Parse and wrap ansi() codes without per-code allocations

[HarryCordewener]

Requested by Grave · project thread

Before: AnsiCodeParser.Parse("hr") took 139 ns and allocated 312 B (an iterator, a StringBuilder, a string per code, a new colour per letter). Wrapping plain text in the result took 351 ns and 640 B, and wrapping styled text again took 552 ns.

After: parsing takes 54 ns and 88 B (the markup is the only allocation). Wrapping plain text takes 154 ns and 208 B, and wrapping again takes 246 ns.

How:

• The parser reads codes as spans of the input through a ref struct reader; palette colours (Standard, Xterm) are shared instances.
• MarkupSet keeps the canonical one-layer set per layer and the result of Append(set, layer), both bounded like the intern table, and Equals checks reference first (sets are interned).
• MarkupText returns runs unchanged when they are already in normal form instead of copying them, and Wrap(layer, plain text) builds its one run directly.
• AnsiStyle compares and hashes its switches as one bit field; AnsiMarkup caches its hash (a with that sets Style forgets it).

Checked: all 1107 tests pass, including new ones for the hand-written equality (fails if a property is left out; verified by dropping Clear), the with/hash interaction, and allocation bounds. The new parser was also compared against the old one on 2,000,000 random code strings with identical results. Numbers are from BenchmarkDotNet (short job, in-process) on the cloud session's machine.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HxaBeF4BjQBGHyZCqibsLX

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Generated by Claude Code

Summary by CodeRabbit

• Performance
  • ANSI parsing and repeated style wrapping are faster and use fewer allocations. Standard palette colors and previously used style combinations are reused.
  • Updated benchmarks report timing and allocation measurements.
• Bug Fixes
  • Malformed or out-of-range color codes continue to be ignored, and unterminated color groups are handled as letter codes.
  • Style equality and hash behavior now consistently reflect style changes.

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Review configuration:

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: ASSERTIVE
• Plan: Essentials
• Run ID: fddf2d3a-22ca-4ee5-a201-bc761a70976a

📥 Commits

Reviewing files that changed from the base of the PR and between 14851c9 and 6df77a7.

📒 Files selected for processing (2)

• CHANGELOG.md
• MarkupString.Ansi/AnsiCodeParser.cs

Walkthrough

The changes update ANSI parsing and color reuse, add value-based style equality and cached markup hashes, and add reuse paths for markup sets and text runs. Tests cover parser allocations, wrapping reuse, style equality, and hash behavior.

Changes

ANSI and markup performance

Layer / File(s)	Summary
Direct ANSI parsing and shared colors MarkupString.Ansi/AnsiCodeParser.cs, MarkupString.Ansi/AnsiColor.cs, MarkupString.Tests/AllocationTests.cs, CHANGELOG.md	The parser reads codes from spans and updates reader state. Standard and xterm colors use shared instances. An allocation test measures parsing of ANSI letter codes.
Style equality and markup hash caching MarkupString.Ansi/AnsiStyle.cs, MarkupString.Ansi/AnsiMarkup.cs, MarkupString.Tests/Ansi/AnsiStyleTests.cs	AnsiStyle compares and hashes its style fields. AnsiMarkup caches its style hash and clears the cache when Style is assigned. Tests cover equality, hash codes, and style replacement.
Markup-set and text-run reuse MarkupString/MarkupSet.cs, MarkupString/MarkupText.cs, MarkupString.Tests/AllocationTests.cs, CHANGELOG.md	MarkupSet caches single-markup and appended sets. MarkupText returns directly for empty inner runs and for runs already in normal form. A test checks reuse of the same Markups collection.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Refactor

Suggested reviewers: claude

Merge Risk: 🔵 Low · up to 14851

Normal wrapping remains mergeable. Malformed internally constructed runs can throw, and the allocation description should be narrowed to avoid promising the measured result for RGB codes.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 54.55% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 33 functions across 8 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: reducing per-code allocations while parsing and wrapping ansi() codes.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 54.55% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 33 functions across 8 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @MarkupString.Ansi/AnsiCodeParser.cs:
- Around line 55-57: Qualify the allocation claim in the parser remark to cover
only codes that use shared colours and do not construct RGB values. In
CHANGELOG.md at lines 47–48, limit the allocation claim to the measured hr case.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: ASSERTIVE
• Plan: Essentials
• Run ID: b579632a-9f33-41a7-a210-9276979ed504

📥 Commits

Reviewing files that changed from the base of the PR and between b47d2c1 and 14851c9.

📒 Files selected for processing (9)

• CHANGELOG.md
• MarkupString.Ansi/AnsiCodeParser.cs
• MarkupString.Ansi/AnsiColor.cs
• MarkupString.Ansi/AnsiMarkup.cs
• MarkupString.Ansi/AnsiStyle.cs
• MarkupString.Tests/AllocationTests.cs
• MarkupString.Tests/Ansi/AnsiStyleTests.cs
• MarkupString/MarkupSet.cs
• MarkupString/MarkupText.cs

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