[Bug 51774] New: quartz:mpegsplit triggers an assertion in winegstreamer's src_seek_data()

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51774

Bug ID: 51774
           Summary: quartz:mpegsplit triggers an assertion in
                    winegstreamer's src_seek_data()
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: quartz
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

quartz:mpegsplit triggers an assertion in winegstreamer's src_seek_data().

In the test report this shows up as a missing test summary line:

https://test.winehq.org/data/patterns.html#quartz:mpegsplit

quartz:mpegsplit start dlls/quartz/tests/mpegsplit.c
...
mpegsplit.c:1011: Test marked todo: Got hr 0x1.
quartz:mpegsplit:0ad8 done (0) in 0s

(notice the missing 'mpegsplit: nnnn tests executed' line)
This is because the process exits prematurely and one can see that this is
because of an assertion violation by looking into the Wine log ('Show full task
log' in the TestBot):

../wine/dlls/winegstreamer/wg_parser.c:1298: src_seek_data: Assertion
`!parser->read_request.pending' failed.

This impacts all Wine builds (win32 & wow*) in all locales but is not
systematic.

A bisect points to the following commit as the culprit which makes sense since
it added that assertion:

commit 1aa359a100bae859b278007e8bf90673eebd7db0
Author: Derek Lesho 
Date:   Wed Sep 15 18:00:10 2021 -0500

winegstreamer: Replace source pad interface with GstAppSrc.

Signed-off-by: Derek Lesho 
    Signed-off-by: Zebediah Figura 
    Signed-off-by: Alexandre Julliard