1" Vim indent file
2" Language:         Rust
3" Author:           Chris Morgan <me@chrismorgan.info>
4" Last Change:      2017 Jun 13
5" For bugs, patches and license go to https://github.com/rust-lang/rust.vim
6
7" Only load this indent file when no other was loaded.
8if exists("b:did_indent")
9	finish
10endif
11let b:did_indent = 1
12
13setlocal cindent
14setlocal cinoptions=L0,(0,Ws,J1,j1
15setlocal cinkeys=0{,0},!^F,o,O,0[,0]
16" Don't think cinwords will actually do anything at all... never mind
17setlocal cinwords=for,if,else,while,loop,impl,mod,unsafe,trait,struct,enum,fn,extern
18
19" Some preliminary settings
20setlocal nolisp		" Make sure lisp indenting doesn't supersede us
21setlocal autoindent	" indentexpr isn't much help otherwise
22" Also do indentkeys, otherwise # gets shoved to column 0 :-/
23setlocal indentkeys=0{,0},!^F,o,O,0[,0]
24
25setlocal indentexpr=GetRustIndent(v:lnum)
26
27" Only define the function once.
28if exists("*GetRustIndent")
29	finish
30endif
31
32let s:save_cpo = &cpo
33set cpo&vim
34
35" Come here when loading the script the first time.
36
37function! s:get_line_trimmed(lnum)
38	" Get the line and remove a trailing comment.
39	" Use syntax highlighting attributes when possible.
40	" NOTE: this is not accurate; /* */ or a line continuation could trick it
41	let line = getline(a:lnum)
42	let line_len = strlen(line)
43	if has('syntax_items')
44		" If the last character in the line is a comment, do a binary search for
45		" the start of the comment.  synID() is slow, a linear search would take
46		" too long on a long line.
47		if synIDattr(synID(a:lnum, line_len, 1), "name") =~ 'Comment\|Todo'
48			let min = 1
49			let max = line_len
50			while min < max
51				let col = (min + max) / 2
52				if synIDattr(synID(a:lnum, col, 1), "name") =~ 'Comment\|Todo'
53					let max = col
54				else
55					let min = col + 1
56				endif
57			endwhile
58			let line = strpart(line, 0, min - 1)
59		endif
60		return substitute(line, "\s*$", "", "")
61	else
62		" Sorry, this is not complete, nor fully correct (e.g. string "//").
63		" Such is life.
64		return substitute(line, "\s*//.*$", "", "")
65	endif
66endfunction
67
68function! s:is_string_comment(lnum, col)
69	if has('syntax_items')
70		for id in synstack(a:lnum, a:col)
71			let synname = synIDattr(id, "name")
72			if synname == "rustString" || synname =~ "^rustComment"
73				return 1
74			endif
75		endfor
76	else
77		" without syntax, let's not even try
78		return 0
79	endif
80endfunction
81
82function GetRustIndent(lnum)
83
84	" Starting assumption: cindent (called at the end) will do it right
85	" normally. We just want to fix up a few cases.
86
87	let line = getline(a:lnum)
88
89	if has('syntax_items')
90		let synname = synIDattr(synID(a:lnum, 1, 1), "name")
91		if synname == "rustString"
92			" If the start of the line is in a string, don't change the indent
93			return -1
94		elseif synname =~ '\(Comment\|Todo\)'
95					\ && line !~ '^\s*/\*'  " not /* opening line
96			if synname =~ "CommentML" " multi-line
97				if line !~ '^\s*\*' && getline(a:lnum - 1) =~ '^\s*/\*'
98					" This is (hopefully) the line after a /*, and it has no
99					" leader, so the correct indentation is that of the
100					" previous line.
101					return GetRustIndent(a:lnum - 1)
102				endif
103			endif
104			" If it's in a comment, let cindent take care of it now. This is
105			" for cases like "/*" where the next line should start " * ", not
106			" "* " as the code below would otherwise cause for module scope
107			" Fun fact: "  /*\n*\n*/" takes two calls to get right!
108			return cindent(a:lnum)
109		endif
110	endif
111
112	" cindent gets second and subsequent match patterns/struct members wrong,
113	" as it treats the comma as indicating an unfinished statement::
114	"
115	" match a {
116	"     b => c,
117	"         d => e,
118	"         f => g,
119	" };
120
121	" Search backwards for the previous non-empty line.
122	let prevlinenum = prevnonblank(a:lnum - 1)
123	let prevline = s:get_line_trimmed(prevlinenum)
124	while prevlinenum > 1 && prevline !~ '[^[:blank:]]'
125		let prevlinenum = prevnonblank(prevlinenum - 1)
126		let prevline = s:get_line_trimmed(prevlinenum)
127	endwhile
128
129	" Handle where clauses nicely: subsequent values should line up nicely.
130	if prevline[len(prevline) - 1] == ","
131				\ && prevline =~# '^\s*where\s'
132		return indent(prevlinenum) + 6
133	endif
134
135	if prevline[len(prevline) - 1] == ","
136				\ && s:get_line_trimmed(a:lnum) !~ '^\s*[\[\]{}]'
137				\ && prevline !~ '^\s*fn\s'
138				\ && prevline !~ '([^()]\+,$'
139				\ && s:get_line_trimmed(a:lnum) !~ '^\s*\S\+\s*=>'
140		" Oh ho! The previous line ended in a comma! I bet cindent will try to
141		" take this too far... For now, let's normally use the previous line's
142		" indent.
143
144		" One case where this doesn't work out is where *this* line contains
145		" square or curly brackets; then we normally *do* want to be indenting
146		" further.
147		"
148		" Another case where we don't want to is one like a function
149		" definition with arguments spread over multiple lines:
150		"
151		" fn foo(baz: Baz,
152		"        baz: Baz) // <-- cindent gets this right by itself
153		"
154		" Another case is similar to the previous, except calling a function
155		" instead of defining it, or any conditional expression that leaves
156		" an open paren:
157		"
158		" foo(baz,
159		"     baz);
160		"
161		" if baz && (foo ||
162		"            bar) {
163		"
164		" Another case is when the current line is a new match arm.
165		"
166		" There are probably other cases where we don't want to do this as
167		" well. Add them as needed.
168		return indent(prevlinenum)
169	endif
170
171	if !has("patch-7.4.355")
172		" cindent before 7.4.355 doesn't do the module scope well at all; e.g.::
173		"
174		" static FOO : &'static [bool] = [
175		" true,
176		"	 false,
177		"	 false,
178		"	 true,
179		"	 ];
180		"
181		"	 uh oh, next statement is indented further!
182
183		" Note that this does *not* apply the line continuation pattern properly;
184		" that's too hard to do correctly for my liking at present, so I'll just
185		" start with these two main cases (square brackets and not returning to
186		" column zero)
187
188		call cursor(a:lnum, 1)
189		if searchpair('{\|(', '', '}\|)', 'nbW',
190					\ 's:is_string_comment(line("."), col("."))') == 0
191			if searchpair('\[', '', '\]', 'nbW',
192						\ 's:is_string_comment(line("."), col("."))') == 0
193				" Global scope, should be zero
194				return 0
195			else
196				" At the module scope, inside square brackets only
197				"if getline(a:lnum)[0] == ']' || search('\[', '', '\]', 'nW') == a:lnum
198				if line =~ "^\\s*]"
199					" It's the closing line, dedent it
200					return 0
201				else
202					return shiftwidth()
203				endif
204			endif
205		endif
206	endif
207
208	" Fall back on cindent, which does it mostly right
209	return cindent(a:lnum)
210endfunction
211
212let &cpo = s:save_cpo
213unlet s:save_cpo
214