Enable setting and updating diagnostics on a single quickfix list

Author: ajayvigneshk

autoload/LSP.vim

@@ -1,5 +1,18 @@
 " TODO: make buffer aware.
 
+function! LSP#GetQfListIdForTitle(title)
+	echom a:title
+	let headnr=getqflist({ 'id':0 ,'nr':'$', 'title': 0}).nr
+	while headnr >= 0
+		let qflistat= getqflist({'id':0,'nr':headnr,'title':0})
+		if qflistat.title==a:title
+			return qflistat.id
+		endif
+		let headnr = headnr-1
+	endwhile
+	return-1 "not found
+endfunction
+
 function! LSP#filename() abort
     " When executing autocommand, `%` might have already changed.
     let l:filename = expand('<afile>:p')

src/language_server_protocol.rs

@@ -684,7 +684,15 @@ impl LanguageClient {
         let diagnostics_list = self.get(|state| state.diagnostics_list)?;
         match diagnostics_list {
             DiagnosticsList::Quickfix => {
-                self.vim()?.setqflist(&qflist, "r", title)?;
+                //Has to be atomic
+                self.update(|state|  {
+                    let id = state.vim.getqfid(title)?;
+                    if id != -1 {
+                        state.vim.updateqflist(&qflist,title,id)
+                    }else {
+                        state.vim.addnewqflist(&qflist, title)
+                    }
+                })?;
             }
             DiagnosticsList::Location => {
                 self.vim()?.setloclist(&qflist, "r", title)?;

src/vim.rs

@@ -206,6 +206,25 @@ impl Vim {
         Ok(())
     }
 
+    pub fn updateqflist(&self, list: &[QuickfixEntry],title: &str, id: i32) -> Result<()> {
+        info!("Begin updateqflist");
+        let parms = json!([[], "r" ,{"title":title,"id":id, "items":list}]);
+        self.rpcclient.notify("setqflist", parms)?;
+        Ok(())
+    }
+
+    pub fn addnewqflist(&self, list: &[QuickfixEntry],title: &str) -> Result<()> {
+        info!("Begin addnewqflist");
+        let parms = json!([[], " ",{"title":title, "items":list}]);
+        self.rpcclient.notify("setqflist", parms)?;
+        Ok(())
+    }
+
+    pub fn getqfid(&self, title: &str) -> Result<i32> {
+        info!("Begin getqfid");
+        self.rpcclient.call("LSP#GetQfListIdForTitle",title)
+    }
+
     pub fn setqflist(&self, list: &[QuickfixEntry], action: &str, title: &str) -> Result<()> {
         info!("Begin setqflist");
         let parms = json!([list, action]);