test: add unit tests for RpcTimeoutError and configure timeout backoff (PR #1275)

Author: karthiknadig

src/managers/common/nativePythonFinder.ts

@@ -25,6 +25,15 @@ const MAX_RESTART_ATTEMPTS = 3;
 const RESTART_BACKOFF_BASE_MS = 1_000; // 1 second base, exponential: 1s, 2s, 4s
 const MAX_CONFIGURE_TIMEOUTS_BEFORE_KILL = 2; // Kill on the 2nd consecutive timeout
 
+/**
+ * Computes the configure timeout with exponential backoff.
+ * @param retryCount Number of consecutive configure timeouts so far
+ * @returns Timeout in milliseconds: 30s, 60s, 120s, ... capped at REFRESH_TIMEOUT_MS
+ */
+export function getConfigureTimeoutMs(retryCount: number): number {
+    return Math.min(CONFIGURE_TIMEOUT_MS * Math.pow(2, retryCount), REFRESH_TIMEOUT_MS);
+}
+
 export async function getNativePythonToolsPath(): Promise<string> {
     const envsExt = getExtension(ENVS_EXTENSION_ID);
     if (envsExt) {
@@ -123,7 +132,7 @@ interface RefreshOptions {
 /**
  * Error thrown when a JSON-RPC request times out.
  */
-class RpcTimeoutError extends Error {
+export class RpcTimeoutError extends Error {
     constructor(
         public readonly method: string,
         timeoutMs: number,
@@ -602,7 +611,7 @@ class NativePythonFinderImpl implements NativePythonFinder {
         }
         this.outputChannel.info('[pet] configure: Sending configuration update:', JSON.stringify(options));
         // Exponential backoff: 30s, 60s on retry. Capped at REFRESH_TIMEOUT_MS.
-        const timeoutMs = Math.min(CONFIGURE_TIMEOUT_MS * Math.pow(2, this.configureTimeoutCount), REFRESH_TIMEOUT_MS);
+        const timeoutMs = getConfigureTimeoutMs(this.configureTimeoutCount);
         if (this.configureTimeoutCount > 0) {
             this.outputChannel.info(
                 `[pet] configure: Using extended timeout of ${timeoutMs}ms (retry ${this.configureTimeoutCount})`,

src/test/managers/common/nativePythonFinder.configureTimeout.unit.test.ts

@@ -0,0 +1,45 @@
+import assert from 'node:assert';
+import { RpcTimeoutError, getConfigureTimeoutMs } from '../../../managers/common/nativePythonFinder';
+
+suite('RpcTimeoutError', () => {
+    test('has correct name property', () => {
+        const error = new RpcTimeoutError('configure', 30000);
+        assert.strictEqual(error.name, 'RpcTimeoutError');
+    });
+
+    test('has correct method property', () => {
+        const error = new RpcTimeoutError('configure', 30000);
+        assert.strictEqual(error.method, 'configure');
+    });
+
+    test('message includes method name and timeout', () => {
+        const error = new RpcTimeoutError('resolve', 5000);
+        assert.strictEqual(error.message, "Request 'resolve' timed out after 5000ms");
+    });
+
+    test('is instanceof Error', () => {
+        const error = new RpcTimeoutError('configure', 30000);
+        assert.ok(error instanceof Error);
+        assert.ok(error instanceof RpcTimeoutError);
+    });
+});
+
+suite('getConfigureTimeoutMs', () => {
+    test('returns base timeout (30s) on first attempt', () => {
+        assert.strictEqual(getConfigureTimeoutMs(0), 30_000);
+    });
+
+    test('doubles timeout on first retry (60s)', () => {
+        assert.strictEqual(getConfigureTimeoutMs(1), 60_000);
+    });
+
+    test('doubles again on second retry (120s)', () => {
+        assert.strictEqual(getConfigureTimeoutMs(2), 120_000);
+    });
+
+    test('caps at REFRESH_TIMEOUT_MS (120s) for higher retries', () => {
+        // 30_000 * 2^3 = 240_000, but capped at 120_000
+        assert.strictEqual(getConfigureTimeoutMs(3), 120_000);
+        assert.strictEqual(getConfigureTimeoutMs(10), 120_000);
+    });
+});