no-import-type-side-effects
Enforce the use of top-level import type qualifier when an import only has specifiers with inline type qualifiers.
Some problems reported by this rule are automatically fixable by the --fix
ESLint command line option.
The --verbatimModuleSyntax
compiler option causes TypeScript to do simple and predictable transpilation on import declarations.
Namely, it completely removes import declarations with a top-level type
qualifier, and it removes any import specifiers with an inline type
qualifier.
The latter behavior does have one potentially surprising effect in that in certain cases TS can leave behind a "side effect" import at runtime:
import { type A, type B } from 'mod';
// is transpiled to
import {} from 'mod';
// which is the same as
import 'mod';
For the rare case of needing to import for side effects, this may be desirable - but for most cases you will not want to leave behind an unnecessary side effect import.
module.exports = {
"rules": {
"@typescript-eslint/no-import-type-side-effects": "error"
}
};
Try this rule in the playground ↗
Examples
This rule enforces that you use a top-level type
qualifier for imports when it only imports specifiers with an inline type
qualifier
- ❌ Incorrect
- ✅ Correct
import { type A } from 'mod';
import { type A as AA } from 'mod';
import { type A, type B } from 'mod';
import { type A as AA, type B as BB } from 'mod';
Open in Playgroundimport type { A } from 'mod';
import type { A as AA } from 'mod';
import type { A, B } from 'mod';
import type { A as AA, B as BB } from 'mod';
import T from 'mod';
import type T from 'mod';
import * as T from 'mod';
import type * as T from 'mod';
import { T } from 'mod';
import type { T } from 'mod';
import { T, U } from 'mod';
import type { T, U } from 'mod';
import { type T, U } from 'mod';
import { T, type U } from 'mod';
import type T, { U } from 'mod';
import T, { type U } from 'mod';
Open in PlaygroundOptions
This rule is not configurable.
When Not To Use It
If you're not using TypeScript 5.0's verbatimModuleSyntax
option and your project is built with a bundler that manages import side effects for you, this rule may not be as useful for you.
Related To
consistent-type-imports
import/consistent-type-specifier-style
import/no-duplicates
with{"prefer-inline": true}