util: create hex style cache and fast path

[araujogui]

Improve styleText performance by caching and fast-path

Benchmark

util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='boolean'                -0.71 %       ±1.04%  ±1.38%  ±1.80%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='invalid'                 0.80 %       ±0.86%  ±1.14%  ±1.49%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='number'                 -0.59 %       ±0.93%  ±1.24%  ±1.62%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='string'         ***   1135.88 %      ±31.19% ±42.04% ±55.81%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='boolean'                -0.09 %       ±1.43%  ±1.90%  ±2.47%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='invalid'                -0.02 %       ±0.98%  ±1.30%  ±1.69%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='number'                  0.83 %       ±1.79%  ±2.40%  ±3.15%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='string'           *     -1.19 %       ±0.97%  ±1.29%  ±1.68%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='boolean'                 -0.24 %       ±1.16%  ±1.55%  ±2.02%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='invalid'                  0.60 %       ±0.92%  ±1.23%  ±1.60%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='number'                   0.81 %       ±1.22%  ±1.63%  ±2.14%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='string'                   1.47 %       ±3.09%  ±4.12%  ±5.36%
util/style-text.js n=1000 validateStream=0 format='red' messageType='boolean'              *      1.17 %       ±1.03%  ±1.37%  ±1.79%
util/style-text.js n=1000 validateStream=0 format='red' messageType='invalid'                     0.73 %       ±0.99%  ±1.32%  ±1.72%
util/style-text.js n=1000 validateStream=0 format='red' messageType='number'                     -0.34 %       ±0.94%  ±1.25%  ±1.63%
util/style-text.js n=1000 validateStream=0 format='red' messageType='string'                      4.92 %       ±6.11%  ±8.17% ±10.72%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='boolean'                -0.50 %       ±1.32%  ±1.76%  ±2.29%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='invalid'                 0.62 %       ±0.89%  ±1.19%  ±1.56%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='number'                 -0.14 %       ±0.79%  ±1.06%  ±1.37%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='string'                 -0.27 %       ±1.23%  ±1.64%  ±2.14%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='boolean'                -0.31 %       ±0.97%  ±1.29%  ±1.68%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='invalid'                 0.61 %       ±0.85%  ±1.13%  ±1.48%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='number'                 -0.05 %       ±0.78%  ±1.04%  ±1.35%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='string'                  0.69 %       ±1.55%  ±2.07%  ±2.70%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='boolean'                 -0.01 %       ±1.07%  ±1.42%  ±1.85%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='invalid'                 -0.27 %       ±1.09%  ±1.45%  ±1.90%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='number'                   0.04 %       ±1.04%  ±1.38%  ±1.80%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='string'                  -0.41 %       ±0.91%  ±1.21%  ±1.58%
util/style-text.js n=1000 validateStream=1 format='red' messageType='boolean'                     0.56 %       ±1.18%  ±1.57%  ±2.05%
util/style-text.js n=1000 validateStream=1 format='red' messageType='invalid'                    -0.41 %       ±0.94%  ±1.26%  ±1.64%
util/style-text.js n=1000 validateStream=1 format='red' messageType='number'                     -0.88 %       ±0.96%  ±1.28%  ±1.67%
util/style-text.js n=1000 validateStream=1 format='red' messageType='string'                     -0.04 %       ±1.00%  ±1.33%  ±1.73%

[Copilot]

Pull request overview

This PR improves util.styleText() performance for hex colors by introducing a cached hex-style lookup and a fast path for the common case where validateStream: false.

Changes:

• Add a module-level hexStyleCache and helper (getHexStyle) to memoize computed ANSI sequences for #RGB/#RRGGBB.
• Reuse a shared close sequence constant for 24-bit foreground colors (\u001b[39m) and integrate hex handling into the validateStream: false fast path.
• Refactor hex handling in the main formatting loop to use cached sequences instead of re-parsing on every call.

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[ljharb]

isn't the maximum possible permutations here 16,781,312 - is the memory size of 17 million key/value pairs a massive concern?

[araujogui]

Great point, altought a LRU doesn't seem a bad idea

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.57%. Comparing base (27c7f4d) to head (10facb7).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62999      +/-   ##
==========================================
- Coverage   89.67%   89.57%   -0.11%     
==========================================
  Files         707      708       +1     
  Lines      219509   220246     +737     
  Branches    42093    42188      +95     
==========================================
+ Hits       196851   197286     +435     
- Misses      14551    14828     +277     
- Partials     8107     8132      +25     

Files with missing lines	Coverage Δ
lib/util.js	94.49% <100.00%> (+0.23%)	⬆️

... and 66 files with indirect coverage changes

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[Renegade334]

I note the benchmarks are all repeating the same lookup – I imagine that using a plain object as the map here could end up deoptimising if the cache miss rate is high, eg. colours being randomised by the user? Appreciate this is probably quite niche in reality, but might be worth a benchmark case to see how something like a SafeMap would compare.