         assert not await store.exists("foo/zarr.json")
 
+    async def test_delete_zip_store(self, store: S) -> None:
+        if not isinstance(store, ZipStore):
+            pytest.skip("store is not a ZipStore")
+        await store.set("foo/zarr.json", self.buffer_cls.from_bytes(b"bar"))
+        assert await store.exists("foo/zarr.json")
+        await store.delete("foo/zarr.json")
+        result = await store.get("foo/zarr.json", default_buffer_prototype())
+        assert result == self.buffer_cls.from_bytes(b"")
+
     async def test_delete_dir(self, store: S) -> None:
         if not store.supports_deletes:
             pytest.skip("store does not support deletes")

tests/test_store/test_zip.py

@@ -83,8 +83,8 @@ def test_api_integration(self, store: ZipStore) -> None:
 
         # TODO: assigning an entire chunk to fill value ends up deleting the chunk which is not supported
         # a work around will be needed here.
-        with pytest.raises(NotImplementedError):
-            z[0:10, 0:10] = 99
+
+        z[0:10, 0:10] = 99
 
         bar = root.create_group("bar", attributes={"hello": "world"})
         assert "hello" in dict(bar.attrs)