tweag/ormolu

Line breaks ignored in data type declarations.

jonathanknowles opened this issue · 1 comments

jonathanknowles commented

Describe the bug
Ormolu sometimes eats line breaks within data type declarations.

To Reproduce
Run ormolu on code similar to the following, with a line break before the =:

data SomeReasonablyDescriptiveRecordType someParam1 someParam2 someParam3
 = SomeReasonablyDescriptiveRecordType
   { foo :: someParam1,
     bar :: someParam2,
     baz :: someParam3
   }

or with the line break after the =:

data SomeReasonablyDescriptiveRecordType someParam1 someParam2 someParam3 =
 SomeReasonablyDescriptiveRecordType
   { foo :: someParam1,
     bar :: someParam2,
     baz :: someParam3
   }

Expected behaviour
The line break is preserved, and the data constructor name is indented one level to the right.

Actual behaviour
Ormolu eats the line break, and prints the data constructor name on the same line, resulting in a rather long line:

data SomeReasonablyDescriptiveRecordType someParam1 someParam2 someParam3 = SomeReasonablyDescriptiveRecordType
{ foo :: someParam1,
  bar :: someParam2,
  baz :: someParam3
}

Environment

  • OS name + version: Linux 5.4.0-135-generic #152-Ubuntu SMP Wed Nov 23 20:19:22 UTC 2022 x86_64 GNU/Linux
  • Version of the code: ormolu 0.5.1.0 UNKNOWN UNKNOWN using ghc-lib-parser 9.4.3.20221104

Additional context

  • We have a rather large code base (> 200,000 lines) that's formatted by hand, and we're interested in adopting an auto-formatter.
  • Our team coding standard encourages an 80-column limit.

We realise that ormolu does not provide support for a column limit, but we're wondering if we can get by with manually inserting line breaks where necessary.

Many thanks!
Jonathan

amesgen commented

I think respecting line breaks here sounds reasonable, it gets even more annoying with CTYPE pragmas:

data
  {-# CTYPE "header.h" "an-ffi-type-with-along-name"  #-} 
  AnFFITypeWithAlongName = AnFFITypeWithAlongName
  { a :: X,
    b :: Y
  }

is formatted to

data {-# CTYPE "header.h" "an-ffi-type-with-along-name" #-} AnFFITypeWithAlongName = AnFFITypeWithAlongName
  { a :: X,
    b :: Y
  }

without a way to force line breaks without adding bogus comments.

  • 👍1