json2xml 6.3.0

json2xml 6.3.0 and json2xml_rs 0.4.0

Released 2026-06-10.

Highlights

• Reduced allocation pressure in the pure Python serializer hot paths for dicts, lists, scalar values, XML names, and emitted attributes.
• Kept the Python and Rust release line aligned: json2xml[fast] now requires json2xml-rs>=0.4.0.
• Documented the Rust memory benchmark in enough detail to reproduce the 100,000-record RSS measurement and understand the throughput tradeoff.

Why Upgrade

This release is focused on large conversion workloads. The 6.2.0 Rust release moved accelerator output directly into Python bytes to reduce peak serializer memory; 6.3.0 follows that with Python-side allocation reductions so fallback and unsupported-option paths also benefit.

No XML shape changes are intended. Existing callers should see the same output for supported options, including invalid-name normalization, @attrs/@val handling, list wrapping, XPath mode, and pure Python fallback behavior.

Package Versions

• Python package: json2xml==6.3.0
• Rust accelerator package: json2xml-rs==0.4.0
• Fast install: pip install "json2xml[fast]"

Changelog

• feat: reduce pure Python serializer allocations in hot dict, list, and scalar paths.
• feat: preserve XML output semantics while reusing validated element-name and attribute work.
• perf: lower peak memory pressure for large conversions after the 6.2.0 Rust bytes-writer release.
• docs: add hyperfine Rust memory benchmark notes with reproduction details and the measured throughput tradeoff.
• chore: release json2xml-rs 0.4.0 and require it from json2xml[fast] for accelerated installs.

Verification

The release changes are covered by the existing serializer, fast-backend, and Rust parity tests. The benchmark documentation records the measurement setup separately from the functional test suite so release consumers can reproduce performance results on their own hardware.