Use @preferred_cli_env

[josevalim]

Elixir provides the ability to use @preferred_cli_env directly on the task since version v1.3.0. This PR declares those attributes by default.

Keep in mind that:

1. This won't work for Elixir versions earlier than v1.3.0. If you still support them, you may want to add the line about preferred_cli_env back to the README

2. The README will be outdated as soon as this is merged, so you may want to consider a new release

Thank you! ❤️

[coveralls]

Coverage remained the same at 92.26% when pulling e5e00f7 on josevalim:master into 9721961 on parroty:master.

[joshsmith]

Thanks @josevalim! ❤️ 💚 💜 💛 💙

@parroty LGTM whenever you have a chance to cut a new release.

[parroty]

Thanks, I wasn't aware of the feature, and will be updating the release ❤️.

[parroty]

Hi @josevalim.
I'm trying to apply this preferred_cli_env to other locations, but facing some errors. I'm wondering about what the good practice definition is like.
(I think I'm misunderstanding something but any helps are appreciated. Also, I'm sorry about spreading around bad practices 😓.)

1. Test dependency

If I try to remove the definition from excoveralls' mix.exs like 497b2f6 , module Mock is not loaded is occuring.

It seems modified preferred_cli_env allows to identify mix coveralls task (without MIX_ENV=test, but it seems test only dependencies are not loading (MIX_ENV=test mix coveralls works). How they should be defined?

$ mix coveralls
** (CompileError) test/circle_test.exs:3: module Mock is not loaded and could not be found
    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
    (elixir) lib/code.ex:370: Code.require_file/2
    (elixir) lib/kernel/parallel_require.ex:57: anonymous fn/2 in Kernel.ParallelRequire.spawn_requires/5

$ MIX_ENV=test mix coveralls
----------------
COV    FILE                                        LINES RELEVANT   MISSED
 44.4% lib/excoveralls.ex                            105       18       10
 93.3% lib/excoveralls/circle.ex                      72       15        1
 88.9% lib/excoveralls/conf_server.ex                 44        9        1
 50.0% lib/excoveralls/cover.ex                       43       10        5
100.0% lib/excoveralls/exceptions.ex                  11        0        0
100.0% lib/excoveralls/html.ex                        43       12        0
100.0% lib/excoveralls/html/safe.ex                   28        2        0
 90.0% lib/excoveralls/html/view.ex                   44       10        1
100.0% lib/excoveralls/json.ex                        39       10        0
100.0% lib/excoveralls/local.ex                      148       49        0
100.0% lib/excoveralls/path_reader.ex                 20        2        0
 80.0% lib/excoveralls/post.ex                        33        5        1
 85.7% lib/excoveralls/poster.ex                      47       14        2
 92.9% lib/excoveralls/semaphore.ex                   67       14        1
100.0% lib/excoveralls/settings.ex                    89       19        0
100.0% lib/excoveralls/stat_server.ex                 21        4        0
100.0% lib/excoveralls/stats.ex                      223       60        0
100.0% lib/excoveralls/stop_words.ex                  37        7        0
100.0% lib/excoveralls/sub_apps.ex                    21        5        0
100.0% lib/excoveralls/task/util.ex                   43        1        0
 88.9% lib/excoveralls/travis.ex                      39        9        1
 95.8% lib/mix/tasks.ex                              215       48        2
[TOTAL]  92.3%

2. Loading mix tasks from test dependency

I' trying to load updated library from other project like the following, but fails to identify mix tasks.

• parroty/extwitter@f6aa8f6

It's defined as {:excoveralls, "~> 0.6", only: :test},, but this should be modified too? (ex. make it as only: [:dev, :test] works though).

➜  extwitter git:(fix/preferred_cli_env) mix coveralls
** (Mix) The task "coveralls" could not be found

Current environment is

$ elixir -v
Erlang/OTP 19 [erts-8.2] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Elixir 1.4.2

[josevalim]

(I think I'm misunderstanding something but any helps are appreciated. Also, I'm sorry about spreading around bad practices 😓.)

It was not a bad practice, it was the only way to do until more recent Elixir versions. :) I will investigate what is happening.

[josevalim]

Ok, this has actually been a misunderstanding from my side. @preferred_cli_env only applies to tasks in the current project. I was not quite aware of this limitation before but I don't think we can fix it.

So I would recommend reverting my changes and adding the previous recommendations back to the README. I will update Elixir documentation to make this clearer. Sorry for the confusion! :(

[parroty]

Thanks for checking! I'll update the README.