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Auto merge of rust-lang#115183 - flip1995:clippyup, r=Manishearth,oli…
…-obk
Update Clippy
r? `@oli-obk` Assigning you, because something broke with ui_test:
```
tests/ui/crashes/ice-7272.rs FAILED:
command: "<unknown>"
A bug in `ui_test` occurred: called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
full stderr:
```
(and that 103 times)
Thought I would ping you, before starting to investigate. Maybe you know what's going on.- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,205 @@ | ||
| # Define New Lints | ||
|
|
||
| The first step in the journey of a new lint is the definition | ||
| and registration of the lint in Clippy's codebase. | ||
| We can use the Clippy dev tools to handle this step since setting up the | ||
| lint involves some boilerplate code. | ||
|
|
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| #### Lint types | ||
|
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| A lint type is the category of items and expressions in which your lint focuses on. | ||
|
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| As of the writing of this documentation update, there are 12 _types_ of lints | ||
| besides the numerous standalone lints living under `clippy_lints/src/`: | ||
|
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||
| - `cargo` | ||
| - `casts` | ||
| - `functions` | ||
| - `loops` | ||
| - `matches` | ||
| - `methods` | ||
| - `misc_early` | ||
| - `operators` | ||
| - `transmute` | ||
| - `types` | ||
| - `unit_types` | ||
| - `utils / internal` (Clippy internal lints) | ||
|
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||
| These types group together lints that share some common behaviors. For instance, | ||
| `functions` groups together lints that deal with some aspects of functions in | ||
| Rust, like definitions, signatures and attributes. | ||
|
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||
| For more information, feel free to compare the lint files under any category | ||
| with [All Clippy lints][all_lints] or ask one of the maintainers. | ||
|
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| ## Lint name | ||
|
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| A good lint name is important, make sure to check the [lint naming | ||
| guidelines][lint_naming]. Don't worry, if the lint name doesn't fit, a Clippy | ||
| team member will alert you in the PR process. | ||
|
|
||
| --- | ||
|
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| We'll name our example lint that detects functions named "foo" `foo_functions`. | ||
| Check the [lint naming guidelines][lint_naming] to see why this name makes | ||
| sense. | ||
|
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| ## Add and Register the Lint | ||
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| Now that a name is chosen, we shall register `foo_functions` as a lint to the | ||
| codebase. There are two ways to register a lint. | ||
|
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| ### Standalone | ||
|
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| If you believe that this new lint is a standalone lint (that doesn't belong to | ||
| any specific [type](#lint-types) like `functions` or `loops`), you can run the | ||
| following command in your Clippy project: | ||
|
|
||
| ```sh | ||
| $ cargo dev new_lint --name=lint_name --pass=late --category=pedantic | ||
| ``` | ||
|
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| There are two things to note here: | ||
|
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| 1. `--pass`: We set `--pass=late` in this command to do a late lint pass. The | ||
| alternative is an `early` lint pass. We will discuss this difference in a | ||
| later chapter. | ||
| <!-- FIXME: Link that "later chapter" when lint_passes.md is merged --> | ||
| 2. `--category`: If not provided, the `category` of this new lint will default | ||
| to `nursery`. | ||
|
|
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| The `cargo dev new_lint` command will create a new file: | ||
| `clippy_lints/src/foo_functions.rs` as well as [register the | ||
| lint](#lint-registration). | ||
|
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| Overall, you should notice that the following files are modified or created: | ||
|
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||
| ```sh | ||
| $ git status | ||
| On branch foo_functions | ||
| Changes not staged for commit: | ||
| (use "git add <file>..." to update what will be committed) | ||
| (use "git restore <file>..." to discard changes in working directory) | ||
| modified: CHANGELOG.md | ||
| modified: clippy_lints/src/lib.register_lints.rs | ||
| modified: clippy_lints/src/lib.register_pedantic.rs | ||
| modified: clippy_lints/src/lib.rs | ||
|
|
||
| Untracked files: | ||
| (use "git add <file>..." to include in what will be committed) | ||
| clippy_lints/src/foo_functions.rs | ||
| tests/ui/foo_functions.rs | ||
| ``` | ||
|
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||
|
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| ### Specific Type | ||
|
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| > **Note**: Lint types are listed in the ["Lint types"](#lint-types) section | ||
| If you believe that this new lint belongs to a specific type of lints, | ||
| you can run `cargo dev new_lint` with a `--type` option. | ||
|
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| Since our `foo_functions` lint is related to function calls, one could | ||
| argue that we should put it into a group of lints that detect some behaviors | ||
| of functions, we can put it in the `functions` group. | ||
|
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| Let's run the following command in your Clippy project: | ||
|
|
||
| ```sh | ||
| $ cargo dev new_lint --name=foo_functions --type=functions --category=pedantic | ||
| ``` | ||
|
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||
| This command will create, among other things, a new file: | ||
| `clippy_lints/src/{type}/foo_functions.rs`. | ||
| In our case, the path will be `clippy_lints/src/functions/foo_functions.rs`. | ||
|
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||
| Notice how this command has a `--type` flag instead of `--pass`. Unlike a standalone | ||
| definition, this lint won't be registered in the traditional sense. Instead, you will | ||
| call your lint from within the type's lint pass, found in `clippy_lints/src/{type}/mod.rs`. | ||
|
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| A _type_ is just the name of a directory in `clippy_lints/src`, like `functions` in | ||
| the example command. Clippy groups together some lints that share common behaviors, | ||
| so if your lint falls into one, it would be best to add it to that type. | ||
|
|
||
| Overall, you should notice that the following files are modified or created: | ||
|
|
||
| ```sh | ||
| $ git status | ||
| On branch foo_functions | ||
| Changes not staged for commit: | ||
| (use "git add <file>..." to update what will be committed) | ||
| (use "git restore <file>..." to discard changes in working directory) | ||
| modified: CHANGELOG.md | ||
| modified: clippy_lints/src/declared_lints.rs | ||
| modified: clippy_lints/src/functions/mod.rs | ||
|
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||
| Untracked files: | ||
| (use "git add <file>..." to include in what will be committed) | ||
| clippy_lints/src/functions/foo_functions.rs | ||
| tests/ui/foo_functions.rs | ||
| ``` | ||
|
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| ## The `define_clippy_lints` macro | ||
|
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| After `cargo dev new_lint`, you should see a macro with the name | ||
| `define_clippy_lints`. It will be in the same file if you defined a standalone | ||
| lint, and it will be in `mod.rs` if you defined a type-specific lint. | ||
|
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| The macro looks something like this: | ||
|
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| ```rust | ||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// | ||
| /// // Describe here what does the lint do. | ||
| /// | ||
| /// Triggers when detects... | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// | ||
| /// // Describe why this pattern would be bad | ||
| /// | ||
| /// It can lead to... | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// // example code where clippy issues a warning | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// // example code which does not raise clippy warning | ||
| /// ``` | ||
| #[clippy::version = "1.70.0"] // <- In which version was this implemented, keep it up to date! | ||
| pub LINT_NAME, // <- The lint name IN_ALL_CAPS | ||
| pedantic, // <- The lint group | ||
| "default lint description" // <- A lint description, e.g. "A function has an unit return type." | ||
| } | ||
| ``` | ||
|
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| ## Lint registration | ||
|
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| If we run the `cargo dev new_lint` command for a new lint, the lint will be | ||
| automatically registered and there is nothing more to do. | ||
|
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| However, sometimes we might want to declare a new lint by hand. In this case, | ||
| we'd use `cargo dev update_lints` command afterwards. | ||
|
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| When a lint is manually declared, we might need to register the lint pass | ||
| manually in the `register_plugins` function in `clippy_lints/src/lib.rs`: | ||
|
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| ```rust | ||
| store.register_late_pass(|_| Box::new(foo_functions::FooFunctions)); | ||
| ``` | ||
|
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| As you might have guessed, where there's something late, there is something | ||
| early: in Clippy there is a `register_early_pass` method as well. More on early | ||
| vs. late passes in a later chapter. | ||
| <!-- FIXME: Link that "later chapter" when lint_passes.md is merged --> | ||
|
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| Without a call to one of `register_early_pass` or `register_late_pass`, the lint | ||
| pass in question will not be run. | ||
|
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| [all_lints]: https://rust-lang.github.io/rust-clippy/master/ | ||
| [lint_naming]: https://rust-lang.github.io/rfcs/0344-conventions-galore.html#lints |
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