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Re: Issue 1771 in lilypond: Nested reverts fail for properties which are
From: |
lilypond |
Subject: |
Re: Issue 1771 in lilypond: Nested reverts fail for properties which aren't set as defaults in define-grobs.scm |
Date: |
Mon, 01 Aug 2011 08:28:07 +0000 |
Updates:
Status: Duplicate
Labels: -Priority-Critical Priority-Medium
Mergedinto: 1063
Comment #3 on issue 1771 by address@hidden: Nested reverts fail for
properties which aren't set as defaults in define-grobs.scm
http://code.google.com/p/lilypond/issues/detail?id=1771
This one is likely Invalid. 1063 is not possible to fix without breaking
other aspects of nested properties -- they are broken by design. You can't
make an alist one property and transparently have the full
context-hierarchic override/revert functionality for its sublevels
independently.
The notation manual (node "Modifying alists") is not particularly
informative regarding the fine details. It just mentions that using nested
properties will not work for properties which are themselves alists. But
as far as I can see, this is exactly what the implementation of nested
lists is now. So it is my understanding that it will be easy for any
implementation relying on the current design of the data structure and the
transparently accessible alists to write a regtest that fails. More
obfuscated code, like the one in the patch leading to this regression, will
just make it harder to predict the behavior and create a matching failing
regtest.
Since the report is not technically invalid, I merge it into 1063. The
error symptoms are, of course, different, but both, to my understanding,
can't be fixed simultaneously, at least not without breaking functionality
at yet another place. So they are both a result of the same design error,
and need a common strategy to tackle.
Feel free to prove me wrong.