Tracking issue for style_edition #5720

Tracking issue for the rustfmt specifics of implementing/supporting RFC 3338, Style Evolution

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They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
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Steps

• Create new configuration option style_edition
• Soft deprecate version option with auto-mapping to corresponding style_edition value
• Add --style-edition flag to cargo-fmt and rustfmt
• Update configuration mechanism to support varying option availability, stability, and default values based on style_edition
• Update CLIs (cargo-fmt & rustfmt) to support varying surface of option/arg availability and stability
• Update configuration documentation approaches to delineate by style edition

Associated Issues/Discussions

• Design Discussion for style_edition Configuration in rustfmt #5650 - Design Discussion for style_edition

Unresolved Questions

• Should the rolling "vNext" variant of style_edition be made available on stable? I.e. the current latest formatting-stable version of style_edition would be 2021, where 2024 would be analogous to version=Two, so would 2024 only be available on nightly?

Implementation history

• implement Style Edition support #6247
• update changelog for v1.9.0 release #6432
• subtree-push nightly-2025-01-02 #6431
• Stabilize style_edition = "2024" in-tree rust#134929