CLI

Flint’s CLI comes as part of the flint npm package. You can run it with npx or an equivalent:

npm

npx flint

pnpm

pnpx flint

yarn

yarn dlx flint

--cache-ignore

Whether to ignore any existing cache data on disk. This will cause a full re-lint of all linted files.

npm

npx flint --cache-ignore

pnpm

pnpx flint --cache-ignore

yarn

yarn dlx flint --cache-ignore

Tip

Flint stores linting caches under node_modules/.cache/flint.json. Open that file in an editor to see which files are cached as well as dependencies between files.

--fix

Enables auto-fixing “fixes” from rule reports.

npm

npx flint --fix

pnpm

pnpx flint --fix

yarn

yarn dlx flint --fix

Rule reports may include safe “fixer” changes that show how to fix source code. Adding --fix will instruct Flint to continuously re-run (up to 10 times), fixing code and re-linting files.

--fix-suggestions

Enables auto-fixing any number of specific “suggestions” from rule reports.

npm

npx flint --fix-suggestions cspell:addWordToWords

pnpm

pnpx flint --fix-suggestions cspell:addWordToWords

yarn

yarn dlx flint --fix-suggestions cspell:addWordToWords

Unlike --fix, --fix-suggestions requires passing in explicit names of suggestions to apply. Suggestion names are comprised of the rule name, and a suggestion ID, all joined by :.

Note

🚀 Feature: Comment directives and suggestions should prefix with plugin IDs will soon change suggestion keys.

--help

Prints a help text dialog that explains options and links to this website.

npm

npx flint --help

pnpm

pnpx flint --help

yarn

yarn dlx flint --help

--interactive

Whether to run Flint with an interactive “one file at a time” viewer.

npm

npx flint --interactive

pnpm

pnpx flint --interactive

yarn

yarn dlx flint --interactive

Flint’s interactive CLI view can be controlled by using the arrow keys printed in the output:

📌 Displaying Flint reports in --interactive mode (file 1 of 2).
   [<] previous file  [>] next file  [q] quit

╭./example.ts
│
│ [forInArrays] For-in loops over arrays have surprising behavior that often leads to bugs.
│
│  6:1 │ for (const i in ["a", "b", "c"]) {
│      │ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
│
│  A for-in loop (`for (const i in o)`) iterates over all enumerable properties of an object, including those that are not array indices.
│  This can lead to unexpected behavior when used with arrays, as it may include properties that are not part of the array's numeric indices.
│  It also returns the index key (`i`) as a string, which is not the expected numeric type for array indices.
│
│  Suggestion: Use a construct more suited for arrays, such as a for-of loop (`for (const i of o)`).
│  → flint.fyi/rules/ts/forInArrays
│
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

✖ Found 3 reports across 2 files.

Tip

The --interactive mode switches the default --presenter from brief to detailed. It does not, however, enable --watch by default. Run with --interactive --watch to use both modes.

--presenter

Which “presenter” to output results using: brief (default) or detailed.

npm

npx flint

pnpm

pnpx flint

yarn

yarn dlx flint

The brief presenter shows a terse output with just file locations, primary report messages, and report IDs.

Linting with flint.config.ts...

/Users/josh/repos/flint/packages/cli/src/presenters/getPresenterFactory.ts
  6:1  For-in loops over arrays have surprising behavior that often leads to bugs.  forInArrays

✖ Found 1 report across 1 file.

The detailed presenter shows a rich formatted output containing full report messages and syntax locations.

Linting with flint.config.ts...
╭./packages/cli/src/presenters/getPresenterFactory.ts
│
│ [forInArrays] For-in loops over arrays have surprising behavior that often leads to bugs.
│
│  6:1 │ for (const i in ["a", "b", "c"]) {
│      │ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
│
│  A for-in loop (`for (const i in o)`) iterates over all enumerable properties of an object, including those that are not array indices.
│  This can lead to unexpected behavior when used with arrays, as it may include properties that are not part of the array's numeric indices.
│  It also returns the index key (`i`) as a string, which is not the expected numeric type for array indices.
│
│  Suggestion: Use a construct more suited for arrays, such as a for-of loop (`for (const i of o)`).
│  → flint.fyi/rules/forInArrays
│
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

✖ Found 1 report across 1 file.

--skip-diagnostics

Whether to skip reporting language “diagnostics” after linting.

npm

npx flint --skip-diagnostics

pnpm

pnpx flint --skip-diagnostics

yarn

yarn dlx flint --skip-diagnostics

Language plugins such as are able to report additional checks from the languages after linting. For example, Flint’s core TypeScript plugin reports TypeScript type errors (effectively running tsc --noEmit) by re-using the TypeScript type services used in linting.

--skip-diagnostics can be used to disable those checks. You may wish to do this for performance and/or if you run tools like tsc separately from Flint.

--version

Prints the current package version of Flint.

npm

npx flint --version

pnpm

pnpx flint --version

yarn

yarn dlx flint --version

--watch

Whether to keep the linting process running, re-linting files as they change.

npm

npx flint --watch

pnpm

pnpx flint --watch

yarn

yarn dlx flint --watch

Flint’s --watch mode is similar to the watch mode in other developer tools CLIs such as tsc --watch, tsdown --watch, and vitest --watch. It will lint files once on startup, then again whenever any linted files are changed on disk.