Automated summary
Guides configuration of Dialyzer (through Dialyxir) for Erlang/Elixir projects: PLT management, analysis flags, warning ignore files, and CI integration.
Strengths
- Provides concrete config snippets for mix.exs, .dialyzer_ignore.exs, and dialyzer.ignore-warnings
- Covers PLT management (plt_add_apps, plt_core_path, plt_file, plt_add_deps) to speed up analysis
- Explains each analysis flag (:underspecs, :unmatched_returns, :error_handling, :overspecs, :unknown)
- Includes a GitHub Actions example using --format github plus incremental-adoption best practices
Limitations
- Covers only Mix/Dialyxir configuration, not raw dialyzer CLI usage or rebar3 setups
- Does not explain how to fix the reported warnings or how to write thorough @spec annotations
- Ignore-filter semantics (exact match vs regex, per-module scoping) are only lightly described
Use it when setting up or tuning Dialyzer static analysis in an Elixir/Erlang project, especially PLTs, analysis flags, and warning exclusions.
Skip it for non-Elixir/Erlang projects, or when the task is to diagnose and fix one specific Dialyzer warning rather than configure the tool.
Security analysis
SafeThe skill is purely documentation about Dialyzer configuration for Erlang/Elixir. It contains no instructions to execute destructive commands, exfiltrate data, obfuscate payloads, or disable safety mechanisms.
No concerns found
How this analysis is madeExamples
Add Dialyxir to my Elixir project with a project-local PLT in priv/plts, enable :underspecs and :unmatched_returns, and turn on list_unused_filters.Create a .dialyzer_ignore.exs that ignores :unknown_function warnings for everything under lib/legacy/ but keeps unused-filter reporting enabled.Add a GitHub Actions step that runs mix dialyzer --format github, and show the conditional mix.exs dependency setup for dev and test only.name: dialyzer-configuration description: Use when configuring Dialyzer for Erlang/Elixir type checking and static analysis. allowed-tools: []
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 PLTplt_core_path: Directory for core PLT filesplt_file: Custom PLT file locationplt_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 ignorelist_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
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Claude Code
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