Dylint
A tool for running Rust lints from dynamic libraries
Dylint is a Rust linting tool, similar to Clippy. But whereas Clippy runs a predetermined, static set of lints, Dylint runs lints from user-specified, dynamic libraries. Thus, Dylint allows developers to maintain their own personal lint collections.
Contents
Quick start
The next five commands install Dylint, build one of its example libraries, and run the library's lint on the Dylint source code itself:
You can start writing your own Dylint libraries by forking the dylint-template
repository.
How libraries are found
When Dylint is started, the following locations are searched:
- the colon-separated paths in
DYLINT_LIBRARY_PATH
(if set) - the current package's
target/debug
directory (if in a package) - the current package's
target/release
directory (if in a package)
Any file found in the above locations with a name of the form DLL_PREFIX LIBRARY_NAME '@' TOOLCHAIN DLL_SUFFIX
(see Library requirements below) is considered a Dylint library.
In an invocation of the form cargo dylint <names>
, each name
in names
is compared to the libraries found in the above manner. If name
matches a discovered library's LIBRARY_NAME
, then name
resolves to that library. It is considered an error if a name
resolves to multiple libraries.
If the above process does not resolve name
to a library, then name
is treated as a path.
If --lib name
is used, then name
is is treated only as a library name, and not as a path.
If --path name
is used, then name
is is treated only as a path, and not as a library name.
Library requirements
A Dylint library must satisfy four requirements. Note: before trying to satisfy these explicitly, see Utilities below.
-
Have a filename of the form:
DLL_PREFIX LIBRARY_NAME '@' TOOLCHAIN DLL_SUFFIX
The following is a concrete example on Linux:
libquestion_mark_in_expression@nightly-2021-04-08-x86_64-unknown-linux-gnu.so
The filename components are as follows:
DLL_PREFIX
andDLL_SUFFIX
are OS-specific strings. For example, on Linux, they arelib
and.so
, respectively.LIBARY_NAME
is a name chosen by the library's author.TOOLCHAIN
is the Rust toolchain for which the library is compiled, e.g.,nightly-2021-04-08-x86_64-unknown-linux-gnu
.
-
Export a
dylint_version
function:extern "C"
This function should return
0.1.0
. This may change in future versions of Dylint. -
Export a
register_lints
function:This is a function called by the Rust compiler. It is documented here.
-
Link against the
rustc_driver
dynamic library. This ensures the library uses Dylint's copies of the Rust compiler crates. This requirement can be satisfied by including the following declaration in your library'slib.rs
file:extern crate rustc_driver;
Dylint provides utilities to help meet the above requirements. If your library uses the dylint-link
tool and the dylint_library!
macro, then all you should have to do is implement the register_lints
function.
Utilities
The following utilities can be helpful for writing Dylint libraries:
dylint-link
is a wrapper around Rust's default linker (cc
) that creates a copy of your library with a filename that Dylint recognizes.dylint_library!
is a macro that automatically defines thedylint_version
function and adds theextern crate rustc_driver
declaration.ui_test
is a function that can be used to test Dylint libraries. It provides convenient access to thecompiletest_rs
package.clippy_utils
is a collection of utilities to make writing lints easier. It is generously made public by the Rust Clippy Developers. Note that, likerustc
,clippy_utils
provides no stability guarantees for its APIs.
Limitations
To run a library's lints on a package, Dylint tries to build the package with the same toolchain used to build the library. So if a package requires a specific toolchain to build, Dylint may not be able to apply certain libraries to that package.
One way this problem can manifest itself is if you try to run one library's lints on the source code of another library. That is, if two libraries use different toolchains, they may not be applicable to each other.
Resources
Helpful resources for writing lints include the following:
- Adding a new lint (targeted at Clippy but still useful)
- Common tools for writing lints
rustc_hir
documentation