feat(message): avoid spam on failed os_msg

also de-dupe the code

2 files changed, 21 insertions, 18 deletions

diff --git a/src/nvim/message.c b/src/nvim/message.c
index 041e5ed6c3..118d144617 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -3003,31 +3003,36 @@ static int do_more_prompt(int typed_char)
 }
 
 #if defined(MSWIN)
-void os_errmsg(char *str)
+/// Headless (no UI) error message handler.
+static void do_msg(char *str, bool errmsg)
 {
+  static bool did_err = false;
   assert(str != NULL);
   wchar_t *utf16str;
   int r = utf8_to_utf16(str, -1, &utf16str);
-  if (r != 0) {
+  if (r != 0 && !did_err) {
+    did_err = true;
     fprintf(stderr, "utf8_to_utf16 failed: %d", r);
-  } else {
-    fwprintf(stderr, L"%ls", utf16str);
+    ELOG("utf8_to_utf16 failed: %d", r);
+  } else if (r == 0) {
+    if (errmsg) {
+      fwprintf(stderr, L"%ls", utf16str);
+    } else {
+      wprintf(L"%ls", utf16str);
+    }
     xfree(utf16str);
   }
 }
 
-/// Give a message.  To be used when the UI is not initialized yet.
+void os_errmsg(char *str)
+{
+  do_msg(str, true);
+}
+
+/// Headless (no UI) message handler.
 void os_msg(char *str)
 {
-  assert(str != NULL);
-  wchar_t *utf16str;
-  int r = utf8_to_utf16(str, -1, &utf16str);
-  if (r != 0) {
-    fprintf(stderr, "utf8_to_utf16 failed: %d", r);
-  } else {
-    wprintf(L"%ls", utf16str);
-    xfree(utf16str);
-  }
+  do_msg(str, false);
 }
 #endif  // MSWIN
 
diff --git a/src/nvim/vim.h b/src/nvim/vim.h
index bfe75ef9f7..df24e423cf 100644
--- a/src/nvim/vim.h
+++ b/src/nvim/vim.h
@@ -245,12 +245,10 @@ enum { FOLD_TEXT_LEN = 51, };  //!< buffer size for get_foldtext()
 /// plus six following composing characters of three bytes each.
 #define MB_MAXBYTES    21
 
-// This has to go after the include of proto.h, as proto/gui.pro declares
-// functions of these names. The declarations would break if the defines had
-// been seen at that stage.  But it must be before globals.h, where error_ga
-// is declared.
 #ifndef MSWIN
+/// Headless (no UI) error message handler.
 # define os_errmsg(str)        fprintf(stderr, "%s", (str))
+/// Headless (no UI) message handler.
 # define os_msg(str)           printf("%s", (str))
 #endif