[jbosstools-dev] Unnecessary Dependencies

Fri Feb 13 14:12:54 EST 2009

> > WHY are people reaching into other unrelated plugins and using classes 
> > and adding unnecessary dependencies?!

Why aren't you using the export-packages mechanism available to Eclipse plug-ins 
which allows you the specify exactly what parts of your plug-in, in any, are intended
for use by others?

Regarding copying/depending on code: There's no absolute rule one way or the other, but
the collective wisdom in software engineering strongly favors reuse through dependency
over copying. The "professional" bit comes in by realizing that ultimately design is a matter
of judgment, and even the strongest rules need to be broken sometimes. Another aspect of
"professional" is realizing what needs to be done when, and hence sometimes taking on technical
debt for short term gains.

-- John

On Fri, 2009-02-13 at 17:00 +0800, Rob Stryker wrote:
> WHY are people reaching into other unrelated plugins and using classes 
> and adding unnecessary dependencies?!
> 
> If so many people are doing this, then the code *should* be in a common 
> area!  There is ZERO reason that we should be reaching into unrelated 
> plugins and adding dependencies. This is absolutely disgusting.
> 
> If everyone just starts reaching into each others plugins and using code 
> without permission or some type of process, then before you know it we 
> get spaghetti linkages and cyclical dependencies and all sorts of 
> things. We can NOT just go around adding dependencies for this kind of 
> stuff! 
> 
> I would never reach into Denny's code or Grid's code or VPE code or any 
> other code without careful consideration to how the dependencies will be 
> affected... as should everyone else.
> 
> We need to have a clear process as to what types of projects are allowed 
> to depend on others and when. This type of lawlessness is horrific.
> 
> As far as I can see it, if someone else has some code you want to use, 
> the process should be done in this order:
> 1) if you already depend on the plugin, go ahead and use it the class.
> 2) If you have no reason to depend on it, try to copy or abstract the 
> code into a common area, and use it there.
> 3) If other difficulties make it so you cannot copy or abstract the code 
> into a common area, then copy  it into your own plugin
> 4) Only as a last resort do you go about adding dependencies.
> 
> I'm quite certain Max will disagree with me, but my point is, you cannot 
> just go extending classes in other plugins without looking at how it 
> will affect the dependency tree. We're heading down a dangerous road 
> where plugins just willy-nilly link up with each other and can't be 
> extricated. This is not professional at all.
> 
> Snjezana Peco wrote:
> > We need to take into consideration that the 
> > AbstractClasspathContainer, AbstractClasspathContainerInitializer, 
> > ClasspathDecorations and ClasspathDecorationsManager classes are also 
> > being used in the WS and portlet plugins.
> >
> > Snjeza
> >
> > Rob Stryker wrote:
> >> Perhaps a more articulate way to explain my point is that copying the 
> >> code is the best solution because
> >>
> >> 1) It does not make real "code" changes before release. IE if this 
> >> code which has been stable for months continues to be stable, there's 
> >> no problem.
> >> 2) It severs an unnecessary dependency, thus allowing users to use a 
> >> deployment method of their choosing (project archives, ant)
> >> 3) It does not make big structural changes by introducing a new 
> >> module or some such.
> >> 4) It provides a stop-gap to the proper solution (new common code 
> >> area) once structural changes are permitted.
> >>
> >> Max Rydahl Andersen wrote:
> >>> Maybe showing  the +/- of each scenario would make it more obvious:
> >>>
> >>> A) We keep the ESB to AS dependency:
> >>> + Does not require module structure/dependency changes shortly 
> >>> before GA
> >>> ++ if there is a bug in the shared code it will be fixed once and 
> >>> work for all
> >>> - I have to download AS to get the shared functionality (but this is 
> >>> not a big minus if you use the updatesite since there would be a 
> >>> dependency)
> >>>
> >>> B) We copy code from AS to ESB:
> >>> + ESB can be downloaded separately
> >>> - Changes dependency changes shortly before GA (a small minus but it 
> >>> needs to be checked after all)
> >>> -- if one fixes a bug in the copied code in ESB he also need to fix 
> >>> this where the code was copied from (i.e. which will be forgotten 
> >>> because we are all humans)
> >>> - I have to download AS to get the ESB projects to actually deploy  
> >>> (but this is not a big minus if you use the updatesite since there 
> >>> would be a dependency)
> >>>
> >>> C) We share code between AS to ESB in a common core
> >>> + ESB can be downloaded separately
> >>> ++ if there is a bug in the shared code it will be fixed once and 
> >>> work for all
> >>> - I have to download common core (but this is not a big minus if you 
> >>> use the updatesite since there would be a dependency)
> >>> -- Require module structure/dependency changes shortly before GA
> >>>
> >>> So for me the copy option is the worst of all choices. Since it has 
> >>> a big minus (duplication of code), but no real benefits plus moving 
> >>> from A to C is easier then B to C.
> >>>
> >>> If ESB and AS did not have a natural dependency and the duplicated 
> >>> code was just simple - things would be different. It all depends on 
> >>> the context.
> >>> Dependencies are not a bad thing - but yes, in general we should 
> >>> modularize our code so we don't get *unnatural* dependencies.
> >>> /max
> >>>> On 12-02-2009 06:34, Rob Stryker wrote:
> >>>>> So today I decided to work on JBIDE-3772 and I create a workspace 
> >>>>> with just ESB projects.
> >>>>>
> >>>>> I see immediately that it requires XModel (bleh), but that's fine 
> >>>>> I guess. It provides a lot of functionality. I also see, however, 
> >>>>> that it requires as.classpath.core.
> >>>>>
> >>>>> Requiring XModel is maybe justifiable as it's "common" code. The 
> >>>>> requirement on as.classpath.core is just to make use of an 
> >>>>> Abstract classpath provider that's in there.
> >>>>>
> >>>>> I'm not trying to call any plugin or developer out here, but I'd 
> >>>>> like to suggest that we try to decouple our code as much as is 
> >>>>> possible. If you're just borrowing one or two classes with minimal 
> >>>>> dependencies, would it be better to copy that class?  I think it 
> >>>>> would be better but I'd like to hear other's thoughts.
> >>>> No, copy/paste of code that is doing more than just very simple 
> >>>> things should not just be copied.
> >>>>
> >>>> You don't tell what classpath provider you are copying so I can't 
> >>>> see what it does (and fisheye is down), but my guess is that it is 
> >>>> the classpth container
> >>>> that manages the sourcecode and javadoc attachements - that is 
> >>>> excellent candidates for code to be shared.
> >>>>
> >>>> This does not mean you should not decouple your code, but 
> >>>> decoupling is much more than just avoiding plugin dependencies 
> >>>> between our plugins.
> >>>> i.e. if having ESB classpath containers and deployment being 
> >>>> dependent on AS plugin saves us from a lot of possibly maintanence 
> >>>> duplication then why bother
> >>>> separating them when the only adapter and server in the world that 
> >>>> will work with ESB is our AS plugin...in other words ESB has (IMO) 
> >>>> a natural dependeny on AS
> >>>> hence having common code in AS does not hurt anyone.
> >>>>
> >>>> If ESB one day can be deployed to other servers or the classpath 
> >>>> container start being used by other parts of our code that is not 
> >>>> 100% dependent on AS by nature then
> >>>> separating those base classes out makes a lot of sense.
> >>>>
> >>>> /max
> >>>> _______________________________________________
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> >>>> jbosstools-dev at lists.jboss.org
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> >>>
> >>
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