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Elixir & Phoenix: Scalable Backend Development · Lesson

Documentation and Static Analysis with Dialyzer

Write self-documenting Elixir with doc attributes, typespecs, and doctests, then catch type errors before runtime using Dialyzer and Credo.

Documentation and Static Analysis with Dialyzer is a free Elixir & Phoenix: Scalable Backend Development lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Elixir & Phoenix: Scalable Backend Development learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Code That Explains Itself

Maintainable Elixir is well documented and statically checked. Elixir bakes documentation and type hints right into the language, and tools verify them automatically.

Module Documentation

Use @moduledoc for a module overview and @doc for each public function. These power generated docs and editor tooltips.

defmodule Calculator do
  @moduledoc "Simple arithmetic helpers."
  @doc "Adds two numbers."
  def add(a, b), do: a + b
end

Typespecs

@spec declares the types a function accepts and returns. It documents intent and feeds static analysis.

@spec add(number(), number()) :: number()
def add(a, b), do: a + b

Custom Types

Define reusable types with @type to keep specs readable.

@type user :: %{name: String.t(), age: non_neg_integer()}
@spec greet(user()) :: String.t()

Doctests

Examples in a @doc can double as tests. Write an iex prompt and expected output, then ExUnit runs them via doctest.

@doc """
    iex> Calculator.add(2, 3)
    5
"""
def add(a, b), do: a + b

Running Doctests

Hook doctests into your test module so they run with the rest of the suite. Now your docs can never go stale.

defmodule CalculatorTest do
  use ExUnit.Case
  doctest Calculator
end

Generating HTML Docs

ExDoc turns your moduledocs and specs into a polished HTML site. Add it as a dev dependency and run mix docs.

{:ex_doc, "~> 0.31", only: :dev, runtime: false}

What is Dialyzer?

Dialyzer performs success typing — it finds code that can never succeed (type mismatches, unreachable clauses, bad spec usage) without you annotating everything.

Dialyxir Workflow

The dialyxir wrapper makes Dialyzer easy. It builds a PLT (persistent lookup table) once, then checks fast.

{:dialyxir, "~> 1.4", only: :dev, runtime: false}
# mix dialyzer

Linting with Credo

Credo enforces style and surfaces refactoring opportunities — overly complex functions, inconsistent naming, code smells. Run it in CI to keep quality high.

# mix credo --strict

Putting It in CI

A healthy Elixir pipeline runs:

  • mix format --check-formatted
  • mix credo --strict
  • mix dialyzer
  • mix test (including doctests)

Together they keep the codebase consistent and correct.

Quick Check

Test your documentation and analysis knowledge.

Recap

You learned documentation and static analysis:

  • @moduledoc/@doc document modules and functions
  • @spec and @type declare types
  • Doctests keep examples verified
  • ExDoc generates HTML docs
  • Dialyzer finds type errors; Credo enforces style

These tools make Elixir codebases maintainable at scale.

Frequently asked questions

Is the “Documentation and Static Analysis with Dialyzer” lesson free?

Yes — the full text of “Documentation and Static Analysis with Dialyzer” is free to read here on the web, and the Elixir & Phoenix: Scalable Backend Development course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Elixir & Phoenix: Scalable Backend Development course, upgrade to CoddyKit PRO.

What will I learn in “Documentation and Static Analysis with Dialyzer”?

Write self-documenting Elixir with doc attributes, typespecs, and doctests, then catch type errors before runtime using Dialyzer and Credo. You practise Elixir & Phoenix: Scalable Backend Development with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Elixir & Phoenix: Scalable Backend Development?

No prior experience is required. Elixir & Phoenix: Scalable Backend Development on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Documentation and Static Analysis with Dialyzer” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Elixir & Phoenix: Scalable Backend Development lesson?

Yes. Every Elixir & Phoenix: Scalable Backend Development lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Popular Elixir Libraries and Tools
  2. Security Best Practices for Phoenix
  3. Writing Maintainable Elixir and Phoenix
  4. Documentation and Static Analysis with Dialyzer
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