Add reason support, closes #266

1 files changed, 221 insertions, 0 deletions

diff --git a/indent/reason.vim b/indent/reason.vim
new file mode 100644
index 00000000..4901a4f5
--- /dev/null
+++ b/indent/reason.vim
@@ -0,0 +1,221 @@
+if exists('g:polyglot_disabled') && index(g:polyglot_disabled, 'reason') != -1
+  finish
+endif
+
+" Vim indent file
+" Language:         Reason (adapted from Rust)
+" Author:           Chris Morgan <me@chrismorgan.info> (Modifications by Jordan W)
+" Portions Copyright (c) 2015-present, Facebook, Inc. All rights reserved
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+  finish
+endif
+let b:did_indent = 1
+
+" m1 is needed to make parens line up correct:
+"
+"   let result = callSomething (
+"      1,
+"      2
+"   );
+"
+" fN (See the docs) - additional indentation *w.r.t the "prevailing indent" only applies to blocks
+" *not* in nested braces!  We want it to match the blocks *inside* nested braces - and be zero, but
+" the problem is that the "prevailing indent" not inside of braces is different than inside braces.
+setlocal cinoptions=L0,(0,Ws,J1,j1,m1,{0,f0s
+" cinkeys is ignored if indentexpr is activated so this setting is useless. See indentkeys below.
+setlocal cinkeys=0{,0},0),!^F,o,O,0[,0]
+" Don't think cinwords will actually do anything at all... never mind
+setlocal cinwords=for,if,else,while,loop,impl,mod,unsafe,trait,struct,enum,fun,let,extern
+
+" Some preliminary settings
+setlocal nolisp		" Make sure lisp indenting doesn't supersede us
+setlocal autoindent	" indentexpr isn't much help otherwise
+" Also do indentkeys, otherwise # gets shoved to column 0 :-/
+setlocal indentkeys=0{,0},0),!^F,o,O,0[,0]
+
+
+setlocal indentexpr=GetReasonIndent(v:lnum)
+
+" Only define the function once.
+if exists("*GetReasonIndent")
+  finish
+endif
+
+" Come here when loading the script the first time.
+
+function! s:get_line_trimmed(lnum)
+	" Get the line and remove a trailing comment.
+	" Use syntax highlighting attributes when possible.
+	" NOTE: this is not accurate; /* */ or a line continuation could trick it
+	let line = getline(a:lnum)
+	let line_len = strlen(line)
+	if has('syntax_items')
+		" If the last character in the line is a comment, do a binary search for
+		" the start of the comment.  synID() is slow, a linear search would take
+		" too long on a long line.
+		if synIDattr(synID(a:lnum, line_len, 1), "name") =~ 'Comment\|Todo'
+			let min = 1
+			let max = line_len
+			while min < max
+				let col = (min + max) / 2
+				if synIDattr(synID(a:lnum, col, 1), "name") =~ 'Comment\|Todo'
+					let max = col
+				else
+					let min = col + 1
+				endif
+			endwhile
+			let line = strpart(line, 0, min - 1)
+		endif
+		return substitute(line, "\s*$", "", "")
+	else
+		" Sorry, this is not complete, nor fully correct (e.g. string "//").
+		" Such is life.
+		return substitute(line, "\s*//.*$", "", "")
+	endif
+endfunction
+
+function! s:is_string_comment(lnum, col)
+	if has('syntax_items')
+		for id in synstack(a:lnum, a:col)
+			let synname = synIDattr(id, "name")
+			if synname == "rustString" || synname =~ "^rustComment"
+				return 1
+			endif
+		endfor
+	else
+		" without syntax, let's not even try
+		return 0
+	endif
+endfunction
+
+function GetReasonIndent(lnum)
+
+	" Starting assumption: cindent (called at the end) will do it right
+	" normally. We just want to fix up a few cases.
+
+	let line = getline(a:lnum)
+
+	if has('syntax_items')
+		let synname = synIDattr(synID(a:lnum, 1, 1), "name")
+		if synname == "rustString"
+			" If the start of the line is in a string, don't change the indent
+			return -1
+		elseif synname =~ '\(Comment\|Todo\)'
+					\ && line !~ '^\s*/\*'  " not /* opening line
+			if synname =~ "CommentML" " multi-line
+				if line !~ '^\s*\*' && getline(a:lnum - 1) =~ '^\s*/\*'
+					" This is (hopefully) the line after a /*, and it has no
+					" leader, so the correct indentation is that of the
+					" previous line.
+					return GetReasonIndent(a:lnum - 1)
+				endif
+			endif
+			" If it's in a comment, let cindent take care of it now. This is
+			" for cases like "/*" where the next line should start " * ", not
+			" "* " as the code below would otherwise cause for module scope
+			" Fun fact: "  /*\n*\n*/" takes two calls to get right!
+			return cindent(a:lnum)
+		endif
+	endif
+
+	" cindent gets second and subsequent match patterns/struct members wrong,
+	" as it treats the comma as indicating an unfinished statement::
+	"
+	" switch a {
+	"   | b => c
+	"     | d => e
+	"     | f => g
+	" };
+
+	" Search backwards for the previous non-empty line.
+	let prevlinenum = prevnonblank(a:lnum - 1)
+	let prevline = s:get_line_trimmed(prevlinenum)
+	while prevlinenum > 1 && prevline !~ '[^[:blank:]]'
+		let prevlinenum = prevnonblank(prevlinenum - 1)
+		let prevline = s:get_line_trimmed(prevlinenum)
+	endwhile
+
+	" Handle where clauses nicely: subsequent values should line up nicely.
+	if prevline[len(prevline) - 1] == ","
+				\ && prevline =~# '^\s*where\s'
+		return indent(prevlinenum) + 6
+	endif
+
+	if prevline =~ "\s*|.*[{(\[]$"
+				" \ && s:get_line_trimmed(a:lnum) !~ '^\s*[\[\]{}]'
+				" \ && prevline !~ '^\s*fun\s'
+				" \ && prevline !~ '([^()]\+,$'
+		" Oh ho! The previous line ended in a comma! I bet cindent will try to
+		" take this too far... For now, let's normally use the previous line's
+		" indent.
+
+		" One case where this doesn't work out is where *this* line contains
+		" square or curly brackets; then we normally *do* want to be indenting
+		" further.
+		"
+		" Another case where we don't want to is one like a function
+		" definition with arguments spread over multiple lines:
+		"
+		" fun foo(baz: Baz,
+		"        baz: Baz) // <-- cindent gets this right by itself
+		"
+		" Another case is similar to the previous, except calling a function
+		" instead of defining it, or any conditional expression that leaves
+		" an open paren:
+		"
+		" foo(baz,
+		"     baz);
+		"
+		" if baz && (foo ||
+		"            bar) {
+		"
+		" There are probably other cases where we don't want to do this as
+		" well. Add them as needed.
+		return indent(prevlinenum) + &shiftwidth
+	endif
+	if prevline =~ "\s*|"
+		return indent(prevlinenum)
+	endif
+
+	if !has("patch-7.4.355")
+		" cindent before 7.4.355 doesn't do the module scope well at all; e.g.::
+		"
+		" static FOO : &'static [bool] = [
+		" true,
+		"	 false,
+		"	 false,
+		"	 true,
+		"	 ];
+		"
+		"	 uh oh, next statement is indented further!
+
+		" Note that this does *not* apply the line continuation pattern properly;
+		" that's too hard to do correctly for my liking at present, so I'll just
+		" start with these two main cases (square brackets and not returning to
+		" column zero)
+
+		call cursor(a:lnum, 1)
+		if searchpair('{\|(', '', '}\|)', 'nbW',
+					\ 's:is_string_comment(line("."), col("."))') == 0
+			if searchpair('\[', '', '\]', 'nbW',
+						\ 's:is_string_comment(line("."), col("."))') == 0
+				" Global scope, should be zero
+				return 0
+			else
+				" At the module scope, inside square brackets only
+				"if getline(a:lnum)[0] == ']' || search('\[', '', '\]', 'nW') == a:lnum
+				if line =~ "^\\s*]"
+					" It's the closing line, dedent it
+					return 0
+				else
+					return &shiftwidth
+				endif
+			endif
+		endif
+	endif
+
+	" Fall back on cindent, which does it mostly right
+	return cindent(a:lnum)
+endfunction