Re: [Caml-list] Package installation assumptions made by odb

["Török Edwin" <edwintorok@gmail.com>]

On 02/13/2012 03:39 PM, Romain Bardou wrote:
> Le 13/02/2012 14:04, Edgar Friendly a écrit :
>> On 02/13/2012 06:01 AM, Arnaud Spiwack wrote:
>>> I see an immediate problem with packages that install several executable
>>> files (for instance, Melt provides a library and a collection of tools,
>>> none of them named melt, by the way). I haven't spent time looking more
>>> than superficially into oasis or odb yet, but it strikes me as a
>>> possibly important limitation.
>>>
>>
>> It looks like the executable is now named melt-build. In this case, odb
>> would expect the melt project name to be "melt-build" so that its simple
>> logic can detect if melt is already installed. This does not have any
>> affect beyond changing the name that must be typed on the command line
>> to install melt (`odb melt-build` instead of `odb melt`), and the name
>> for dependencies by other projects (projects depending on melt would
>> have to specify `dep=melt-build` instead of `dep=melt`).
>>
>> Also, if melt installs an ocamlfind library named melt, then its odb
>> package name could be melt or melt-build, depending on which part of
>> melt should be used to detect its installation. At the moment, odb
>> doesn't really do version handling (mainly because it's difficult to get
>> a version number from an executable), although this is a weakness where
>> odb might improve.
>>
>> This assumption of executables and libraries being named the same as the
>> package isn't critical to the design of odb, it's just a simplifying
>> assumption that works quite well (and would work for melt up to the last
>> version when its executable was renamed). If there's good reason to have
>> more complex installed-program detection, this is easily doable, but the
>> workarounds are simple enough at the moment that this doesn't seem to be
>> a problem.
>>
>> E.
>>
> 
> Hello,
> 
> I agree with Arnaud: although this behavior is simple to implement and understand (which is good) I see several cases where it would be a problem. For instance, I'm currently working on a suite of
> tools named like foo-feature1, foo-feature2, foo-feature3 and so on. The package would obviously be named foo, but it does not make sense to have a single "foo" executable. It does not make sense to
> have once package per executable either. So I guess you need some way to override this behavior when needed. Can odb extract this kind of information from an _oasis file, or from a META file? I'm not
> very familiar with those.
> 
> Regarding Melt, I'm a bit confused: you say in this mail that "its odb
> package name could be melt or melt-build, depending on which part of
> melt should be used to detect its installation". But in your guidelines it is written: "Programs that are both should do both". By the way, Melt actually installs two libraries: Melt and Latex.
> 
> Regarding the version number, if you need to define a standard I think it would be good if this standard was to call the executable with the "-version" option. It is, after all, the behavior of
> "ocamlc". This does not work for libraries though; here there are several possibilities:
> - compute a hash of the .cma / .cmxa, but you need a database of hashtables -> version;
> - dynamically link with the .cma / .cmxa, assuming a module "Version" with a variable containing the version (but this is not very practical for many reasons).

- Use the 'version' from the library's META file (if any):
$ ocamlfind query -format '%v' sexplib
7.0.4


Best regards,
--Edwin