Add an option to choose between guru and gopls for :GoReferrers

autoload/go/config.vim

@@ -485,6 +485,10 @@ function! go#config#Updatetime() abort
   return go_updatetime == 0 ? &updatetime : go_updatetime
 endfunction
 
+function! go#config#ReferrersMode() abort
+  return get(g:, 'go_referrers_mode', 'gopls')
+endfunction
+
 " Set the default value. A value of "1" is a shortcut for this, for
 " compatibility reasons.
 if exists("g:go_gorename_prefill") && g:go_gorename_prefill == 1

autoload/go/guru.vim

@@ -404,10 +404,26 @@ endfunction
 
 " Show all refs to entity denoted by selected identifier
 function! go#guru#Referrers(selected) abort
-  let [l:line, l:col] = getpos('.')[1:2]
-  let [l:line, l:col] = go#lsp#lsp#Position(l:line, l:col)
-  let l:fname = expand('%:p')
-  call go#lsp#Referrers(l:fname, l:line, l:col, funcref('s:parse_guru_output'))
+  let l:mode = go#config#ReferrersMode()
+  if l:mode == 'guru'
+    let args = {
+            \ 'mode': 'referrers',
+            \ 'format': 'plain',
+            \ 'selected': a:selected,
+            \ 'needs_scope': 0,
+            \ }
+
+    call s:run_guru(args)
+    return
+  elseif l:mode == 'gopls'
+    let [l:line, l:col] = getpos('.')[1:2]
+    let [l:line, l:col] = go#lsp#lsp#Position(l:line, l:col)
+    let l:fname = expand('%:p')
+    call go#lsp#Referrers(l:fname, l:line, l:col, funcref('s:parse_guru_output'))
+    return
+  else
+    call go#util#EchoWarning('unknown value for g:go_referrers_mode')
+  endif
 endfunction
 
 function! go#guru#SameIds(showstatus) abort

autoload/go/lsp.vim

@@ -681,17 +681,26 @@ endfunction
 function! s:referencesHandler(next, msg) abort dict
   let l:result = []
 
+  call sort(a:msg, funcref('s:compareLocations'))
+
   for l:loc in a:msg
     let l:fname = go#path#FromURI(l:loc.uri)
     let l:line = l:loc.range.start.line+1
     let l:bufnr = bufnr(l:fname)
+    let l:bufinfo = getbufinfo(l:fname)
 
     try
-      if l:bufnr == -1
-        let l:content = readfile(l:fname, '', l:line)[-1]
+      if l:bufnr == -1 || len(l:bufinfo) == 0 || l:bufinfo[0].loaded == 0
+        let l:filecontents = readfile(l:fname, '', l:line)
       else
-        let l:content = getbufline(l:fname, l:line)[-1]
+        let l:filecontents = getbufline(l:fname, l:line)
+      endif
+
+      if len(l:filecontents) == 0
+        continue
       endif
+
+      let l:content = l:filecontents[-1]
     catch
       call go#util#EchoError(printf('%s (line %s): %s at %s', l:fname, l:line, v:exception, v:throwpoint))
     endtry
@@ -969,6 +978,26 @@ function! s:debug(event, data, ...) abort
   call timer_start(10, function('s:debugasync', [a:event, a:data]))
 endfunction
 
+function! s:compareLocations(left, right) abort
+  if a:left.uri < a:right.uri
+    return -1
+  endif
+
+  if a:left.uri == a:right.uri && a:left.range.start.line < a:right.range.start.line
+    return -1
+  endif
+
+  if a:left.uri == a:right.uri && a:left.range.start.line == a:right.range.start.line && a:left.range.start.character < a:right.range.start.character
+    return -1
+  endif
+
+  if a:left.uri == a:right.uri && a:left.range.start.line == a:right.range.start.line && a:left.range.start.character == a:right.range.start.character
+    return 0
+  endif
+
+  return 1
+endfunction
+
 " restore Vi compatibility settings
 let &cpo = s:cpo_save
 unlet s:cpo_save

doc/vim-go.txt

@@ -1404,6 +1404,16 @@ accuracy or `godef` for its performance. Valid options are `godef`, `gopls`,
 and `guru`.
 >
   let g:go_def_mode = 'gopls'
+<
+                                                       *'g:go_referrers_mode'*
+
+Use this option to define the command to be used for |:GoReferrers|. By
+default `gopls` is used, because it is the fastest and works with Go modules.
+One might also use `guru` for its ability to show references from other
+packages.  This option will be removed after `gopls` can show references from
+other packages. Valid options are `gopls` and `guru`.
+>
+  let g:go_referrers_mode = 'gopls'
 <
                                                   *'g:go_def_mapping_enabled'*