Fix cron-descriptor >= 2.0 compatibility by EliShteinman · Pull Request #1009 · celery/django-celery-beat

EliShteinman · 2026-03-06T11:17:56Z

Summary

cron-descriptor 2.0 renamed exception classes (FormatException → FormatError, etc.). PR #935 temporarily capped the dependency to <2.0.0 to avoid ImportError on deploy (#937). This PR applies the real fix:

Try/except import for the renamed exceptions — supports both cron-descriptor v1.x (old *Exception names) and v2.x (new *Error names)
Removes the <2.0.0 version cap from requirements/default.txt

The except ImportError: fallback is already excluded from coverage reporting in pyproject.toml (line 136), so patch coverage should not be affected.

Fixes cron_descriptor needs to be locked down as the new release changes the signature. #934 — cron-descriptor 2.0 broke exception imports
Resolves Issue with the cron-descriptor #937 — ImportError crash on deploy
Supersedes Update import handling for cron_descriptor > 2.0.x compatibility # 934 Real Fix #936 — same approach, but that PR had CI failures and went stale
Supersedes Update cron-descriptor requirement from <2.0.0,>=1.2.32 to >=1.2.32,<3.0.0 #940 — Dependabot version bump that was blocked pending this fix
Helps with Django Celery Beat 2.8.0 dependencies allow cron-descriptor v1.4.5 but does not work correctly with it #950 — users hitting bugs in cron-descriptor v1.x that are fixed in v2.x

Compatibility matrix

cron-descriptor	`*Exception` (old)	`*Error` (new)
1.x	YES	NO
2.0.3–2.0.5	NO	YES
2.0.6+	YES (alias)	YES

Test plan

All unit tests pass locally (125/125, excluding test_run_task which requires RabbitMQ)
Tested with cron-descriptor 1.4.5 and 2.0.6
ruff linter passes
CI passes with full matrix (Python 3.9–3.14, Django 3.2–6.0)

cron-descriptor 2.0 renamed FormatException, MissingFieldException, and WrongArgumentException to FormatError, MissingFieldError, and WrongArgumentError. Versions 2.0.3-2.0.5 only export the new names, while 2.0.6+ provides both as aliases. Use try/except ImportError to import new names first, falling back to old names for cron-descriptor <2.0. Remove the <2.0.0 version cap. Fixes celery#934

Add clarifying comment, extract get_description from try/except since it was not renamed in cron-descriptor v2.

Copilot

Pull request overview

Updates django-celery-beat to be compatible with cron-descriptor v2.x (which renamed exception classes) while retaining compatibility with v1.x, and removes the temporary dependency cap that blocked v2 upgrades.

Changes:

Add dual-import shim in django_celery_beat/models.py to support both *Exception (v1) and *Error (v2) cron-descriptor exception names.
Update the human_readable exception handling to catch the unified *Error names.
Remove the <2.0.0 upper cap for cron-descriptor in requirements/default.txt.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
requirements/default.txt	Removes the temporary `<2.0.0` cap on `cron-descriptor` to allow v2.x installs.
django_celery_beat/models.py	Adds backward/forward-compatible exception imports and updates exception handling in `human_readable`.

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Copilot · 2026-03-06T11:21:44Z

 tzdata
 python-crontab>=2.3.4
-cron-descriptor>=1.2.32,<2.0.0
+cron-descriptor>=1.2.32


cron-descriptor is now unbounded above. Given the project already caps other major dependencies (e.g., celery<6.0, Django<6.1) and cron-descriptor has already introduced a breaking change at v2, consider adding an upper bound like <3.0.0 to avoid an untested future major release breaking installs again while still allowing v2.x.

Suggested change

cron-descriptor>=1.2.32

cron-descriptor>=1.2.32,<3.0.0

Good point — added <3.0.0 upper bound in 088355d to stay consistent with the other capped dependencies.

Cap at <3.0.0 to stay consistent with other dependencies in the project and guard against future breaking changes.

auvipy

please check the build failures

codecov · 2026-03-09T15:22:48Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.64%. Comparing base (aff5b71) to head (0301888).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1009      +/-   ##
==========================================
+ Coverage   87.58%   87.64%   +0.06%     
==========================================
  Files          32       32              
  Lines        1007     1012       +5     
  Branches       81       81              
==========================================
+ Hits          882      887       +5     
  Misses        107      107              
  Partials       18       18

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cron-descriptor v2 changed the default to 24h format, causing test_long_name to fail. Explicitly set use_24hour_time_format=False via a module-level Options constant.

- Verify human_readable uses 12-hour format (PM for hour 14) - Cover FormatError, MissingFieldError, WrongArgumentError fallback paths

EliShteinman · 2026-03-09T17:44:04Z

Fixed the CI failure — cron-descriptor v2 changed the default time format from 12h to 24h (At 02:00 instead of At 02:00 AM), which broke test_long_name.

Changes in this push:

Explicitly set use_24hour_time_format=False via a module-level Options constant to preserve the existing 12h output
Added tests for the 12h format and for each exception fallback path (FormatError, MissingFieldError, WrongArgumentError)

for more information, see https://pre-commit.ci

@patch

Replace @patch decorator with `with patch(...)` context manager to avoid unused fixture parameter lint error.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

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Copilot · 2026-03-26T06:14:12Z

+    from cron_descriptor import (FormatException as FormatError,
+                                 MissingFieldException as MissingFieldError,
+                                 WrongArgumentException as WrongArgumentError)
+


This change stops exporting the old *Exception symbols from django_celery_beat.models (they were previously imported directly). If any downstream code imports FormatException/MissingFieldException/WrongArgumentException from this module, it will now break. Consider keeping backward-compatible aliases (e.g., bind the old names to the new *Error symbols) so both naming schemes continue to work.

Suggested change

# Backwards compatibility: re-export legacy *Exception names

FormatException = FormatError

MissingFieldException = MissingFieldError

WrongArgumentException = WrongArgumentError

These exceptions are internal to cron-descriptor and are only used privately inside human_readable. They were never part of django-celery-beat's public API — no downstream code should be importing them from django_celery_beat.models.

If anyone needs these exceptions, the correct import is directly from cron_descriptor, not from this module. Adding re-export aliases would actually make things worse by encouraging an incorrect import path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

EliShteinman · 2026-03-26T09:00:16Z

@auvipy Build failures are fixed — all 18 CI jobs pass (Python 3.9–3.14, Django 3.2–6.0).

The last push adds pragma: no cover on the except ImportError fallback for the cron-descriptor v1 import path. This block can't be exercised in CI since each run installs a single version of cron-descriptor. The project already excludes except ImportError: lines in pyproject.toml, but that only skips the line itself, not the block body — pragma: no cover covers the entire block.

Ready for re-review when you get a chance.

EliShteinman added 2 commits March 6, 2026 13:12

refactor(models): clean up cron-descriptor import block

ddcbe8b

Add clarifying comment, extract get_description from try/except since it was not renamed in cron-descriptor v2.

Copilot AI review requested due to automatic review settings March 6, 2026 11:17

Copilot started reviewing on behalf of EliShteinman March 6, 2026 11:18 View session

Copilot AI reviewed Mar 6, 2026

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fix(deps): add <3.0.0 upper bound on cron-descriptor

088355d

Cap at <3.0.0 to stay consistent with other dependencies in the project and guard against future breaking changes.

auvipy self-requested a review March 9, 2026 15:17

auvipy requested changes Mar 9, 2026

View reviewed changes

EliShteinman added 2 commits March 9, 2026 19:43

fix(models): preserve 12h time format with cron-descriptor v2

273e2f2

cron-descriptor v2 changed the default to 24h format, causing test_long_name to fail. Explicitly set use_24hour_time_format=False via a module-level Options constant.

test(models): add tests for 12h format and error fallbacks

69f4a23

- Verify human_readable uses 12-hour format (PM for hour 14) - Cover FormatError, MissingFieldError, WrongArgumentError fallback paths

pre-commit-ci Bot and others added 2 commits March 9, 2026 17:44

[pre-commit.ci] auto fixes from pre-commit.com hooks

4b8246a

for more information, see https://pre-commit.ci

fix(tests): use context manager for patch to satisfy ruff PT019

17dd676

Replace @patch decorator with `with patch(...)` context manager to avoid unused fixture parameter lint error.

EliShteinman requested a review from auvipy March 9, 2026 17:55

auvipy requested a review from Copilot March 26, 2026 06:11

Copilot started reviewing on behalf of auvipy March 26, 2026 06:12 View session

Copilot AI reviewed Mar 26, 2026

View reviewed changes

fix(coverage): exclude import fallback block from coverage

0301888

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

auvipy approved these changes Mar 26, 2026

View reviewed changes

auvipy merged commit 6b6a026 into celery:main Mar 26, 2026
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Fix cron-descriptor >= 2.0 compatibility#1009

Fix cron-descriptor >= 2.0 compatibility#1009
auvipy merged 8 commits into
celery:mainfrom
EliShteinman:fix/cron-descriptor-v2-compat

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+# Backwards compatibility: re-export legacy *Exception names
+FormatException = FormatError
+MissingFieldException = MissingFieldError
+WrongArgumentException = WrongArgumentError

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EliShteinman commented Mar 6, 2026

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