Implement a preview window for selecting locations to open

autoload/ale/definition.vim

@@ -13,26 +13,10 @@ function! ale#definition#SetMap(map) abort
     let s:go_to_definition_map = a:map
 endfunction
 
-" This function is used so we can check the execution of commands without
-" running them.
-function! ale#definition#Execute(expr) abort
-    execute a:expr
-endfunction
-
 function! ale#definition#ClearLSPData() abort
     let s:go_to_definition_map = {}
 endfunction
 
-function! ale#definition#Open(options, filename, line, column) abort
-    if a:options.open_in_tab
-        call ale#definition#Execute('tabedit ' . fnameescape(a:filename))
-    else
-        call ale#definition#Execute('edit ' . fnameescape(a:filename))
-    endif
-
-    call cursor(a:line, a:column)
-endfunction
-
 function! ale#definition#HandleTSServerResponse(conn_id, response) abort
     if get(a:response, 'command', '') is# 'definition'
     \&& has_key(s:go_to_definition_map, a:response.request_seq)
@@ -43,7 +27,7 @@ function! ale#definition#HandleTSServerResponse(conn_id, response) abort
             let l:line = a:response.body[0].start.line
             let l:column = a:response.body[0].start.offset
 
-            call ale#definition#Open(l:options, l:filename, l:line, l:column)
+            call ale#util#Open(l:filename, l:line, l:column, l:options)
         endif
     endif
 endfunction
@@ -67,7 +51,7 @@ function! ale#definition#HandleLSPResponse(conn_id, response) abort
             let l:line = l:item.range.start.line + 1
             let l:column = l:item.range.start.character
 
-            call ale#definition#Open(l:options, l:filename, l:line, l:column)
+            call ale#util#Open(l:filename, l:line, l:column, l:options)
             break
         endfor
     endif

autoload/ale/preview.vim

@@ -2,13 +2,16 @@
 " Description: Preview windows for showing whatever information in.
 
 " Open a preview window and show some lines in it.
-function! ale#preview#Show(lines) abort
+" An optional second argument can set an alternative filetype for the window.
+function! ale#preview#Show(lines, ...) abort
+    let l:filetype = get(a:000, 0, 'ale-preview')
+
     silent pedit ALEPreviewWindow
     wincmd P
     setlocal modifiable
     setlocal noreadonly
     setlocal nobuflisted
-    setlocal filetype=ale-preview
+    let &l:filetype = l:filetype
     setlocal buftype=nofile
     setlocal bufhidden=wipe
     :%d
@@ -16,3 +19,50 @@ function! ale#preview#Show(lines) abort
     setlocal nomodifiable
     setlocal readonly
 endfunction
+
+" Show a location selection preview window, given some items.
+" Each item should have 'filename', 'line', and 'column' keys.
+function! ale#preview#ShowSelection(item_list) abort
+    let l:lines = []
+
+    " Create lines to display to users.
+    for l:item in a:item_list
+        call add(
+        \   l:lines,
+        \   l:item.filename
+        \       . ':' . l:item.line
+        \       . ':' . l:item.column,
+        \)
+    endfor
+
+    call ale#preview#Show(l:lines, 'ale-preview-selection')
+    let b:ale_preview_item_list = a:item_list
+endfunction
+
+function! s:Open(open_in_tab) abort
+    let l:item_list = get(b:, 'ale_preview_item_list', [])
+    let l:item = get(l:item_list, getcurpos()[1] - 1, {})
+
+    if empty(l:item)
+        return
+    endif
+
+    if !a:open_in_tab
+        :q!
+    endif
+
+    call ale#util#Open(
+    \   l:item.filename,
+    \   l:item.line,
+    \   l:item.column,
+    \   {'open_in_tab': a:open_in_tab},
+    \)
+endfunction
+
+function! ale#preview#OpenSelectionInBuffer() abort
+    call s:Open(0)
+endfunction
+
+function! ale#preview#OpenSelectionInTab() abort
+    call s:Open(1)
+endfunction

autoload/ale/util.vim

@@ -11,6 +11,11 @@ function! ale#util#FeedKeys(...) abort
     return call('feedkeys', a:000)
 endfunction
 
+" A wrapper function for execute, so we can test executing some commands.
+function! ale#util#Execute(expr) abort
+    execute a:expr
+endfunction
+
 if !exists('g:ale#util#nul_file')
     " A null file for sending output to nothing.
     let g:ale#util#nul_file = '/dev/null'
@@ -33,6 +38,16 @@ function! ale#util#GetFunction(string_or_ref) abort
     return a:string_or_ref
 endfunction
 
+function! ale#util#Open(filename, line, column, options) abort
+    if get(a:options, 'open_in_tab', 0)
+        call ale#util#Execute('tabedit ' . fnameescape(a:filename))
+    else
+        call ale#util#Execute('edit ' . fnameescape(a:filename))
+    endif
+
+    call cursor(a:line, a:column)
+endfunction
+
 let g:ale#util#error_priority = 5
 let g:ale#util#warning_priority = 4
 let g:ale#util#info_priority = 3
@@ -341,8 +356,10 @@ if !exists('s:patial_timers')
 endif
 
 function! s:ApplyPartialTimer(timer_id) abort
-    let [l:Callback, l:args] = remove(s:partial_timers, a:timer_id)
-    call call(l:Callback, [a:timer_id] + l:args)
+    if has_key(s:partial_timers, a:timer_id)
+        let [l:Callback, l:args] = remove(s:partial_timers, a:timer_id)
+        call call(l:Callback, [a:timer_id] + l:args)
+    endif
 endfunction
 
 " Given a delay, a callback, a List of arguments, start a timer with