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https://github.com/denoland/deno_lint

Blazing fast linter for JavaScript and TypeScript written in Rust
https://github.com/denoland/deno_lint

deno javascript linters typescript

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Blazing fast linter for JavaScript and TypeScript written in Rust

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README 

        
# `deno_lint`



[![](https://img.shields.io/crates/v/deno_lint.svg)](https://crates.io/crates/deno_lint)

[![Discord Chat](https://img.shields.io/discord/684898665143206084?logo=discord&style=social)](https://discord.gg/deno)



A Rust crate for writing fast JavaScript and TypeScript linters.



This crate powers [`deno lint`](https://deno.land/manual/tools/linter), but is

not Deno specific and can be used to write linters for Node as well.



_Supports `recommended` set of rules from ESLint and `@typescript-eslint` out of

the box with no config._



See [the roadmap](https://github.com/denoland/deno_lint/issues/176)



---



## Supported rules



Visit https://lint.deno.land for the list of available rules.



## Performance



Blazing fast, see comparison with ESLint:



```json

[

  {

    "name": "deno_lint",

    "totalMs": 105.3750100000002,

    "runsCount": 5,

    "measuredRunsAvgMs": 21.07500200000004,

    "measuredRunsMs": [

      24.79783199999997,

      19.563640000000078,

      20.759051999999883,

      19.99068000000011,

      20.26380600000016

    ]

  },

  {

    "name": "eslint",

    "totalMs": 11845.073306000002,

    "runsCount": 5,

    "measuredRunsAvgMs": 2369.0146612000003,

    "measuredRunsMs": [

      2686.1039550000005,

      2281.501061,

      2298.6185210000003,

      2279.5962849999996,

      2299.2534840000008

    ]

  }

]

```



_Benchmarks are run during CI on Ubuntu, using the same set of rules for both

linters. Test subject is [`oak` server](https://github.com/oakserver/oak)

consisting of about 50 files. See [`./benchmarks/`](./benchmarks/) directory for

more info._



## Node.js bindings



If you want to use `deno_lint` with Node, please refer to

[`@node-rs/deno-lint`](https://www.npmjs.com/package/@node-rs/deno-lint) package

which provides programmatic API as well as Webpack loader for `deno_lint`.



## Example



`examples/dlint/main.rs` provides a minimal standalone binary demonstrating how

`deno_lint` can be used as a crate.



```shell

# Build standalone binary

$ cargo build --example dlint --features="docs"



$ ./target/debug/examples/dlint --help



dlint



USAGE:

    dlint 



FLAGS:

    -h, --help       Prints help information

    -V, --version    Prints version information



SUBCOMMANDS:

    help     Prints this message or the help of the given subcommand(s)

    rules

    run



$ ./target/debug/examples/dlint run ../deno/std/http/server.ts ../deno/std/http/file_server.ts

(no-empty) Empty block statement

  --> ../deno/std/http/server.ts:93:14

   |

93 |       } catch {}

   |               ^^

   |

(no-empty) Empty block statement

   --> ../deno/std/http/server.ts:111:44

    |

111 |     while ((await body.read(buf)) !== null) {}

    |                                             ^^

    |

(no-empty) Empty block statement

   --> ../deno/std/http/server.ts:120:41

    |

120 |   constructor(public listener: Listener) {}

    |                                          ^^

    |

(ban-untagged-todo) TODO should be tagged with (@username) or (#issue)

 --> ../deno/std/http/file_server.ts:5:0

  |

5 | // TODO Stream responses instead of reading them into memory.

  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  |

(ban-untagged-todo) TODO should be tagged with (@username) or (#issue)

 --> ../deno/std/http/file_server.ts:6:0

  |

6 | // TODO Add tests like these:

  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  |

(ban-untagged-todo) TODO should be tagged with (@username) or (#issue)

   --> ../deno/std/http/file_server.ts:137:0

    |

137 | // TODO: simplify this after deno.stat and deno.readDir are fixed

    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    |

(no-empty) Empty block statement

   --> ../deno/std/http/file_server.ts:155:16

    |

155 |     } catch (e) {}

    |                 ^^

    |

Found 7 problems

```



For more concrete implementation visit

[`deno`](https://github.com/denoland/deno/blob/main/cli/tools/lint/mod.rs)



## Developing



Make sure to have latest stable version of Rust installed (1.56.0).



```shell

// check version

$ rustc --version

rustc 1.56.0 (09c42c458 2021-10-18)



// build all targets

$ cargo build --all-targets



// test it

$ cargo test

```



### Generating flamegraph (Linux)



Prerequisites:



- Install [`perf`](https://perf.wiki.kernel.org/index.php/Main_Page),

  [`stackcollapse-perf`](https://github.com/brendangregg/FlameGraph/blob/master/flamegraph.pl),

  [`c++filt`](https://sourceware.org/binutils/docs/binutils/c_002b_002bfilt.html)

  and

  [`flamegraph`](https://github.com/brendangregg/FlameGraph/blob/master/flamegraph.pl)



```shell

$ RUSTFLAGS='-g' cargo build --release --all-targets # build target

$ sudo perf record --call-graph dwarf ./target/release/examples/dlint benchmarks/oak/**.ts # create performance profile

$ perf script | stackcollapse-perf | c++filt | flamegraph > flame.svg # generate flamegraph

```



You can use

[rust-unmangle](https://github.com/Yamakaky/rust-unmangle/blob/master/rust-unmangle)

or [rustfilt](https://github.com/luser/rustfilt) instead of c++filt.



These commands can take a few minutes to run.



## Contributing



- If you are going to work on an issue, mention so in the issue comments

  _before_ you start working on the issue.



- Please be professional in the forums. We follow

  [Rust's code of conduct](https://www.rust-lang.org/policies/code-of-conduct)

  (CoC) Have a problem? Email [email protected].



- Ask for help in the [community chat room](https://discord.gg/TGMHGv6).



## Submitting a Pull Request



Before submitting, please make sure the following is done:



1. That there is a related issue and it is referenced in the PR text.

2. There are tests that cover the changes.

3. Ensure `cargo test` passes.

4. Format your code with `deno run --allow-run tools/format.ts`

5. Make sure `deno run --allow-run --allow-env tools/lint.ts` passes.

6. If you've added a new rule:

   1. Run `cargo build --example dlint --all-features`

   2. Update docs by running the generated binary with these arguments

      `./target/debug/examples/dlint rules --json > www/static/docs.json`

   3. Update schema via `deno task update-schemas`