Re: [Libreoffice] Extension dependencies

Hi,

I am responding to the first message in this thread because it seems 
to be relevant to Java-based extensions.


At 09:59 4-11-2011, Stephan Bergmann wrote:
> Hi all,
>
> As already mentioned briefly in my talk at LOCon, we need to make up 
> our mind how to handle LO extension dependencies.
>
> Each .oxt extension can carry any number of dependencies, specifying 
> conditions that need to be met by the hosting LO installation for 
> the extension to be successfully deployable (see 
> <http://wiki.services.openoffice.org/wiki/Documentation/DevGuide/Extensions/Dependencies>).

This page links to 
<http://openoffice.org/extensions/description/2006>, which returns an 
ERROR 404, so even if an extension developer wanted to document more 
detailed dependencies, they would not know what syntax or elements to 
use in their description.xml file.

I was confronted with this problem just today because a new 
Java-based extension cannot be installed on some Ubuntu systems even 
though it installs without problems on Windows and some other Ubuntu systems.
The extension manager displayed the following error dialog:
(com.sun.star.deployment.DeploymentException) { { Message = "An error 
occurred while enabling: accessodf-addon.jar", Context = 
(com.sun.star.uno.XInterface) @a403870 }, Cause = (any) { 
(com.sun.star.registry.CannotRegisterImplementationException) {{ 
Message = "", Context = (com.sun.star.uno.XInterface)} @0 } } } }

It turns out that this issue can be solved with
    sudo apt-get install libreoffice-java-common

So I thought about how to document that dependency in 
description.xml, but I couldn't ... (And libreoffice-java-common or 
openoffice.org-java-common may be rather broad.)

Best regards,

Christophe



> The mechanism was designed to allow for any number of fine-grained 
> dependency specifications ("this extension requires availability of 
> com.sun.star.whatever.Service"), but only a coarse-grained 
> OpenOffice.org-minimal-version ever got defined (and also a 
> maximal-version one).  After all, it is hard (or at least tedious) 
> for extension developers to come up with a precise list of features 
> they depend on, which would be needed to specify a precise list of 
> fine-grained dependencies.  A single minimal-version dependency 
> appeared so much easier to use.
>
> The OpenOffice.org-minimal-version dependency worked fine as long as 
> OOo was the de-facto standard, with derivatives tracking OOo 
> development rather closely and producing new versions in sync with 
> upstream OOo. The minimal-version dependency's version value was to 
> be interpreted as the version of the underlying OOo reference 
> version, so even if a derivative used a different versioning scheme 
> everything worked out.  An extension developed for one product could 
> also be deployed in a different one (at least in theory; of course 
> there are always minor glitches that spoil the picture).
>
> Now, LO and OOo (now AOOo) are no longer in such close relation.  LO 
> is heading towards its version 3.5 already while AOOo did not yet 
> publish its version 3.4, and new features are routinely added to LO 
> that are unlikely to be included into AOOo.  This leads to the following items:
>
> ** How shall LO handle the OpenOffice.org-minimal-version dependency?
>
> Strictly speaking, LO 3.4/3.5 should still check against an 
> OpenOffice.org-minimal-version value of 3.3, as that's the latest 
> available (A)OOo version.  However, for LO 3.4, this check has 
> (probably accidentally) been changed to "3.4" (and with the current 
> code towards LO 3.5 it has yet again changed to "3.5").  I would 
> argue to leave it at "3.4" for both LO 3.4 and LO 3.5.  (For one, it 
> can obviously no longer be changed back to "3.3" for LO 3.4, and 
> changing it back to "3.3" for LO 3.5 would probably cause more 
> confusion than its worth.  For another, semantically the check will 
> likely be more-or-less correct, matching the features an AOOo 3.4 
> will presumably come out with.)  If no one objects, I will adapt LO 
> 3.5 so that it still checks for "3.4," not "3.5."
>
> In the future, when AOOo releases new versions after AOOo 3.4, we 
> would need to check whether it semantically makes sense for LO to 
> bump its OpenOffice.org-minimal-version check (i.e., whether the 
> features of that new AOOo version are also available in LO).
>
> ** How to specify dependencies for newly introduced LO features?
>
> One option would be to add an additional LibreOffice-minimal-version 
> dependency.  Another option would be to actually make use of 
> fine-grained dependencies and introduce them as needed (i.e., 
> whenever an extension developer wants to make use of a new LO 
> feature, a corresponding dependency would have to be added).
>
> The former has as pro its ease of use.  The latter has as pro that 
> it shows a way out of the problems caused by 
> OpenOffice.org-minimal-version and for an opportunity of continued 
> sharing of extensions across products:  If each extension only lists 
> the features it requires, regardless of any product's version 
> numbers, it becomes much easier to match that extension against a 
> given product's capabilities, regardless of brand.
>
> I'd tend to give the fine-grained dependencies a try.  That would 
> require cooperation from extension developers (they would need to 
> voice their demand for dependencies for specific features, and they 
> would need to make accurate use of those dependencies in their 
> extensions).  To achieve cross-product extension compatibility, it 
> would also require some sort of advertising of LO's newly introduced 
> fine-grained dependencies (so that other products---where 
> possible---would pick them up together with the corresponding 
> features), but we would need a place to document any newly 
> introduced dependencies, anyway.
>
> What do other people think here?
>
> ** What happens when LO 4 becomes incompatible?
>
> In that case, any OpenOffice.org-minimal-version dependency, 
> regardless of version value, should be considered as not satisfied 
> by LO 4. Similarly, if we did introduce a 
> LibreOffice.org-minimal-version dependency, any version value of 
> that dependency less than 4 should be considered as not 
> satisfied.  On the other hand, treatment of any fine-grained 
> dependencies would have to be handled on a case-by-case basis.
>
> Stephan


--
Christophe Strobbe
K.U.Leuven - Dept. of Electrical Engineering - SCD
Research Group on Document Architectures
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