deno_lint

A Rust crate for writing fast JavaScript and TypeScript linters.

This crate powers deno lint, 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

Supported rules

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

Performance

Blazing fast, see comparison with ESLint:

[
  {
    "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 consisting of about 50 files. See ./benchmarks/ directory for more info.

Node.js bindings

If you want to use deno_lint with Node, please refer to @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.

# Build standalone binary
$ cargo build --example dlint --features="docs"

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

dlint

USAGE:
    dlint <SUBCOMMAND>

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

Developing

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

// 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, stackcollapse-perf, c++filt and flamegraph

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

• Ask for help in the community chat room.

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