Allow to disable LSP or Kernel completions independently.

Some use love LSP for many of its features, but prefer to keep
completions via the kernel.

This adds two boolean flags in the configuration to not send completions
request to LSP and not send completions requests to the kernel.

See #440

Author: Carreau

packages/jupyterlab-lsp/schema/completion.json

@@ -41,6 +41,18 @@
       "type": "number",
       "description": "The time to wait for the kernel completions suggestions in milliseconds. Set to 0 to disable kernel completions, or to -1 to wait indefinitely (not recommended)."
     },
+    "useKernelCompletions": {
+      "title": "Request Kernel Completion",
+      "type": "boolean",
+      "default": true,
+      "description": "Whether to send completions request to the kernel."
+    },
+    "useLspCompletions": {
+      "title": "Request LSP Completion",
+      "type": "boolean",
+      "default": true,
+      "description": "Whether to send completions request to the lsp server."
+    },
     "waitForBusyKernel": {
       "title": "Wait for kernel if busy",
       "default": true,

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

@@ -78,6 +78,14 @@ export class LSPConnector
     return this.options.settings.composite.kernelCompletionsFirst;
   }
 
+  protected get use_lsp_completions(): boolean {
+    return this.options.settings.composite.useLspCompletions;
+  }
+
+  protected get use_kernel_completions(): boolean {
+    return this.options.settings.composite.useKernelCompletions;
+  }
+
   protected get suppress_continuous_hinting_in(): string[] {
     return this.options.settings.composite.suppressContinuousHintingIn;
   }
@@ -213,15 +221,19 @@ export class LSPConnector
       cursor_in_root
     );
 
-    const lsp_promise = this.fetch_lsp(
-      token,
-      typed_character,
-      virtual_start,
-      virtual_end,
-      virtual_cursor,
-      document,
-      position_in_token
-    );
+    const lsp_promise: Promise<CompletionHandler.ICompletionItemsReply> = this
+      .use_lsp_completions
+      ? this.fetch_lsp(
+          token,
+          typed_character,
+          virtual_start,
+          virtual_end,
+          virtual_cursor,
+          document,
+          position_in_token
+        )
+      : Promise.resolve(null);
+
     let promise: Promise<CompletionHandler.ICompletionItemsReply> = null;
 
     try {
@@ -271,12 +283,16 @@ export class LSPConnector
           promise = Promise.all([
             kernel_promise.catch(p => p),
             lsp_promise.catch(p => p)
-          ]).then(([kernel, lsp]) =>
-            this.merge_replies(
-              [this.transform_reply(kernel), lsp],
-              this._editor
-            )
-          );
+          ]).then(([kernel, lsp]) => {
+            let replies = [];
+            if (this.use_kernel_completions) {
+              replies.push(this.transform_reply(kernel));
+            }
+            if (this.use_lsp_completions) {
+              replies.push(lsp);
+            }
+            return this.merge_replies(replies, this._editor);
+          });
         }
       }
       if (!promise) {