[erlang-questions] Rebar dependency recursion

Tim Watson <>
Thu Nov 1 20:00:24 CET 2012


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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