An option to squash consequtive newlines.

[phadej]

When editing files I sometimes end up wth something like

foo : Bool
foo = true









bar : Bool
Bar = false

and while this an extreme example, it would be great if fix-whitespace had an option to disallow (and fix) more then 2 (or configurable amount) of consequtive newline characters.

EDIT: I can write a patch if this feature is ok to have.

[ulysses4ever]

I've found myself wanting it often. Students do this all the time.

It's a pity that it's not entirely trivial because of the configurable amount of new lines in a row. But I agree that this configuration is desirable.

[phadej]

I made a PoC.

I tried it on GHC codebase, there are 796 files in compiler/. Out of these:

% fix-whitespace compiler/**/*.hs --check -n 4
[ Violation detected ] compiler/GHC/ByteCode/Linker.hs
[ Violation detected ] compiler/GHC/CmmToAsm/X86/Instr.hs
[ Violation detected ] compiler/GHC/StgToCmm/Prof.hs
[ Violation detected ] compiler/GHC/StgToJS/Monad.hs
[polinukli] /code/ghc wip/fix-whitespace % fix-whitespace compiler/**/*.hs --check -n 3 2>&1 | wc
     24     120    1291
[polinukli] /code/ghc wip/fix-whitespace % fix-whitespace compiler/**/*.hs --check -n 2 2>&1 | wc
    150     750    8241

So it feels that if this functionality is enabled by default, then 3 (i.e. allowing 2 empty lines) is not too controversial. Allowing only one empty line (with --consecutive 2) is already quite intrusive.