Wikimedia Bugzilla is closed!

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Reproductions steps
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* Install the Score extension on a Windows machine (I was able to reproduce on Windows XP and Windows 7)

* Create a page with the following wikitext:
<score midi="1">\relative c' { d }</score>

* Click "Show Preview". The following error appears:

No MIDI file generated despite being requested. If you are working in raw LilyPond mode, make sure to provide a proper \midi block.


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Cause
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* Score.body.php uses ".midi" throughout the file as the extension for MIDI files

* However, on Windows, Lilypond treats ".mid" as the default extension for MIDI files. See the following Lilypond page (http://lilypond.org/doc/v2.15/Documentation/notation/creating-midi-files):

Due to some limitations on Windows, the default extension for MIDI files on Windows is .mid.  

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Recommendation
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* Add the "-dmidi-extension=midi" command line arg as per http://www.lilypond.org/doc/v2.17/Documentation/usage/command_002dline-usage

Specifically:
midi-extension	"midi"	Set the default file extension for MIDI output file to given string.

The recommended area of change would be here:
$cmd = wfEscapeShellArg( $wgScoreLilyPond )
			. ' ' . wfEscapeShellArg( '-dsafe=#t' )
			. ' -dmidi-extension=midi'
			. ' -dbackend=ps --png --header=texidoc '
			. wfEscapeShellArg( $factoryLy )
			. ' 2>&1';

The above change allows me to generate MIDI files on my Windows XP box.

I've also tested the "-dmidi-extension=midi" command-line argument on Windows XP, Windows 7, and Linux Mint Nadia. In each case, the output MIDI file has an extension of ".midi" (i.e.: manually specifying "midi" on Linux seems to be benign)