vim-patch:8.1.0619: :echomsg and :echoerr do not handle List and Dict

Problem:    :echomsg and :echoerr do not handle List and Dict like :echo does.
            (Daniel Hahler)
Solution:   Be more tolerant about the expression result type.
461a7fcfce

Add lua functional tests for :echo,:echon,:echomsg,:echoerr
because nvim did not port "test_" functions from Vim
that modify internal state.

Testing :echoerr via try/catch is sufficient.

src/nvim/eval.c

@@ -9459,6 +9459,27 @@ void set_selfdict(typval_T *rettv, dict_T *selfdict)
   }
 }
 
+// Turn a typeval into a string.  Similar to tv_get_string_buf() but uses
+// string() on Dict, List, etc.
+static const char *tv_stringify(typval_T *varp, char *buf)
+  FUNC_ATTR_NONNULL_ALL
+{
+  if (varp->v_type == VAR_LIST
+      || varp->v_type == VAR_DICT
+      || varp->v_type == VAR_FUNC
+      || varp->v_type == VAR_PARTIAL
+      || varp->v_type == VAR_FLOAT) {
+    typval_T tmp;
+
+    f_string(varp, &tmp, NULL);
+    const char *const res = tv_get_string_buf(&tmp, buf);
+    tv_clear(varp);
+    *varp = tmp;
+    return res;
+  }
+  return tv_get_string_buf(varp, buf);
+}
+
 // Find variable "name" in the list of variables.
 // Return a pointer to it if found, NULL if not found.
 // Careful: "a:0" variables don't have a name.
@@ -10349,7 +10370,10 @@ void ex_execute(exarg_T *eap)
     }
 
     if (!eap->skip) {
-      const char *const argstr = tv_get_string(&rettv);
+      char buf[NUMBUFLEN];
+      const char *const argstr = eap->cmdidx == CMD_execute
+        ? tv_get_string_buf(&rettv, buf)
+        : tv_stringify(&rettv, buf);
       const size_t len = strlen(argstr);
       ga_grow(&ga, len + 2);
       if (!GA_EMPTY(&ga)) {

src/nvim/eval/funcs.c

@@ -9558,7 +9558,7 @@ static void f_stridx(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 /*
  * "string()" function
  */
-static void f_string(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+void f_string(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
   rettv->v_type = VAR_STRING;
   rettv->vval.v_string = (char_u *)encode_tv2string(&argvars[0], NULL);

src/nvim/testdir/test_messages.vim

@@ -1,4 +1,4 @@
-" Tests for :messages
+" Tests for :messages, :echomsg, :echoerr
 
 function Test_messages()
   let oldmore = &more
@@ -65,6 +65,35 @@ func Test_message_completion()
   call assert_equal('"message clear', @:)
 endfunc
 
+func Test_echomsg()
+  call assert_equal("\nhello", execute(':echomsg "hello"'))
+  call assert_equal("\n", execute(':echomsg ""'))
+  call assert_equal("\n12345", execute(':echomsg 12345'))
+  call assert_equal("\n[]", execute(':echomsg []'))
+  call assert_equal("\n[1, 2, 3]", execute(':echomsg [1, 2, 3]'))
+  call assert_equal("\n{}", execute(':echomsg {}'))
+  call assert_equal("\n{'a': 1, 'b': 2}", execute(':echomsg {"a": 1, "b": 2}'))
+  if has('float')
+    call assert_equal("\n1.23", execute(':echomsg 1.23'))
+  endif
+  call assert_match("function('<lambda>\\d*')", execute(':echomsg {-> 1234}'))
+endfunc
+
+func Test_echoerr()
+  throw 'skipped: Nvim does not support test_ignore_error()'
+  call test_ignore_error('IgNoRe')
+  call assert_equal("\nIgNoRe hello", execute(':echoerr "IgNoRe hello"'))
+  call assert_equal("\n12345 IgNoRe", execute(':echoerr 12345 "IgNoRe"'))
+  call assert_equal("\n[1, 2, 'IgNoRe']", execute(':echoerr [1, 2, "IgNoRe"]'))
+  call assert_equal("\n{'IgNoRe': 2, 'a': 1}", execute(':echoerr {"a": 1, "IgNoRe": 2}'))
+  if has('float')
+    call assert_equal("\n1.23 IgNoRe", execute(':echoerr 1.23 "IgNoRe"'))
+  endif
+  call test_ignore_error('<lambda>')
+  call assert_match("function('<lambda>\\d*')", execute(':echoerr {-> 1234}'))
+  call test_ignore_error('RESET')
+endfunc
+
 func Test_echospace()
   set noruler noshowcmd laststatus=1
   call assert_equal(&columns - 1, v:echospace)