[erlang-questions] Rebar dependency recursion

Fredrik Linder <>
Thu Nov 1 20:10:31 CET 2012


-r: +1

/Fredrik

On 1 nov 2012, at 12:00, Tim Watson <> wrote:

> This is all fine, but it's mighty annoying to have run rebar repeatedly because you want to get-deps first then do something else. 
> 
> Modules already have a way to indicate that they want recursion - preprocess/2.  Can this be extended so that modules can say 'I want recursion' or [predirs] or ok/nothing? Then you'd get a nice interplay where rebar_deps says [predirs] and rebar_compile says 'yes please' to the recursion into those predirs but rebar_templater says 'no thanks' to them and you can chain commands cleanly without invoking rebar multiple times.
> 
> In that scheme, -r means 'override the guys who said no to recrusion'
> 
> Sent from my iPhone.
> 
> On 1 Nov 2012, at 17:07, Tuncer Ayaz <> wrote:
> 
>> On Thu, Nov 1, 2012 at 5:47 PM, Eric Merrit wrote:
>>> Guys,
>>> 
>>> I have been talking with Tuncer and seeing the various bits on going
>>> on about handling dependency recursion in rebar. That is `skip_deps`
>>> vs `-r`. When you mix into that things like config inheritance it
>>> becomes a mess. I thought I would see if I can get some consensus on
>>> the matter. Just as a short FYI, here are some issues on this topic.
>>> 
>>> * https://github.com/basho/rebar/issues/303
>>> * https://github.com/basho/rebar/issues/275
>>> * https://github.com/basho/rebar/pull/293 - (this has been merged)
>>> 
>>> I think the default case in rebar is that you *do not want it to
>>> recurse*. Only in the case of a `get-deps` followed by a `compile`
>>> do you want to do things recursively. This is almost always true in
>>> my case, other`s experiences may vary.
>>> 
>>> That being the case I think the default behavior should be the
>>> non-recursive option and you explicitly tell rebar to recurse with
>>> the `-r`. As a variation it will probably be worthwhile to support a
>>> list of applications to talk about app specific recursion. In this
>>> model `-r`/`--recursive` would do recursion as it normally does
>>> while `--recursive=app1,app2,app3` would only recurse into app1,
>>> app2 and app3 respectively. There is a branch implementing basic
>>> -r/--recursive linked in rebar/issues/303 (dss-fix-skip-deps).
>>> 
>>> This seems to be the most simplest solution to the problem and
>>> doesn't really introduce new semantics though it does inverse
>>> semantics. The downside to this is that its backwards incompatible.
>>> However, we are coming up on a new major version so it's a good
>>> opportunity to do backwards incompatible changes. I don't see a
>>> solid way for rebar to automatically decide which tasks to carry out
>>> recursively and which not considering you can have many variations
>>> of commands to run in a single rebar invocation.
>>> 
>>> In any case, it would be nice to settle the issue, with either
>>> `skip_deps` is the way going forward or we will be moving to the
>>> `-r`. Obviously, I would like to see the `-r` option, but settling
>>> the issue on way or the other is best.
>> 
>> All solutions considered so far, I think introducing an explicit
>> -r/--recursive as found in dizzy's dss-fix-skip-deps branch is a good
>> solution.
>> 
>> If someone can come up with a solid way to make rebar aware of what
>> commands are going to be run and use that as a way to dynamically
>> enable/disable recursion, I'd be very interested to read that. I hope
>> there is a better solution which keeps the ease of use for the initial
>> 'get-deps compile' step while not forcing us to use skip_deps and/or
>> apps=/skip_apps= afterwards. Config inheritance is a related problem
>> and discussed in the above ticket #275.
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