patch 9.0.1939: still a problem when processing LSP RPC requests

Problem:  still a problem when processing LSP RPC requests
Solution: When processing async LSP RPC requests, compare sequence
          numbers only in response messages

A LSP request message can be sent to the language server either
synchronously (ch_evalexpr) or asynchronously (ch_sendexpr). In both
cases, when looking for response messages by using the sequence number,
LSP requests messages from the language server with the same sequence
number should not be used. Patch 9.0.1927 fixed this issue for
synchronous requests. This PR fixes the issue for asynchronous requests
and adds additional tests.

closes: #13158

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/channel.c

@@ -3052,13 +3052,27 @@ may_invoke_callback(channel_T *channel, ch_part_T part)
     {
 	// JSON or JS or LSP mode: invoke the one-time callback with the
 	// matching nr
-	for (cbitem = cbhead->cq_next; cbitem != NULL; cbitem = cbitem->cq_next)
+	int lsp_req_msg = FALSE;
-	    if (cbitem->cq_seq_nr == seq_nr)
+
+	// Don't use a LSP server request message with the same sequence number
+	// as the client request message as the response message.
+	if (ch_mode == CH_MODE_LSP && argv[1].v_type == VAR_DICT
+		&& dict_has_key(argv[1].vval.v_dict, "method"))
+	    lsp_req_msg = TRUE;
+
+	if (!lsp_req_msg)
+	{
+	    for (cbitem = cbhead->cq_next; cbitem != NULL;
+		    cbitem = cbitem->cq_next)
 	    {
-		invoke_one_time_callback(channel, cbhead, cbitem, argv);
+		if (cbitem->cq_seq_nr == seq_nr)
-		called_otc = TRUE;
+		{
-		break;
+		    invoke_one_time_callback(channel, cbhead, cbitem, argv);
+		    called_otc = TRUE;
+		    break;
+		}
 	    }
+	}
     }
 
     if (seq_nr > 0 && (ch_mode != CH_MODE_LSP || called_otc))

src/testdir/test_channel.vim

@@ -2478,23 +2478,32 @@ func Test_job_start_with_invalid_argument()
   call assert_fails('call job_start([0zff])', 'E976:')
 endfunc
 
-" Test for the 'lsp' channel mode
+" Process requests received from the LSP server
-func LspCb(chan, msg)
+func LspProcessServerRequests(chan, msg)
-  call add(g:lspNotif, a:msg)
+  if a:msg['method'] == 'server-req-in-middle'
-  if a:msg->has_key('method')
+        \ && a:msg['params']['text'] == 'server-req'
-    " Requests received from the LSP server
+    call ch_sendexpr(a:chan, #{method: 'server-req-in-middle-resp',
-    if a:msg['method'] == 'server-req-in-middle'
+          \ id: a:msg['id'], params: #{text: 'client-resp'}})
-          \ && a:msg['params']['text'] == 'server-req'
-      call ch_sendexpr(a:chan, #{method: 'server-req-in-middle-resp',
-            \ id: a:msg['id'], params: #{text: 'client-resp'}})
-    endif
   endif
 endfunc
 
-func LspOtCb(chan, msg)
+" LSP channel message callback function
-  call add(g:lspOtMsgs, a:msg)
+func LspCb(chan, msg)
+  call add(g:lspNotif, a:msg)
+  if a:msg->has_key('method')
+    call LspProcessServerRequests(a:chan, a:msg)
+  endif
 endfunc
 
+" LSP one-time message callback function (used for ch_sendexpr())
+func LspOtCb(chan, msg)
+  call add(g:lspOtMsgs, a:msg)
+  if a:msg->has_key('method')
+    call LspProcessServerRequests(a:chan, a:msg)
+  endif
+endfunc
+
+" Test for the 'lsp' channel mode
 func LspTests(port)
   " call ch_logfile('Xlspclient.log', 'w')
   let ch = ch_open(s:localhost .. a:port, #{mode: 'lsp', callback: 'LspCb'})
@@ -2661,7 +2670,7 @@ func LspTests(port)
   call assert_equal('alive', ch_evalexpr(ch, #{method: 'ping'}).result)
 
   " Test for processing a request message from the server while the client
-  " is waiting for a response with the same identifier.
+  " is waiting for a response with the same identifier (sync-rpc)
   let g:lspNotif = []
   let resp = ch_evalexpr(ch, #{method: 'server-req-in-middle',
         \ params: #{text: 'client-req'}})
@@ -2673,6 +2682,44 @@ func LspTests(port)
         \ #{id: 28, jsonrpc: '2.0', method: 'server-req-in-middle',
         \   params: #{text: 'server-req'}}], g:lspNotif)
 
+  " Test for processing a request message from the server while the client
+  " is waiting for a response with the same identifier (async-rpc using the
+  " channel callback function)
+  let g:lspNotif = []
+  call ch_sendexpr(ch, #{method: 'server-req-in-middle', id: 500,
+        \ params: #{text: 'client-req'}})
+  " Send three pings to wait for all the notification messages to arrive
+  for i in range(3)
+    call assert_equal('alive', ch_evalexpr(ch, #{method: 'ping'}).result)
+  endfor
+  call assert_equal([
+        \ #{id: -1, jsonrpc: '2.0', method: 'server-req-in-middle',
+        \   params: #{text: 'server-notif'}},
+        \ #{id: 500, jsonrpc: '2.0', method: 'server-req-in-middle',
+        \   params: #{text: 'server-req'}},
+        \ #{id: 500, jsonrpc: '2.0', result: #{text: 'server-resp'}}
+        \ ], g:lspNotif)
+
+  " Test for processing a request message from the server while the client
+  " is waiting for a response with the same identifier (async-rpc using a
+  " one-time callback function)
+  let g:lspNotif = []
+  let g:lspOtMsgs = []
+  call ch_sendexpr(ch, #{method: 'server-req-in-middle',
+        \ params: #{text: 'client-req'}}, #{callback: 'LspOtCb'})
+  " Send a ping to wait for all the notification messages to arrive
+  for i in range(3)
+    call assert_equal('alive', ch_evalexpr(ch, #{method: 'ping'}).result)
+  endfor
+  call assert_equal([
+        \ #{id: 32, jsonrpc: '2.0', result: #{text: 'server-resp'}}],
+        \ g:lspOtMsgs)
+  call assert_equal([
+        \ #{id: -1, jsonrpc: '2.0', method: 'server-req-in-middle',
+        \ params: #{text: 'server-notif'}},
+        \ #{id: 32, jsonrpc: '2.0', method: 'server-req-in-middle',
+        \ params: {'text': 'server-req'}}], g:lspNotif)
+
   " Test for invoking an unsupported method
   let resp = ch_evalexpr(ch, #{method: 'xyz', params: {}}, #{timeout: 200})
   call assert_equal({}, resp)

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1939,
 /**/
     1938,
 /**/