This tool finds the crates that rely on a target crate and builds them locally with an updated version of the target crate. This can be used to evaluate the scope of a breaking change before it is released.

1. Install the tool

   cargo install --git https://github.com/shepmaster/mini-crater
   

2. Run the tool. Provide the crate name, the version to upgrade from, and one or more patch lines to substitute in. You can set the environment variable RUST_LOG=trace to have more detail about the process.

This evaluates crates that use SNAFU 0.6 to see if they will all build with a locally-modified version of snafu and snafu-derive.

mini-crater snafu \
  --version 0.8.9 \
  --patch 'snafu = { path = "/Users/shep/Projects/snafu" }' \
  --patch 'snafu-derive = { path = "/Users/shep/Projects/snafu/snafu-derive" }'

This runs a user-specified script called adjust-code.sh as the second build step:

mini-crater snafu \
  --version 0.8.9 \
  --patch 'snafu = { path = "/Users/shep/Projects/snafu" }' \
  --patch 'snafu-derive = { path = "/Users/shep/Projects/snafu/snafu-derive" }' \
  --use-git \
  --post-command /tmp/adjust-code.sh

User-specified scripts have the following environment variables available:

• MINI_CRATER_WORKING_DIR - The root working directory.
• MINI_CRATER_EXPERIMENT_NAME - The name of the current crate being experimented on.
• MINI_CRATER_EXPERIMENT_CHECKOUT_DIR - When a git checkout has been performed, this points to the top of the checkout.