msilib Fetch raises MSIError rather than return None

[JasonMatthew]

BPO	29364
Nosy	@berkerpeksag
Superseder	bpo-1102: Add support for _msi.Record.GetString() and _msi.Record.GetInteger()

^{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 2017-02-01.19:32:23.738>
created_at = <Date 2017-01-24.18:54:25.739>
labels = ['type-bug', 'library']
title = 'msilib Fetch raises MSIError rather than return None'
updated_at = <Date 2017-02-01.19:34:04.237>
user = 'https://bugs.python.org/JasonMatthew'

bugs.python.org fields:

activity = <Date 2017-02-01.19:34:04.237>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2017-02-01.19:32:23.738>
closer = 'Jason Matthew'
components = ['Library (Lib)']
creation = <Date 2017-01-24.18:54:25.739>
creator = 'Jason Matthew'
dependencies = []
files = []
hgrepos = []
issue_num = 29364
keywords = []
message_count = 3.0
messages = ['286204', '286669', '286679']
nosy_count = 2.0
nosy_names = ['berker.peksag', 'Jason Matthew']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '1102'
type = 'behavior'
url = 'https://bugs.python.org/issue29364'
versions = ['Python 2.7']

[JasonMatthew]

Fairly new to MSIs here. Working towards extracting the same information which is available via Orca graphical interfaces.

I believe I've hit a bug within _msi.View class, namely the inability to safely determine the number of records in my result.

Examples I've found depicting how to obtain query results lead me to believe _msi.View.Fetch() will return None if no more rows exist. My development using python 2.7.11, Windows 7 enterprise and 2.7.13, Windows Server 2016, has shown Fetch() will raise a msilib.MSIError when no more rows are available. MSIError is commonly used within msilib which means explicit error handling (or leniency in this case) may incorrectly suppress other error scenarios.

Entering a bug with the hope either a patch addresses this issue or documentation can be updated to reflect proper usage. Example provided below.

    >>> import msilib
    >>> db = msilib.OpenDatabase("msi-1.0.0.8.msi", msilib.MSIDBOPEN_READONLY)
    >>> v = db.OpenView("select * from Property")
    >>> v.Execute(None)
    >>> while 1:
    ...     r = v.Fetch()
    ...     if not r:break
    ...     print r.GetString(1)
    ...
    UpgradeCode
    WixSharp_UI_INSTALLDIR
    WixSharp_InstallDialogs
    WIXUI_INSTALLDIR
    Manufacturer
    ProductCode
    ProductLanguage
    ProductName
    ProductVersion
    SecureCustomProperties
    Traceback (most recent call last):
      File "<stdin>", line 2, in <module>
    _msi.MSIError: unknown error 103

[berkerpeksag]

Thanks for the report, Jason. I think this is a duplicate of bpo-1102. The second patch (_msi_fetch.patch.txt) there should fix your problem (if I read MSDN correctly, 103 is ERROR_NO_MORE_ITEMS.)

I don't have access to a Windows box at the moment so could you please verify my theory so we can close this as a duplicate?

[JasonMatthew]

Thanks for pointing that one out Berker. I agree, this is a dup.