Skip hidden line-range syntax prefix text

[KRRT7]

Workload

Render a large Python Syntax object with a late line_range and no wrapping or line numbers:

PYTHONPATH=. uvx --with pytest-benchmark pytest /tmp/rich_pytest_bench_syntax.py --benchmark-only --benchmark-min-rounds=15 --benchmark-max-time=1 --benchmark-cprofile=cumtime --benchmark-cprofile-top=15 --benchmark-columns="min,median,mean,rounds,iterations"

Input: snippets.PYTHON_SNIPPET * 120, lexer="python", word_wrap=False, line_numbers=False, line_range=(3000, 3060), width 80.

This matters for callers that render only a small late slice of a large highlighted source file.

Results

Before, at 6d54cb8d:

• test_highlight_line_range_3000: 65.1610 ms median over 15 rounds
• test_render_line_range_3000: 71.1404 ms median over 15 rounds

After, at 06406dd2:

• test_highlight_line_range_3000: 62.9820 ms median over 15 rounds
• test_render_line_range_3000: 68.3597 ms median over 15 rounds

The pytest-benchmark cProfile output shows the previous path spent extra time in Text.append_tokens appending skipped prefix tokens before the requested range. The new path still tokenizes the prefix so lexer state is preserved, but emits only newline placeholders for skipped lines.

Correctness

• python3 -m pytest tests/test_syntax.py tests/test_console.py
• uvx black --check rich/syntax.py benchmarks/benchmarks.py tests/test_syntax.py

Tradeoffs

No behavior change intended. Late line ranges still tokenize from the beginning of the source to keep Pygments lexer state correct. This only avoids storing the skipped source text in the intermediate Text.

Stack

Order	PR	Branch	Depends on
1	#4177	optimize-syntax-word-wrap	main
2	#4178	perf/syntax-line-numbers-word-wrap	#4177
3	#4179	perf/syntax-direct-word-wrap	#4178
4	#4181	perf/syntax-direct-no-wrap	#4179
5	This PR	perf/syntax-line-range-skip-prefix	#4181

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4182   +/-   ##
=======================================
  Coverage        ?   97.81%           
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  Files           ?       96           
  Lines           ?     8392           
  Branches        ?        0           
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  Hits            ?     8209           
  Misses          ?      183           
  Partials        ?        0           

Flag	Coverage Δ
unittests	97.81% <100.00%> (?)

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