[Pika-dev] xl as config file, programmatic manipulation pitfall

[Jeremy Shaw]

Hello,

If xl is to be used in 'config files', it also seems reasonable to
expect that some one will want to write a program to manipulate the
config file. (Indeed, there are already several GUI frontends for
gnu/arch).

Looking at existing config file formats, it is clear that the authors
of the file formats imagined that the files would only be modified by
hand, or entirely programmatically. However, this is not always the
case. 

One example is /etc/samba/smb.conf. This config file is often edited
by hand and contains many comments, but is also manipulated by
programs that allow users to share directories in their home
directories.

The problem becomes how to correctly preserve comments. Here is an
example illustrating the problem:


----> example start <----

# Some header comments
# blah blah blah blah

[group1]
key1=value1
; some comment
key2=value2
 # comment2
key3=value3

# some header comments for group2
[group2]
key1=value1
; some internal comment for group 2
key2=value2
; some other comment for group 2

#[group3]
#key1=value1
#key2=value2
[group4]
key1=value1
key2=value2

---> end example <--

If I write a program that needs to delete group2, it should probably
delete the comments associated with group2.  It is fairly safe to
assume that 'some internal comment for group2' can be deleted since it
appears between two keys that belong to [group2]. As I person I can
see that I should delete "some header comments for group2" and "some
other comment for group2". But any algorithms I can devise to do this
will likely delete the commented out [group3], either when I delete
[group2] or [group4].

It is my suggestion that the xl comments be designed so that programs
can be programmatically transformed without screwing up the comments.

Jeremy Shaw.
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