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[import/no-duplicates] prefer-inline option should work with Flow #2686

@valscion

Description

@valscion

Hi!

I noticed that the prefer-inline option for import/no-duplicates actively forbids using that option with Flow:

const preferInline = context.options[0] && context.options[0]['prefer-inline'];
// a user might set prefer-inline but not have a supporting TypeScript version. Flow does not support inline types so this should fail in that case as well.
if (preferInline && (!typescriptPkg || !semver.satisfies(typescriptPkg.version, '>= 4.5'))) {
throw new Error('Your version of TypeScript does not support inline type imports.');
}

However, Flow does support inline types (See this Try flow online REPL):

import React, { type Element } from 'react';

function Example(): Element<'div'> {
  return <div>Hello</div>;
}

So we don't need this:

import React from 'react';
import type { Element } from 'react';

function Example(): Element<'div'> {
  return <div>Hello</div>;
}

This is even implemented as explicitly allowed in another rule, import/consinstent-type-specifier-style: https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/consistent-type-specifier-style.md

I spotted this when upgrading from eslint-plugin-import v2.26.0 to v2.27.5 that this old code that works and didn't show lint errors:

import type { Localizable } from 'common/types/locale';
import { localize, localizable } from 'common/types/locale';
import type { FormattedMoney } from 'common/types/money';
import { money, formatMoney, type Money } from 'common/types/money';

Now should be written like this instead:

import type { Localizable } from 'common/types/locale';
import { localize, localizable } from 'common/types/locale';
import {
  money,
  formatMoney,
  type Money,
  type FormattedMoney
} from 'common/types/money';

Notice how the imports from common/types/localeremained the same while the imports from common/types/money showed errors.

  5:37  warning  '/path/to/common/types/money.js' imported multiple times  import/no-duplicates
  6:48  warning  '/path/to/common/types/money.js' imported multiple times  import/no-duplicates

Expected outcome

I'd expect this to work with Flow:

'import/no-duplicates': ['warn', { 'prefer-inline': true }]

Actual outcome

Error:

Your version of TypeScript does not support inline type imports. Occurred while linting /path/to/inquiry/utils/priceRangeToText.js:3

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