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v3.0.0

Croner 3.0 Release Notes

Version 3.0 is a significant release, introducing powerful new features, major API enhancements for improved safety and flexibility, and important bug fixes.

Major New Features

• Reverse Lookup: You can now search for previous occurrences of a cron pattern. The new find_previous_occurrence() method and iter_before() iterator allow for iterating backwards in time from a given point.
• Flexible Parser Configuration with Builder Pattern: The CronParser has been enhanced with a builder pattern (CronParser::builder()) for a more type-safe and explicit configuration. This allows you to precisely control:
  • How the seconds field is handled (Optional, Required, Disallowed).
  • Whether the year field is supported (Optional, Required, Disallowed).
  • The logical combination of Day-of-Month and Day-of-Week fields (dom_and_dow).
  • Support for forcing alternative (Quartz-style) weekdays.
• Logical AND for Day-of-Month and Day-of-Week with + modifier: Introduced the + prefix in the day-of-week field (e.g., 0 0 1 * +MON) to explicitly enforce a logical AND relationship between the day-of-month and day-of-week conditions, overriding the default OR behavior.
• EXPERIMENTAL Human-Readable Descriptions: Croner can now generate human-readable, English descriptions for any cron pattern using the new .describe() method. This feature is also extensible with internationalization support, demonstrated with an initial Swedish translation.

Enhancements

• Common Trait Implementation: Cron and CronPattern now implement common traits including Eq, PartialEq, Ord, PartialOrd, and Hash. This allows Cron instances to be reliably compared, sorted, and used in hash-based collections like HashMap.
• Robust Whitespace Parsing: The parser is now more robust and correctly handles leading, trailing, and mixed whitespace separators in cron patterns.
• Improved DST Handling: Fixed an issue where fixed-time jobs scheduled within a Daylight Saving Time (DST) spring forward gap would incorrectly skip to the next day. These jobs now execute immediately at the first valid time following the gap on the same calendar day, aligning with the OCPS and Vixie-cron behavior.
• Improved Specification Conformance: This release improves conformance with the draft Open Cron Pattern Specification (OCPS). This includes better handling of 5, 6, and 7-field patterns and special characters like L, #, and W. Validation logic has been refined to ensure that the ? wildcard is only permitted in the day-of-month and day-of-week fields, improving pattern integrity.

Bug Fixes

• Constrained Closest Weekday (W): The W modifier is now correctly constrained within the given month. The search for the closest weekday will no longer incorrectly cross into a previous or subsequent month.

Migrating to the New Parser Configuration

From this version on, the initialization of Cron instances has been updated to use a flexible builder pattern, which is more idiomatic to Rust, and provides greater control and type safety.

Previous Method (Before v3.0)

Previously, Cron was typically initialized directly from a string, which used a default parser configuration:

    // Parse cron expression
    let cron_all = Cron::new("18 * * * 5")
      // <options>
      .parse()
      .expect("Couldn't parse cron string");

New Recommended Method (v3.0 and later)

For v3.0 and later, there are two primary ways to construct a Cron object, depending on your needs.

1. Directly, using default settings: For simple cases that do not require special configuration, the Cron::from_str() method is the most convenient option.

... (truncated)

• 6e7b30d Update README
• cbf9ce4 Bump version
• 602d877 Feature/separate interval vs fixed jobs (#33)
• 05b94f7 Implement plus-modifier for full OCPS-conformance. (#32)
• 5820e63 Fix year search (#31)
• 0e78d79 Merge pull request #30 from Hexagon/fix/ensure-7-fields-years-required
• 7fbd4d4 Ensure 7 fields when years are required
• f2aec12 Merge pull request #27 from Hexagon/feature/ocps-1.4-compliance
• caf7993 Add --all-features to development docs. Fix serde test.
• f32a8e6 Merge pull request #28 from Hexagon/docs/readme
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