no-anonymous-default-export.js

import { test, testVersion, SYNTAX_CASES } from '../utils';

import { RuleTester } from 'eslint';

const ruleTester = new RuleTester();
const rule = require('rules/no-anonymous-default-export');

ruleTester.run('no-anonymous-default-export', rule, {
  valid: [].concat(
    // Exports with identifiers are valid
    test({ code: 'const foo = 123\nexport default foo' }),
    test({ code: 'export default function foo() {}' }),
    test({ code: 'export default class MyClass {}' }),

    // Allow each forbidden type with appropriate option
    test({ code: 'export default []', options: [{ allowArray: true }] }),
    test({ code: 'export default () => {}', options: [{ allowArrowFunction: true }] }),
    test({ code: 'export default class {}', options: [{ allowAnonymousClass: true }] }),
    test({ code: 'export default function() {}', options: [{ allowAnonymousFunction: true }] }),
    test({ code: 'export default 123', options: [{ allowLiteral: true }] }),
    test({ code: 'export default \'foo\'', options: [{ allowLiteral: true }] }),
    test({ code: 'export default `foo`', options: [{ allowLiteral: true }] }),
    test({ code: 'export default {}', options: [{ allowObject: true }] }),
    test({ code: 'export default foo(bar)', options: [{ allowCallExpression: true }] }),
    test({ code: 'export default new Foo()', options: [{ allowNew: true }] }),

    // Allow forbidden types with multiple options
    test({ code: 'export default 123', options: [{ allowLiteral: true, allowObject: true }] }),
    test({ code: 'export default {}', options: [{ allowLiteral: true, allowObject: true }] }),

    // Sanity check unrelated export syntaxes
    test({ code: 'export * from \'foo\'' }),
    test({ code: 'const foo = 123\nexport { foo }' }),
    test({ code: 'const foo = 123\nexport { foo as default }' }),
    // es2022: Arbitrary module namespace identifier names
    testVersion('>= 8.7', () => ({
      code: 'const foo = 123\nexport { foo as "default" }',
      parserOptions: { ecmaVersion: 2022 },
    })),

    // Allow call expressions by default for backwards compatibility
    test({ code: 'export default foo(bar)' }),

    ...SYNTAX_CASES,
  ),

  invalid: [
    test({ code: 'export default []', errors: [{ message: 'Assign array to a variable before exporting as module default' }] }),
    test({ code: 'export default () => {}', errors: [{ message: 'Assign arrow function to a variable before exporting as module default' }] }),
    test({ code: 'export default class {}', errors: [{ message: 'Unexpected default export of anonymous class' }] }),
    test({ code: 'export default function() {}', errors: [{ message: 'Unexpected default export of anonymous function' }] }),
    test({ code: 'export default 123', errors: [{ message: 'Assign literal to a variable before exporting as module default' }] }),
    test({ code: 'export default \'foo\'', errors: [{ message: 'Assign literal to a variable before exporting as module default' }] }),
    test({ code: 'export default `foo`', errors: [{ message: 'Assign literal to a variable before exporting as module default' }] }),
    test({ code: 'export default {}', errors: [{ message: 'Assign object to a variable before exporting as module default' }] }),
    test({ code: 'export default foo(bar)', options: [{ allowCallExpression: false }], errors: [{ message: 'Assign call result to a variable before exporting as module default' }] }),
    test({ code: 'export default new Foo()', errors: [{ message: 'Assign instance to a variable before exporting as module default' }] }),

    // Test failure with non-covering exception
    test({ code: 'export default 123', options: [{ allowObject: true }], errors: [{ message: 'Assign literal to a variable before exporting as module default' }] }),
  ],
});