View Source Formatter Rules

The Funx library now exports formatter rules for its Either DSL, allowing projects that depend on Funx to automatically format DSL code without extra parentheses.

Exported Rules

The following Either DSL functions are configured to format without parentheses:

• either/2 - DSL entry point
• bind/1 - Chain operations that return Either or result tuples
• map/1 - Transform values with plain functions
• ap/1 - Apply function in Either to value in Either
• validate/1 - Collect all errors from validators
• filter_or_else/2 - Filter with predicate, fallback if fails
• or_else/1 - Provide fallback on error
• map_left/1 - Transform error values
• tap - Run a side-effecting function inside the chain without changing the data

Note that flip/0 - Swap Left and Right still requires parentheses.

Usage in Dependent Projects

Step 1: Add to Dependencies

Make sure your mix.exs includes Funx as a dependency:

def deps do
  [
    {:funx, "~> 0.2"}
  ]
end

Step 2: Update .formatter.exs

In your project's .formatter.exs, add :funx to import_deps:

[
  import_deps: [:funx],
  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
]

Example

With this configuration, your DSL code will format cleanly:

either user_input do
  bind ParseUser
  map ValidateEmail
  validate [CheckLength, CheckFormat]
  bind SaveToDatabase
  or_else default_user()
end

Instead of:

either(user_input) do
  bind(ParseUser)
  map(ValidateEmail)
  validate([CheckLength, CheckFormat])
  bind(SaveToDatabase)
  or_else(default_user())
end

Verification

To verify the formatter rules are being imported correctly, you can run:

mix format --check-formatted

Your DSL code should format without adding parentheses.