vim-patch:8.2.4343: when reloading not all properties are detected

Problem:    When reloading not all properties are detected.
Solution:   Add the "edit" value to v:fcs_choice. (Rob Pilling, closes vim/vim#9579)
https://github.com/vim/vim/commit/8196e94a8b72ed8618605cb66615571313097d78

Cherry-pick some test changes from patch 8.1.1826.

8 files changed, 215 insertions, 41 deletions

diff --git a/runtime/doc/editing.txt b/runtime/doc/editing.txt
index 3d0287b0cd..8ddc661c0e 100644
--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -1450,6 +1450,11 @@ If you don't get warned often enough you can use the following command.
 			if it exists now.
 			Once a file has been checked the timestamp is reset,
 			you will not be warned again.
+			Syntax highlighting, marks, diff status,
+			'fileencoding', 'fileformat' and 'binary' options
+			are not changed.  See |v:fcs_choice| to reload these
+			too (for example, if a code formatting tools has
+			changed the file).
 
 :[N]checkt[ime] {filename}
 :[N]checkt[ime] [N]
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index fc788fba59..fc422f13e5 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1882,6 +1882,11 @@ v:fcs_choice	What should happen after a |FileChangedShell| event was
 		do with the affected buffer:
 			reload		Reload the buffer (does not work if
 					the file was deleted).
+			edit		Reload the buffer and detect the
+					values for options such as
+					'fileformat', 'fileencoding', 'binary'
+					(does not work if the file was
+					deleted).
 			ask		Ask the user what to do, as if there
 					was no autocommand.  Except that when
 					only the timestamp changed nothing
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 110981159f..f5824d83be 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -2013,10 +2013,8 @@ static linenr_T readfile_linenr(linenr_T linecnt, char_u *p, char_u *endp)
   return lnum;
 }
 
-/*
- * Fill "*eap" to force the 'fileencoding', 'fileformat' and 'binary to be
- * equal to the buffer "buf".  Used for calling readfile().
- */
+/// Fill "*eap" to force the 'fileencoding', 'fileformat' and 'binary' to be
+/// equal to the buffer "buf".  Used for calling readfile().
 void prep_exarg(exarg_T *eap, const buf_T *buf)
   FUNC_ATTR_NONNULL_ALL
 {
@@ -4901,13 +4899,11 @@ static int move_lines(buf_T *frombuf, buf_T *tobuf)
   return retval;
 }
 
-/*
- * Check if buffer "buf" has been changed.
- * Also check if the file for a new buffer unexpectedly appeared.
- * return 1 if a changed buffer was found.
- * return 2 if a message has been displayed.
- * return 0 otherwise.
- */
+/// Check if buffer "buf" has been changed.
+/// Also check if the file for a new buffer unexpectedly appeared.
+/// return 1 if a changed buffer was found.
+/// return 2 if a message has been displayed.
+/// return 0 otherwise.
 int buf_check_timestamp(buf_T *buf)
   FUNC_ATTR_NONNULL_ALL
 {
@@ -4916,7 +4912,11 @@ int buf_check_timestamp(buf_T *buf)
   char *mesg = NULL;
   char *mesg2 = "";
   bool helpmesg = false;
-  bool reload = false;
+  enum {
+    RELOAD_NONE,
+    RELOAD_NORMAL,
+    RELOAD_DETECT
+  } reload = RELOAD_NONE;
   bool can_reload = false;
   uint64_t orig_size = buf->b_orig_size;
   int orig_mode = buf->b_orig_mode;
@@ -4969,7 +4969,7 @@ int buf_check_timestamp(buf_T *buf)
       // If 'autoread' is set, the buffer has no changes and the file still
       // exists, reload the buffer.  Use the buffer-local option value if it
       // was set, the global option value otherwise.
-      reload = true;
+      reload = RELOAD_NORMAL;
     } else {
       if (!file_info_ok) {
         reason = "deleted";
@@ -5000,7 +5000,9 @@ int buf_check_timestamp(buf_T *buf)
         }
         s = get_vim_var_str(VV_FCS_CHOICE);
         if (STRCMP(s, "reload") == 0 && *reason != 'd') {
-          reload = true;
+          reload = RELOAD_NORMAL;
+        } else if (STRCMP(s, "edit") == 0) {
+          reload = RELOAD_DETECT;
         } else if (STRCMP(s, "ask") == 0) {
           n = false;
         } else {
@@ -5064,9 +5066,15 @@ int buf_check_timestamp(buf_T *buf)
         xstrlcat(tbuf, "\n", tbuf_len - 1);
         xstrlcat(tbuf, mesg2, tbuf_len - 1);
       }
-      if (do_dialog(VIM_WARNING, (char_u *)_("Warning"), (char_u *)tbuf,
-                    (char_u *)_("&OK\n&Load File"), 1, NULL, true) == 2) {
-        reload = true;
+      switch (do_dialog(VIM_WARNING, (char_u *)_("Warning"), (char_u *)tbuf,
+                        (char_u *)_("&OK\n&Load File\nLoad File &and Options"),
+                        1, NULL, true)) {
+        case 2:
+          reload = RELOAD_NORMAL;
+          break;
+        case 3:
+          reload = RELOAD_DETECT;
+          break;
       }
     } else if (State > NORMAL_BUSY || (State & CMDLINE) || already_warned) {
       if (*mesg2 != NUL) {
@@ -5100,9 +5108,9 @@ int buf_check_timestamp(buf_T *buf)
     xfree(tbuf);
   }
 
-  if (reload) {
+  if (reload != RELOAD_NONE) {
     // Reload the buffer.
-    buf_reload(buf, orig_mode);
+    buf_reload(buf, orig_mode, reload == RELOAD_DETECT);
     if (buf->b_p_udf && buf->b_ffname != NULL) {
       char_u hash[UNDO_HASH_SIZE];
 
@@ -5120,13 +5128,11 @@ int buf_check_timestamp(buf_T *buf)
   return retval;
 }
 
-/*
- * Reload a buffer that is already loaded.
- * Used when the file was changed outside of Vim.
- * "orig_mode" is buf->b_orig_mode before the need for reloading was detected.
- * buf->b_orig_mode may have been reset already.
- */
-void buf_reload(buf_T *buf, int orig_mode)
+/// Reload a buffer that is already loaded.
+/// Used when the file was changed outside of Vim.
+/// "orig_mode" is buf->b_orig_mode before the need for reloading was detected.
+/// buf->b_orig_mode may have been reset already.
+void buf_reload(buf_T *buf, int orig_mode, bool reload_options)
 {
   exarg_T ea;
   pos_T old_cursor;
@@ -5141,11 +5147,15 @@ void buf_reload(buf_T *buf, int orig_mode)
   // set curwin/curbuf for "buf" and save some things
   aucmd_prepbuf(&aco, buf);
 
-  // We only want to read the text from the file, not reset the syntax
-  // highlighting, clear marks, diff status, etc.  Force the fileformat and
-  // encoding to be the same.
+  // Unless reload_options is set, we only want to read the text from the
+  // file, not reset the syntax highlighting, clear marks, diff status, etc.
+  // Force the fileformat and encoding to be the same.
+  if (reload_options) {
+    memset(&ea, 0, sizeof(ea));
+  } else {
+    prep_exarg(&ea, buf);
+  }
 
-  prep_exarg(&ea, buf);
   old_cursor = curwin->w_cursor;
   old_topline = curwin->w_topline;
 
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 93742ccbdb..b39450cdc6 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -3464,6 +3464,7 @@ void msg_advance(int col)
 ///
 /// @param textfiel  IObuff for inputdialog(), NULL otherwise
 /// @param ex_cmd  when TRUE pressing : accepts default and starts Ex command
+/// @returns 0 if cancelled, otherwise the nth button (1-indexed).
 int do_dialog(int type, char_u *title, char_u *message, char_u *buttons, int dfltbutton,
               char_u *textfield, int ex_cmd)
 {
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index f6b95f37b1..d7b220b3f6 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -5654,7 +5654,7 @@ void spell_add_word(char_u *word, int len, SpellAddType what, int idx, bool undo
 
     // If the .add file is edited somewhere, reload it.
     if (buf != NULL) {
-      buf_reload(buf, buf->b_orig_mode);
+      buf_reload(buf, buf->b_orig_mode, false);
     }
 
     redraw_all_later(SOME_VALID);
diff --git a/src/nvim/testdir/setup.vim b/src/nvim/testdir/setup.vim
index fdae0697c3..15e3b31498 100644
--- a/src/nvim/testdir/setup.vim
+++ b/src/nvim/testdir/setup.vim
@@ -10,6 +10,7 @@ let s:did_load = 1
 set backspace=
 set directory^=.
 set fillchars=vert:\|,fold:-
+set fsync
 set laststatus=1
 set listchars=eol:$
 set joinspaces
diff --git a/src/nvim/testdir/test_filechanged.vim b/src/nvim/testdir/test_filechanged.vim
index b4c32fcc16..06ccd6e85f 100644
--- a/src/nvim/testdir/test_filechanged.vim
+++ b/src/nvim/testdir/test_filechanged.vim
@@ -1,9 +1,10 @@
 " Tests for when a file was changed outside of Vim.
 
+source check.vim
+
 func Test_FileChangedShell_reload()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
+
   augroup testreload
     au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'reload'
   augroup END
@@ -90,11 +91,107 @@ func Test_FileChangedShell_reload()
   call delete('Xchanged_r')
 endfunc
 
+func Test_FileChangedShell_edit()
+  CheckUnix
+
+  new Xchanged_r
+  call setline(1, 'reload this')
+  set fileformat=unix
+  write
+
+  " File format changed, reload (content only, no 'ff' etc)
+  augroup testreload
+    au!
+    au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'reload'
+  augroup END
+  call assert_equal(&fileformat, 'unix')
+  sleep 10m  " make the test less flaky in Nvim
+  call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+  let g:reason = ''
+  checktime
+  call assert_equal('changed', g:reason)
+  call assert_equal(&fileformat, 'unix')
+  call assert_equal("line1\r", getline(1))
+  call assert_equal("line2\r", getline(2))
+  %s/\r
+  write
+
+  " File format changed, reload with 'ff', etc
+  augroup testreload
+    au!
+    au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'edit'
+  augroup END
+  call assert_equal(&fileformat, 'unix')
+  sleep 10m  " make the test less flaky in Nvim
+  call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+  let g:reason = ''
+  checktime
+  call assert_equal('changed', g:reason)
+  call assert_equal(&fileformat, 'dos')
+  call assert_equal('line1', getline(1))
+  call assert_equal('line2', getline(2))
+  set fileformat=unix
+  write
+
+  au! testreload
+  bwipe!
+  call delete(undofile('Xchanged_r'))
+  call delete('Xchanged_r')
+endfunc
+
+func Test_FileChangedShell_edit_dialog()
+  throw 'Skipped: requires a UI to be active'
+  CheckNotGui
+
+  new Xchanged_r
+  call setline(1, 'reload this')
+  set fileformat=unix
+  write
+
+  " File format changed, reload (content only) via prompt
+  augroup testreload
+    au!
+    au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'ask'
+  augroup END
+  call assert_equal(&fileformat, 'unix')
+  call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+  let g:reason = ''
+  call feedkeys('L', 'L') " load file content only
+  checktime
+  call assert_equal('changed', g:reason)
+  call assert_equal(&fileformat, 'unix')
+  call assert_equal("line1\r", getline(1))
+  call assert_equal("line2\r", getline(2))
+  %s/\r
+  write
+
+  " File format changed, reload (file and options) via prompt
+  augroup testreload
+    au!
+    au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'ask'
+  augroup END
+  call assert_equal(&fileformat, 'unix')
+  call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+  let g:reason = ''
+  call feedkeys('a', 'L') " load file content and options
+  checktime
+  call assert_equal('changed', g:reason)
+  call assert_equal(&fileformat, 'dos')
+  call assert_equal("line1", getline(1))
+  call assert_equal("line2", getline(2))
+  set fileformat=unix
+  write
+
+  au! testreload
+  bwipe!
+  call delete(undofile('Xchanged_r'))
+  call delete('Xchanged_r')
+endfunc
+
 func Test_file_changed_dialog()
-  throw 'Skipped: requires a UI to a active'
-  if !has('unix') || has('gui_running')
-    return
-  endif
+  throw 'Skipped: requires a UI to be active'
+  CheckUnix
+  CheckNotGui
   au! FileChangedShell
 
   new Xchanged_d
diff --git a/test/functional/legacy/filechanged_spec.lua b/test/functional/legacy/filechanged_spec.lua
index fed7b27b0c..6eb853d630 100644
--- a/test/functional/legacy/filechanged_spec.lua
+++ b/test/functional/legacy/filechanged_spec.lua
@@ -11,6 +11,11 @@ describe('file changed dialog', function()
     clear()
     meths.ui_attach(80, 24, {})
     meths.set_option('autoread', false)
+    meths.set_option('fsync', true)
+  end)
+
+  it('works', function()
+    if helpers.pending_win32(pending) then return end
     source([[
       func Test_file_changed_dialog()
         au! FileChangedShell
@@ -66,11 +71,61 @@ describe('file changed dialog', function()
         call delete('Xchanged_d')
       endfunc
     ]])
+    call('Test_file_changed_dialog')
+    expected_empty()
   end)
 
-  it('works', function()
-    if helpers.pending_win32(pending) then return end
-    call('Test_file_changed_dialog')
+  it('works with FileChangedShell', function()
+    source([[
+      func Test_FileChangedShell_edit_dialog()
+        new Xchanged_r
+        call setline(1, 'reload this')
+        set fileformat=unix
+        silent write  " Use :silent to prevent a hit-enter prompt
+
+        " File format changed, reload (content only) via prompt
+        augroup testreload
+          au!
+          au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'ask'
+        augroup END
+        call assert_equal(&fileformat, 'unix')
+        sleep 10m  " make the test less flaky in Nvim
+        call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+        let g:reason = ''
+        call nvim_input('L') " load file content only
+        checktime
+        call assert_equal('changed', g:reason)
+        call assert_equal(&fileformat, 'unix')
+        call assert_equal("line1\r", getline(1))
+        call assert_equal("line2\r", getline(2))
+        %s/\r
+        silent write  " Use :silent to prevent a hit-enter prompt
+
+        " File format changed, reload (file and options) via prompt
+        augroup testreload
+          au!
+          au FileChangedShell Xchanged_r let g:reason = v:fcs_reason | let v:fcs_choice = 'ask'
+        augroup END
+        call assert_equal(&fileformat, 'unix')
+        sleep 10m  " make the test less flaky in Nvim
+        call writefile(["line1\r", "line2\r"], 'Xchanged_r')
+        let g:reason = ''
+        call nvim_input('a') " load file content and options
+        checktime
+        call assert_equal('changed', g:reason)
+        call assert_equal(&fileformat, 'dos')
+        call assert_equal("line1", getline(1))
+        call assert_equal("line2", getline(2))
+        set fileformat=unix
+        silent write  " Use :silent to prevent a hit-enter prompt
+
+        au! testreload
+        bwipe!
+        call delete(undofile('Xchanged_r'))
+        call delete('Xchanged_r')
+      endfunc
+    ]])
+    call('Test_FileChangedShell_edit_dialog')
     expected_empty()
   end)
 end)