vim-patch:8.1.1610: there is no way to add or load a buffer without side effects

Problem:    There is no way to add or load a buffer without side effects.
Solution:   Add the bufadd() and bufload() functions.
https://github.com/vim/vim/commit/15e248e37f3925d430f96e945d52d3dc423cdc83

3 files changed, 51 insertions, 0 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 1935478f15..659f957fd1 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -7289,6 +7289,12 @@ static buf_T *find_buffer(typval_T *avar)
   return buf;
 }
 
+// "bufadd(expr)" function
+static void f_bufadd(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  rettv->vval.v_number = buflist_add(tv_get_string(&argvars[0]), 0);
+}
+
 /*
  * "bufexists(expr)" function
  */
@@ -7308,6 +7314,21 @@ static void f_buflisted(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   rettv->vval.v_number = (buf != NULL && buf->b_p_bl);
 }
 
+// "bufload(expr)" function
+static void f_bufload(typval_T *argvars, typval_T *rettv unused)
+{
+  buf_T *buf = get_buf_arg(&argvars[0]);
+
+  if (buf != NULL && buf->b_ml.ml_mfp == NULL) {
+    aco_save_T aco;
+
+    aucmd_prepbuf(&aco, buf);
+    swap_exists_action = SEA_NONE;
+    open_buffer(FALSE, NULL, 0);
+    aucmd_restbuf(&aco);
+  }
+}
+
 /*
  * "bufloaded(expr)" function
  */
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index 9deee69f32..089b08d5d1 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -40,11 +40,13 @@ return {
     atan2={args=2},
     browse={args=4},
     browsedir={args=2},
+    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
     buflisted={args=1},
+    bufload={args=1},
     bufloaded={args=1},
     bufname={args=1},
     bufnr={args={1, 2}},
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index 0c3c356622..64f1c0abd9 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -1188,3 +1188,31 @@ func Test_libcall_libcallnr()
   call assert_fails("call libcall('Xdoesnotexist_', 'getenv', 'HOME')", 'E364:')
   call assert_fails("call libcallnr('Xdoesnotexist_', 'strlen', 'abcd')", 'E364:')
 endfunc
+
+func Test_bufadd_bufload()
+  call assert_equal(0, bufexists('someName'))
+  let buf = bufadd('someName')
+  call assert_notequal(0, buf)
+  call assert_equal(1, bufexists('someName'))
+  call assert_equal(0, getbufvar(buf, '&buflisted'))
+  call assert_equal(0, bufloaded(buf))
+  call bufload(buf)
+  call assert_equal(1, bufloaded(buf))
+  call assert_equal([''], getbufline(buf, 1, '$'))
+
+  let curbuf = bufnr('')
+  call writefile(['some', 'text'], 'otherName')
+  let buf = bufadd('otherName')
+  call assert_notequal(0, buf)
+  call assert_equal(1, bufexists('otherName'))
+  call assert_equal(0, getbufvar(buf, '&buflisted'))
+  call assert_equal(0, bufloaded(buf))
+  call bufload(buf)
+  call assert_equal(1, bufloaded(buf))
+  call assert_equal(['some', 'text'], getbufline(buf, 1, '$'))
+  call assert_equal(curbuf, bufnr(''))
+
+  bwipe someName
+  bwipe otherName
+  call assert_equal(0, bufexists('someName'))
+endfunc