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0.1.13 | Oct 31, 2024 |
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0.1.12 | May 28, 2024 |
0.1.11 | Feb 15, 2024 |
0.1.10 | Oct 19, 2023 |
0.1.6 | Nov 28, 2022 |
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cargo-check-external-types
cargo-check-external-types
is a static analysis tool for Rust library authors
to set and verify which types from other libraries are allowed to be exposed in
their public API. This is useful for ensuring that a breaking change to a
dependency doesn't force a breaking change in the library that's using it.
The tool has two output formats to cover different use-cases:
errors
(the default): Output error messages for each type that is exposed in the public API and exit with status 1 if there is at least one error. This is useful for continuous integration.markdown-table
: Output the places types are exposed as a Markdown table. This is intended as a discovery tool for established projects.
The tool has an optional configuration file where types can by explicitly allowed.
Example Output
The test suite has a Rust library that relies on some external types. When the tool is run against this library without any configuration, it emits errors for each occurrence of an external type in the public API.
When a config file is provided, the allowed external types no longer show up in the output.
When the output format is set to markdown-table
, then a table of external
types is output.
How to Use
Important: This tool requires a nightly build of Rust to be installed since it
relies on the rustdoc JSON
output, which hasn't been
stabilized yet. It was last tested against nightly-2024-06-30
.
To install, run the following from this README path:
cargo install --locked cargo-check-external-types
Then, in your library crate path, run:
cargo +nightly check-external-types
This will produce errors if any external types are used in a public API at all.
That's not terribly useful on its own, so the tool can be given configuration in
your crate's Cargo.toml
to allow certain types. For example, we can allow any
type in bytes
by adding this metadata to your crate's Cargo.toml
:
[package.metadata.cargo_check_external_types]
allowed_external_types = ["bytes::*"]
Or, if you'd prefer, you can create a separate configuration file with the content:
allowed_external_types = [
"bytes::*",
]
Save that file somewhere in your project (in this example, we choose the name
external-types.toml
), and then run the command with:
cargo +nightly check-external-types --config external-types.toml
If both a Cargo.toml
package metadata section and a --config
flag are
provided, the --config
flag will be used instead of the package metadata.
Caveats
When public types and modules declared inside a #[doc(hidden)]
module are
reexported from a public module, they aren't checked for external types. This is
because of how they are recorded in RustDoc's index. When such types and modules
are encountered by this tool, a warning will be logged.
Updating rustdoc-types
and the Rust toolchain version
rustdoc-types
defines an unstable JSON format that this tool is based on. When
updating rustdoc-types
, the Rust toolchain version must be updated to a
nightly version that supports the version of the JSON format being used.
It's usually enough to update the toolchain to whatever the most recent nightly version is. All in all, you must update:
- The
rustdoc-types
dependency inCargo.toml
to the new version. - The
rust-toolchain
file to point to the new nightly version. - The
README.md
file, specifically the "It was last tested againstnightly-XXXX-XX-XX
." of the "How to Use" section. - The
rust_version
in the CI workflow file.
Then, PR your changes.
Security
See CONTRIBUTING for more information.
License
This project is licensed under the Apache-2.0 License.
Dependencies
~9–17MB
~224K SLoC