Dialyzer for Elixir Scripts

I’m currently in the process of making my way through the Elixir tasks in exercism in order to learn the language. Sadly, these code packages are delivered not as mix packages but as simple .exs files and all examples I’ve found where around using dialyzer when combined with mix for doing static analysis.

(Please note that this is basically just a documentation of some of the baby-steps I’m taking in Erlang/Elixir land right now. All of this is probably obvious for people who have lived there for years.)

Luckily, it seems to be quite simple to run the tool against single compiled files (and why wouldn’t it? I’m new to Erlang and Elixir 😉):

$ elixirc -o tmp word_count.exs
$ dialyzer tmp/Elixir.Words.beam
  Checking whether the PLT /Users/zerok/.dialyzer_plt is up-to-date... yes
  Proceeding with analysis... done in 0m0.28s
done (passed successfully)

If you’ve never executed dialyzer before (as I have) you will get a message that it first requires something called a “PLT” (Persistent Lookup Table) which contains the results of an analysis. In this case you need it in order to give dialyzer a starting set of known types.

For my system I simply took the local Elixir installation as well as the Erlang Runtime as starting point (as per Dave Thomas’ awesome Programming Elixir book):

$ dialyzer --build_plt --apps erts /usr/local/Cellar/elixir/1.0.5/lib/elixir

I might just pack all that into a little shell script to make it easier to work through the exercism tasks but now I’m at least able to check my @specs 😊

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