John Snow <js...@redhat.com> writes:
> On 10/7/20 7:55 AM, Markus Armbruster wrote:
>> John Snow <js...@redhat.com> writes:
>>
>>> Annotations do not change runtime behavior.
>>> This commit *only* adds annotations.
>>>
>>> A note on typing of __init__: mypy requires init functions with no
>>> parameters to document a return type of None to be considered fully
>>> typed. In the case when there are input parameters, None may be omitted.
>>>
>>> Since __init__ may never return any value, it is preferred to omit the
>>> return annotation whenever possible.
>>>
>>> Signed-off-by: John Snow <js...@redhat.com>
>>> Reviewed-by: Eduardo Habkost <ehabk...@redhat.com>
>>> Reviewed-by: Cleber Rosa <cr...@redhat.com>
>>> Tested-by: Cleber Rosa <cr...@redhat.com>
>>> ---
>>> scripts/qapi/mypy.ini | 5 -----
>>> scripts/qapi/source.py | 31 ++++++++++++++++++-------------
>>> 2 files changed, 18 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/scripts/qapi/mypy.ini b/scripts/qapi/mypy.ini
>>> index 8ab9ac52cc4..1b8555dfa39 100644
>>> --- a/scripts/qapi/mypy.ini
>>> +++ b/scripts/qapi/mypy.ini
>>> @@ -34,11 +34,6 @@ disallow_untyped_defs = False
>>> disallow_incomplete_defs = False
>>> check_untyped_defs = False
>>> -[mypy-qapi.source]
>>> -disallow_untyped_defs = False
>>> -disallow_incomplete_defs = False
>>> -check_untyped_defs = False
>>> -
>>> [mypy-qapi.types]
>>> disallow_untyped_defs = False
>>> disallow_incomplete_defs = False
>>> diff --git a/scripts/qapi/source.py b/scripts/qapi/source.py
>>> index e97b9a8e15e..1cc6a5b82dc 100644
>>> --- a/scripts/qapi/source.py
>>> +++ b/scripts/qapi/source.py
>>> @@ -11,37 +11,42 @@
>>> import copy
>>> import sys
>>> +from typing import List, Optional, TypeVar
>>>
>>> class QAPISchemaPragma:
>>> - def __init__(self):
>>> + def __init__(self) -> None:
>>> # Are documentation comments required?
>>> self.doc_required = False
>>> # Whitelist of commands allowed to return a non-dictionary
>>> - self.returns_whitelist = []
>>> + self.returns_whitelist: List[str] = []
>>> # Whitelist of entities allowed to violate case conventions
>>> - self.name_case_whitelist = []
>>> + self.name_case_whitelist: List[str] = []
>>>
>>> class QAPISourceInfo:
>>> - def __init__(self, fname, line, parent):
>>> + T = TypeVar('T', bound='QAPISourceInfo')
>>> +
>>> + def __init__(self: T, fname: str, line: int, parent: Optional[T]):
>>
>> More ignorant questions (I'm abusing the review process to learn Python
>> type hints)...
>>
>> Why do you need to annotate self here, but not elsewhere?
>
> This is admittedly me being a little extra, but I thought it was a
> good way to show a pattern for people who maybe hadn't been exposed to
> it yet.
>
> This is a pattern that allows for subclassing. I am stating that this
> __init__ method takes a parent of the same type as itself, whatever
> that happens to actually be.
>
> T is a TypeVar that we can use for Generics. By declaring the type of
> self as that TypeVar, we bind T to self's type. When we annotate the
> parent as a T, we are enforcing that the parent we receive is of the
> same type as ourselves.
>
> (Yep, we don't actually subclass QAPISourceInfo and I don't have plans
> to. It felt slightly icky to hard-code the class type name, though. I
> try to avoid that whenever I can. I'm not sure I would go so far as to
> call it a code smell or an antipattern, but it's something I tend to
> avoid anyway.)
Say I define class QSISub as a direct subclass of QAPISourceInfo, and
let it inherit __init__(). What's the type of QSISub.__init__()'s
parameter @parent?
According to my reading of your explanation, it's QSISub. Correct?
If we used QAPISourceInfo instead of T for @parent, then it would be
QAPISourceInfo. Correct?
Now, perhaps any QAPISourceInfo will do as @parent, perhaps it really
needs to be a QSISub. We can't know when we write QAPISourceInfo. But
we don't *have* to get this exactly right for all future subclasses,
because I can always override __init__() when inheritance doesn't give
me the __init__() I want. Correct?
Say I override __init__(), and have it call super().__init__(). I have
to pass it a QAPISourceInfo @parent. A QSISub will do (it's a subtype).
Correct?
One more: is bound='QAPISourceInfo' strictly needed?
>> Why do you use T instead of QAPISourceInfo?
[...]
