Optimize thematic break generation

[leynos]

Summary

• initialize a lazily-evaluated THEMATIC_BREAK_LINE string
• reuse that static string when normalizing thematic breaks

Testing

• markdownlint README.md docs/*.md
• nixie README.md docs/*.md
• cargo +nightly-2025-06-10 fmt --all
• cargo clippy -- -D warnings
• RUSTFLAGS="-D warnings" cargo test

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https://chatgpt.com/codex/tasks/task_e_68743155736c83229ba3a102b7264737

Summary by Sourcery

Optimize thematic break generation by caching the default break string in a lazily initialized static and reusing it during formatting

Enhancements:

• Introduce a lazily evaluated static THEMATIC_BREAK_LINE string for thematic break lines
• Replace dynamic string allocation in format_breaks with reuse of the cached THEMATIC_BREAK_LINE

[sourcery-ai]

Reviewer's Guide

Optimizes thematic break generation by introducing a lazily-initialized static string for the break line and reusing it in the formatting function to eliminate repeated allocations.

Class diagram for static variables and format_breaks function changes

classDiagram
    class THEMATIC_BREAK_RE {
        <<static>>
        Regex
    }
    class THEMATIC_BREAK_LINE {
        <<static>>
        String
    }
    class format_breaks {
        +format_breaks(lines: &[String]) -> Vec<String>
    }
    THEMATIC_BREAK_LINE <.. format_breaks : uses
    THEMATIC_BREAK_RE <.. format_breaks : uses

Loading

File-Level Changes

Change	Details	Files
Introduce a lazily-initialized static THEMATIC_BREAK_LINE	Add a new static LazyLock named THEMATIC_BREAK_LINE Initialize it with a closure that repeats underscore characters to the required length	src/lib.rs
Refactor format_breaks to reuse the static break line	Replace _.repeat(THEMATIC_BREAK_LEN) with THEMATIC_BREAK_LINE.clone() in the break formatting branch	src/lib.rs

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[coderabbitai]

Summary by CodeRabbit

• Refactor
  • Improved performance when formatting thematic break lines by reusing a precomputed line, resulting in more efficient processing.

Walkthrough

Introduce a static, lazily-initialised string constant to cache the thematic break line of underscores. Update the format_breaks function to use this cached string instead of allocating a new string on each call. Add the static variable THEMATIC_BREAK_LINE to src/lib.rs.

Changes

File(s)	Change Summary
src/lib.rs	Add static THEMATIC_BREAK_LINE as a lazy-initialised string. Refactor format_breaks to use the cached string instead of generating a new one each time.

Possibly related PRs

• Add thematic break formatting #57: Introduced the original format_breaks function and thematic break formatting, which is directly optimised by this PR.

Poem

A line of underscores, seventy strong,
Now cached and ready, it won’t take long.
No more repeats, no wasted time,
Just one static string—oh, how sublime!
Thematic breaks, now swift and neat,
Code efficiency can’t be beat.

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📥 Commits

Reviewing files that changed from the base of the PR and between 1320a9d and fa227a0.

📒 Files selected for processing (1)

• src/lib.rs (2 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.rs

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• GitHub Check: build-test

🔇 Additional comments (2)

src/lib.rs (2)

238-240: Well-executed optimisation with proper lazy initialisation.

The static variable correctly uses LazyLock for thread-safe lazy initialisation and centralises the thematic break format definition. This eliminates repeated string generation whilst maintaining consistency across all thematic breaks.

---

573-573: Proper usage of the cached thematic break string.

The replacement of inline string generation with the pre-computed static string is implemented correctly. This change maintains the same functionality whilst potentially improving performance through reduced allocations.

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[sourcery-ai]

Hey @leynos - I've reviewed your changes and found some issues that need to be addressed.

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