Avoid copying entire mappings during type inference

[Alek99]

Mapping type inference samples only 100 keys and values, but currently materializes every key and value before taking that sample. Use bounded iteration so inference keeps the same sample and resulting types without copying or retrieving the rest of a large mapping.

On a local CPython 3.14.5 / Apple M5 Pro benchmark, inference for a one-million-entry dict fell from 5.62 ms to 0.026 ms, with peak traced temporary allocation falling from 8 MB to 360 B. This measures the inference helper, not whole-app compilation. Added a CodSpeed benchmark across mapping sizes and regressions covering empty mappings, the exact sample boundary, and custom Mapping iteration/value access. The bounded-iteration regression fails on the unchanged base.

Validation:

• Full unit suite: 8,303 passed, 18 skipped; 75.95% coverage.
• Focused Var tests and new benchmark: 260 passed.
• Repository-wide Ruff check and format check passed.
• pyright reflex tests and changed-file type checks passed.

Independent of the other performance changes; based directly on main.

[greptile-apps]

Greptile Summary

This PR bounds mapping type inference to the first 100 keys and values without materializing complete mapping views.

• Replaces full key and value copies with bounded islice iteration.
• Adds regressions for empty mappings, the 100-item boundary, and custom mapping access counts.
• Adds CodSpeed coverage across several mapping sizes.
• Adds the required reflex-base performance news fragment.

Confidence Score: 5/5

The PR appears safe to merge, with bounded iteration preserving the established type-inference sample for supported mappings.

No actionable correctness, security, integration, or repository-rule issues remain; the implementation preserves first-100 sampling semantics and the tests cover the changed boundary behavior.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/vars/base.py	Preserves the existing 100-item inference sample while avoiding work and allocation proportional to the entire mapping.
tests/units/reflex_base/vars/test_base.py	Verifies inferred types, exact sample boundaries, empty mappings, and bounded custom-mapping iteration and value access.
tests/benchmarks/test_type_inference.py	Adds a correctly integrated CodSpeed benchmark that measures inference independently of mapping construction.
packages/reflex-base/news/+bounded-mapping-inference.performance.md	Documents the downstream compilation-performance improvement in the package news format.

_{Reviews (1): Last reviewed commit: "perf: bound mapping type inference to th..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 32 untouched benchmarks
🆕 3 new benchmarks
⏩ 8 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	test_mapping_type_inference[100]	N/A	589.5 µs	N/A
🆕	test_mapping_type_inference[10000]	N/A	588.8 µs	N/A
🆕	test_mapping_type_inference[100000]	N/A	590.4 µs	N/A

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_{Comparing codex/perf-bounded-mapping-inference (31905d7) with main (c49a85d)}

Footnotes

1. 8 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. ↩