Use compiled templates to speed up generation

[skatkov]

Cache executable ERB renderers for bundled Aliki and Darkfish pages and partials instead of repeatedly evaluating their Ruby source.

Benchmark

Metric	Clean master	Patched	Change
Generation wall time	17.92s	11.14s	−37.83%
Generation CPU time	17.91s	11.14s	−37.83%
End-to-end wall time	20.19s	13.44s	−33.43%
Parsing wall time	1.80s	1.79s	Essentially unchanged
Generation allocations	24,936,295	24,363,184	−2.30%
Peak RSS	335.3 MiB	366.2 MiB	+9.22%

Individual generation times

Run	Clean master	Patched
1	17.92s	11.14s
2	18.51s	11.18s
3	17.90s	11.14s

This optimization works only for Aliki and Darkfish templates. 'ri' is not affected.

Notes

• ERB#def_module compiles in ERB’s lexical scope, so bare VERSION resolves to ERB::VERSION, not RDoc’s. So this change requires to explicitly define ::RDoc::VERSION.

[github-actions]

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Commit: bbd81c2

[skatkov]

Interesting experiment.

There is an interesting performance gain here, but I can't really find an implementation that doesn't come with drawbacks.

I will close for now.