[orbit-dev] customCallbacks: A small twist on including pre-built bundle

[David M Williams <david_williams@xxxxxxxxxx>]

Jeff has recently mentioned on this
list the technique of having your own "getBaseComponents"
target to pull in pre-built components, but 
lucky or not lucky, right before he
posted his note, I had just spent three days discovering another way, that
I think I might like better. Maybe it's just semantics, 
but there is a way to add "custom
call backs" to your feature/bundle builds, so, I used that mechanism,
at the feature 
level, to get and copy the pre-built
bundles. To make it concrete -- merely to aide discussion, not meant to
be "how to" -- 
here's the rough steps I went through
to get closer to what I believe is the Orbit model we're headed. 
This example is from WTP, using our
 xml_core feature and it's need for xerces from Apache. 

In our previous release, in our xml_core
feature, we "required" the xerces.feature, whose only included
plugin was the xerces bundle. 
So, I removed all that, and added "include"
xerces directly to our xml_core feature. 

Then, in xml_core feature's build.properties
I added the line
    customBuildCallbacks=addPreBuiltComponents.xml

Next I created the addPreBuiltComponents.xml
file, starting with a template from the customCallbacks.xml content, found
in
org.eclipse.pde.build_<version>\templates\features

Then I added my custom "get and
copy" script  ... 
       
<target
name="pre.gather.bin.parts">
       
    <!--
copy our known, pre-built, usually third party pre-reqs into this feature
-->
       
<copy
       
    todir="${destination.temp.folder}"
       
    overwrite="true">
       
    <fileset
dir="${env.BUILD_HOME}/prebuilt/eclipse/plugins/"
includes="org.apache.xerces*/**"
/>
       
</copy>
       
</target>

And, so far seems to be working well
(doesn't seem like that should have taken 3 days, does it? :) 

I like this approach since you can code
all the "knowledge" of the 3rd party requirement right there
in the feature project, and
because you can name the file something
meaningful for this case. (that's the semantics part). 

So, obviously, my "get and copy"
is only copying from our build machine, so far, and the "copy"
relies on some silly ant attribute, 
(to avoid hard coding the exact version
numbers) but I could see those few lines being easily improved to be more
robust. 

So, on the one hand, we could all do
what ever we wanted or needed to do, right there in those few lines of
script code ... 
get from a maven repository? ... download
and unzip an archive file?  ... or whatever. 

I think (part of) Eugene's (and Jeff's)
recent comments is that it'd be great to have a more general "get
and copy task", such as 
get-the-bundle-versioned-2.8.0-but-with-the-most-recent-(highest)-qualifier-from-repository-xyz-using-protocol-abc.

(right?)  If so, seems we could
make incremental progress on that, if anyone happens to develop more robust
ant tasks. 

So ... I post this just for comment
... if anyone has any comments/improvements/warnings on this approach ....
let me know. 
After all, I could not find customCallbacks
mentioned anywhere in the Eclipse RCP book, so maybe it's completely invalid
:) 

And ... soon, we'll get back to talking
about  how to produce Orbit, instead of how we expect to use Orbit
:)