Implement allSettled replacement to show _something_ when one of

the completion sources fails

Author: krassowski

CHANGELOG.md

@@ -11,6 +11,7 @@
 
   - delayed completion suggestions will no longer show up if cursor moved to another line ([#496])
   - changes in notebooks after kernel restart or file rename will now be recorded by the language server again ([#496])
+  - when either of kernel providers: kernel or LSP server fails, the completion from the other will still be shown ([#496])
 
 [#496]: https://github.com/krassowski/jupyterlab-lsp/pull/496
 

packages/jupyterlab-lsp/src/features/completion/completion_handler.ts

@@ -374,11 +374,9 @@ export class LSPConnector
             ]);
           }
 
-          // TODO: use allSettled if available; requires ES2020 or a polyfill
-          // allSettled ensures that the result is not lost if one of the promises rejects
           promise = Promise.all([
-            kernel_promise,
-            lsp_promise
+            kernel_promise.catch(p => p),
+            lsp_promise.catch(p => p)
           ]).then(([kernel, lsp]) =>
             this.merge_replies(this.transform_reply(kernel), lsp, this._editor)
           );
@@ -544,10 +542,17 @@ export class LSPConnector
   ): CompletionHandler.ICompletionItemsReply {
     this.console.debug('Merging completions:', lsp, kernel);
 
-    if (!kernel.items.length) {
+    if (kernel instanceof Error) {
+      this.console.warn('Caught kernel completions error', kernel);
+    }
+    if (lsp instanceof Error) {
+      this.console.warn('Caught LSP completions error', lsp);
+    }
+
+    if (kernel instanceof Error || !kernel.items.length) {
       return lsp;
     }
-    if (!lsp.items.length) {
+    if (lsp instanceof Error || !lsp.items.length) {
       return kernel;
     }