[bitbake-devel] [OE-core] Layer priorities influencing default version selection

[Richard Purdie]

On Tue, 2011-08-02 at 12:26 +0100, Paul Eggleton wrote:
> Hi all,
> 
> Andrea pointed out a situation where he has seen the layer priority overriding 
> version selection, and I've been able to confirm it.
> 
> Basically, if you have a recipe with a lower version in a layer with a higher 
> priority it selects the lower version. What's more after digging further I 
> found there were some rather anomalous interactions with the version logic and 
> BBCLASSEXTEND. Here's an example using Poky:
> 
> 1. Firstly, copy meta/recipes-support/curl to meta-yocto/recipes-support, then 
> rename the version in meta-yocto so that its version is 7.20.0. At this point 
> both meta/ and meta-yocto/ have the same layer priority of 5.
> 
> 2.  "bitbake -s | grep ^curl" reports:
> curl                                               :7.21.7-r0                          
> curl-native                                        :7.21.7-r0                          
> curl-nativesdk                                     :7.21.7-r0                          
> 
> 3. Now increase the layer priority in meta-yocto/conf/layer.conf to 6, and run  
> "bitbake -s | grep ^curl" again:
> curl                                               :7.20.0-r0                          
> curl-native                                        :7.21.7-r0                          
> curl-nativesdk                                     :7.21.7-r0                          

This is clearly broken and needs to be consistent at the very least.

> So the latest version here is a lie, this is not the latest version available. 
> Furthermore it seems not to have affected the BBCLASSEXTENDs.
> 
> 4. Now add PREFERRED_VERSION_curl = "7.21.7" to conf/layer.conf and run 
> "bitbake -s | grep ^curl" again:
> curl                                 :7.20.0-r0                :7.21.7-r0
> curl-native                    :7.21.7-r0                          
> curl-nativesdk               :7.21.7-r0                          
> 
> So it can clearly see the other recipe, it just doesn't acknowledge it until 
> you force the matter.
> 
> This is all rather undesirable behaviour IMHO - even if the BBCLASSEXTEND and 
> reported "latest version available" issues were corrected, I think the policy 
> of "latest version wins unless DEFAULT_PREFERENCE or PREFERRED_VERSION says 
> otherwise" should not be affected by layer priority.
> 
> Thoughts?

We could do with clearly documenting this in the bitbake manual. I
suspect users would expect the highest version to win and we probably
should change the behaviour but I'm open to other opinions.

Cheers,

Richard