[Fedora-packaging] Packaging guidelines - mandatory rebuilding gems

[Toshio Kuratomi]

Sending to packaging at lists.fp.o where this belongs.

On Tue, Feb 14, 2012 at 05:27:06PM -0500, Mo Morsi wrote:
> 
> Thoughts:
> 
>   - I am also not a fan of the current approach of always repackaging the gem,
> seems like extra steps / added complexity which is unneeded, what is the
> justification for it? In the majority of cases, gem install works out of the
> box and the gem doesn't need any modifications.
> 
There's a lot of justification in the ticket.  There's various pieces.

* The historical ruby/gem guidelines are a huge hack that FPC approved because
  it seemed that gems wouldn't work with the normal separation of %prep
  %build %install.  The recent draft showed that this is no longer the case.
* Proper separation allows rpmbuild -b[pci] --shortcircuit to work properly.
* The previous guidelines actually didn't allow patching.  The original
  proposed draft guidelines ended up being overly complex as they had
  separate cases for gem, gem w/ C extension, patched gem, patched gem w/
  C extension, patched gem w/ C extension that fails to build.  This
  strategy has a single way to handle all of this.  The cost is three extra
  lines which are easy to conceptualize and explain.  (unpacking the code
  from an archive, then assembling the code into a form that can be built
  from).
* Proper separation of the steps allows people new to ruby packaging but old
  hands at rpm packaging (a large portion of reviewers) to come to
  understand the basics of packaging rubygems.

>   - what is the rationality behind having a gem package provide ruby
> (RUBYLIBRARY)? Seems like the non-gem and gem package distinction is more
> explicit when the gems provide rubygem(gemname) and non-gems provide ruby
> (libraryname). Since the dependency needs to be represented anyways in any
> other packages that depend on the gem, an explicit dependency on rubygem
> (gemname) might not be a bad idea.
> 
In the old guidelines, rubygems were distinct from plain ruby packages.
This was because at the time they were written:
  require 'rubylibrary'

imported a plain ruby library and:
  gem_require 'rubylibrary'

The had wholly different syntax at the source code level.  The piece of
vondruch's draft that stated that non-gem subpackages were no longer needed
for gem packages lead me to find that the rubygems package now sets up the
ruby library path so that "require 'rubylibrary'" works for both gems and
nongems.  With that change, we don't need to package all ruby libraries in
a non-gem version and the need to have separate requires and provides
lessens.  (The caveat here is that ruby code would need to have require
'rubygems' somewhere early in its code but if that's considered sufficiently
compatible for one of these cases, then it's sufficient for both cases)

When might you absolutely need to use Require: rubygem()?  I know of the
specific case when you are requiring a specific version of code via::
  gem 'rubylibrary'

I also imagine that there's ways that ruby code can make use of the metadata
that gems provide but I don't know how to detect those.  In either of those
cases, the rubygem() require would seem to be most appropriate.

When might you want to use the Require ruby() version?   When a package's
code uses plain "require 'rubylibrary'", it would work whether the rpm
package is shipping a rubygem or a plain ruby library.  Therefore, if the
packager dosn't want to guess whether we're shipping the relevant library as
a rubygem or as a non-gem ruby library, they should be able to do a simple
"Requires: ruby(library)".  If the packager knows that we package that
pacticular library as a rubygem, they can use  the rubygem() version of the
requires instead but they are no longer required to in this case.

So I think answering your question,  whether the dependency is satisfied by
a gem or non-gem library is no longer of interest in the simple case of
a script or piece of code using "require 'rubylibrary'".  For places where
it does matter, the Guideline should require using Requires: rubygem() (if
you have a list of other things to look for, that could be added to flesh
out that section).  

>   - Binary Extensions  - gem install then recompile doesn't make alot of sense
> when the other alternative, gem unpack, patch, rebuild, and them install would
> work in both cases. Why is this split out like this?
> 
I'm not sure I understand this.  Are you referring to the draft guideline
that vondruch originally proposed with the many separate pages or the
changes that I have been making to have only a single case?  The single case
does the gem unpack, patch, rebuild (via gem install), and finally install
via mkdir/cp/mv.

I've forked this to this page:
https://fedoraproject.org/wiki/User:Toshio/RubyPackagingDraft

for now so that people can better see what that proposal looks like.  I'll
have to keep the two pages in sync for a bit until someone does or does not
bring up a rubygem where the reduced-complexity guidelines are as direly
broken as people are claiming.

>   - the rspec package will soon finally be updated to rspec2 so the BR:
> rspec-core in the test guidelines can be changes to a BR: rspec

Nice.  Can you specify what versions of Fedora that will be operable on?
It's nice to note things like that in the Guidelines.

> 
> 
> Answers to specific questions expressed in the draft:
> 
> - Interpreter independence - seems reasonable, how we address supporting these
> libraries on multiple interpreters needs to be flushed out, abliet not
> necessarily for this release as time is short
> 
> - Move text about interpreter independence to here - seems reasonable to me
>
So -- vondruch seems to have issues with this.  Code doesn't seem to be
entirely interpreter independent?  Or rather, only certain code is?  The FPC
really needs to understand this portion of the issue better as it affects
things like where the directories belong in the FHS, whether it makes sense
to share rubygems across interpreters and whether it makes sense to share
vendorlib or vendorarch across interpreters.  Example srpms are the best way
to make clear what's happening here :-).

Note that when you talk about this being possibly something for later
releases -- unfortunately, that seems to be an underlying assumption of the
draft guidelines that we were presented with so we need to be able to get
correct the parts that make sense.

> - Confirm change (remove ruby(rubygems) dep) - also seems reasonable to me
> 
I've finalized this.

> - Give examples? and Do we want to tell what the arguments to gem install do? -
> both would be appreciated
> 
heh :-)  Unfortunately, I don't believe we've had a ruby person on the FPC
since lutter (who came up with the original guidelines).  So if examples and
explanations of arguments are desired, I'll need to recieve them from people
who use ruby.

> - Replacement instructions - as discussed not a huge fan of this
> 
Unless someone can present examples where this doesn't work that aren't
flaws with upstream code, this is likely to become the way to do things.

> - Library placement - the bit about 'foo' is somewhat confusing, perhaps
> replacing it with something like "[ext|lib]" or similar would work instead?
> 
Yeah -- this was in the portion of the guidelines to be replaced.  In my
draft, I've simply removed that section (as it's already in the previous
section where I renamed it $REQUIRE_PATHS with a comment about where
$REQUIRE_PATHS comes from)

-Toshio
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