vim-patch:9.1.0208: winfixbuf does not allow to re-edit current buffer (#28054)

Problem:  winfixbuf does not allow to re-edit current buffer
          (Tim Pope, after v9.1.0147)
Solution: Explicitly allow :e even when 'winfixbuf' is set,
          since it just re-loads the current buffer
          (Colin Kennedy)

fixes: vim/vim#14237
closes: vim/vim#14286

https://github.com/vim/vim/commit/65e580bd5610465bb6b9c1a546b7a8d00c76aa47

2 files changed, 175 insertions, 1 deletions

diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 1009e25081..ee738d9e92 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -216,6 +216,38 @@ static void restore_dbg_stuff(struct dbg_stuff *dsp)
   current_exception = dsp->current_exception;
 }
 
+/// Check if ffname differs from fnum.
+/// fnum is a buffer number. 0 == current buffer, 1-or-more must be a valid buffer ID.
+/// ffname is a full path to where a buffer lives on-disk or would live on-disk.
+static bool is_other_file(int fnum, char *ffname)
+{
+  if (fnum != 0) {
+    if (fnum == curbuf->b_fnum) {
+      return false;
+    }
+
+    return true;
+  }
+
+  if (ffname == NULL) {
+    return true;
+  }
+
+  if (*ffname == NUL) {
+    return false;
+  }
+
+  if (!curbuf->file_id_valid
+      && curbuf->b_sfname != NULL
+      && *curbuf->b_sfname != NUL) {
+    // This occurs with unsaved buffers. In which case `ffname`
+    // actually corresponds to curbuf->b_sfname
+    return path_fnamecmp(ffname, curbuf->b_sfname) != 0;
+  }
+
+  return otherfile(ffname);
+}
+
 /// Repeatedly get commands for Ex mode, until the ":vi" command is given.
 void do_exmode(void)
 {
@@ -5371,11 +5403,13 @@ static void ex_find(exarg_T *eap)
 /// ":edit", ":badd", ":balt", ":visual".
 static void ex_edit(exarg_T *eap)
 {
+  char *ffname = eap->cmdidx == CMD_enew ? NULL : eap->arg;
+
   // Exclude commands which keep the window's current buffer
   if (eap->cmdidx != CMD_badd
       && eap->cmdidx != CMD_balt
       // All other commands must obey 'winfixbuf' / ! rules
-      && !check_can_set_curbuf_forceit(eap->forceit)) {
+      && (is_other_file(0, ffname) && !check_can_set_curbuf_forceit(eap->forceit))) {
     return;
   }
 
diff --git a/test/old/testdir/test_winfixbuf.vim b/test/old/testdir/test_winfixbuf.vim
index 320e73f378..d5e43cf33e 100644
--- a/test/old/testdir/test_winfixbuf.vim
+++ b/test/old/testdir/test_winfixbuf.vim
@@ -1125,6 +1125,146 @@ func Test_edit()
   call assert_equal(l:other, bufnr())
 endfunc
 
+" Fail :e when selecting a buffer from a relative path if in a different folder
+"
+" In this tests there's 2 buffers
+"
+" foo - lives on disk, in some folder. e.g. /tmp/foo
+" foo - an in-memory buffer that has not been saved to disk. If saved, it
+"       would live in a different folder, /other/foo.
+"
+" The 'winfixbuf' is looking at the in-memory buffer and trying to switch to
+" the buffer on-disk (and fails, because it's a different buffer)
+func Test_edit_different_buffer_on_disk_and_relative_path_to_disk()
+  call s:reset_all_buffers()
+
+  let l:file_on_disk = tempname()
+  let l:directory_on_disk1 = fnamemodify(l:file_on_disk, ":p:h")
+  let l:name = fnamemodify(l:file_on_disk, ":t")
+  execute "edit " . l:file_on_disk
+  write!
+
+  let l:directory_on_disk2 = l:directory_on_disk1 . "_something_else"
+
+  if !isdirectory(l:directory_on_disk2)
+    call mkdir(l:directory_on_disk2)
+  endif
+
+  execute "cd " . l:directory_on_disk2
+  execute "edit " l:name
+
+  let l:current = bufnr()
+
+  call assert_equal(l:current, bufnr())
+  set winfixbuf
+  call assert_fails("edit " . l:file_on_disk, "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  call delete(l:directory_on_disk1)
+  call delete(l:directory_on_disk2)
+endfunc
+
+" Fail :e when selecting a buffer from a relative path if in a different folder
+"
+" In this tests there's 2 buffers
+"
+" foo - lives on disk, in some folder. e.g. /tmp/foo
+" foo - an in-memory buffer that has not been saved to disk. If saved, it
+"       would live in a different folder, /other/foo.
+"
+" The 'winfixbuf' is looking at the on-disk buffer and trying to switch to
+" the in-memory buffer (and fails, because it's a different buffer)
+func Test_edit_different_buffer_on_disk_and_relative_path_to_memory()
+  call s:reset_all_buffers()
+
+  let l:file_on_disk = tempname()
+  let l:directory_on_disk1 = fnamemodify(l:file_on_disk, ":p:h")
+  let l:name = fnamemodify(l:file_on_disk, ":t")
+  execute "edit " . l:file_on_disk
+  write!
+
+  let l:directory_on_disk2 = l:directory_on_disk1 . "_something_else"
+
+  if !isdirectory(l:directory_on_disk2)
+    call mkdir(l:directory_on_disk2)
+  endif
+
+  execute "cd " . l:directory_on_disk2
+  execute "edit " l:name
+  execute "cd " . l:directory_on_disk1
+  execute "edit " l:file_on_disk
+  execute "cd " . l:directory_on_disk2
+
+  let l:current = bufnr()
+
+  call assert_equal(l:current, bufnr())
+  set winfixbuf
+  call assert_fails("edit " . l:name, "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  call delete(l:directory_on_disk1)
+  call delete(l:directory_on_disk2)
+endfunc
+
+" Fail to call `:e first` if called from a starting, in-memory buffer
+func Test_edit_first_buffer()
+  call s:reset_all_buffers()
+
+  set winfixbuf
+  let l:current = bufnr()
+
+  call assert_fails("edit first", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  edit! first
+  call assert_equal(l:current, bufnr())
+  edit! somewhere_else
+  call assert_notequal(l:current, bufnr())
+endfunc
+
+" Allow reloading a buffer using :e
+func Test_edit_no_arguments()
+  call s:reset_all_buffers()
+
+  let l:current = bufnr()
+  file some_buffer
+
+  call assert_equal(l:current, bufnr())
+  set winfixbuf
+  edit
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow :e selecting the current buffer
+func Test_edit_same_buffer_in_memory()
+  call s:reset_all_buffers()
+
+  let l:current = bufnr()
+  file same_buffer
+
+  call assert_equal(l:current, bufnr())
+  set winfixbuf
+  edit same_buffer
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow :e selecting the current buffer as a full path
+func Test_edit_same_buffer_on_disk_absolute_path()
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  let l:current = bufnr()
+  execute "edit " . l:file
+  write!
+
+  call assert_equal(l:current, bufnr())
+  set winfixbuf
+  execute "edit " l:file
+  call assert_equal(l:current, bufnr())
+
+  call delete(l:file)
+endfunc
+
 " Fail :enew but :enew! is allowed
 func Test_enew()
   call s:reset_all_buffers()