[news.eclipse.platform] Re: No solution found because the problem in /tm

[Eric Rizzo <eclipse-news@xxxxxxxxxxxx>]

On 12/11/2008 2:54 PM, John J Barton wrote:
> Eric Rizzo wrote:
> > First of all, it is not an option for you to be ignorant about
> > dependencies and installation management if you're going to be a
> > plugin publisher. It is just as important as understanding how to use
> > SWT or what to do in your Activator start/stop methods, etc; it goes
> > with the territory.
>
> Thanks Eric, I agree with you in general: developers need to understand
> how there code works in a system. But the tools/approach that eclipse
> uses are too difficult to use.

I disagree - I find most dependency situations to be easy to specify 
using the PDE tooling. There are some more tricky corner cases (see my 
thread "Transitive dependencies and optional plugins" from yesterday, 
for example), but those are rarely encountered in my experience.
As an example of the ease of the tooling, when I add a dependency to my 
plugin, Eclipse (as of 3.4) automatically inserts the current version of 
that plugin from my target platform as the "minimum required" version. 
That is handy and exactly what is wanted in 90%+ of cases.
Anyway, more below...

> > Now, if you want to target a particular version of particular plugins
> > (remember, each plugin can be updated and change its version
> > independently), you need to specify that in your plugins' Dependency
>
> I do *not* want to do this. It's not practical for me or my users. What
> is practical is what we already do: "use ecilpse jee 3.4.0".

That is fine as a user instruction, but is not enough for the platform 
(OSGi) to go on. Remember that, although Eclipse has coordinated 
releases (named things like Europa, Ganymede, Galileo) and the EPP 
project produces convenient packages that include sets of plugins from 
those coordinated releases, each plugin can evolve independently AND a 
user is free to update or install new plugins at any time. Therefore it 
is impossible to define "Eclipse JEE 3.4.0" unless you spell out what 
versions of what features and plugins that includes. Plus, that is a 
very specific case, not one that most plugins or Eclipse-based products 
want because it would be VERY restrictive. For example, I can't use the 
SR2 (Ganymede 3.4.2, if you want to call it that) with your plugins? 
Really? There's no API changes allowed in an increment release (3.4.x) 
so there should not be such a restriction in most cases. See what I mean 
by the balance between guaranteed compatibility and overly restrictive?

> Or is the simple answer that I have to build my plugin with exactly the
> version of eclipse that I want users to install?

Well, for one thing you should ALWAYS be using a target platform, not 
building against the Eclipse that you are running as your IDE. It really 
irritates me that the default setup for the PDE is to use the running 
Eclipse as the target platform, because it can easily lead newbie plugin 
developers down a path with pitfalls. I suspect that is what has 
happened to you.
Here is one article explaining why: 
http://rcpquickstart.com/2008/04/21/why-create-a-custom-target-platform/
Here's the relevant Help page: 
http://help.eclipse.org/stable/index.jsp?topic=/org.eclipse.pde.doc.user/guide/tools/preference_pages/target_platform.htm


> > list. For each plugin listed as a Dependency, you can (and should)
> > specify a version range that is acceptable. Of course it is not a
> > trivial matter, you have to think about the version ranges you want to
> > allow: too restrictive and your stuff won't be compatible with
> > arbitrary Eclipse instances; too loose and you'll get installed into
> > environments that aren't really compatible with your code.
>
> Fine, but how do I make these choices? Its not like the plugin version
> numbers match the eclipse distro numbers. Some are 3.4.1. If I pick
> 3.4.0 then does my build have any relation to the install? Some are
> 3.2.1. Why? What will my users have in their ecilpse 3.4.1? also 3.2.1?

Hopefully my second paragraph above makes clear why version numbers do 
not line up across plugins. To repeat: each plugin evolves 
independently. I think this wiki page might help, too: 
http://wiki.eclipse.org/index.php/Version_Numbering

> > This is all part of designing a plugin or plugins - you have to think
> > about what your target environment requirements are and embed that
> > info into your plugin(s) dependencies and possibly your Feature
> > definition.
>
> I know the requirements, I don't know how to tell eclipse to use them.

In the Dependencies tab of your plugin(s); select a plugin listed there 
and hit the Properties button.

I really think setting up a target platform will make your life a lot 
easier. That is the first thing I would do if I were on your team ;-)

Hope this helps,
Eric