[Caml-list] Conditional BuildDepends in OASIS

[Caml-list] Conditional BuildDepends in OASIS

[Dario Teixeira]

Hi,

I'm in the process of oasifying PG'OCaml, and I've hit a snag.
By default PG'OCaml depends on ExtLib, but it's possible to
use Batteries instead.  Below is a fragment of my (naïve) first
attempt at telling OASIS about this configuration option:


Flag "use_batteries"
  Description: Use Batteries instead of ExtLib
  Default: false

Library "pgocaml"
  Path:                 src
  Modules:              PGOCaml
  BuildTools:           ocamlbuild, camlp4
  BuildDepends:         calendar
  if flag(use_batteries)
    BuildDepends+:      batteries
    ByteOpt+:           -ppopt -DUSE_BATTERIES
    NativeOpt+:         -ppopt -DUSE_BATTERIES
  else
    BuildDepends+:      extlib

The problem is that OASIS complains about BuildDepends being

placed inside a conditional.  Is this an oversight, or are there good
reasons (and hopefully a standard workaround) for this limitation?

Thanks in advance!
Cheers,
Dario Teixeira

Re: [Caml-list] Conditional BuildDepends in OASIS

[Anil Madhavapeddy]

The Cohttp library generates sub-libraries which can be conditional
based on a flag (which has a portable functorised core, and then an
Async, Mirage or Lwt instance depending on what's available)
https://github.com/avsm/ocaml-cohttp/blob/master/_oasis

However, your use case seems a little different, as I presume the
external interface of pgocaml doesn't vary by your choice of Extlib
or Batteries?

Despite this, it might be easier just to define a "pgocaml.batteries"
and "pgocaml.extlib" and leave the choice with the user as to which
one they would like to select.  You can make the dependency optional
at compile time so the package doesn't generated; e.g.

Library cohttp_lwt_unix
  Build$: flag(lwt)
  Install$: flag(lwt)
  Path: lwt
  Findlibname: lwt
  FindlibParent: cohttp
  BuildDepends: lwt.unix, uri, cohttp, lwt.ssl, lwt.syntax
  Modules: Cohttp_lwt_unix, (etc...)


-anil

On 25 Oct 2012, at 06:57, Dario Teixeira <darioteixeira@yahoo.com> wrote:

> Hi,
> 
> I'm in the process of oasifying PG'OCaml, and I've hit a snag.
> By default PG'OCaml depends on ExtLib, but it's possible to
> use Batteries instead.  Below is a fragment of my (naïve) first
> attempt at telling OASIS about this configuration option:
> 
> 
> Flag "use_batteries"
>   Description: Use Batteries instead of ExtLib
>   Default: false
> 
> Library "pgocaml"
>   Path:                 src
>   Modules:              PGOCaml
>   BuildTools:           ocamlbuild, camlp4
>   BuildDepends:         calendar
>   if flag(use_batteries)
>     BuildDepends+:      batteries
>     ByteOpt+:           -ppopt -DUSE_BATTERIES
>     NativeOpt+:         -ppopt -DUSE_BATTERIES
>   else
>     BuildDepends+:      extlib
> 
> The problem is that OASIS complains about BuildDepends being
> 
> placed inside a conditional.  Is this an oversight, or are there good
> reasons (and hopefully a standard workaround) for this limitation?
> 
> Thanks in advance!
> Cheers,
> Dario Teixeira
> 
> 
> -- 
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs

Re: [Caml-list] Conditional BuildDepends in OASIS

[Dario Teixeira]

Hi,


Thanks for the suggestions, Anil!

> However, your use case seems a little different, as I presume the
> external interface of pgocaml doesn't vary by your choice of Extlib
> or Batteries?

Indeed.

> Despite this, it might be easier just to define a "pgocaml.batteries"
> and "pgocaml.extlib" and leave the choice with the user as to which
> one they would like to select.  You can make the dependency optional
> at compile time so the package doesn't generated; e.g.
> 
> Library cohttp_lwt_unix
>   Build$: flag(lwt)
>   Install$: flag(lwt)
>   Path: lwt
>   Findlibname: lwt
>   FindlibParent: cohttp
>   BuildDepends: lwt.unix, uri, cohttp, lwt.ssl, lwt.syntax
>   Modules: Cohttp_lwt_unix, (etc...)

That would be a satisfactory solution.  I did run into a different problem, though.
I told OASIS that "pgocaml.batteries" and "pgocaml.extlib" should have "pgocaml"
as their findlib parent (fragment below).  Unfortunately, OASIS complains that
library "pgocaml" does not exist.  How would I tell OASIS that "pgocaml" is a
dummy library?

Flag "batteries"
  Description: Use Batteries
  Default: true

Library "pgocaml_batteries"
  Build$:               flag(batteries)
  Install$:             flag(batteries)
  Path:                 src
  Modules:              PGOCaml
  BuildDepends:         calendar, batteries
  ByteOpt+:             -ppopt -DUSE_BATTERIES
  NativeOpt+:           -ppopt -DUSE_BATTERIES
  FindlibParent:        pgocaml
  Findlibname:          batteries

Thanks again for your attention!
Cheers,
Dario

Re: [Caml-list] Conditional BuildDepends in OASIS

[Anil Madhavapeddy]

On 26 Oct 2012, at 10:56, Dario Teixeira <darioteixeira@yahoo.com> wrote:
> 
> That would be a satisfactory solution.  I did run into a different problem, though.
> I told OASIS that "pgocaml.batteries" and "pgocaml.extlib" should have "pgocaml"
> as their findlib parent (fragment below).  Unfortunately, OASIS complains that
> library "pgocaml" does not exist.  How would I tell OASIS that "pgocaml" is a
> dummy library?
> 
> Flag "batteries"
>   Description: Use Batteries
>   Default: true
> 
> Library "pgocaml_batteries"
>   Build$:               flag(batteries)
>   Install$:             flag(batteries)
>   Path:                 src
>   Modules:              PGOCaml
>   BuildDepends:         calendar, batteries
>   ByteOpt+:             -ppopt -DUSE_BATTERIES
>   NativeOpt+:           -ppopt -DUSE_BATTERIES
>   FindlibParent:        pgocaml
>   Findlibname:          batteries

You could just put a dummy library in place (which shouldn't be used by anything
since you don't have to mark a dependency of a findlib child on the parent
library, as far as I understand it.

However, is there a common subset of your code that is portable without either
Batteries or Extlib?  Factoring that out into a core library that both of the
other ones depend on would make future ports (e.g., to Core or Lwt) easier.

Of course, this is easier said than done when dealing with replacement standard
libraries which redefine very common library functions!  It's a lot easier when
factoring over I/O libraries like Lwt vs Async where a straightforward functor
abstraction exists.

-anil

[Caml-list] Re: Conditional BuildDepends in OASIS

[Sylvain Le Gall]

On 26-10-2012, Dario Teixeira <darioteixeira@yahoo.com> wrote:
> Hi,
>
>
> Thanks for the suggestions, Anil!
>
>> However, your use case seems a little different, as I presume the
>> external interface of pgocaml doesn't vary by your choice of Extlib
>> or Batteries?
>
> Indeed.
>
>> Despite this, it might be easier just to define a "pgocaml.batteries"
>> and "pgocaml.extlib" and leave the choice with the user as to which
>> one they would like to select.  You can make the dependency optional
>> at compile time so the package doesn't generated; e.g.
>> 
>> Library cohttp_lwt_unix
>>   Build$: flag(lwt)
>>   Install$: flag(lwt)
>>   Path: lwt
>>   Findlibname: lwt
>>   FindlibParent: cohttp
>>   BuildDepends: lwt.unix, uri, cohttp, lwt.ssl, lwt.syntax
>>   Modules: Cohttp_lwt_unix, (etc...)
>
> That would be a satisfactory solution.  I did run into a different problem, though.
> I told OASIS that "pgocaml.batteries" and "pgocaml.extlib" should have "pgocaml"
> as their findlib parent (fragment below).  Unfortunately, OASIS complains that
> library "pgocaml" does not exist.  How would I tell OASIS that "pgocaml" is a
> dummy library?
>
> Flag "batteries"
>   Description: Use Batteries
>   Default: true
>
> Library "pgocaml_batteries"
>   Build$:               flag(batteries)
>   Install$:             flag(batteries)
>   Path:                 src
>   Modules:              PGOCaml
>   BuildDepends:         calendar, batteries
>   ByteOpt+:             -ppopt -DUSE_BATTERIES
>   NativeOpt+:           -ppopt -DUSE_BATTERIES
>   FindlibParent:        pgocaml
>   Findlibname:          batteries
>

Having pgocaml.batteries and pgocaml.extlib is the best solution,
depending on a flag is perfect. Congrat to have find it yourself ;-)
(don't forget to CC me directly if you want a quicker response, I am a
little bit overloaded and don't spend much time reading caml-list).

Concerning FindlibParent that complains about non-existing pgocaml, you
should use FindlibContainers rather than FindlibParent.

E.g:

Library "pgocaml_batteries"
  Build$:               flag(batteries)
  Install$:             flag(batteries)
  Path:                 src
  Modules:              PGOCaml
  BuildDepends:         calendar, batteries
  ByteOpt+:             -ppopt -DUSE_BATTERIES
  NativeOpt+:           -ppopt -DUSE_BATTERIES
  FindlibContainers:    pgocaml
  Findlibname:          batteries

Containers are virtual by default...

Although, this something I am not proud of and in the upcoming oasis 0.4.0 everything
will go to "FindlibName: pgocaml.batteries" and OASIS will sort
parent/containers/library itself.

Cheers,
Sylvain Le Gall
-- 
My company: http://www.ocamlcore.com
Linkedin:   http://fr.linkedin.com/in/sylvainlegall
Start an OCaml project here: http://forge.ocamlcore.org
OCaml blogs:                 http://planet.ocamlcore.org

Re: [Caml-list] Re: Conditional BuildDepends in OASIS

[Dario Teixeira]

Hi,

> Having pgocaml.batteries and pgocaml.extlib is the best solution,

> depending on a flag is perfect. Congrat to have find it yourself ;-)
> (don't forget to CC me directly if you want a quicker response, I am a
> little bit overloaded and don't spend much time reading caml-list).
> 
> Concerning FindlibParent that complains about non-existing pgocaml, you
> should use FindlibContainers rather than FindlibParent.

Thank you Sylvain and Anil for your suggestions!

Using FindlibContainers does solve the virtual package problem, but
in the meantime I've run into a perplexing issue involving Camlp4.
Here's the relevant fragment from the _oasis file:

BuildTools:             ocamlbuild, camlp4o

Flag "batteries"
  Description: Use Batteries
  Default: true

Library "pgocaml_batteries"
  Build$:               flag(batteries)
  Install$:             flag(batteries)
  Path:                 src
  Modules:              PGOCaml
  BuildDepends:         calendar, csv, pcre, batteries, camlp4.macro
  FindlibContainers:    pgocaml
  Findlibname:          batteries
  ByteOpt+:             -ppopt -DUSE_BATTERIES
  NativeOpt+:           -ppopt -DUSE_BATTERIES

Library "pa_pgocaml_batteries"
  Build$:               flag(batteries)
  Install$:             flag(batteries)
  Path:                 src
  Modules:              Pa_pgsql
  BuildDepends:         pgocaml.batteries, camlp4.macro, camlp4.quotations.o, camlp4.extend
  FindlibContainers:    pgocaml.batteries
  FindlibName:          syntax
  ByteOpt+:             -ppopt -DUSE_BATTERIES
  NativeOpt+:           -ppopt -DUSE_BATTERIES

The problem occurs during the compilation of pa_pgocaml_batteries.
OCamlbuild issues the command below to determine dependencies,
which is manifestly wrong, since there is a "-syntax camlp4o" missing.

ocamlfind ocamldep -package pcre -package extlib -package csv -package camlp4.quotations.o -package camlp4.macro -package camlp4.extend -package calendar -package batteries -modules src/pa_pgsql.ml > src/pa_pgsql.ml.depends

What I find perplexing is that the compilation of pgocaml_batteries had succeeded,
so the required "-syntax camlp4o" must have had been given then, though at first
glance I can see no applicable difference in their declarations.

Any idea on what's going on?

Thanks again for your time!
Cheers,
Dario

Re: [Caml-list] Re: Conditional BuildDepends in OASIS

[Anil Madhavapeddy]

On 1 Nov 2012, at 15:18, Dario Teixeira <darioteixeira@yahoo.com> wrote:
> 
> Library "pa_pgocaml_batteries"
>   Build$:               flag(batteries)
>   Install$:             flag(batteries)
>   Path:                 src
>   Modules:              Pa_pgsql
>   BuildDepends:         pgocaml.batteries, camlp4.macro, camlp4.quotations.o, camlp4.extend

>   FindlibContainers:    pgocaml.batteries
>   FindlibName:          syntax
>   ByteOpt+:             -ppopt -DUSE_BATTERIES
>   NativeOpt+:           -ppopt -DUSE_BATTERIES
> 
> The problem occurs during the compilation of pa_pgocaml_batteries.
> OCamlbuild issues the command below to determine dependencies,
> which is manifestly wrong, since there is a "-syntax camlp4o" missing.
> 
> ocamlfind ocamldep -package pcre -package extlib -package csv -package camlp4.quotations.o -package camlp4.macro -package camlp4.extend -package calendar -package batteries -modules src/pa_pgsql.ml > src/pa_pgsql.ml.depends
> 
> What I find perplexing is that the compilation of pgocaml_batteries had succeeded,
> so the required "-syntax camlp4o" must have had been given then, though at first
> glance I can see no applicable difference in their declarations.
> 

It's probably your _tags file that is missing a:

<**/*.ml>: syntax_camlp4o

for the syntax extension.  OASIS doesn't fully support using syntax extensions yet, so you need to be careful to keep the _tags file manually in sync.

-anil

Re: [Caml-list] Re: Conditional BuildDepends in OASIS

[Dario Teixeira]

Hi,

> It's probably your _tags file that is missing a:

> 
> <**/*.ml>: syntax_camlp4o
> 
> for the syntax extension.  OASIS doesn't fully support using syntax 
> extensions yet, so you need to be careful to keep the _tags file manually in 
> sync.

Thanks Anil, you were spot on -- the problem was indeed in the _tags file.

Anyway, most of the process of oasifying PG'OCaml is now complete,
and I took the time also for a general cleanup of the project.  The code
can be fetched from the SVN repo:

svn export svn://scm.ocamlcore.org/svn/pgocaml/branches/oasification

As discussed previously, the project can be compiled against Batteries
and/or ExtLib.  Users should reference findlib package's pgocaml.batteries
and  pgocaml.batteries.syntax if using Batteries, for example.


It would be very helpful if PG'OCaml users and packagers were to give
me some feedback concerning the new version.  Most stuff is working,
there being only a few minor outstanding issues:

- To build the documentation, "make doc" has to be issued twice!

- The highlevel test isn't compiling.  For some reason OASIS is
  ignoring the BuildDepends directive.
- OASIS issues a warning during setup.  This seems to be a known
  bug in OASIS, however:

  https://forge.ocamlcore.org/tracker/index.php?func=detail&aid=1043&group_id=54&atid=291


Best regards,
Dario Teixeira