mix_credence

A mix credence command-line wrapper for the credence semantic linter.

Credence detects performance issues and non-idiomatic Elixir via AST analysis and automatically rewrites them — think mix format but for idioms. mix_credence lets you run it directly from the command line on specific files or glob patterns.

Installation

Add mix_credence to your dependencies in mix.exs. Because it's a dev/test tool, mark it runtime: false.

To pin a specific release tag:

def deps do
  [
    {:mix_credence, git: "https://github.com/chrislaskey/mix_credence", tag: "v0.1.0", only: [:dev, :test], runtime: false}
  ]
end

Or to always pull the latest from the main branch:

def deps do
  [
    {:mix_credence, git: "https://github.com/chrislaskey/mix_credence", branch: "main", only: [:dev, :test], runtime: false}
  ]
end

Then fetch:

mix deps.get

Usage

Pass one or more file paths, directories, or glob patterns:

# Directory (recursively finds all .ex and .exs files)
mix credence ./lib

# Single file
mix credence lib/my_app/router.ex

# Multiple explicit files
mix credence lib/my_app/router.ex lib/my_app/user.ex

# Glob pattern (quoted so the task expands it, works in all shells)
mix credence "lib/**/*.ex"

# Multiple glob patterns
mix credence "lib/**/*.ex" "test/**/*.exs"

Each matched file is read, passed through Credence.fix/2, and written back in place with the fixed source. Rules applied and any remaining issues are printed to the terminal.

Options

Flag	Description
`--check`	Report issues without modifying files. Exits with code `1` if any unfixable issues are found — useful for CI.
`-v` / `--verbose`	Show debug-level log output from the fix pipeline.

# Check mode — no writes, exit 1 on issues (good for CI)
mix credence --check "lib/**/*.ex"

# Verbose mode — see the full debug pipeline output
mix credence -v ./lib

Example output

lib/my_app/scores.ex: fixed
  Credence.Pattern.NoExplicitSumReduce (1)
  Credence.Pattern.NoSortThenReverse (1)

3 file(s) checked — 2 rule(s) applied, no remaining issues.

How it works

mix credence delegates entirely to the credence library. Each file is passed as a string to Credence.fix/2, which runs the code through three phases:

Syntax — fixes code that won't parse
Semantic — fixes compiler warnings (unused variables, undefined functions)
Pattern — rewrites ~117 AST-level anti-patterns to idiomatic Elixir

See the credence documentation for the full list of rules.

License

MIT