[msilib] Obscure exception message when trying to open a non-existent MSI database

[RobinJarry]

BPO	12382
Nosy	@loewis, @pfmoore, @tjguk, @berkerpeksag, @zware, @zooba
PRs	bpo-12382: Make OpenDatabase() raise better exception messages #4528 [3.6] bpo-12382: Make OpenDatabase() raise better exception messages (GH-4528) #4538
Files	12382_msi-open-error-message.patch

^{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 2017-11-24.10:32:50.118>
created_at = <Date 2011-06-21.12:12:16.493>
labels = ['3.7', 'type-bug', 'library', 'OS-windows']
title = '[msilib] Obscure exception message when trying to open a non-existent MSI database'
updated_at = <Date 2017-11-24.10:32:50.113>
user = 'https://bugs.python.org/RobinJarry'

bugs.python.org fields:

activity = <Date 2017-11-24.10:32:50.113>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-24.10:32:50.118>
closer = 'berker.peksag'
components = ['Library (Lib)', 'Windows']
creation = <Date 2011-06-21.12:12:16.493>
creator = 'Robin.Jarry'
dependencies = []
files = ['35098']
hgrepos = []
issue_num = 12382
keywords = ['patch']
message_count = 9.0
messages = ['138781', '138782', '139024', '139049', '139203', '217552', '306880', '306883', '306884']
nosy_count = 10.0
nosy_names = ['loewis', 'paul.moore', 'markmcmahon', 'tim.golden', 'markm', 'Robin.Jarry', 'berker.peksag', 'zach.ware', 'steve.dower', 'tiwilliam']
pr_nums = ['4528', '4538']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12382'
versions = ['Python 3.6', 'Python 3.7']

[RobinJarry]

When trying to open a non existing MSI database, an obscure "unknown error 6e" is raised.

Could it be possible to get a more explicit message such as "File not found" or whatever ?

Thanks :)

Here is a example:

--------------------------------

D:\>ll
total 0
drwxr-xr-x 4 tcinteg Administ 0 Nov 30 2010 RECYCLER
drwxr-xr-x 0 tcinteg Administ 0 Jul 6 2009 System Volume Information
drwxr-xr-x 4 tcinteg Administ 0 Apr 29 16:03 TC
drwxr-xr-x 3 tcinteg Administ 0 Apr 29 15:43 stgloc

D:\>python
Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import msilib
>>> db = msilib.OpenDatabase("I_Do_Not_Exist.msi", msilib.MSIDBOPEN_READONLY)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
_msi.MSIError: unknown error 6e
>>>

[RobinJarry]

changed the headline of the defect for something more meaningful :)

[markm]

The following two error conditions that can be returned by MsiOpenDatabase do not have specific handling:

ERROR_CREATE_FAILED (1631)
The database could not be created.

ERROR_OPEN_FAILED (110)
The database could not be opened as requested.

(the messages are those copied from MSDN).

Should extra cases for these go into the case statement in msierror? or should they be handled directly in OpenDatabase.

Does the error text above sound OK - should we add ": '%s'" % msi_file ?

[RobinJarry]

This sounds OK as long as the error message is explicit :)

[loewis]

I'd add them to msierror, with no inclusion of the file name.

If you want the file name in the exception, you should uniformly apply this to all errors in OpenDatabase, and then subclass MSIError to, say, MSIOpenError which includes a .filename attribute.

[tiwilliam]

Found this a simple fix for an annoying and time consuming error. Patched as discussed earlier and decided to leave the filename out.

[berkerpeksag]

New changeset 4864a61 by Berker Peksag in branch 'master':
bpo-12382: Make OpenDatabase() raise better exception messages (GH-4528)
4864a61

[berkerpeksag]

New changeset bfa89b2 by Berker Peksag (Miss Islington (bot)) in branch '3.6':
bpo-12382: Make OpenDatabase() raise better exception messages (GH-4528)
bfa89b2

[berkerpeksag]

Thank you for your patch, William. I added a test case, a NEWS entry and committed it to 3.6 and master branches.