cargo-echoes

By chance two separate functions meet, and I am you and what I see is me.

cargo echoes finds duplicated Rust doctests, and optionally duplicated functions and code blocks, across a workspace or across every crate of a GitHub organization. The wiki explains each check, the options and the Action in depth.

Usage

cargo install echoes
cargo echoes --functions --context-blocks
cargo echoes --organization --functions

Check	Enable	Default minimum size	Set the size
Doctests	On by default	0 tokens	--min-tokens
Functions	--functions	30 weighted body tokens	--fn-min-tokens
Contexts	--context-blocks	30 canonical weighted tokens	--context-min-tokens

Options can also live in .echoes.toml at the workspace root, and cargo echoes --help lists them all. Leave out whole paths, such as benchmarks, with gitignore-style exclude globs or --exclude, and keep an intentional copy with a rust,echoes fence or a // echoes: allow line above the function. The wiki lists what counts as the same code.

--organization scans the default branch of every repository of a GitHub organization or user that the GH_TOKEN or GITHUB_TOKEN credential can read, private ones included, and compares functions across crates and modules. Without a name it scans the owner of the current repository, from GITHUB_REPOSITORY_OWNER or the origin remote. Repeat it to join several owners, and pass --repository OWNER/REPO once per repository to add repositories of any owner, alone or beside the organizations. Downloaded repositories never configure the scan or run code, so pass --config for options, and the exit status is 2 whenever a repository could not be analyzed, even with --no-fail.

GitHub Action

on: pull_request
jobs:
  echoes:
    runs-on: ubuntu-26.04
    permissions:
      contents: write
      pull-requests: write
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
      - uses: LucaCappelletti94/cargo-echoes@v1
        with:
          pr-number: ${{ github.event.pull_request.number }}
          functions: true

The action reviews the pull request and suggests removing each copy it introduces, with links to report a wrong review and support echoes. On every new commit it dismisses its earlier requests for changes, updates its earlier comment-only summaries and resolves the threads of copies that are gone, which needs contents: write. action.yml lists every input, and these two workflows review pull requests from forks.

Library

let report = echoes::Echoes::default()
    .functions()
    .context_blocks()
    .run(".")
    .unwrap();
println!("{}", echoes::human(&report, false));

Use default-features = false, features = ["std"] to drop the CLI. Coding agents get the same guidance from the echoes skill.

npx skills add LucaCappelletti94/cargo-echoes