[python-win32] win32com, server/policy.py bug? policy.py Line 639

[Wuping Xin]

Thanks. I'll submit a PR.

When calling from a Delphi COM client (using OleVariant ),  arg[0] will be set by Delphi a value of 0x8002000C, when the target Python method has NO argument (i.e., taking only "self"). This makes args non-empty.

When calling from a C++ MFC/COM client, arg[0] will be set a value of "None", when the target Python method has NO argument (i.e., talking only "self"). This makes args non-empty.

The following code would be a "protection" for parameterless Python method.

    import inspect
    if len(inspect.getfullargspec(func).args) == 1:
        return func()
    else:
        return func(*args)

Wuping


------ Original Message ------
From "Mark Hammond" <mhammond at skippinet.com.au<mailto:mhammond at skippinet.com.au>>
To "Wuping Xin" <wuping at caliper.com<mailto:wuping at caliper.com>>
Cc "Python-win32 at python.org<mailto:Python-win32 at python.org>" <Python-win32 at python.org<mailto:Python-win32 at python.org>>
Date 4/17/2023 8:14:31 AM
Subject Re: win32com, server/policy.py bug? policy.py Line 639

WARNING EXTERNAL EMAIL




On 16/4/2023 11:48 pm, Wuping Xin wrote:
A better fix is to change Line 639 of win32com/server/policy.py to the following:

                    import inspect
                    if len(inspect.getfullargspec(func).args) == 1:
                        return func()
                    else:
                        return func(*args)

Then we can make VBA, Delphi, C++ .... all clients happy.

Agree? Should I submit a pull request?

I'm not sure ATM - I'd be quite surprised if there was a bug in COM functions with no args, so it may be more subtle than that. But you should certainly get either a PR or issue on github for this, ideally with a complete repro. It might be quite some time (ie, many weeks) before I can look at this in more detail.

Thanks,

Mark


Wuping

------ Original Message ------
From "Wuping Xin" <wuping at caliper.com<mailto:wuping at caliper.com>>
To "Mark Hammond" <mhammond at skippinet.com.au<mailto:mhammond at skippinet.com.au>>
Cc "Python-win32 at python.org<mailto:Python-win32 at python.org>" <Python-win32 at python.org<mailto:Python-win32 at python.org>>
Date 4/16/2023 9:28:48 AM
Subject win32com, server/policy.py bug? policy.py Line 639

For the following code, the method "GetPerson" has no explicit argument (except self).
class MyCOMObject:
    _public_methods_ = ["GetPerson"]
    #_reg_clsid_ = '{44ee76c7-1290-4ea6-8189-00d5d7cd712a}'
    #_reg_desc_ = "My COM server"
    #_reg_progid_ = "MyCOMObject"
    def get_person(self):
        person = Person("haha", 45)
        wrapped = win32com.server.util.wrap(person, useDispatcher = my_dispatcher)
        return wrapped
When calling from VBA, like below , it works fine.
    Set o = CreateObject("MyCOMObject")
    Set p = o.get_person()
However, when calling from C++, or Delphi, the following error will be thrown:
"TypeError: MyCOMObject.get_person() takes 1 positional argument but 2 were given"
Delphi code:
procedure TForm1.Button1Click(Sender: TObject);
var
  o: OleVariant;
  p: OleVariant;
begin
  o := CreateOleObject('MyCOMObject');
  p := o.get_person(); // error will be thrown
  s := p.name;
  age := p.age;
  ShowMessage(s);
end;
The fix is to change Line 639 of policy.py to the following:

                 if len(args) == 1 and (args[0] == -2147352572 or args[0] == None):
                 return func()
                 else:
                 return func(*args)
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