CoMix

Common mix.exs code that all projects can benefit from

Features

• CoMix.version/0: Enables easy versioning in any git project through git tags
  • One can run git flow release start $VERSION; git flow release finish $VERSION and be done
  • If git errors instead of getting a tag, and the environment variable CO_MIX_TAGLESS is set, a version suffixed with -tagless is used

Installation

Add this to the top of your mix.exs file:

unless Kernel.function_exported?(CoMix, :version, 0) do
  {:ok, _} = Application.ensure_all_started(:hex)
  Mix.install([{:co_mix, "~> 1.0", runtime: false}])
end

Then set version = CoMix.version() inside of the def project, instead of using a hardcoded version.

Troubleshooting

Issue: Adding the Mix.install line to mix.exs causes mix commands like mix deps.get to error:

  (exit) exited in: GenServer.call(Hex.Registry.Server, {:open, []}, 60000)
     (EXIT) no process: the process is not alive or there’s no process currently associated with the given name, possibly because its application isn’t started
    (elixir 1.13.4) lib/gen_server.ex:1019: GenServer.call/3
    (hex 1.0.1) lib/hex/remote_converger.ex:28: Hex.RemoteConverger.converge/2
    (mix 1.13.4) lib/mix/dep/converger.ex:95: Mix.Dep.Converger.all/4
    (mix 1.13.4) lib/mix/dep/converger.ex:51: Mix.Dep.Converger.converge/4
    (mix 1.13.4) lib/mix/dep/fetcher.ex:16: Mix.Dep.Fetcher.all/3
    (mix 1.13.4) lib/mix/tasks/deps.get.ex:31: Mix.Tasks.Deps.Get.run/1
    (mix 1.13.4) lib/mix/task.ex:397: anonymous fn/3 in Mix.Task.run_task/3
    (mix 1.13.4) lib/mix/cli.ex:84: Mix.CLI.run_task/2

Solution

Be sure to include the call to Application.ensure_all_started(:hex) before calling Mix.install/2, to explicitly ensure hex is started.

Issue: mix commands fail with Hex 2.0

Since updating to Hex 2.0, Mix commands fail with an error similar to

** (Protocol.UndefinedError) protocol String.Chars not implemented for %Hex.Solver.Constraints.Range{min: %Version{major: 0, minor: 2, patch: 0}, max: %Version{major: 0, minor: 3, patch: 0, pre: [0]}, include_min: true, include_max: false} of type Hex.Solver.Constraints.Range (a struct). This protocol is implemented for the following type(s): Atom, BitString, Date, DateTime, Float, Integer, List, NaiveDateTime, Time, URI, Version, Version.Requirement
    (elixir 1.14.1) lib/string/chars.ex:3: String.Chars.impl_for!/1
    (elixir 1.14.1) lib/string/chars.ex:22: String.Chars.to_string/1
    (hex 2.0.0) lib/hex/mix.ex:168: Hex.Mix.registry_dep_to_def/1
    (elixir 1.14.1) lib/enum.ex:1658: Enum."-map/2-lists^map/1-0-"/2
    (hex 2.0.0) lib/hex/mix.ex:120: anonymous fn/1 in Hex.Mix.to_lock/1
    (elixir 1.14.1) lib/enum.ex:1658: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.14.1) lib/enum.ex:1658: Enum."-map/2-lists^map/1-0-"/2
    (elixir 1.14.1) lib/map.ex:263: Map.new_from_enum/2

Solution

This is due to a known bug that was fixed in Elixir 1.14.2, update and try again.

Issue: Commands like mix local.hex --force are failing (common for Travis):

** (MatchError) no match of right hand side value: {:error, {:hex, {'no such file or directory', 'hex.app'}}}
    mix.exs:1: (file)
    (mix 1.13.2) lib/mix/cli.ex:42: Mix.CLI.load_mix_exs/0
    (mix 1.13.2) lib/mix/cli.ex:29: Mix.CLI.proceed/1
The command "mix local.hex --force" failed and exited with 1 during .

Solution

This is because mix.exs needs to ensure hex is started, so the machine needs to install hex first before mix can run with the updated mix.exs

1. cd over to a directory without a mix.exs
   • Short and to the point, cd will take you to the home dir, which is unlikely to have this file
2. Run whichever mix commands were failing
3. Run cd - to return to your previous directory, and proceed as usual

In .travis.yml, this usually looks something like

install:
  - cd
  - mix do local.rebar --force, local.hex --force
  - cd -

Issue: The release build is failing to upload from Travis:

Solution

First, make sure that everything is being run with MIX_ENV set the same (or defaulted)

There may be a script trying to pull the version by reading mix.exs A good solution to this that we've found is to look for and update these scripts:

• If they already have hex installed, go ahead and use mix app.version
  • If you don't have this command yet, it's easy to implement, see here (Archived)
• In other cases, it may be cleaner to have the script call the binary, after it has been built, with a version argument Such solutions can look like VERSION=$(_build/prod/rel/my_app/bin/my_app version | cut -d ' ' -f2)

Testing

Testing is done by running mix test.

Releasing

You should be using git flow here.

However, since this repo enables simplified versioning, we have chosen for the moment not to have it depend on itself.

As such, after running git flow release start <X.Y.Z>, you must create a commit bumping the version in mix.exs before running git flow release finish <X.Y.Z>.