vscode: gracefully handle cancellation errors

editors/code/src/util.ts

@@ -1,3 +1,6 @@
+import * as lc from "vscode-languageclient";
+import * as vscode from "vscode";
+
 let enabled: boolean = false;
 
 export const log = {
@@ -16,3 +19,40 @@ export const log = {
         enabled = yes;
     }
 };
+
+export async function sendRequestWithRetry<R>(
+    client: lc.LanguageClient,
+    method: string,
+    param: unknown,
+    token?: vscode.CancellationToken,
+): Promise<R> {
+    for (const delay of [2, 4, 6, 8, 10, null]) {
+        try {
+            return await (token
+                ? client.sendRequest(method, param, token)
+                : client.sendRequest(method, param)
+            );
+        } catch (error) {
+            if (delay === null) {
+                log.error("LSP request timed out", { method, param, error });
+                throw error;
+            }
+
+            if (error.code === lc.ErrorCodes.RequestCancelled) {
+                throw error;
+            }
+
+            if (error.code !== lc.ErrorCodes.ContentModified) {
+                log.error("LSP request failed", { method, param, error });
+                throw error;
+            }
+
+            await sleep(10 * (1 << delay));
+        }
+    }
+    throw 'unreachable';
+}
+
+function sleep(ms: number) {
+    return new Promise(resolve => setTimeout(resolve, ms));
+}