fix(scheduling): strip quotes from cron schedule spec before parsing

[nicholas-fedor]

This PR implements input validation for values wrapped with quotations to Watchtower's schedule configuration option.

Problem

When users configure WATCHTOWER_SCHEDULE in Docker Compose with quotes (e.g., WATCHTOWER_SCHEDULE="0 0 2 * * *"), Docker Compose passes the literal quote characters as part of the environment variable value. The cron parser (robfig/cron/v3) then fails with strconv.Atoi: parsing "\"0": invalid syntax because it tries to parse "0 as an integer. This is a common Docker Compose pattern and was not handled by Watchtower.

Solution

Strip single and double quotes from the schedule specification string before passing it to the cron parser, following the same pattern already used for DOCKER_API_VERSION in the flags package. The fix is applied at the point of consumption in the scheduling code, protecting against quotes from any source (env var or CLI flag).

Changes

• internal/scheduling/scheduling.go -- Added strings.Trim(scheduleSpec, "') to strip wrapping quotes from the schedule spec before cron parsing, and added "strings" import
• internal/scheduling/scheduling_test.go -- Added TestRunUpgradesOnSchedule_QuotedScheduleSpec with 6 test cases covering double-quoted cron, single-quoted cron, double-quoted descriptor, unquoted variants, and double-quoted invalid specs

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Schedule specifications now properly handle quoted cron expressions, accepting both single and double-quoted inputs alongside unquoted formats (e.g., "0 0 2 * * *", '0 0 2 * * *', or @hourly).

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ed9ef551-8ff5-416c-a42a-972efb65d49f

📥 Commits

Reviewing files that changed from the base of the PR and between 0b2ed83 and a693f0b.

📒 Files selected for processing (2)

• internal/scheduling/scheduling.go
• internal/scheduling/scheduling_test.go

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Walkthrough

The PR adds quote normalization to the schedule specification input in RunUpgradesOnSchedule. The implementation trims surrounding single and double quote characters before registering the schedule with the cron scheduler, with test coverage verifying both quoted and unquoted specs work correctly.

Changes

Schedule spec quote normalization

Layer / File(s)	Summary
Schedule spec quote normalization and test coverage internal/scheduling/scheduling.go, internal/scheduling/scheduling_test.go	The strings import is added, scheduleSpec is trimmed of surrounding quote characters before scheduler.AddFunc is called, and a table-driven test validates that quoted and unquoted cron expressions with seconds, descriptor formats like @hourly, and invalid specs are all handled correctly.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• nicholas-fedor/watchtower#1208: Both PRs modify the RunUpgradesOnSchedule path that feeds scheduleSpec into scheduler.AddFunc—Update cron package to v3 with enhanced concurrency control #1208 upgrades the cron-v3 scheduling setup, while this PR normalizes quoted schedule specification strings before calling AddFunc.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: stripping quotes from cron schedule specifications before parsing, which matches the primary code modification in scheduling.go.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

🟢 Metrics 12 complexity · 17 duplication

Metric	Results
Complexity	12
Duplication	17

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main    #1686      +/-   ##
==========================================
+ Coverage   74.60%   74.79%   +0.19%     
==========================================
  Files          59       59              
  Lines        9839     9949     +110     
==========================================
+ Hits         7340     7441     +101     
- Misses       2237     2243       +6     
- Partials      262      265       +3     

Files with missing lines	Coverage Δ
internal/scheduling/scheduling.go	88.52% <100.00%> (+0.09%)	⬆️

... and 1 file with indirect coverage changes

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