The action is using cargo metadata with format version 1 to collect the information about crates and workspace.

• Reads manifests to get info about crates and dependencies
• Checks versions of external dependencies to be exists in registry
• Checks matching paths and versions of internal dependencies
• Checks that no changes happened since published release when version of internal dependency is not changed
• Skips publishing of internal dependencies which does not updated
• Publishes updated crates in right order according to dependencies
• Awaits when published crate will be available in registry before publishing crates which depends from it
• Works fine in workspaces without cyclic dependencies
• Support { workspace = true } syntax in the Cargo.toml. This feature was stabilized in Rust 1.64.

• Support different registries than crates.io

• token GitHub API token (github.token by default)
• path Sets path to crate or workspace ('.' by default)
• args Extra arguments for cargo publish command
• registry-token Cargo registry token (not used when dry-run: true)
• dry-run Set to true to bypass exec cargo publish
• check-repo Set to false to bypass check local packages for modifications since last published version
• publish-delay Optional delay in milliseconds applied after publishing each package before publishing others
• no-verify Set to true to bypass cyclic dependency detection and cargo packaging verification (uses --no-verify)
• ignore-unpublished-changes Set to true to exit the workflow gracefully if package does not have a new version to publish

Each local package (workspace member) potentially may be modified since last published version without corresponding version bump. This situation is dangerous and should be prevented. In order to do it this action uses GitHub API to get date of latest commit which modified contents by path of corresponding package. This date compares with date of last published version of that package. When option check-repo set to true (which is by default) this action will throw error in case when last commit date cannot be determined. This happenned in case of detached refs (like pull requests). Usually you should never publish packages via pull-requests so you may simply disable this action for run in such cases (via if expression as example). When you want to run action (say with dry-run set to true) prevent failing you may simply set check-repo to false too.

NOTE: You should avoid setting both check-repo and dry-run to false.

Usually you don't need to set publish-delay because this action check availability of previously published packages before publishing other but in some cases it may help work around crates.io inconsistency problems.

• published JSON formatted string with published crates as array of objects with name and version fields.

You may want to use it with fromJSON function and object filters syntax 1, 2.

This works whether "dry-run" is enabled or not. That means that when dry-run: true you will get packages that could have been published.

Basic usage (Cargo.toml sits in repository root):

steps:
    - uses: actions/checkout@v3
    - uses: actions-rs/toolchain@v1
      with:
          toolchain: stable
          override: true
    - uses: katyo/publish-crates@v2
      with:
          registry-token: ${{ secrets.CARGO_REGISTRY_TOKEN }}

Advanced usage (Cargo.toml sits in 'packages' subdir, and you would like to skip verification and bypass real publishing):

steps:
    - uses: actions/checkout@v3
    - uses: actions-rs/toolchain@v1
      with:
          toolchain: stable
          override: true
    - uses: katyo/publish-crates@v2
      with:
          path: './packages'
          args: --no-verify
          dry-run: true

Do all checks in both push and pull requests, but only publish on push:

steps:
    - uses: actions/checkout@v3
    - uses: actions-rs/toolchain@v1
      with:
          toolchain: stable
          override: true
    - uses: katyo/publish-crates@v2
      with:
          dry-run: ${{ github.event_name != 'push' }}

Prevent failing when there is no new version to publish:

steps:
    - uses: actions/checkout@v3
    - uses: actions-rs/toolchain@v1
      with:
          toolchain: stable
          override: true
    - uses: katyo/publish-crates@v2
      with:
          registry-token: ${{ secrets.CARGO_REGISTRY_TOKEN }}
          ignore-unpublished-changes: true

Output usage:

    - uses: katyo/publish-crates@v2
      id: publish-crates
      with:
          registry-token: ${{ secrets.CARGO_REGISTRY_TOKEN }}

    - name: if my-crate published
          if: fromJSON(steps.publish-crates.outputs.published).*
          run: |
            LIST="${{ join(fromJSON(steps.publish-crates.outputs.published).*.name, ', ')) }}"
            echo "Published crates: $LIST"

NOTE: This is also works if dry-run is enabled. It explained in Outputs.