Dialyzer Configuration

Dialyzer is a static analysis tool for Erlang and Elixir that identifies software discrepancies such as type errors, unreachable code, and unnecessary tests.

Configuration Files

dialyzer.ignore-warnings

Ignore specific warnings

lib/my_module.ex:42:pattern_match_cov

.dialyzer_ignore.exs

[ {"lib/generated_code.ex", :no_return}, {~r/lib/legacy/.*/, :unknown_function} ]

mix.exs Configuration

def project do [ app: :my_app, dialyzer: [ plt_add_apps: [:mix, :ex_unit], plt_core_path: "priv/plts", plt_file: {:no_warn, "priv/plts/dialyzer.plt"}, flags: [:error_handling, :underspecs, :unmatched_returns], ignore_warnings: ".dialyzer_ignore.exs", list_unused_filters: true ] ] end

Common Configuration Options

PLT Management

• plt_add_apps : Additional applications to include in PLT

• plt_core_path : Directory for core PLT files

• plt_file : Custom PLT file location

• plt_add_deps : Include dependencies (:app_tree , :apps_direct , :transitive )

Analysis Flags

• :error_handling

• Check error handling

• :underspecs

• Warn on under-specified functions

• :unmatched_returns

• Warn on unmatched return values

• :unknown

• Warn on unknown functions/types

• :overspecs

• Warn on over-specified functions

Filter Options

• ignore_warnings : File with warning patterns to ignore

• list_unused_filters : Show unused ignore patterns

Best Practices

• Incremental PLT Building: Use project-specific PLTs to speed up analysis

• Gradual Adoption: Start with subset of checks, expand over time

• CI Integration: Run Dialyzer in continuous integration

• Type Specs: Add comprehensive @spec annotations

• Warning Management: Document intentional ignores

Common Patterns

Conditional Analysis

if Mix.env() in [:dev, :test] do {:dialyxir, "~> 1.4", only: [:dev, :test], runtime: false} end

Custom Check Script

#!/bin/bash mix dialyzer --format github

GitHub Actions Integration

• name: Run Dialyzer run: mix dialyzer --format github