Configuration

Configuration options may be specified in either a fourmolu.yaml file or via command-line options. Fourmolu looks for a fourmolu.yaml file in all parents of the current directory, followed by the XDG config directory.

A configuration file with the default values filled in can be generated with:

$ fourmolu --print-defaults > fourmolu.yaml

For example, the indentation option may be specified in fourmolu.yaml as:

indentation: 2

or on the command line as --indentation 2 or --indentation=2.

Every option also has a setting that matches Ormolu's formatting.

Available options

Option name Description
indentation Number of spaces per indentation step
column-limit Max line length for automatic line breaking
function-arrows Styling of arrows in type signatures
comma-style How to place commas in multi-line lists, records, etc.
import-export-style Styling of import/export lists
indent-wheres Whether to full-indent or half-indent 'where' bindings past the preceding body
record-brace-space Whether to leave a space before an opening record brace
newlines-between-decls Number of spaces between top-level declarations
haddock-style How to print Haddock comments
haddock-style-module How to print module docstring
let-style Styling of let blocks
in-style How to align the 'in' keyword with respect to the 'let' keyword
single-constraint-parens Whether to put parentheses around a single constraint
single-deriving-parens Whether to put parentheses around a single deriving class
unicode Output Unicode syntax
respectful Give the programmer more choice on where to insert blank lines
fixities Fixity information for operators
reexports Module reexports Fourmolu should know about
import-grouping Rules for grouping import declarations
local-modules Modules defined by the current Cabal package for import grouping
sort-constraints Whether to sort constraints