api/msgpack-rpc: Improve error infrastructure

- Add error type information to `Error`
- Rename `set_api_error` to `api_set_error` for consistency with other api_*
  functions/macros.
- Refactor the api_set_error macro to accept formatted strings and error types
- Improve error messages
- Wrap error messages with gettext macro
- Refactor msgpack-rpc serialization to transform Error instances into [type,
  message] arrays
- Add error type information to API metadata
- Normalize nvim->client and client->nvim error handling(change
  channel_send_call to accept an Error pointer instead of the `errored` boolean
  pointer)
- Use macro to initialize Error structures

1 files changed, 4 insertions, 5 deletions

diff --git a/src/nvim/os/provider.c b/src/nvim/os/provider.c
index 2e7a677793..d4fffaa053 100644
--- a/src/nvim/os/provider.c
+++ b/src/nvim/os/provider.c
@@ -107,12 +107,11 @@ Object provider_call(char *method, Array args)
     return NIL;
   }
 
-  bool error = false;
-  Object result = NIL;
-  channel_send_call(f->channel_id, method, args, &result, &error);
+  Error err = ERROR_INIT;
+  Object result = NIL = channel_send_call(f->channel_id, method, args, &err);
 
-  if (error) {
-    vim_report_error(result.data.string);
+  if (err.set) {
+    vim_report_error(cstr_as_string(err.msg));
     api_free_object(result);
     return NIL;
   }