fix: don't crash when tail event is null

Sometime the "event" on a tail can be null. This patch makes sure we don't crash when that happens. Fixes #918

.changeset/khaki-starfishes-draw.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+fix: don't crash when tail event is null
+
+Sometime the "event" on a tail can be null. This patch makes sure we don't crash when that happens. Fixes https://github.com/cloudflare/wrangler2/issues/918

packages/wrangler/src/__tests__/tail.test.ts

@@ -295,6 +295,31 @@ describe("tail", () => {
       `);
     });
 
+    it("should not crash when the tail message has a void event", async () => {
+      const api = mockWebsocketAPIs();
+      await runWrangler("tail test-worker --format pretty");
+
+      const message = generateMockEventMessage({ event: null });
+      const serializedMessage = serialize(message);
+
+      api.ws.send(serializedMessage);
+      expect(
+        std.out
+          .replace(
+            new Date(mockEventTimestamp).toLocaleString(),
+            "[mock timestamp string]"
+          )
+          .replace(
+            mockTailExpiration.toLocaleString(),
+            "[mock expiration date]"
+          )
+      ).toMatchInlineSnapshot(`
+        "Successfully created tail, expires at [mock expiration date]
+        Connected to test-worker, waiting for logs...
+        [missing request] - Ok @ [mock timestamp string]"
+      `);
+    });
+
     it("defaults to logging in pretty format when the output is a TTY", async () => {
       setIsTTY(true);
       const api = mockWebsocketAPIs();
@@ -414,17 +439,18 @@ function serialize(message: TailEventMessage): WebSocket.RawData {
     // This isn't a problem outside of testing since deserialization
     // works just fine and wrangler never _sends_ any event messages,
     // it only receives them.
-    const request = (message.event as RequestEvent).request;
+    const request = ((message.event as RequestEvent | undefined | null) || {})
+      .request;
     const stringified = JSON.stringify(message, (key, value) => {
       if (key !== "request") {
         return value;
       }
 
       return {
         ...request,
-        url: request.url,
-        headers: request.headers,
-        method: request.method,
+        url: request?.url,
+        headers: request?.headers,
+        method: request?.method,
       };
     });
 
@@ -439,9 +465,9 @@ function serialize(message: TailEventMessage): WebSocket.RawData {
  * @returns whether event is a ScheduledEvent (true) or a RequestEvent
  */
 function isScheduled(
-  event: ScheduledEvent | RequestEvent
+  event: ScheduledEvent | RequestEvent | undefined | null
 ): event is ScheduledEvent {
-  return "cron" in event;
+  return Boolean(event && "cron" in event);
 }
 
 /**
@@ -607,15 +633,19 @@ function mockWebsocketAPIs(env?: string, legacyEnv = false): MockAPI {
  * @param opts Any specific parts of the message to use instead of defaults
  * @returns a `TailEventMessage` that wrangler can process and display
  */
-function generateMockEventMessage(
-  opts?: Partial<TailEventMessage>
-): TailEventMessage {
+function generateMockEventMessage({
+  outcome = "ok",
+  exceptions = [],
+  logs = [],
+  eventTimestamp = mockEventTimestamp,
+  event = generateMockRequestEvent(),
+}: Partial<TailEventMessage>): TailEventMessage {
   return {
-    outcome: opts?.outcome || "ok",
-    exceptions: opts?.exceptions || [],
-    logs: opts?.logs || [],
-    eventTimestamp: opts?.eventTimestamp || mockEventTimestamp,
-    event: opts?.event || generateMockRequestEvent(),
+    outcome,
+    exceptions,
+    logs,
+    eventTimestamp,
+    event,
   };
 }
 

packages/wrangler/src/tail/index.ts

@@ -179,7 +179,7 @@ export type TailEventMessage = {
    * Until workers-types exposes individual types for export, we'll have
    * to just re-define these types ourselves.
    */
-  event: RequestEvent | ScheduledEvent;
+  event: RequestEvent | ScheduledEvent | undefined | null;
 };
 
 /**

packages/wrangler/src/tail/printing.ts

@@ -15,12 +15,16 @@ export function prettyPrintLogs(data: WebSocket.RawData): void {
 
     logger.log(`"${cronPattern}" @ ${datetime} - ${outcome}`);
   } else {
-    const requestMethod = eventMessage.event.request.method.toUpperCase();
-    const url = eventMessage.event.request.url;
+    const requestMethod = eventMessage.event?.request.method.toUpperCase();
+    const url = eventMessage.event?.request.url;
     const outcome = prettifyOutcome(eventMessage.outcome);
     const datetime = new Date(eventMessage.eventTimestamp).toLocaleString();
 
-    logger.log(`${requestMethod} ${url} - ${outcome} @ ${datetime}`);
+    logger.log(
+      url
+        ? `${requestMethod} ${url} - ${outcome} @ ${datetime}`
+        : `[missing request] - ${outcome} @ ${datetime}`
+    );
   }
 
   if (eventMessage.logs.length > 0) {
@@ -41,9 +45,9 @@ export function jsonPrintLogs(data: WebSocket.RawData): void {
 }
 
 function isScheduledEvent(
-  event: RequestEvent | ScheduledEvent
+  event: RequestEvent | ScheduledEvent | undefined | null
 ): event is ScheduledEvent {
-  return "cron" in event;
+  return Boolean(event && "cron" in event);
 }
 
 function prettifyOutcome(outcome: Outcome): string {