Filter completion items from language server by starts_with word under cursor (#883)

* filter items by starts_with pre nth char of cursor

* add config for filter completion items by starts_with

* filter items by starts_with pre nth char of cursor

* add config for filter completion items by starts_with

* remove completion items pre filter configuratio

helix-term/src/commands.rs

@@ -4142,6 +4142,7 @@ pub fn completion(cx: &mut Context) {
     iter.reverse();
     let offset = iter.take_while(|ch| chars::char_is_word(*ch)).count();
     let start_offset = cursor.saturating_sub(offset);
+    let prefix = text.slice(start_offset..cursor).to_string();
 
     cx.callback(
         future,
@@ -4154,7 +4155,7 @@ pub fn completion(cx: &mut Context) {
                 return;
             }
 
-            let items = match response {
+            let mut items = match response {
                 Some(lsp::CompletionResponse::Array(items)) => items,
                 // TODO: do something with is_incomplete
                 Some(lsp::CompletionResponse::List(lsp::CompletionList {
@@ -4164,6 +4165,18 @@ pub fn completion(cx: &mut Context) {
                 None => Vec::new(),
             };
 
+            if !prefix.is_empty() {
+                items = items
+                    .into_iter()
+                    .filter(|item| {
+                        item.filter_text
+                            .as_ref()
+                            .unwrap_or(&item.label)
+                            .starts_with(&prefix)
+                    })
+                    .collect();
+            }
+
             if items.is_empty() {
                 // editor.set_error("No completion available".to_string());
                 return;