[erlang-questions] Dependencies on library applications

Loïc Hoguin essen@REDACTED
Mon Dec 17 17:00:43 CET 2012

On 12/17/2012 04:54 PM, Garrett Smith wrote:
> On Mon, Dec 17, 2012 at 8:25 AM, Loïc Hoguin <essen@REDACTED> wrote:
>> On 12/17/2012 03:20 PM, Garrett Smith wrote:
>>> On Mon, Dec 17, 2012 at 3:05 AM, Loďc Hoguin <essen@REDACTED> wrote:
>>> -snip-
>>>> On 12/17/2012 04:48 AM, Anders Nygren wrote:
>>>>> In the documentation it says, in
>>>>> http://www.erlang.org/doc/design_principles/applications.html#id73720
>>>>> about the .app file
>>>>> "applications
>>>>> All applications which must be started before this application is
>>>>> started. systools uses this list to generate correct boot scripts.
>>>>> Defaults to [], but note that all applications have dependencies to at
>>>>> least kernel and stdlib."
>>>>> a few years ago I complained about an OTP application that did not
>>>>> list a library application that it depended on, but did not have to be
>>>>> started and was told that I was wrong.
>>>>> see, http://erlang.org/pipermail/erlang-bugs/2007-April/000333.html
>>>>> for more details
>>>> Alright.
>>>> But, directing my question to OTP guys now, wouldn't it be simpler if
>>>> we'd
>>>> list library applications there too? Building releases would be much
>>>> easier
>>>> if all dependencies were listed somewhere and it appears this has no
>>>> negative impact to put them in applications. Correct me if I'm wrong.
>>> Are you not talking about included applications?
>>> http://www.erlang.org/doc/design_principles/included_applications.html
>> No.
>> Included applications are normal applications that are included into another
>> application's supervision tree directly.
> You're just quoting the docs :)

No I know about them, because...

> They don't *have* to be included in anything -- but they are
> nonetheless listed as a dependency. The point is that they aren't
> started by init on behalf of your app.
> Does listing the app in the included_applications list present a
> particular problem for your case?

AFAIK, you can only have one application defined as an 
included_application anywhere. You can't have 2 applications depend on 
app_X with both listing it in included_applications.

That's pretty much all I know about them, but maybe I'm wrong. :)

Loïc Hoguin
Erlang Cowboy
Nine Nines

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