vim-haskell -> hasksyn

1 files changed, 268 insertions, 57 deletions

diff --git a/indent/haskell.vim b/indent/haskell.vim
index 4e6a1eff..c584e940 100644
--- a/indent/haskell.vim
+++ b/indent/haskell.vim
@@ -1,85 +1,296 @@
 " Vim indent file
-" Language:     Haskell
-" Author:       motemen <motemen@gmail.com>
-" Version:      0.1
-" Last Change:  2007-07-25
-"
-" Modify g:haskell_indent_if and g:haskell_indent_case to
-" change indentation for `if'(default 3) and `case'(default 5).
-" Example (in .vimrc):
-" > let g:haskell_indent_if = 2
+" Language: Haskell
+" Maintainer: Tristan Ravitch
 
 if exists('b:did_indent')
-    finish
+  finish
 endif
 
 let b:did_indent = 1
 
-if !exists('g:haskell_indent_if')
-    " if bool
-    " >>>then ...
-    " >>>else ...
-    let g:haskell_indent_if = 2
+if !exists('g:hasksyn_indent_search_backward')
+  let g:hasksyn_indent_search_backward = 100
+endif
+
+if !exists('g:hasksyn_dedent_after_return')
+  let g:hasksyn_dedent_after_return = 1
+endif
+
+if !exists('g:hasksyn_dedent_after_catchall_case')
+  let g:hasksyn_dedent_after_catchall_case = 1
 endif
 
-if !exists('g:haskell_indent_case')
-    " case xs of
-    " >>>>>[] -> ...
-    " >>>>>(y:ys) -> ...
-    let g:haskell_indent_case = 2
+setlocal noautoindent
+setlocal indentexpr=HIndent(v:lnum)
+setlocal indentkeys+=0=where
+setlocal indentkeys+=0=->
+setlocal indentkeys+=0==>
+setlocal indentkeys+=0=in
+setlocal indentkeys+=0=class,0=instance,0=import
+setlocal indentkeys+=<Bar>
+setlocal indentkeys+=0\,
+
+if exists("*HIndent")
+  finish
 endif
 
-setlocal indentexpr=GetHaskellIndent()
-setlocal indentkeys=!^F,o,O
 
-function! GetHaskellIndent()
-    let line = substitute(getline(getpos('.')[1] - 1), '\t', repeat(' ', &tabstop), 'g')
+function! HIndent(lnum)
+  " Don't do anything boneheaded if we are inside of a block comment
+  if s:IsInBlockComment()
+    return -1
+  endif
+
+  let plnum = s:PrevNonCommentLineNum(a:lnum)
+  if plnum == 0
+    return 0
+  endif
+
+  let prevl = s:GetAndStripTrailingComments(plnum)
+  let thisl = s:GetAndStripTrailingComments(a:lnum)
+  let previ = indent(plnum)
 
-    if line =~ '[!#$%&*+./<=>?@\\^|~-]$\|\<do$'
-        return match(line, '\s*where \zs\|\S') + &shiftwidth
+  " If this is a bare where clause, indent it one step.  where as part of an
+  " instance should be unaffected unless you put it in an odd place.
+  " This is the wrong thing if you are deeply indented already and want to put
+  " a where clause on the top-level construct, but there isn't much that can
+  " be done about that case...
+  if thisl =~ '^\s*where\s*$'
+    return previ + &sw
+  endif
+
+  " If we start a new line for a type signature, see if we can line it up with
+  " the previous line.
+  if thisl =~ '^\s*\(->\|=>\)\s*'
+    let tokPos = s:BackwardPatternSearch(a:lnum, '\(::\|->\|=>\)')
+    if tokPos != -1
+      return tokPos
     endif
+  endif
+
+  if prevl =~ '\Wof\s*$' || prevl =~ '\Wdo\s*$'
+    return previ + &sw
+  endif
 
-    if line =~ '{$'
-        return match(line, '\s*where \zs\|\S') + &shiftwidth
+  " Now for commas.  Commas will align pretty naturally for simple pattern
+  " guards, so don't worry about that for now.  If we see the line is just a
+  " comma, search up for something to align it to.  In the easy case, look
+  " for a [ or { (the last in their line).  Also consider other commas that
+  " are preceeded only by whitespace.  This isn't just a previous line check
+  " necessarily, though that would cover most cases.
+  if thisl =~ '^\s*,'
+    let cmatch = match(prevl, '\(^\s*\)\@<=,')
+    if cmatch != -1
+      return cmatch
     endif
 
-    if line =~ '^\(instance\|class\).*\&.*where$'
-        return &shiftwidth
+    let bmatch = match(prevl, '\({\|\[\)')
+    if bmatch != -1
+      return bmatch
     endif
+  endif
 
-    if line =~ ')$'
-        let pos = getpos('.')
-        normal k$
-        let paren_end   = getpos('.')
-        normal %
-        let paren_begin = getpos('.')
-        call setpos('.', pos)
-        if paren_begin[1] != paren_end[1]
-            return paren_begin[2] - 1
-        endif
+  " Match an 'in' keyword with the corresponding let.  Unfortunately, if the
+  " name of your next binding happens to start with 'in', this will muck with
+  " it.  Not sure if there is a workaround because we can't force an
+  " auto-indent after 'in ' as far as I can see.
+  if thisl =~ '\s*in$'
+    let letStart = s:BackwardPatternSearch(a:lnum, '\(\W\)\@<=let\W')
+    if letStart != -1
+      return letStart
     endif
+  endif
 
-    if line !~ '\<else\>'
-        let s = match(line, '\<if\>.*\&.*\zs\<then\>')
-        if s > 0
-            return s
-        endif
+  " We don't send data or type to column zero because they can be indented
+  " inside of 'class' definitions for data/type families
+  if thisl =~ '^\s*\(class\|instance\|newtype\|import\)'
+    return 0
+  endif
 
-        let s = match(line, '\<if\>')
-        if s > 0
-            return s + g:haskell_indent_if
-        endif
+  " FIXME: Only do this if the previous line was not already indented for the
+  " same reason.  Also be careful of -> in type signatures.  Make sure we have
+  " an earlier rule to line those up properly.
+  if prevl =~ '[=>\$\.\^+\&`(-]\s*$'
+    return previ + &sw
+  endif
+
+  " We have a special case for dealing with trailing '*' operators.  If the *
+  " is the end of a kind signature in a type family/associated type, we don't
+  " want to indent the next line.  We do if it is just being a * operator in
+  " an expression, though.
+  if prevl =~ '\(\(type\|data\).*\)\@<!\*\s*$'
+    return previ + &sw
+  endif
+
+  " If the previous line ends in a where, indent us a step
+  if prevl =~ '\Wwhere\s*$'
+    return previ + &sw
+  endif
+
+  " If we see a |, first try to line it up with the pipe on the previous line.
+  " Search backward on nearby lines, giving up if we hit a line with a \w at
+  " column 0. Otherwise, indent it relative to the previous line
+  "
+  " Here we can also handle the case of lining up data declarations.  The
+  " backwards pipe search will fail for a data declaration (since data is at
+  " column 0), so we can have an extra check after the pipe search for
+  " data..=.
+  if thisl =~ '^\s*|$'
+    let nearestPipeIndex = s:BackwardPatternSearch(a:lnum, '\(^\s*\)\@<=|')
+    if nearestPipeIndex != -1
+      return nearestPipeIndex
+    endif
+
+    let dataEquals = match(prevl, '\(data.*\)\@<==')
+    if dataEquals != -1
+      return dataEquals
     endif
 
-    let s = match(line, '\<do\s\+\zs[^{]\|\<where\s\+\zs\w\|\<let\s\+\zs\S\|^\s*\zs|\s')
-    if s > 0
-        return s
+    return previ + &sw
+  endif
+
+  " If the previous line has a let, line the cursor up with the start of the
+  " first binding name.  Autoindent handles subsequent cases.
+  "
+  " This should come after the 'in' aligner so that 'in' is not treated as
+  " just something to be aligned to the previous binding.
+  let lbindStart = match(prevl, '\(\Wlet\s\+\)\@<=\w')
+  if lbindStart != -1
+    return lbindStart
+  endif
+
+  " If requested, dedent from a bare return (presumably in a do block).
+  " This comes after the trailing operator case - hopefully that will avoid
+  " returns on lines by themselves but not really in a do block.  This is a
+  " heuristic.
+  if g:hasksyn_dedent_after_return && prevl =~ '^\s*return\W'
+    return previ - &sw
+  endif
+
+  " Similar to the return dedent - after a catchall case _ -> ..., we can
+  " almost certainly dedent.  Again, it comes after the line continuation
+  " heuristic so we don't dedent while someone is making an obviously
+  " multi-line construct
+  if g:hasksyn_dedent_after_catchall_case && prevl =~ '^\s*_\s*->\W'
+    return previ - &sw
+  endif
+
+  " On the other hand, if the previous line is a where with some bindings
+  " following it on the same line, accommodate and align with the first non-ws
+  " char after the where
+  if prevl =~ '\Wwhere\s\+\w'
+    let bindStart = match(prevl, '\(\Wwhere\s\+\)\@<=\w')
+    if bindStart != -1
+      return bindStart
+    endif
+
+    return previ + &sw
+  endif
+
+  return previ
+endfunction
+
+" Search backwards for a token from the cursor position
+function! s:FindTokenNotInCommentOrString(tok)
+  return search('\(--.*\|"\([^"]\|\\"\)*\)\@<!' . tok, 'bcnW')
+endfunction
+
+" Should return -1 if the given line is inside of an unclosed block comment.
+" This is meant to let us exit early from the indenter if we are in a comment.
+" Look for the nearest -} and {- such that they are not between "" or in a
+" line comment
+"
+" Note: we may need to restrict how far back this will search.  On the other
+" hand, the native vim 'search' function might be efficient enough to support
+" entire buffers.
+function! s:IsInBlockComment()
+  let openCommPos = s:FindTokenNotInCommentOrString('{-')
+  " If there is no open comment, then we don't have to look for a close
+  if openCommPos == 0
+    return 0
+  endif
+
+  " Or if there is a close comment marker that comes after the open marker, we
+  " are not in a comment.  Note that we potentially need to check the position
+  " in the line if they are both on the same line.  I'll fix it later.
+  let closeCommPos = s:FindTokenNotInCommentOrString('-}')
+  if closeCommPos >= openCommPos
+    return 0
+  endif
+
+  return 1
+endfunction
+
+" Get the previous line that is not a comment.  Pass in the *current* line
+" number.  Also skips blank lines.
+function! s:PrevNonCommentLineNum(lnum)
+  if a:lnum <= 1
+    return 0
+  endif
+
+  let lnum = a:lnum - 1
+
+  while 1
+    if lnum == 0
+      return 0
+    endif
+
+    let aline = getline(lnum)
+    if aline =~ '^\s*--'
+      let lnum = lnum - 1
+    else
+      return lnum
+    endif
+  endwhile
+endfunction
+
+function! s:GetAndStripTrailingComments(lnum)
+  let aline = getline(a:lnum)
+  " We can't just remove the string literal since that leaves us with a
+  " trailing operator (=), so replace it with a fake identifier
+  let noStrings = substitute(aline, '"\([^"]\|\\"\)*"', 's', '')
+  let noLineCom = substitute(noStrings, '--.*$', '', '')
+
+  " If there are no fancy block comments involved, skip some of this extra
+  " work
+  if noLineCom !~ '\({-\|-}\)'
+    return noLineCom
+  endif
+
+  " We stripped line comments, now we need to strip out any relevant multiline
+  " comments.  This includes comments starting much earlier but ending on this
+  " line or comments starting on this line and continuing to the next.  This
+  " is probably easiest in two steps: {- to (-}|$) and then ^ to -}.
+  " Note we are using a non-greedy match here so that only the minimal {- -}
+  " pair is consumed.
+  let noBlock1 = substitute(noLineComm, '{-.\{-}-}', '', '')
+  let noBlock2 = substitute(noBlock1, '{-.\{-}$', '', '')
+  let noBlock3 = substitute(noBlock2, '^.\{-}-}', '', '')
+  return noBlock3
+endfunction
+
+" Search backwards from lnum for pat, returning the starting index if found
+" within the search range or -1 if not found.  Stops searching at lines
+" starting at column 0 with an identifier character.
+function! s:BackwardPatternSearch(lnum, pat)
+  let lnum = s:PrevNonCommentLineNum(a:lnum)
+  while 1
+    let aline = s:GetAndStripTrailingComments(lnum)
+    if a:lnum - lnum > g:hasksyn_indent_search_backward
+      return -1
     endif
 
-    let s = match(line, '\<case\>')
-    if s > 0
-        return s + g:haskell_indent_case
+    let theMatch = match(aline, a:pat)
+    if theMatch != -1
+      return theMatch
+    else
+      " We want to be able to consider lines starting in column 0, but we don't
+      " want to search back past them.
+      if aline =~ '^\w'
+        return -1
+      endif
+      let lnum = s:PrevNonCommentLineNum(lnum)
     endif
+  endwhile
+endfunction
 
-    return match(line, '\S')
-endfunction
\ No newline at end of file