fix(lsp): send didOpen if name changes on write (#19583)

`:saveas newName` changes the name of an existing buffer.
Due to the buffer re-use it skips the lsp attach phase and immediately
sends a `didSave` notification to the server.
Servers get confused about this, because they expect a `didOpen`
notification first.

Closes https://github.com/neovim/neovim/issues/18688

1 files changed, 26 insertions, 4 deletions

diff --git a/test/functional/fixtures/fake-lsp-server.lua b/test/functional/fixtures/fake-lsp-server.lua
index 0dc0c8c2db..aa47198f7a 100644
--- a/test/functional/fixtures/fake-lsp-server.lua
+++ b/test/functional/fixtures/fake-lsp-server.lua
@@ -67,10 +67,12 @@ local function expect_notification(method, params, ...)
   local message = read_message()
   assert_eq(method, message.method,
       ..., "expect_notification", "method")
-  assert_eq(params, message.params,
-      ..., "expect_notification", method, "params")
-  assert_eq({jsonrpc = "2.0"; method=method, params=params}, message,
-      ..., "expect_notification", "message")
+  if params then
+    assert_eq(params, message.params,
+        ..., "expect_notification", method, "params")
+    assert_eq({jsonrpc = "2.0"; method=method, params=params}, message,
+        ..., "expect_notification", "message")
+  end
 end
 
 local function expect_request(method, handler, ...)
@@ -257,6 +259,26 @@ function tests.basic_check_capabilities()
   }
 end
 
+function tests.text_document_save_did_open()
+  skeleton {
+    on_init = function()
+      return {
+        capabilities = {
+          textDocumentSync = {
+            save = true
+          }
+        }
+      }
+    end;
+    body = function()
+      notify('start')
+      expect_notification('textDocument/didOpen')
+      expect_notification('textDocument/didSave')
+      notify('shutdown')
+    end;
+  }
+end
+
 function tests.text_document_sync_save_bool()
   skeleton {
     on_init = function()