vim-patch:8.1.1924: using empty string for current buffer is unexpected

Problem:    Using empty string for current buffer is unexpected.
Solution:   Make the argument optional for bufname() and bufnr().
https://github.com/vim/vim/commit/a8eee21e75324d199acb1663cb5009e03014a13a

3 files changed, 28 insertions, 17 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 0a884fdca2..06254953cb 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -7353,14 +7353,19 @@ static buf_T * get_buf_arg(typval_T *arg)
  */
 static void f_bufname(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
+  const buf_T *buf;
   rettv->v_type = VAR_STRING;
   rettv->vval.v_string = NULL;
-  if (!tv_check_str_or_nr(&argvars[0])) {
-    return;
+  if (argvars[0].v_type == VAR_UNKNOWN) {
+    buf = curbuf;
+  } else {
+    if (!tv_check_str_or_nr(&argvars[0])) {
+      return;
+    }
+    emsg_off++;
+    buf = tv_get_buf(&argvars[0], false);
+    emsg_off--;
   }
-  emsg_off++;
-  const buf_T *const buf = tv_get_buf(&argvars[0], false);
-  emsg_off--;
   if (buf != NULL && buf->b_fname != NULL) {
     rettv->vval.v_string = (char_u *)xstrdup((char *)buf->b_fname);
   }
@@ -7371,15 +7376,21 @@ static void f_bufname(typval_T *argvars, typval_T *rettv, FunPtr fptr)
  */
 static void f_bufnr(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
+  const buf_T *buf;
   bool error = false;
 
   rettv->vval.v_number = -1;
-  if (!tv_check_str_or_nr(&argvars[0])) {
-    return;
+
+  if (argvars[0].v_type == VAR_UNKNOWN) {
+    buf = curbuf;
+  } else {
+    if (!tv_check_str_or_nr(&argvars[0])) {
+      return;
+    }
+    emsg_off++;
+    buf = tv_get_buf(&argvars[0], false);
+    emsg_off--;
   }
-  emsg_off++;
-  const buf_T *buf = tv_get_buf(&argvars[0], false);
-  emsg_off--;
 
   // If the buffer isn't found and the second argument is not zero create a
   // new buffer.
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index 6b63003e69..c87fb534c6 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -44,13 +44,13 @@ return {
     bufadd={args=1},
     bufexists={args=1},
     buffer_exists={args=1, func='f_bufexists'},  -- obsolete
-    buffer_name={args=1, func='f_bufname'},  -- obsolete
-    buffer_number={args=1, func='f_bufnr'},  -- obsolete
+    buffer_name={args={0, 1}, func='f_bufname'},  -- obsolete
+    buffer_number={args={0, 1}, func='f_bufnr'},  -- obsolete
     buflisted={args=1},
     bufload={args=1},
     bufloaded={args=1},
-    bufname={args=1},
-    bufnr={args={1, 2}},
+    bufname={args={0, 1}},
+    bufnr={args={0, 2}},
     bufwinid={args=1},
     bufwinnr={args=1},
     byte2line={args=1},
diff --git a/src/nvim/testdir/test_arglist.vim b/src/nvim/testdir/test_arglist.vim
index df72ff0a32..6e7583ade3 100644
--- a/src/nvim/testdir/test_arglist.vim
+++ b/src/nvim/testdir/test_arglist.vim
@@ -379,10 +379,10 @@ func Test_argedit()
   " make sure to use a new buffer number for x when it is loaded
   bw! x
   new
-  let a = bufnr('')
+  let a = bufnr()
   argedit x
-  call assert_equal(a, bufnr(''))
-  call assert_equal('x', bufname(''))
+  call assert_equal(a, bufnr())
+  call assert_equal('x', bufname())
   %argd
   bw! x
 endfunc