# `ExDNA.Credo`
[🔗](https://github.com/elixir-vibe/ex_dna/blob/main/lib/ex_dna/integrations/credo.ex#L2)

## Basics

> #### This check is disabled by default. {: .neutral}
>
> [Learn how to enable it](`e:credo:config_file.html#checks`) via `.credo.exs`.

This check has a base priority of `higher` and works with any version of Elixir.

## Explanation

Code should not be copy-pasted in a codebase when there is room to
abstract the copied functionality in a meaningful way.

ExDNA detects three types of clones:

- **Type I** — exact copies (modulo whitespace/comments)
- **Type II** — same structure with renamed variables or different literals
- **Type III** — near-miss clones (similar structure with minor edits)

Each clone comes with a refactoring suggestion: extract function,
extract macro, or extract behaviour.

Run `mix ex_dna.explain N` for a detailed breakdown of any clone.

## Check-Specific Parameters

Use the following parameters to configure this check:

### `:min_mass`

  Minimum AST node count for a code fragment to be considered.

*This parameter defaults to* `30`.

### `:min_occurrences`

  Minimum number of code occurrences to label a clone

*This parameter defaults to* `2`.

### `:literal_mode`

  `keep` for exact clones only (Type-I), `abstract` to also detect renamed-variable clones (Type-II).

*This parameter defaults to* `:keep`.

### `:excluded_macros`

  List of macro names whose bodies are skipped entirely (e.g. `[:schema, :pipe_through]`).

*This parameter defaults to* `[]`.

### `:normalize_pipes`

  When `true`, `x |> f()` and `f(x)` are treated as identical.

*This parameter defaults to* `false`.

### `:min_similarity`

  Similarity threshold for near-miss clones (0.0–1.0). Values below 1.0 enable Type-III detection.

*This parameter defaults to* `1.0`.

### `:paths`

  Files or directories to analyze. Defaults to ExDNA's CLI default: lib/.

*This parameter defaults to* `["lib/"]`.

### `:ignore`

  Glob patterns to exclude from analysis.

*This parameter defaults to* `[]`.

## General Parameters

Like with all checks, [general params](`e:credo:check_params.html`) can be applied.

Parameters can be configured via the [`.credo.exs` config file](`e:credo:config_file.html`).

# `init`

Initializes ExDNA as a Credo plugin.

Registers the duplication check and disables the built-in `DuplicatedCode`.
Plugin params are forwarded as check params:

    plugins: [{ExDNA.Credo, [min_mass: 40, literal_mode: :abstract]}]

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*Consult [api-reference.md](api-reference.md) for complete listing*