perf: replace source size

[SyMind]

This PR optimizes the size() method implementation for ReplaceSource to calculate the accurate size by simulating the replacement process, rather than simply returning the byte length of the original source. This ensures the size reflects the actual output after all replacements are applied.

• Implemented accurate size calculation in ReplaceSource::size() by iterating through replacements and adjusting for length differences
• Added caching for CachedSource::size() using OnceLock to avoid repeated calculations
• Added comprehensive test case and benchmark for the new size calculation logic

[codspeed-hq]

CodSpeed Performance Report

Merging #193 will not alter performance

_{Comparing perf-replace-source-size (74b8ac2) with main (42b4f9f)}

Summary

✅ 10 untouched
🆕 1 new
⏩ 5 skipped¹

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
🆕	complex_replace_source_size	N/A	294.1 µs	N/A

Footnotes

1. 5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[SyMind]

[Copilot]

Pull Request Overview

This PR optimizes the size() method implementation for ReplaceSource to calculate the accurate size by simulating the replacement process, rather than simply returning the byte length of the original source. This ensures the size reflects the actual output after all replacements are applied.

• Implemented accurate size calculation in ReplaceSource::size() by iterating through replacements and adjusting for length differences
• Added caching for CachedSource::size() using OnceLock to avoid repeated calculations
• Added comprehensive test case and benchmark for the new size calculation logic

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/replace_source.rs	Replaced simple byte length calculation with accurate size simulation that accounts for all replacements; added test case validating size matches generated content
src/cached_source.rs	Added size caching using OnceLock to improve performance by avoiding redundant size calculations
benches/bench_complex_replace_source.rs	Added benchmark function for measuring size() performance on complex replace sources
benches/bench.rs	Integrated new size benchmark into the benchmark suite

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