Introspection: adds backward compatibility tests

[Tpt]

Introspect crates using old PyO3 versions and check if the output is still correct

Will be useful if we do breaking change to the introspection format

[codspeed-hq]

Merging this PR will improve performance by 12.89%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 104 untouched benchmarks
⏩ 1 skipped benchmark¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	bench_pyclass_create	4.6 µs	4.1 µs	+12.89%

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_{Comparing Tpt:tpt/back-compat (f831993) with main (f57bda7)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[davidhewitt]

Interesting, this makes a ton of sense to do. I wonder, how far do you expect we want to test backwards compatibility in this way?

[Tpt]

I wonder, how far do you expect we want to test backwards compatibility in this way?

I see two possible interpretation of your question so I will try to answer both:

• I would hope we can keep backward compatibility as much as possible i.e. be able to introspect builds with quite old versions of pyo3.
• The current test is indeed currently quite basic. Expending it would be great. Topic for a follow up?