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.

src/evalfunc.c

@@ -71,8 +71,10 @@ static void f_balloon_split(typval_T *argvars, typval_T *rettv);
 #endif
 static void f_browse(typval_T *argvars, typval_T *rettv);
 static void f_browsedir(typval_T *argvars, typval_T *rettv);
+static void f_bufadd(typval_T *argvars, typval_T *rettv);
 static void f_bufexists(typval_T *argvars, typval_T *rettv);
 static void f_buflisted(typval_T *argvars, typval_T *rettv);
+static void f_bufload(typval_T *argvars, typval_T *rettv);
 static void f_bufloaded(typval_T *argvars, typval_T *rettv);
 static void f_bufname(typval_T *argvars, typval_T *rettv);
 static void f_bufnr(typval_T *argvars, typval_T *rettv);
@@ -526,11 +528,13 @@ static struct fst
 #endif
     {"browse",		4, 4, f_browse},
     {"browsedir",	2, 2, f_browsedir},
+    {"bufadd",		1, 1, f_bufadd},
     {"bufexists",	1, 1, f_bufexists},
     {"buffer_exists",	1, 1, f_bufexists},	/* obsolete */
     {"buffer_name",	1, 1, f_bufname},	/* obsolete */
     {"buffer_number",	1, 1, f_bufnr},		/* obsolete */
     {"buflisted",	1, 1, f_buflisted},
+    {"bufload",		1, 1, f_bufload},
     {"bufloaded",	1, 1, f_bufloaded},
     {"bufname",		1, 1, f_bufname},
     {"bufnr",		1, 2, f_bufnr},
@@ -1919,6 +1923,15 @@ find_buffer(typval_T *avar)
     return buf;
 }
 
+/*
+ * "bufadd(expr)" function
+ */
+    static void
+f_bufadd(typval_T *argvars, typval_T *rettv)
+{
+    rettv->vval.v_number = buflist_add(tv_get_string(&argvars[0]), 0);
+}
+
 /*
  * "bufexists(expr)" function
  */
@@ -1940,6 +1953,25 @@ f_buflisted(typval_T *argvars, typval_T *rettv)
     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
  */

src/testdir/test_functions.vim

@@ -1515,3 +1515,31 @@ endfunc
 func Test_eventhandler()
   call assert_equal(0, eventhandler())
 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

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1610,
 /**/
     1609,
 /**/