load-config.ts

import { existsSync, readFileSync } from "node:fs";
import path from "node:path";

import {
	cosmiconfig,
	defaultLoadersSync,
	type Loader,
	defaultLoaders,
} from "cosmiconfig";
import { TypeScriptLoader } from "cosmiconfig-typescript-loader";

export interface LoadConfigResult {
	config: unknown;
	filepath: string;
	isEmpty?: boolean;
}

const moduleName = "commitlint";
const searchStrategy = "global";

export async function loadConfig(
	cwd: string,
	configPath?: string
): Promise<LoadConfigResult | null> {
	let tsLoaderInstance: Loader | undefined;
	const tsLoader: Loader = (...args) => {
		if (!tsLoaderInstance) {
			tsLoaderInstance = TypeScriptLoader();
		}
		return tsLoaderInstance(...args);
	};

	// If dynamic await is supported (Node >= v20.8.0) or directory uses ESM, support
	// async js/cjs loaders (dynamic import). Otherwise, use synchronous js/cjs loaders.
	const loaders =
		isDynamicAwaitSupported() || isEsmModule(cwd)
			? defaultLoaders
			: defaultLoadersSync;

	const explorer = cosmiconfig(moduleName, {
		searchStrategy,
		searchPlaces: [
			// cosmiconfig overrides default searchPlaces if any new search place is added (For e.g. `*.ts` files),
			// we need to manually merge default searchPlaces from https://github.com/davidtheclark/cosmiconfig#searchplaces
			"deno.json",
			"package.json",
			"package.yaml",
			`.${moduleName}rc`,
			`.${moduleName}rc.json`,
			`.${moduleName}rc.yaml`,
			`.${moduleName}rc.yml`,
			`.${moduleName}rc.js`,
			`.${moduleName}rc.cjs`,
			`.${moduleName}rc.mjs`,
			`${moduleName}.config.js`,
			`${moduleName}.config.cjs`,
			`${moduleName}.config.mjs`,

			// files supported by TypescriptLoader
			`.${moduleName}rc.ts`,
			`.${moduleName}rc.cts`,
			`${moduleName}.config.ts`,
			`${moduleName}.config.cts`,
		],
		loaders: {
			".ts": tsLoader,
			".cts": tsLoader,
			".cjs": loaders[".cjs"],
			".js": loaders[".js"],
		},
	});

	const explicitPath = configPath ? path.resolve(cwd, configPath) : undefined;
	const explore = explicitPath ? explorer.load : explorer.search;
	const searchPath = explicitPath ? explicitPath : cwd;
	const local = await explore(searchPath);

	if (local) {
		return local;
	}

	return null;
}

// See the following issues for more context, contributing to failing Jest tests:
//  - Issue: https://github.com/nodejs/node/issues/40058
//  - Resolution: https://github.com/nodejs/node/pull/48510 (Node v20.8.0)
export const isDynamicAwaitSupported = () => {
	const [major, minor] = process.version
		.replace("v", "")
		.split(".")
		.map((val) => parseInt(val));

	return major >= 20 && minor >= 8;
};

// Is the given directory set up to use ESM (ECMAScript Modules)?
export const isEsmModule = (cwd: string) => {
	const packagePath = path.join(cwd, "package.json");

	if (!existsSync(packagePath)) {
		return false;
	}

	const packageJSON = readFileSync(packagePath, { encoding: "utf-8" });
	return (
		JSON.parse(packageJSON)?.type === "module" ||
		existsSync(path.join(cwd, "deno.json"))
	);
};