xo/dist/lib/xo-to-eslint.js

JavaScript/TypeScript linter (ESLint wrapper) with great defaults

/* eslint-disable complexity -- Translating every XO config option into ESLint rules is inherently branchy. */
import arrify from 'arrify';
import { getPrettierConfig } from 'eslint-config-xo';
import { config } from './config.js';
import { xoToEslintConfigItem } from './utils.js';
/**
Merge all plugins from every config into a single config entry at the start of the array, ensuring user-provided plugins take precedence. This avoids ESLint's flat config rejecting duplicate plugin names.
*/
const hoistPlugins = (configs, userPluginOverrides) => {
    const plugins = {};
    const configsWithoutPlugins = [];
    for (const configItem of configs) {
        const { plugins: configPlugins } = configItem;
        if (!configPlugins) {
            configsWithoutPlugins.push(configItem);
            continue;
        }
        // ESLint flat config rejects duplicate plugin names, so merge all plugins into one config.
        Object.assign(plugins, configPlugins);
        const { plugins: _ignored, ...configWithoutPlugins } = configItem;
        if (Object.keys(configWithoutPlugins).length > 0) {
            configsWithoutPlugins.push(configWithoutPlugins);
        }
    }
    for (const [pluginName, plugin] of userPluginOverrides) {
        plugins[pluginName] = plugin;
    }
    if (Object.keys(plugins).length === 0) {
        return configsWithoutPlugins;
    }
    return [
        {
            name: 'xo/plugins',
            plugins,
        },
        ...configsWithoutPlugins,
    ];
};
/**
Takes an XO flat config and returns an ESLint flat config.
*/
export function xoToEslintConfig(flatXoConfig) {
    const baseConfig = [...config];
    const userPluginOverrides = new Map();
    for (const xoConfigItem of flatXoConfig ?? []) {
        const { plugins } = xoConfigItem;
        if (!plugins) {
            continue;
        }
        for (const [pluginName, plugin] of Object.entries(plugins)) {
            userPluginOverrides.set(pluginName, plugin);
        }
    }
    /**
    Since configs are merged and the last config takes precedence this means we need to handle both true AND false cases for each option. For example, we need to turn `prettier`, `space`, `semi`, etc. on or off for a specific file.
    */
    for (const xoConfigItem of flatXoConfig ?? []) {
        const keysOfXoConfig = Object.keys(xoConfigItem);
        if (keysOfXoConfig.length === 0) {
            continue;
        }
        /** Special case global ignores */
        if (xoConfigItem.ignores !== undefined) {
            if (keysOfXoConfig.length === 1) {
                baseConfig.push({ ignores: arrify(xoConfigItem.ignores) });
                continue;
            }
            if (keysOfXoConfig.length === 2 && xoConfigItem.name !== undefined) {
                baseConfig.push({ name: xoConfigItem.name, ignores: arrify(xoConfigItem.ignores) });
                continue;
            }
        }
        /**
        An ESLint config item derived from the XO config item with rules and files initialized.
        */
        const eslintConfigItem = xoToEslintConfigItem(xoConfigItem);
        const isUsingSpaces = Boolean(xoConfigItem.space);
        if (xoConfigItem.semicolon === false) {
            eslintConfigItem.rules ??= {};
            eslintConfigItem.rules['@stylistic/semi'] = ['error', 'never'];
            eslintConfigItem.rules['@stylistic/semi-spacing'] = ['error', { before: false, after: true }];
            eslintConfigItem.rules['@stylistic/member-delimiter-style'] = [
                'error',
                {
                    multiline: { delimiter: 'none' },
                    singleline: { delimiter: 'comma', requireLast: false },
                },
            ];
        }
        if (isUsingSpaces) {
            const spaces = typeof xoConfigItem.space === 'number' ? xoConfigItem.space : 2;
            eslintConfigItem.rules ??= {};
            eslintConfigItem.rules['@stylistic/indent'] = ['error', spaces, { SwitchCase: 1 }]; // eslint-disable-line @typescript-eslint/naming-convention
            eslintConfigItem.rules['@stylistic/indent-binary-ops'] = ['error', spaces];
        }
        else if (xoConfigItem.space === false) {
            eslintConfigItem.rules ??= {};
            eslintConfigItem.rules['@stylistic/indent'] = ['error', 'tab', { SwitchCase: 1 }]; // eslint-disable-line @typescript-eslint/naming-convention
            eslintConfigItem.rules['@stylistic/indent-binary-ops'] = ['error', 'tab'];
        }
        // Delegate Prettier integration to `eslint-config-xo`. Its config is pushed after `eslintConfigItem` below so it comes last, disabling the conflicting stylistic rules set above.
        const prettierConfig = getPrettierConfig({
            prettier: xoConfigItem.prettier,
            // `Space` allows `string` for legacy reasons, but Prettier only needs `boolean | number`.
            space: xoConfigItem.space,
            semicolon: xoConfigItem.semicolon,
            files: eslintConfigItem.files,
        });
        if (xoConfigItem.prettier === false) {
            // Turn Prettier off for a subset of files
            eslintConfigItem.rules ??= {};
            eslintConfigItem.rules['prettier/prettier'] = 'off';
        }
        if (Object.keys(eslintConfigItem).length > 0) {
            baseConfig.push(eslintConfigItem);
        }
        if (prettierConfig) {
            baseConfig.push(prettierConfig);
        }
    }
    // User plugins should always win, even if XO injects plugins later in the config list.
    return hoistPlugins(baseConfig, userPluginOverrides);
}
export default xoToEslintConfig;
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