feat: ✨ write and manipulate eslint.config.js files

packages/cli/package.json

@@ -37,6 +37,7 @@
 		"yaml": "^2.3.1"
 	},
 	"devDependencies": {
+		"@types/estree": "^1.0.1",
 		"@types/node": "^20.4.2",
 		"@types/prompts": "^2.4.4"
 	}

packages/cli/src/cli.js

@@ -84,7 +84,11 @@ export default class Cli {
 
 		console.log(packages[0].config);
 
-		packages.map(pkg => {pkg.configFile = writer.generateFileObj(pkg); return pkg;});
+		packages.map(async pkg => {
+			pkg.configFile = writer.generateObj(pkg);
+			console.log(await writer.write(pkg.configFile));
+			return pkg;
+		});
 
 	}
 

packages/cli/src/configsWriter.js

@@ -1,6 +1,8 @@
 import path from 'node:path';
-import {} from 'recast';
 import notNull from './lib/notNull.js';
+import * as recast from 'recast';
+import fs from 'node:fs/promises';
+import { existsSync } from 'node:fs';
 
 /**
  * @param {import('./types').ConfigFile['imports']} map1 - The map to has it values merged from map2
@@ -68,7 +70,7 @@ export default class ConfigsWriter {
 	 * @param {import('./types').Package} pkg The package to generate the config string from
 	 * @returns {import('./types').ConfigFile} The config file object
 	 */
-	generateFileObj(pkg) {
+	generateObj(pkg) {
 		/** @type {import('./types').ConfigFile} */
 		const configObj = {
 			path: path.join(pkg.path, 'eslint.config.js'),
@@ -118,9 +120,175 @@ export default class ConfigsWriter {
 
 		}
 
-		console.log(configObj);
-
 		return configObj;
 	}
 
+	/**
+	 * ! NOTE:
+	 * These functions declared bellow are notably hard to read and have lots of exceptions and
+	 * disabled eslint and typescript checks. Unfortunately this is something that I wasn't able to
+	 * prevent because a lot of the AST typescript types are somewhat wrong or simply hard to work
+	 * with them.
+	 *
+	 * But for somewhat help developing and prevent unwanted errors in the future, the types and eslint
+	 * errors are explicitly disabled and types are explicitly overridden. This is why there are so
+	 * many JSDoc type annotations and comments in general.
+	 *
+	 * Any help to make this code more readable and robust is appreciated
+	 */
+
+	/**
+	 * @param {import('./types').ConfigFile['configs']} configs The configs objects defined in the config file
+	 * @returns {(import('estree').MemberExpression | import('estree').Identifier | import('estree').CallExpression)[]}
+	 * The ast expressions nodes to be printed
+	 */
+	createConfigExpressions(configs) {
+		return configs
+			.map(c => {
+				/** @type {import('estree').MemberExpression | import('estree').Identifier | import('estree').CallExpression} */
+				// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access
+				const e = recast.parse(c).program.body[0].expression; return e;
+			})
+			.filter(e => ['MemberExpression', 'Identifier', 'CallExpression'].includes(e.type));
+	}
+
+	/**
+	 * @param {import('./types').ConfigFile['presets']} presets The presets objects defined in the config file
+	 * @returns {import('estree').SpreadElement[]}
+	 * The ast expressions nodes to be printed
+	 */
+	createPresetExpressions(presets) {
+		return presets
+			.map(p => {
+				/** @type {import('estree').MemberExpression | import('estree').Identifier | import('estree').CallExpression} */
+				// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access
+				const e = recast.parse(p).program.body[0].expression; return e;
+			})
+			.filter(e => ['MemberExpression', 'Identifier', 'CallExpression'].includes(e.type))
+			.map(e => {
+				/** @type {import('estree').SpreadElement} */
+				const spreadElement = {
+					type: 'SpreadElement',
+					argument: e,
+				};
+				return spreadElement;
+			});
+	}
+
+	/**
+	 * @param {import('./types').ConfigFile['rules']} rules The rules objects defined in the config file
+	 * @returns {import('estree').ObjectExpression}
+	 * The ast object expression nodes to be printed
+	 */
+	createRulesExpression(rules) {
+		/** @type {import('estree').ObjectExpression} */
+		const rulesObjectExpression = rules
+			.map(r => {
+				/** @type {import('estree').MemberExpression | import('estree').Identifier | import('estree').CallExpression} */
+				// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access
+				const e = recast.parse(r).program.body[0].expression; return e;
+			})
+			.filter(e => ['MemberExpression', 'Identifier', 'CallExpression'].includes(e.type))
+			.map(e => {
+				/** @type {import('estree').SpreadElement} */
+				const spreadElement = {
+					type: 'SpreadElement',
+					argument: e,
+				};
+				return spreadElement;
+			}).reduce((acc, spreadElement) => {
+				acc.properties.push(spreadElement);
+				return acc;
+			}, {
+				/** @type {import('estree').ObjectExpression['type']} */
+				type: 'ObjectExpression',
+				/** @type {import('estree').ObjectExpression['properties']} */
+				properties: [],
+			});
+		/** @type {import('estree').ObjectExpression} */
+		const rulesExpression = {
+			type: 'ObjectExpression',
+			properties: [{
+				// @ts-expect-error because ObjectProperty doesn't exist in estree types
+				type: 'ObjectProperty',
+				key: { type: 'Identifier', name: 'rules' },
+				value: rulesObjectExpression,
+			}],
+		};
+		return rulesExpression;
+	}
+
+	/**
+	 * @param {import('./types').ConfigFile} config The config file object to be transformed into a eslint.config.js file
+	 * @returns {Promise<void>}
+	 */
+	async write(config) {
+
+		const existingConfig = existsSync(config.path) ? await fs.readFile(config.path, 'utf-8') : '';
+
+		/** @type {import('estree').ExportDefaultDeclaration}} */
+		// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
+		const defaultExportTemplate = recast.parse([
+			'/** @type {import(\'eslint\').Linter.FlatConfig[]} */',
+			'export default [',
+			'',
+			'];',
+		].join('\n'), {
+			parser: (await import('recast/parsers/babel.js')),
+		}).program.body.find((/** @type {{ type: string; }} */ n) => n.type === 'ExportDefaultDeclaration');
+
+
+		/** @type {{program: import('estree').Program}} */
+		// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+		const { program: ast } = recast.parse(existingConfig, { parser: (await import('recast/parsers/babel.js')) });
+
+		/** @type {import('estree').ExportDefaultDeclaration | undefined} */
+		// @ts-expect-error because the types don't match, but are expected to be correct here
+		// as the type needs to be ExportDefaultDeclaration
+		let defaultExport = ast.body.find(n => n.type === 'ExportDefaultDeclaration');
+		if (!defaultExport) {
+			defaultExport = defaultExportTemplate;
+		}
+		else if (defaultExport.declaration.type !== 'ArrayExpression') {
+			ast.body.push({
+				type: 'VariableDeclaration',
+				kind: 'const',
+				declarations: [{
+					type: 'VariableDeclarator',
+					id: { type: 'Identifier', name: 'oldConfig' },
+					// @ts-expect-error because defaultExport's declaration is a ArrayExpression
+					init: defaultExport.declaration,
+				}],
+			});
+			defaultExport = defaultExportTemplate;
+			// @ts-expect-error because defaultExport's declaration is a ArrayExpression
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
+			defaultExport.declaration.elements.push({
+				type: 'SpreadElement',
+				argument: { type: 'Identifier', name: 'oldConfig' },
+			});
+		}
+
+		const elementsExpressions = [];
+
+		if (config.presets.length > 0)
+			elementsExpressions.push(...this.createPresetExpressions(config.presets));
+		if (config.configs.length > 0)
+			elementsExpressions.push(...this.createConfigExpressions(config.configs));
+		if (config.rules.length > 0)
+			elementsExpressions.push(this.createRulesExpression(config.rules));
+
+		// @ts-expect-error because defaultExport's declaration is a ArrayExpression
+		// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
+		defaultExport.declaration.elements.push(...elementsExpressions);
+
+		const idx = ast.body.findIndex(n => n.type === 'ExportDefaultDeclaration');
+		if (idx > -1) ast.body.splice(idx, 1);
+		ast.body.push(defaultExport);
+
+		const finalCode = recast.prettyPrint(ast, { parser: (await import('recast/parsers/babel.js')) }).code;
+		console.log(finalCode);
+
+	}
+
 }

pnpm-lock.yaml

@@ -121,6 +121,9 @@ importers:
         specifier: ^2.3.1
         version: 2.3.1
     devDependencies:
+      '@types/estree':
+        specifier: ^1.0.1
+        version: 1.0.1
       '@types/node':
         specifier: ^20.4.2
         version: 20.4.2