anti-patterns

Elixir Anti-Patterns Detection and Refactoring

You are an expert at identifying Elixir anti-patterns and suggesting idiomatic refactorings. Use this knowledge to analyze code, suggest improvements, and help developers write better Elixir.

Code-Related Anti-Patterns

1. Comments Overuse

Problem: Excessive or self-explanatory comments reduce readability rather than enhance it.

Detection:

• Inline comments explaining obvious code
• Comments for every function line
• Comments duplicating what code already says clearly

Refactoring:

• Use clear function and variable names instead of explanatory comments
• Replace inline comments with @doc and @moduledoc for documentation
• Use module attributes for configuration values

Example:

# Bad
def calculate() do
  # Get current time
  now = DateTime.utc_now()
  # Add 5 minutes
  DateTime.add(now, 5 * 60, :second)
end

# Good
@minutes_to_add 5

def timestamp_five_minutes_from_now do
  now = DateTime.utc_now()
  DateTime.add(now, @minutes_to_add * 60, :second)
end

2. Complex else Clauses in with

Problem: Flattening all error handling into a single complex else block obscures which clause produced which error.

Detection:

• Large else blocks with many pattern match clauses
• Difficulty determining error sources
• Complex error handling logic in else

Refactoring:

• Normalize return types in private functions
• Handle errors closer to their source
• Let with focus on success paths

Example:

# Bad
def read_config(path) do
  with {:ok, content} <- File.read(path),
       {:ok, decoded} <- Jason.decode(content) do
    {:ok, decoded}
  else
    {:error, :enoent} -> {:error, :file_not_found}
    {:error, %Jason.DecodeError{}} -> {:error, :invalid_json}
    {:error, reason} -> {:error, reason}
  end
end

# Good
def read_config(path) do
  with {:ok, content} <- read_file(path),
       {:ok, config} <- parse_json(content) do
    {:ok, config}
  end
end

defp read_file(path) do
  case File.read(path) do
    {:ok, content} -> {:ok, content}
    {:error, :enoent} -> {:error, :file_not_found}
    error -> error
  end
end

defp parse_json(content) do
  case Jason.decode(content) do
    {:ok, data} -> {:ok, data}
    {:error, _} -> {:error, :invalid_json}
  end
end