All issues on Clippy are mentored, if you want help with a bug just ask @Manishearth, @llogiq, @mcarton or @oli-obk.
-Some issues are easier than others. The [E-easy](https://github.com/rust-lang-nursery/rust-clippy/labels/E-easy)
+Some issues are easier than others. The [`good first issue`](https://github.com/rust-lang-nursery/rust-clippy/labels/good%20first%20issue)
label can be used to find the easy issues. If you want to work on an issue, please leave a comment
so that we can assign it to you!
-Issues marked [T-AST](https://github.com/rust-lang-nursery/rust-clippy/labels/T-AST) involve simple
+Issues marked [`T-AST`](https://github.com/rust-lang-nursery/rust-clippy/labels/T-AST) involve simple
matching of the syntax tree structure, and are generally easier than
-[T-middle](https://github.com/rust-lang-nursery/rust-clippy/labels/T-middle) issues, which involve types
+[`T-middle`](https://github.com/rust-lang-nursery/rust-clippy/labels/T-middle) issues, which involve types
and resolved paths.
-Issues marked [E-medium](https://github.com/rust-lang-nursery/rust-clippy/labels/E-medium) are generally
+[`T-AST`](https://github.com/rust-lang-nursery/rust-clippy/labels/T-AST) issues will generally need you to match against a predefined syntax structure. To figure out
+how this syntax structure is encoded in the AST, it is recommended to run `rustc -Z ast-json` on an
+example of the structure and compare with the
+[nodes in the AST docs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ast). Usually
+the lint will end up to be a nested series of matches and ifs,
+[like so](https://github.com/rust-lang-nursery/rust-clippy/blob/de5ccdfab68a5e37689f3c950ed1532ba9d652a0/src/misc.rs#L34).
+
+[`E-medium`](https://github.com/rust-lang-nursery/rust-clippy/labels/E-medium) issues are generally
pretty easy too, though it's recommended you work on an E-easy issue first. They are mostly classified
as `E-medium`, since they might be somewhat involved code wise, but not difficult per-se.
+[`T-middle`](https://github.com/rust-lang-nursery/rust-clippy/labels/T-middle) issues can
+be more involved and require verifying types. The
+[`ty`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty) module contains a
+lot of methods that are useful, though one of the most useful would be `expr_ty` (gives the type of
+an AST expression). `match_def_path()` in Clippy's `utils` module can also be useful.
+
+### Writing code
+
+Compiling clippy from scratch can take almost a minute or more depending on your machine.
+However, since Rust 1.24.0 incremental compilation is enabled by default and compile times for small changes should be quick.
+
[Llogiq's blog post on lints](https://llogiq.github.io/2015/06/04/workflows.html) is a nice primer
to lint-writing, though it does get into advanced stuff. Most lints consist of an implementation of
`LintPass` with one or more of its default methods overridden. See the existing lints for examples
of this.
-T-AST issues will generally need you to match against a predefined syntax structure. To figure out
-how this syntax structure is encoded in the AST, it is recommended to run `rustc -Z ast-json` on an
-example of the structure and compare with the
-[nodes in the AST docs](http://manishearth.github.io/rust-internals-docs/syntax/ast/). Usually
-the lint will end up to be a nested series of matches and ifs,
-[like so](https://github.com/rust-lang-nursery/rust-clippy/blob/de5ccdfab68a5e37689f3c950ed1532ba9d652a0/src/misc.rs#L34).
-T-middle issues can be more involved and require verifying types. The
-[`ty`](http://manishearth.github.io/rust-internals-docs/rustc/ty) module contains a
-lot of methods that are useful, though one of the most useful would be `expr_ty` (gives the type of
-an AST expression). `match_def_path()` in Clippy's `utils` module can also be useful.
+#### Author lint
-### Writing code
+There is also the internal `author` lint to generate clippy code that detects the offending pattern. It does not work for all of the Rust syntax, but can give a good starting point.
+
+Create a new UI test with the pattern you want to match:
-Compiling clippy can take almost a minute or more depending on your machine.
-You can set the environment flag `CARGO_INCREMENTAL=1` to cut down that time to
-almost a third on average, depending on the influence your change has.
+```rust
+// ./tests/ui/my_lint.rs
+
+// The custom_attribute needs to be enabled for the author lint to work
+#![feature(plugin, custom_attribute)]
+
+fn main() {
+ #[clippy(author)]
+ let arr: [i32; 1] = [7]; // Replace line with the code you want to match
+}
+```
+
+Now you run `TESTNAME=ui/my_lint cargo test --test compile-test` to produce
+the file with the generated code:
+
+```rust
+// ./tests/ui/my_lint.stdout
+
+if_chain! {
+ if let Expr_::ExprArray(ref elements) = stmt.node;
+ if elements.len() == 1;
+ if let Expr_::ExprLit(ref lit) = elements[0].node;
+ if let LitKind::Int(7, _) = lit.node;
+ then {
+ // report your lint here
+ }
+}
+```
+
+#### Documentation
Please document your lint with a doc comment akin to the following:
/// **Known problems:** None. (Or describe where it could go wrong.)
///
/// **Example:**
+///
/// ```rust
-/// Insert a short example if you have one.
+/// // Bad
+/// Insert a short example of code that triggers the lint
+///
+/// // Good
+/// Insert a short example of improved code that doesn't trigger the lint
/// ```
```
+Once your lint is merged it will show up in the [lint list](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
+
### Running test suite
Clippy uses UI tests. UI tests check that the output of the compiler is exactly as expected.
Of course there's little sense in writing the output yourself or copying it around.
-Therefore you can simply run `tests/ui/update-all-references.sh` and check whether
-the output looks as you expect with `git diff`. Commit all `*.stderr` files, too.
+Therefore you can simply run `tests/ui/update-all-references.sh` (after running
+`cargo test`) and check whether the output looks as you expect with `git diff`. Commit all
+`*.stderr` files, too.
+
+If you don't want to wait for all tests to finish, you can also execute a single test file by using `TESTNAME` to specify the test to run:
+
+```bash
+TESTNAME=ui/empty_line_after_outer_attr cargo test --test compile-test
+```
### Testing manually
Manually testing against an example file is useful if you have added some
`println!`s and test suite output becomes unreadable. To try clippy with your
-local modifications, run `cargo run -- -L ./target/debug input.rs` from the
+local modifications, run `cargo run --bin clippy-driver -- -L ./target/debug input.rs` from the
working copy root. Your test file, here `input.rs`, needs to have clippy
enabled as a plugin:
projects / rust.git / blobdiff