[wildfly-dev] selecting packages from feature-packs

[Brian Stansberry]

> On Oct 21, 2016, at 9:20 AM, Alexey Loubyansky <alexey.loubyansky at redhat.com> wrote:
> 
> On 10/21/2016 03:50 PM, Brian Stansberry wrote:
>> 
>>> On Oct 19, 2016, at 7:27 AM, Alexey Loubyansky <alexey.loubyansky at redhat.com> wrote:
>>> 
>>> Me and Stuart have been thinking about how to express feature-pack
>>> package selection in an XML. Each one came up with a proposal but we
>>> appear to have slightly different preferences. In case anybody has an
>>> opinion or a better suggestion, please, share.
>>> 
>>> Brief description: feature-pack consists of packages. A package is a
>>> unit of content. So a set of packages determines the target installation
>>> content-wise. Feature-pack has a set of default packages. These are the
>>> packages that get installed by default, i.e. when the user installs the
>>> feature-pack w/o specifying any package preferences. In addition to the
>>> default ones a feature-pack may contains non-default packages, these are
>>> present in the feature-pack but will be installed only if the user
>>> explicitly asks for them.
>>> So, the question is how to express these package preferences in an XML.
>>> 
>>> Proposal 1.
>>> 
>>> - include-default flag (element or attribute) which defaults to true
>>> (meaning the default packages will be included by default);
>>> 
>> 
>> Th “include” element is still supported here, right? So, I can get all the default ones and then use include elements to pull in additional ones.
> 
> Right.
> 
>>> - if include-default is false (meaning nothing is installed by default),
>>> then 'include' element can be used to pick the specific packages
>>> (default and non-default ones) to be installed;
>>> 
>>> - otherwise (when include-default is true) 'exclude' element can be used
>>> to exclude specific undesired default packages.
>>> 
>> 
>> Can “exclude” be used to exclude dependencies? So I want “a” but not its dependency “b”? If the answer is yes for optional dependencies, what if the dependency isn’t optional?
> 
> Yes, it can be used to exclude dependencies. If a required (non-optional) dependency is excluded, that'll be an error.
> 
>>> Proposal 2.
>>> 
>>> - exclude element - applicable to any package and means do not install
>>> the package (and its dependencies);
>>> 
>>> - include element - applicable to non-default packages and means do
>>> install the non-default package (and its dependencies);
>>> 
>> What happens if it’s used for a default package? The tool forgives this, right?
> 
> That would be redundant, of course. We could ignore that or issue a warning.

That question was kind of a tangent. I asked because I could imagine a case where a package is not default in version 1, so the user adds an “include”. Then in a later version the package is now a default one. You don’t want to break the user for no good reason.

> 
>>> - pick element - applicable to any package and means install only the
>>> picked package(s)
>> 
>> and it’s dependencies? If yes, all its dependencies or only non-optional?
> 
> No, the dependencies would have to be picked explicitly. Otherwise, we have to allow exclude and include to be used in combination with pick which will look too confusing.
> 

Ok, then assuming that in Proposal 1 an “include” element always means pull in dependencies, I prefer Proposal 1. Forcing people to list everything just to get a subset of the default packages is painful and will likely break things if the feature-pack adds a new dependency in a later version.

But…

There are cases where people do want to explicitly list things and not have unexpected things brought in. See discussion on https://issues.apache.org/jira/browse/MNG-2315 (for which I voted). I do think it’s good to account for that kind of use case.

>>> ignoring other default and non-default ones. pick
>>> cannot be used in combination with exclude and include.
>>> 
>>> 
>>> Basically, 'include' and 'exclude' in both proposals are practically the
>>> same. The difference is how the picking is expressed. In the first one,
>>> everything is explicitly excluded and then the desired ones are
>>> explicitly included, in the second one the desired ones are simply
>>> explicitly picked.
>>> 
>> 
>> The answers to my questions on Proposal 1 impact the semantics of include/exclude in different cases, so I’ll defer expressing an opinion for now. :)
> 
> Thanks,
> Alexey
> 
>> 
>>> 
>>> Thanks,
>>> Alexey
>>> _______________________________________________
>>> wildfly-dev mailing list
>>> wildfly-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev

-- 
Brian Stansberry
Manager, Senior Principal Software Engineer
JBoss by Red Hat