WARNING. This an alpha release meant to find bugs. Overwrite files at your peril!

Width-sensitive formatter for Julia code. Inspired by gofmt and refmt.

]add https://github.com/domluna/JLFmt.jl

JLFmt exports a singular function:

format(text::String; indent_size=4, print_width=80)

• indent_size - the number of spaces used for an indentation.
• print_width - the maximum number of characters of code on a single line. Lines over the limit will be nested if possible.

JLFmt parses the .jl source file into a Concrete Syntax Tree (CST) using CSTParser.

The CST is prettified using pretty, creating a PTree. The printing output of a PTree is a canonical representation of the code removing unnecessary whitespace and joining or separating lines of code. The pretty testset displays these transformations.

Example 1:

function  foo
end

becomes

function foo end

Example 2:

for cond 1; 2; 3 end

becomes

for cond
    1
    2
    3
end

PTree is nested using nest! to disjoin lines going over the print width. The PTree is modified in-place. All expressions are nested front to back with the exception of binary operations and conditionals.

Binary Ops

arg1 && arg2

->

arg1 && 
arg2

foo() = body

->

# The indentation of the body is based on `indent_size`
foo() =
    body

Conditionals

cond ? e1 : e2

->

cond ? e1 :
e2

->

cond ? 
e1 :
e2

Calls (also applies to {}, (), [], etc)

f(arg1, arg2, arg3)

->

f(
  arg1,
  arg2,
  arg3
)

function longfunctionname_that_is_long(lots, of, args, even, more, args)
    ..code..
end

->

# The arg is placed `indent_size` spaces after the start of the
# function name or one space after the opening parenthesis.
function longfunctionname_that_is_long(
             lots, 
             of, 
             args,
             even, 
             more, 
             args
         )
    ..code..
end

S <: Union{Type1,Type2,Type3}

->

S <: Union{
         Type1,
         Type2,
         Type3
     }

Finally, the PTree to an IOBuffer with print_tree which is then consumed as a String.

If a comment is at the end of a line of code it will be removed.

var x = 10 # comment about x

Formatting will produce:

var x = 10

To get around with this write comments on separate lines.