LexCredo provides custom Credo checks for Elixir projects, targeting anti-patterns that are commonly introduced by both AI coding agents and human developers.

The checks are drawn primarily from:

• Elixir's official anti-patterns guide
• Chris Keathley's "Good and Bad Elixir"

Available Checks

Design

• LexCredo.Check.Design.NoNestedModules — flags defmodule nested inside another defmodule. Each module should live in its own file.

Readability

• LexCredo.Check.Readability.DocExamplesSection (controversial) — flags @doc strings on public functions that are missing a ## Examples section.

Refactor

• LexCredo.Check.Refactor.NoEnumWrapperFunctions (controversial) — flags named functions whose entire body is a single Enum.* or Stream.* transformation call.

Warning

• LexCredo.Check.Warning.StructMatchInFunctionHead — flags %Struct{} = param at the top level of a function body when param is a plain-variable argument; moving the struct match to the function head makes the type visible in the signature and enables type inference.

• LexCredo.Check.Warning.NoComplexWithElse — flags with expressions whose else block exceeds max_else_clauses (default: 1).

• LexCredo.Check.Warning.NoEnumAllAssert (test files only) — flags assert Enum.all?/2 in tests; prefer a for loop with individual assertions that report the failing element.

• LexCredo.Check.Warning.NoProcessSleepInTests (test files only) — flags Process.sleep/1 and Process.alive?/1 in tests; use Process.monitor/1 and assert_receive instead.

• LexCredo.Check.Warning.NonBooleanWithStrictOperator — flags and/or/not when an operand is clearly non-boolean (struct field access without ? suffix, non-boolean literal, etc.); suggests &&/||/! to avoid a runtime ArgumentError and to signal truthy/falsy intent.

• LexCredo.Check.Warning.PreferBooleanOperators (controversial) — flags &&, ||, ! when at least one operand is clearly boolean-returning; prefer and, or, not.

• LexCredo.Check.Warning.UsePositiveTypeGuards — flags negated type guards in function heads (e.g. when not is_nil(x), when x != nil); use a precise positive guard instead.

• LexCredo.Check.Warning.UseStartSupervised (test files only) — flags direct GenServer.start_link/2 and similar calls in tests; use start_supervised!/1 for automatic cleanup.