Fix impossible function cron schedules

[ChiragAgg5k]

What does this PR do?

Prevents impossible function cron expressions from crashlooping the function scheduler.

The cron library can parse expressions like */5 22-3 * * *, but later throws RuntimeException: Impossible CRON expression when calculating the next run date. This PR validates cron expressions by calculating the next run date and makes the function scheduler silently skip impossible legacy schedules.

Test Plan

• vendor/bin/phpunit tests/unit/Task/Validator/CronTest.php --display-warnings
• composer lint src/Appwrite/Task/Validator/Cron.php
• composer lint src/Appwrite/Platform/Tasks/ScheduleFunctions.php
• composer lint tests/unit/Task/Validator/CronTest.php

Note: The targeted PHPUnit run passes assertions but reports a warning from dragonmantank/cron-expression while evaluating the intentionally invalid wrapped-hour expression.

Related PRs and Issues

• #XXXX

Checklist

• Have you read the Contributing Guidelines on issues?
• If the PR includes a change to an API's metadata (desc, label, params, etc.), does it also include updated API specs and example docs?

[greptile-apps]

Greptile Summary

This PR fixes a crashloop in the function scheduler caused by cron expressions that are syntactically valid but impossible to execute (e.g., */5 22-3 * * * with a wrapped-hour range). The fix applies in two places: the Cron validator now rejects such expressions at save time, and the scheduler loop catches RuntimeException to silently skip any impossible legacy schedules already stored in the database.

• Cron.php: Wraps getNextRunDate() in a try/catch so impossible expressions are rejected during input validation, preventing them from ever being persisted.
• ScheduleFunctions.php: Moves getNextRunDate() inside the existing try block and adds a RuntimeException catch branch, so pre-existing impossible schedules in the database no longer crash the enqueue loop.
• CronTest.php: Adds two assertions — one for the valid comma-separated cross-midnight form (22-23,0-3) and one for the invalid wrapped-range form (22-3) — directly exercising the new validation path.

Confidence Score: 5/5

Safe to merge — the change is minimal and targeted, touching only the validation path and the scheduler's exception-handling block.

Both code sites are straightforward: the validator adds a single try/catch around an existing library call, and the scheduler moves one line inside an already-guarded block. The new test cases directly cover the happy path and the failure path introduced by this change. No existing behavior is removed or altered beyond expanding the set of expressions that are treated as invalid.

No files require special attention.

Important Files Changed

Filename	Overview
src/Appwrite/Task/Validator/Cron.php	Adds getNextRunDate() execution check inside a try/catch to reject syntactically-valid but impossible cron expressions at validation time.
src/Appwrite/Platform/Tasks/ScheduleFunctions.php	Moves getNextRunDate() inside the try block and adds a RuntimeException catch so impossible legacy schedules are silently skipped instead of crashing the scheduler loop.
tests/unit/Task/Validator/CronTest.php	Adds test cases for the valid comma-separated cross-midnight range (/5 22-23,0-3) and the invalid wrapped-range expression (/5 22-3) to exercise the new validation logic.

_{Reviews (3): Last reviewed commit: "Revert "Fix deployment cancel race in bu..." | Re-trigger Greptile}

[github-actions]

✨ Benchmark results

Comparing 1.9.x (before) to fix/schedule-functions-impossible-cron (after).

Before

Scenario	P50 (ms)	P95 (ms)	Requests	RPS
API total	15.24	145.94	185	32.51
Account	26.94	173.1	35	6.72
TablesDB	15.2	23.01	35	7.99
Storage	12.8	48.84	75	16.87
Functions	21.28	31.09	40	9.19

After

Scenario	P50 (ms)	P95 (ms)	Requests	RPS
API total	17.25	149.36	185	30.78
Account	28.52	200.18	35	6.35
TablesDB	15.84	24.57	35	7.46
Storage	14.37	50.79	75	15.69
Functions	22.5	36.08	40	8.48

Delta

Scenario	P95 delta (ms)
API total	+3.42
Account	+27.08
TablesDB	+1.57
Storage	+1.95
Functions	+4.99

Top API waits

API request	Max wait (ms)
account.sessions.email.create	642.6
account.password.update	200.03
account.create	161.88

[github-actions]

🔄 PHP-Retry Summary

Flaky tests detected across commits:

Commit 9b45853 - 1 flaky test

Test	Retries	Total Time	Details
RealtimeCustomClientTest::testChannelDatabase	1	40ms	Logs

Commit 902b1d5 - 1 flaky test

Test	Retries	Total Time	Details
DocumentsDBCustomServerTest::testTimeout	1	126.40s	Logs

Commit 939d2f4 - 1 flaky test

Test	Retries	Total Time	Details
LegacyCustomServerTest::testTimeout	1	131.40s	Logs