credo-custom-checks

Credo Custom Checks

Creating custom Credo checks for project-specific rules.

Creating a Custom Check

defmodule MyApp.Credo.Check.NoHardcodedSecrets do
  use Credo.Check,
    category: :warning,
    base_priority: :high,
    explanations: [
      check: """
      Detects hardcoded secrets in code.
      """
    ]

@impl true def run(%SourceFile{} = source_file, params) do issue_meta = IssueMeta.for(source_file, params)

Credo.Code.prewalk(source_file, &traverse(&1, &2, issue_meta))

end

defp traverse( {:@, _, [{:secret_key, _, [value]}]} = ast, issues, issue_meta ) when is_binary(value) do new_issue = issue_for(issue_meta, value) {ast, [new_issue | issues]} end

defp traverse(ast, issues, _issue_meta) do {ast, issues} end

defp issue_for(issue_meta, value) do format_issue( issue_meta, message: "Hardcoded secret found: #{String.slice(value, 0..5)}...", trigger: value ) end end

## Using Custom Checks

```elixir
# .credo.exs
%{
  configs: [
    %{
      name: "default",
      requires: ["./lib/my_app/credo/check/*.ex"],
      checks: %{
        enabled: [
          {MyApp.Credo.Check.NoHardcodedSecrets, []}
        ]
      }
    }
  ]
}