Contributing to Ecto

Recently I sent a Pull Request to allow lateral joins in Ecto. Ecto as the documentation specifies is a domain specific language for writing queries and interacting with databases in Elixir.

I decided to test my code by writing a simple Phoenix app linked to my local Ecto repository to see if I was doing any progress, but I had a few issues trying to do it and that is exactly what made me write this post.

So, how do we use our custom Ecto with Phoenix?

The first thing I did was edit my mix.exs file and add my local ecto repository as a direct depedency of the project by setting the :path option, as below:

  defp deps do
    [
      # other dependencies ...,
      {:ecto, path: "/my/local/path/ecto"}
    ]
  end

This didn’t work since ecto is a dependency of a dependency (phoenix_ecto), so after running mix help deps I realized that I should add the :override option, since the documentation specifies the following:

:override - if set to true the dependency will override any other definitions of itself by other dependencies

Changing mix.exs again:

defp deps do
  [
    # other dependencies ...,
    {:ecto, path: "/my/local/path/ecto", override: true}
  ]
end

Turns out this still didn’t solve the problem, after running iex -S mix phoenix.new I got an error trying to compile phoenix_ecto, the reason probably being due to the stable phoenix_ecto expecting another version of ecto instead of master branch (which I was currently using).

To solve this problem we need to make our phoenix_ecto also point to master, since we don’t have a local phoenix_ecto repository how do we do this? Relying again on mix help deps we can see that it supports the :github and :branch options, just what we need:

defp deps do
  [
    # other dependencies ...,
    {:phoenix_ecto, github: "phoenixframework/phoenix_ecto", branch: "master"},
    {:ecto, path: "/my/local/path/ecto", override: true}
  ]
end

After running mix deps.get and iex -S mix phoenix.server we get the same problem with phoenix_html:

defp deps do
[
  # other dependencies ...,
  {:phoenix_ecto, github: "phoenixframework/phoenix_ecto", branch: "master"},
  {:phoenix_html, github: "phoenixframework/phoenix_html", branch: "master"},
  {:ecto, path: "/my/local/path/ecto", override: true}
]
end

And finally everything works fine after mix deps.get and iex -S mix phoenix.server.

That is all I wanted to show, hope it helps someone out there! Also, thank you Igor Florian for the help and for this awesome post about project dependencies.

See you in the next post!