piscisaureus/deno_lint

Blazing fast linter for JavaScript and TypeScript written in Rust

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.

---

NOTE Work-in-progress

Current focus is on getting recommended set of rules from ESLint and @typescript-eslint working out of the box.

See the roadmap

---

Performance

Blazing fast, see comparison with ESLint:

[
  {
    "name": "deno_lint",
    "totalMs": 830.5838349999995,
    "runsCount": 5,
    "runsAvgMs": 166.1167669999999,
    "runsMs": [
      163.71872200000007,
      160.46893499999987,
      169.2397719999999,
      167.75393099999974,
      169.40247499999987
    ]
  },
  {
    "name": "eslint",
    "totalMs": 11783.570954999997,
    "runsCount": 5,
    "runsAvgMs": 2356.7141909999996,
    "runsMs": [
      2559.053129,
      2383.412156999999,
      2261.1746249999997,
      2306.645263999999,
      2273.28578
    ]
  }
]

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.

Supported rules

• adjacent-overload-signatures
• ban-ts-comment
• ban-ts-ignore
• ban-types
• ban-untagged-ignore
• ban-untagged-todo
• constructor-super
• default-param-last
• eqeqeq
• explicit-function-return-type
• for-direction
• getter-return
• no-array-constructor
• no-async-promise-executor
• no-await-in-loop
• no-case-declarations
• no-class-assign
• no-compare-neg-zero
• no-cond-assign
• no-const-assign
• no-control-regex
• no-debugger
• no-delete-var
• no-dupe-args
• no-dupe-class-members
• no-dupe-else-if
• no-dupe-keys
• no-duplicate-case
• no-empty-character-class
• no-empty-interface
• no-empty-pattern
• no-empty
• no-eval
• no-ex-assign
• no-explicit-any
• no-extra-boolean-cast
• no-extra-non-null-assertion
• no-extra-semi
• no-func-assign
• no-inferrable-types
• no-misused-new
• no-namespace
• no-new-symbol
• no-non-null-assertion
• no-obj-calls
• no-octal
• no-prototype-builtins
• no-regex-spaces
• no-setter-return
• no-shadow-restricted-names
• no-sparse-array
• no-this-alias
• no-this-before-super
• no-throw-literal
• no-unsafe-finally
• no-unsafe-negation
• no-unused-labels
• no-var
• no-with
• prefer-as-const
• prefer-namespace-keyword
• require-yield
• single-var-declarator
• triple-slash-reference
• use-isnan
• valid-typeof

Ignore directives

Files

To ignore whole file // deno-lint-ignore-file directive should placed at the top of the file.

// deno-lint-ignore-file

function foo(): any {
  // ...
}

Ignore directive must be placed before first stament or declaration:

// Copyright 2020 the Deno authors. All rights reserved. MIT license.

/**
 * Some JS doc
 **/

// deno-lint-ignore-file

import { bar } from "./bar.js";

function foo(): any {
  // ...
}

Diagnostics

To ignore certain diagnostic // deno-lint-ignore <codes...> directive should be placed before offending line.

// deno-lint-ignore no-explicit-any
function foo(): any {
  // ...
}

// deno-lint-ignore no-explicit-any explicit-function-return-type
function bar(a: any) {
  // ...
}

Specyfing rule code that will be ignored is required.

Example

examples/dlint/main.rs provides a minimal standalone binary demonstrating how deno_lint can be used as a crate.

$ ▶ target/debug/examples/dlint ../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 (1.44.0).

// check version
$ rustc --version
rustc 1.44.0 (49cae5576 2020-06-01)

// build all targets
$ cargo build --all-targets

// test it
$ cargo test

Generating flamegraph (Linux)

Prerequisites:

• Install perf, (stackcollapse-perf)[https://github.com/brendangregg/FlameGraph/blob/master/flamegraph.pl], rust-unmangle 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 | rust-unmangle | flamegraph > flame.svg # generate flamegraph

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 tools/lint.ts passes.