Merge pull request #9300 from bfredl/asyncerr

rpc: fix invalid responses, turn errors from async calls into notifications

runtime/doc/api.txt

@@ -79,6 +79,19 @@ As Nvim evolves the API may change in compliance with this CONTRACT:
   - Existing items will not be removed (after release).
 - Deprecated functions will not be removed until Nvim version 2.0
 
+==============================================================================
+Global events						    *api-global-events*
+
+When a client invokes an API request as an async notification, it is not
+possible for Nvim to send an error response. Instead, in case of error, the
+following notification will be sent to the client:
+
+                                                             *nvim_error_event*
+nvim_error_event[{type}, {message}]
+
+{type} is a numeric id as defined by `api_info().error_types`, and {message} is
+a string with the error message.
+
 ==============================================================================
 Buffer update events					*api-buffer-updates*
 
@@ -206,7 +219,7 @@ Example using the Nvim python-client:
     buf.clear_highlight(src)
 <
 If the highlights don't need to be deleted or updated, just pass -1 as
-src_id (this is the default in python). Use |nvim_buf_clear_highlight()| to
+src_id (this is the default in python). Use |nvim_buf_clear_namespace()| to
 clear highlights from a specific source, in a specific line range or the
 entire buffer by passing in the line range 0, -1 (the latter is the default in
 python as used above).
@@ -218,7 +231,7 @@ An example of calling the api from vimscript: >
     call nvim_buf_add_highlight(0, src, "Identifier", 0, 5, -1)
 
     " later
-    call nvim_buf_clear_highlight(0, src, 0, -1)
+    call nvim_buf_clear_namespace(0, src, 0, -1)
 >
 ==============================================================================
 Global Functions                                                  *api-global*

runtime/doc/develop.txt

@@ -181,6 +181,8 @@ Standard Features ~
 - Clients should call |nvim_set_client_info()| after connecting, so users and
   plugins can detect the client by handling the |ChanInfo| event. This
   avoids the need for special variables or other client hints.
+- Clients should handle |nvim_error_event| notifications, which will be sent
+  if an async request to nvim was rejected or caused an error.
 
 Package Naming ~
 

src/nvim/msgpack_rpc/channel.c

@@ -641,7 +641,16 @@ static WBuffer *serialize_response(uint64_t channel_id,
 {
   msgpack_packer pac;
   msgpack_packer_init(&pac, sbuffer, msgpack_sbuffer_write);
-  msgpack_rpc_serialize_response(response_id, err, arg, &pac);
+  if (ERROR_SET(err) && response_id == NO_RESPONSE) {
+    Array args = ARRAY_DICT_INIT;
+    ADD(args, INTEGER_OBJ(err->type));
+    ADD(args, STRING_OBJ(cstr_to_string(err->msg)));
+    msgpack_rpc_serialize_request(0, cstr_as_string("nvim_error_event"),
+                                  args, &pac);
+    api_free_array(args);
+  } else {
+    msgpack_rpc_serialize_response(response_id, err, arg, &pac);
+  }
   log_server_msg(channel_id, sbuffer);
   WBuffer *rv = wstream_new_buffer(xmemdup(sbuffer->data, sbuffer->size),
                                    sbuffer->size,

test/functional/api/vim_spec.lua

@@ -14,6 +14,7 @@ local ok, nvim_async, feed = helpers.ok, helpers.nvim_async, helpers.feed
 local os_name = helpers.os_name
 local request = helpers.request
 local source = helpers.source
+local next_msg = helpers.next_msg
 
 local expect_err = global_helpers.expect_err
 local format_string = global_helpers.format_string
@@ -46,6 +47,15 @@ describe('API', function()
                request, nil)
   end)
 
+  it('handles errors in async requests', function()
+    local error_types = meths.get_api_info()[2].error_types
+    nvim_async("bogus")
+    eq({'notification', 'nvim_error_event',
+        {error_types.Exception.id, 'Invalid method: nvim_bogus'}}, next_msg())
+    -- error didn't close channel.
+    eq(2, eval('1+1'))
+  end)
+
   describe('nvim_command', function()
     it('works', function()
       local fname = helpers.tmpname()

test/functional/helpers.lua

@@ -757,6 +757,14 @@ return function(after_each)
       end
       check_logs()
       check_cores('build/bin/nvim')
+      if session then
+        local msg = session:next_message(0)
+        if msg then
+          if msg[1] == "notification" and msg[2] == "nvim_error_event" then
+            error(msg[3][2])
+          end
+        end
+      end
     end)
   end
   return module