How to upgrade MSRV

This document outlines the process for upgrading the Minimum Supported Rust Version (MSRV) for the brush project.

Overview

Before upgrading MSRV, review the MSRV Policy to ensure the update aligns with project guidelines.

Process

1. Find all MSRV references

Search for the current MSRV version throughout the codebase:

grep -r "<current-version>" .

Typically, MSRV is specified in:

Cargo.toml (workspace rust-version field)
.github/workflows/ci.yaml (CI test matrix)
.github/copilot-instructions.md (GitHub Copilot instructions)

2. Update MSRV references

Update all occurrences to the new version:

Cargo.toml: Update the rust-version field under [workspace.package]
.github/workflows/ci.yaml: Update the version in the test matrix

3. Verify the build

Test that the project builds successfully with the updated MSRV:

cargo check --workspace

4. Run tests

Verify that tests pass with the new MSRV:

cargo test --workspace

5. Run static checks

After upgrading MSRV, it's important to rerun all static checks, as newer Rust versions may introduce new lints and clippy warnings that weren't present in the previous MSRV. These warnings need to be resolved to maintain code quality.

Run clippy with all warnings treated as errors:

cargo clippy --workspace --all-targets --all-features -- -D warnings

Also run other static checks such as formatting:

cargo fmt --all -- --check

Note: Upgrading MSRV often enables new clippy lints (particularly in nursery categories) that may flag code patterns that were previously acceptable. Review and fix these warnings, as they often suggest improvements like adding const to functions or other optimizations that are newly available in the updated Rust version.

6. Update documentation

When merging the MSRV update:

Call out the update in an appropriate Conventional Commit commit description
Include justification for the change in the release notes

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