ALERename: Fix an issue with unlisted buffers

autoload/ale/code_action.vim

@@ -67,9 +67,13 @@ function! ale#code_action#ApplyChanges(filename, changes, should_save) abort
     let l:current_buffer = bufnr('')
     " The buffer is used to determine the fileformat, if available.
     let l:buffer = bufnr(a:filename)
-    let l:is_current_buffer = l:buffer > 0 && l:buffer == l:current_buffer
+    " Buffer might be unlisted after calling :bd on it, we want to behave
+    " as if these buffers don't exist because they cannot be read from or
+    " modified anymore..
+    let l:is_opened = l:buffer > 0 && buflisted(l:buffer)
+    let l:is_current_buffer = l:is_opened && l:buffer == l:current_buffer
 
-    if l:buffer > 0
+    if l:is_opened
         let l:lines = getbufline(l:buffer, 1, '$')
 
         " Add empty line if there's trailing newline, like readfile() does.
@@ -155,7 +159,7 @@ function! ale#code_action#ApplyChanges(filename, changes, should_save) abort
         endif
     endfor
 
-    if l:buffer > 0
+    if l:is_opened
         " Make sure ale#util#{Writefile,SetBufferContents} add trailing
         " newline if and only if it should be added.
         if l:lines[-1] is# '' && getbufvar(l:buffer, '&eol')
@@ -183,7 +187,7 @@ function! ale#code_action#ApplyChanges(filename, changes, should_save) abort
         call setpos('.', [0, l:pos[0], l:pos[1], 0])
     endif
 
-    if a:should_save && l:buffer > 0 && !l:is_current_buffer
+    if a:should_save && l:is_opened && !l:is_current_buffer
         " Set up a one-time use event that will delete itself to reload the
         " buffer next time it's entered to view the changes made to it.
         execute 'augroup ALECodeActionReloadGroup' . l:buffer

test/test_code_action.vader

@@ -36,10 +36,10 @@ Before:
 
 After:
   " Close the extra buffers if we opened it.
-  if bufnr(g:file1) != -1
+  if bufnr(g:file1) != -1 && buflisted(bufnr(g:file1))
     execute ':bp! | :bd! ' . bufnr(g:file1)
   endif
-  if bufnr(g:file2) != -1
+  if bufnr(g:file2) != -1 && buflisted(bufnr(g:file2))
     execute ':bp! | :bd! ' . bufnr(g:file2)
   endif
 
@@ -252,6 +252,45 @@ Execute(Current buffer contents will be reloaded):
   \] + g:test.text, getbufline(g:test.buffer, 1, '$')
 
 
+Execute(Unlisted buffer contents will be modified correctly):
+  let g:test.text = [
+  \ 'class Name {',
+  \ '  value: string',
+  \ '}',
+  \]
+  call writefile(g:test.text, g:file1, 'S')
+
+  execute 'edit ' . g:file1
+  let g:test.buffer = bufnr(g:file1)
+
+  execute 'bd'
+  AssertEqual bufnr(g:file1), g:test.buffer
+
+  call ale#code_action#HandleCodeAction(
+  \ {
+  \   'changes': [{
+  \      'fileName': g:file1,
+  \      'textChanges': [{
+  \        'start': {
+  \          'line': 1,
+  \          'offset': 1,
+  \        },
+  \        'end': {
+  \          'line': 1,
+  \          'offset': 1,
+  \        },
+  \        'newText': "type A: string\ntype B: number\n",
+  \      }],
+  \   }]
+  \ },
+  \ {'should_save': 1},
+  \)
+
+  AssertEqual [
+  \  'type A: string',
+  \  'type B: number',
+  \] + g:test.text + [''], readfile(g:file1, 'b')
+
 # Tests for cursor repositioning. In comments `=` designates change range, and
 # `C` cursor position