msilib VT_EMPTY SummaryInformation properties raise an error (suggest returning None)

[markm]

BPO	12239
Nosy	@loewis, @berkerpeksag, @zooba
PRs	bpo-12239: Make GetProperty() return None for VT_EMPTY #4539 [3.6] bpo-12239: Make GetProperty() return None for VT_EMPTY (GH-4539) #4543
Files	support_vt_empty_in_summary_getproperty.patch: Patch to return None for VT_EMPTY properties of SummaryInformation

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2017-11-24.16:05:42.068>
created_at = <Date 2011-06-02.14:13:43.916>
labels = ['type-bug', '3.7', 'OS-windows']
title = 'msilib VT_EMPTY SummaryInformation properties raise an error (suggest returning None)'
updated_at = <Date 2017-11-24.16:05:42.065>
user = 'https://bugs.python.org/markm'

bugs.python.org fields:

activity = <Date 2017-11-24.16:05:42.065>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-24.16:05:42.068>
closer = 'berker.peksag'
components = ['Windows']
creation = <Date 2011-06-02.14:13:43.916>
creator = 'markm'
dependencies = []
files = ['22332']
hgrepos = []
issue_num = 12239
keywords = ['patch']
message_count = 5.0
messages = ['137478', '235997', '306899', '306901', '306903']
nosy_count = 5.0
nosy_names = ['loewis', 'BreamoreBoy', 'markm', 'berker.peksag', 'steve.dower']
pr_nums = ['4539', '4543']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12239'
versions = ['Python 3.6', 'Python 3.7']

[markm]

Using "some.msi" where the first property is VT_EMPTY

Using COM:
>>> from win32com.client import gencache
>>> com_lib = gencache.EnsureModule('{000C1092-0000-0000-C000-000000000046}', 409, 1, 0)
>>> com_msi = com_lib.Installer()
>>> db = com_msi.OpenDatabase('some.msi', 0)
>>> si = db.GetSummaryInformation(0)
>>> repr(si.Property(0))
'None'

Using msilib:
>>> import msilib
>>> db = msilib.OpenDatabase(r'some.msi', 0)
>>> si = db.GetSummaryInformation(0)
>>> si.GetProperty(0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NotImplementedError: result of type 0

I aim to submit a patch that so that SummaryInformation.GetProperty() with a type of VT_EMPTY will return None.

[BreamoreBoy]

Can we have a patch review please.

[berkerpeksag]

New changeset 19fb134 by Berker Peksag in branch 'master':
bpo-12239: Make GetProperty() return None for VT_EMPTY (GH-4539)
19fb134

[berkerpeksag]

New changeset 412f00b by Berker Peksag in branch '3.6':
[3.6] bpo-12239: Make GetProperty() return None for VT_EMPTY (GH-4539)
412f00b

[berkerpeksag]

Thanks for the patch, Mark. I updated the test code and commit it to 3.6 and master branches.