fix(test-utils): Fix TypeScript errors in spotlight.ts and event-proxy-server.ts

- Add null check for portMatch[1] in spotlight.ts
- Add null check for eventBuffer element in generator
- Refactor buffer pruning loop to avoid 'possibly undefined' error

Author: BYK

.cursor/plans/migrate_e2e_to_spotlight_358ad839.plan.md

@@ -65,50 +65,43 @@ flowchart LR
 1. **Add `@spotlightjs/spotlight` dependency** to [`dev-packages/test-utils/package.json`](dev-packages/test-utils/package.json)
 
 2. **Create new Spotlight-based helpers** in [`dev-packages/test-utils/src/spotlight.ts`](dev-packages/test-utils/src/spotlight.ts):
-
    - `startSpotlight(options)` - Spawns `spotlight run` with dynamic port, parses port from stderr
    - `waitForSpotlightEvent(filter)` - Reads from Spotlight's JSON output stream
    - `waitForTransaction()`, `waitForError()`, etc. - High-level wrappers matching current API
 
 3. **Update [`dev-packages/test-utils/src/playwright-config.ts`](dev-packages/test-utils/src/playwright-config.ts)**:
-
    - Add option to use Spotlight instead of event proxy
    - Configure webServer to run Spotlight with dynamic port
    - Pass port via environment variable to test app
 
 ### Phase 2: Create Migration Path
 
 4. **Design backward-compatible API**:
-
    - Keep existing `waitForTransaction()` signature
    - New implementation reads from Spotlight instead of HTTP streaming
    - Port is passed via `SPOTLIGHT_PORT` env var
 
 5. **Update DSN handling in test apps**:
-
    - Replace `tunnel: 'http://localhost:3031'` with DSN workaround
    - DSN format: `http://spotlight@localhost:${SPOTLIGHT_PORT}/0`
    - This makes SDK operate in "normal" mode (no tunnel)
 
 ### Phase 3: Migrate Test Apps (Incremental)
 
 6. **Migration per test app involves**:
-
    - Remove `start-event-proxy.mjs`
    - Update `playwright.config.mjs` to use new Spotlight config
    - Update Sentry init to use DSN workaround instead of tunnel
    - No changes needed to test files (API stays the same)
 
 7. **Start with problematic apps**:
-
    - `react-router-7-lazy-routes` (the failing one)
    - `react-router-7-framework`
    - Then expand to remaining ~106 apps
 
 ### Phase 4: Cleanup
 
 8. **After all apps migrated**:
-
    - Remove old event proxy code from `event-proxy-server.ts`
    - Update documentation
    - Remove unused dependencies
@@ -129,7 +122,7 @@ Per [Spotlight docs](https://spotlightjs.com/docs/cli/run/#unsupported-sdks-dsn-
 
 ```javascript
 Sentry.init({
-  dsn: `http://spotlight@localhost:${process.env.SPOTLIGHT_PORT}/0`
+  dsn: `http://spotlight@localhost:${process.env.SPOTLIGHT_PORT}/0`,
 });
 ```
 
@@ -139,18 +132,16 @@ Sentry.init({
 // Before
 webServer: [
   { command: 'node start-event-proxy.mjs', port: 3031 },
-  { command: 'yarn start', port: 3030 }
-]
+  { command: 'yarn start', port: 3030 },
+];
 
 // After - spotlight run auto-detects and runs the app
-webServer: [
-  { command: 'yarn spotlight run -p 0 -f json', port: 3030 }
-]
+webServer: [{ command: 'yarn spotlight run -p 0 -f json', port: 3030 }];
 ```
 
 Note: `spotlight run` automatically:
 
 - Detects the start script from package.json (`dev`, `develop`, `serve`, `start`)
 - Starts the Spotlight sidecar on the specified port (or dynamic with `-p 0`)
 - Streams events to stdout in JSON format (with `-f json`)
-- Sets `SENTRY_SPOTLIGHT` env var for the child process
+- Sets `SENTRY_SPOTLIGHT` env var for the child process

dev-packages/test-utils/src/event-proxy-server.ts

@@ -153,8 +153,13 @@ export async function startProxyServer(
     // Prune old events from the buffer that are definitely stale (strictly older than this listener).
     // Use strict < to match the live event behavior (>= at line 103) - same-ms events are kept.
     // This prevents memory buildup and ensures old events can never leak to future listeners.
-    while (eventBuffer.length > 0 && eventBuffer[0].timestamp < listenerTimestamp) {
-      eventBuffer.shift();
+    while (eventBuffer.length > 0) {
+      const firstEvent = eventBuffer[0];
+      if (firstEvent && firstEvent.timestamp < listenerTimestamp) {
+        eventBuffer.shift();
+      } else {
+        break;
+      }
     }
 
     // Send any remaining buffered events (those that arrived after this listener was registered,

dev-packages/test-utils/src/spotlight.ts

@@ -81,7 +81,7 @@ export async function startSpotlight(options: SpotlightOptions = {}): Promise<Sp
 
       // Look for port in various formats
       const portMatch = line.match(/localhost:(\d+)/i) || line.match(/port[:\s]+(\d+)/i);
-      if (portMatch && !resolvedPort) {
+      if (portMatch?.[1] && !resolvedPort) {
         resolvedPort = parseInt(portMatch[1], 10);
       }
 
@@ -156,7 +156,10 @@ function createSpotlightInstance(process: ChildProcess, port: number, _debug: bo
     while (true) {
       // Yield any buffered events first
       while (bufferIndex < eventBuffer.length) {
-        yield eventBuffer[bufferIndex++];
+        const envelope = eventBuffer[bufferIndex++];
+        if (envelope) {
+          yield envelope;
+        }
       }
 
       // Wait for new events