Bug: eventFilterMatches returns false for nested $exists: false when the parent key is missing or null #5017

Summary

eventFilterMatches returns false for a nested $exists: false filter when the parent key is missing or null in the payload. The function returns false for any non-empty filter as soon as it meets an undefined/null payload, before it evaluates $exists. This is user-facing through retry.fetch's bodyFilter, which calls eventFilterMatches on the response body.

Reproduction

1. Setup: packages/core on main.
2. Command: npx tsx repro.ts from packages/core with:

import { eventFilterMatches } from "./src/eventFilterMatches.js";
const f = { user: { email: [{ $exists: false }] } };
console.log(eventFilterMatches({}, f));             // false
console.log(eventFilterMatches({ user: null }, f)); // false
console.log(eventFilterMatches({ user: {} }, f));   // true
console.log(eventFilterMatches({}, { email: [{ $exists: false }] })); // true

3. Trigger: a nested filter whose leaf is $exists: false, used with a payload where an ancestor key is absent or null.

Actual behavior

{} {"user":{"email":[{"$exists":false}]}} => false
{"user":null} {"user":{"email":[{"$exists":false}]}} => false
{"user":{}} {"user":{"email":[{"$exists":false}]}} => true
{} {"email":[{"$exists":false}]} => true

Expected behavior

All four should return true. If user is missing, then user.email doesn't exist either, which is exactly what $exists: false asserts. Top-level $exists: false already behaves that way (case 4, and the existing test "should return true when payload does NOT have a key that $exists = false"). Nesting the same condition one level deeper shouldn't flip the result.

Environment

• Version/commit: main @ 93465d8
• OS: Ubuntu (Linux), Node v24.21.0
• Relevant configuration: none; pure function. Reachable from retry.fetch(url, { retry: { byStatus: { "...": { strategy: "backoff", bodyFilter } } } })

Evidence

• Early return for undefined/null payload with a non-empty filter:

  trigger.dev/packages/core/src/eventFilterMatches.ts

  Lines 7 to 14 in 93465d8

  	export function eventFilterMatches(payload: any, filter: EventFilter): boolean {
  	if (payload === undefined || payload === null) {
  	if (Object.entries(filter).length === 0) {
  	return true;
  	} else {
  	return false;
  	}
  	}

• Recursion into nested object filters:

  trigger.dev/packages/core/src/eventFilterMatches.ts

  Lines 61 to 71 in 93465d8

  	continue;
  	} else if (typeof patternValue === "object") {
  	if (Array.isArray(payloadValue)) {
  	if (!payloadValue.some((item) => eventFilterMatches(item, patternValue))) {
  	return false;
  	}
  	} else {
  	if (!eventFilterMatches(payloadValue, patternValue)) {
  	return false;
  	}
  	}

• retry.fetch bodyFilter path:

  trigger.dev/packages/trigger-sdk/src/v3/retry.ts

  Lines 449 to 460 in 93465d8

  	if (strategy.bodyFilter) {
  	const body = safeJsonParse(await clonedResponse.text());
  	if (!body) {
  	continue;
  	}
  	if (eventFilterMatches(body, strategy.bodyFilter)) {
  	return strategy;
  	} else {
  	continue;
  	}

• bodyFilter: EventFilter in the fetch retry schema:

  trigger.dev/packages/core/src/v3/schemas/fetch.ts

  Line 17 in 93465d8

  bodyFilter: EventFilter.optional(),

  and

  trigger.dev/packages/core/src/v3/schemas/fetch.ts

  Line 39 in 93465d8

  bodyFilter: EventFilter.optional(),

• Existing tests cover only top-level $exists:

  trigger.dev/packages/core/test/eventFilterMatches.test.ts

  Lines 193 to 208 in 93465d8

  	it("should return true when payload does NOT have a key that $exists = false", () => {
  	const payload = {
  	name: "John",
  	age: 30,
  	isAdmin: false,
  	hobbies: ["reading", "swimming"],
  	address: {
  	street: "123 Main St",
  	city: "Anytown",
  	state: "CA",
  	zip: "12345",
  	},
  	};
  	const filter: EventFilter = {
  	foo: [{ $exists: false }],
  	};

Additional context

Confirmed: the four results above, from running the source on main.

Inference: for retry.fetch, a bodyFilter such as { error: { retryAfter: [{ $exists: false }] } } won't match a body that has no error object at all. That strategy is then skipped. I haven't exercised this through retry.fetch end to end.

Possible fix: when the payload is undefined/null, evaluate the filter against an empty object (or recurse with {}) instead of returning false, so that $exists: false and $isNull-style leaves still get evaluated.

Found with an anti-slop oxlint scan (no-runtime-typeof), then checked by hand.