Re: [PULL 3/5] qemu-iotests: 300: Add test case for modifying persistence of bitmap

[Eric Blake <eblake@redhat.com>]

On 2/15/21 1:00 PM, John Snow wrote:
> On 2/15/21 1:25 PM, Eric Blake wrote:
>> -BlockBitmapMapping = List[Dict[str, Union[str, List[Dict[str, str]]]]]
>> +BlockBitmapMapping = List[Dict[str,
>> +                               Union[str,
>> +                                     List[Dict[str,
>> +                                               Union[str, Dict[str,
>> bool]]]]]]]
> 
> That looks *very* beefy.
> 
> Is the Union because that union is valid for every key, or because every
> key has a potentially different value that is specific to that key?
> 
> if it's the latter, I'd ditch the Union and just go with:
> 
> Dict[str, object], or
> Dict[str, Any]
> 
> object: will allow any type, but keeps strict checking enabled. If you
> try to use that value later on without a cast, mypy will warn you if you
> are using it in a manner not guaranteed by the "object" type. Can be
> useful if you are passing values to a function that already does RTTI to
> determine behavior.

We're in luck; both 297 and 300 still pass with this applied on top of
my previous attempt:

diff --git i/tests/qemu-iotests/300 w/tests/qemu-iotests/300
index 7501bd1018e2..adb927629747 100755
--- i/tests/qemu-iotests/300
+++ w/tests/qemu-iotests/300
@@ -22,7 +22,7 @@
 import os
 import random
 import re
-from typing import Dict, List, Optional, Union
+from typing import Dict, List, Optional

 import iotests

@@ -30,10 +30,7 @@ import iotests
 # pylint: disable=wrong-import-order
 import qemu

-BlockBitmapMapping = List[Dict[str,
-                               Union[str,
-                                     List[Dict[str,
-                                               Union[str, Dict[str,
bool]]]]]]]
+BlockBitmapMapping = List[Dict[str, object]]

 mig_sock = os.path.join(iotests.sock_dir, 'mig_sock')



> 
> Any: Also allows any type, but enables gradual typing. If you later
> "assume" the type of this value, mypy will say nothing. Can be useful
> when you've just got a job to do and the right tool would have been a
> recursive type or a TypedDict (unavailable in Python 3.6.)

I'm not too worried about needing to further enhance the type-checking
on an individual iotest.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org