New postprocess function: guards.

The new function ensures line numbers in loclists are not beyond end of
buffer.  The implementation is very inefficient, because it loads all
buffers in memory.

`eslint` and `lessc` checkers need this function.

autoload/syntastic/postprocess.vim

@@ -46,6 +46,25 @@ function! syntastic#postprocess#filterForeignErrors(errors) " {{{2
     return filter(copy(a:errors), 'get(v:val, "bufnr") == ' . bufnr(''))
 endfunction " }}}2
 
+" make sure line numbers are not past end of buffers
+" XXX: this loads all referenced buffers in memory
+function! syntastic#postprocess#guards(errors) " {{{2
+    let buffers = syntastic#util#unique(map(filter(copy(a:errors), 'v:val["valid"]'), 'str2nr(v:val["bufnr"])'))
+
+    let guards = {}
+    for b in buffers
+        let guards[b] = len(getbufline(b, 1, '$'))
+    endfor
+
+    for e in a:errors
+        if e['valid'] && e['lnum'] > guards[e['bufnr']]
+            let e['lnum'] = guards[e['bufnr']]
+        endif
+    endfor
+
+    return a:errors
+endfunction " }}}2
+
 " }}}1
 
 let &cpo = s:save_cpo

plugin/syntastic.vim

@@ -19,7 +19,7 @@ if has('reltime')
     lockvar! g:syntastic_start
 endif
 
-let g:syntastic_version = '3.5.0-3'
+let g:syntastic_version = '3.5.0-6'
 lockvar g:syntastic_version
 
 " Sanity checks {{{1

syntax_checkers/javascript/eslint.vim

@@ -35,7 +35,8 @@ function! SyntaxCheckers_javascript_eslint_GetLocList() dict
 
     let loclist = SyntasticMake({
         \ 'makeprg': makeprg,
-        \ 'errorformat': errorformat })
+        \ 'errorformat': errorformat,
+        \ 'postprocess': ['guards'] })
 
     for e in loclist
         let e['col'] += 1

syntax_checkers/less/lessc.vim

@@ -58,6 +58,7 @@ function! SyntaxCheckers_less_lessc_GetLocList() dict
     return SyntasticMake({
         \ 'makeprg': makeprg,
         \ 'errorformat': errorformat,
+        \ 'postprocess': ['guards'],
         \ 'defaults': {'bufnr': bufnr(""), 'text': "Syntax error"} })
 endfunction