handling circular dependencies

[wookietreiber]

I made a for lvu resolving the infinite recursion of show_tree.

See attachment.


On Sat, Jan 15, 2011 at 10:18:04PM +0100, wookietreiber wrote:
> Hello,
> 
> revising the configuration of 'cairo' and much around it (take a look at the module submission queue) I discovered some circular dependencies ('libspectre', 'poppler' and 'librsvg' should actually be optional dependencies for 'cairo') and how troublesome and annoying they can be ... for now I handled them with POST_INSTALL and POST_REMOVE, which, of course, isn't the most elegant way to do this ...
> 
> ... so, what about a new function (e.g. called 'circ_depends') for '/var/lib/lunar/functions/depends.lunar' or, which would be even better, a revision of 'depends' and 'optional_depends', to handle circular dependencies directly in the lunar tools?
> 
> Generally, I don't know if it's just 'lvu tree module_with_circ_dep' breaking by going in an infinite loop or if it concerns other lunar tools as well -- I'm just not deep enough in it yet, but intend to :)
> 
> The intention of this mail is to encourage us to provide thoughts on what to consider to implement good circular dependency handling functionality and eventually, well, implement it :)
> 
> Best Regards
> Christian Krause aka wookietreiber
> 
> P.S.:   I'll start with some thoughts soon :)
> P.S.S.: Maybe someone knows other functions like 'lvu tree ...' which fail and post it to this thread -- this would help to find everything that breaks or may break.
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<     grep -q "^$DEP$" $TMP_SEEN
<     TEST=$?
<     if [ "$TEST" == "1" -o -z "$SHORTTREE" ] ; then
<       echo "$DEP" >> $TMP_SEEN
<       CUR=${DEP:0:1}
<       # note the FLAG= thingy here
<       FLAG= show_tree ${DEP:1} 2> /dev/null
---
>     # recurse only if module is not root to avoid going on 
>     # indefinetely with circular dependencies
>     if [ ${DEP:1} != $ROOT ]; then
>       grep -q "^$DEP$" $TMP_SEEN
>       TEST=$?
>       if [ "$TEST" == "1" -o -z "$SHORTTREE" ] ; then
>         echo "$DEP" >> $TMP_SEEN
>         CUR=${DEP:0:1}
>         # note the FLAG= thingy here
>         FLAG= show_tree ${DEP:1} 2> /dev/null
>       fi
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>       ROOT="$2"
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>       ROOT="$2"
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>       ROOT="$2"
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>       ROOT="$2"