fix(ConfigManager): Resolve ESM import exception on Windows

import(path) does not accept absolute Windows-paths since those seem to
get confused with URLs.

Before, this was mitigated by always calculating a relative path
(relative to the UI5 linter install directory). This however breaks on
Windows if the target project is located on another drive as reported in
#458

Instead convert all paths to "file://"-URLs before passing them to
import().

Also, in linter.ts, enforce the project root path to always be absolute
to simplify handling the path later on.

Resolves #458

src/linter/linter.ts

@@ -14,6 +14,9 @@ import {Minimatch} from "minimatch";
 export async function lintProject({
 	rootDir, filePatterns, ignorePatterns, coverage, details, configPath, ui5Config, noConfig,
 }: LinterOptions): Promise<LintResult[]> {
+	if (!path.isAbsolute(rootDir)) {
+		throw new Error(`rootDir must be an absolute path. Received: ${rootDir}`);
+	}
 	let config: UI5LintConfigType = {};
 	if (noConfig !== true) {
 		const configMngr = new ConfigManager(rootDir, configPath);

src/utils/ConfigManager.ts

@@ -1,5 +1,5 @@
 import path, {dirname} from "node:path";
-import {fileURLToPath} from "node:url";
+import {fileURLToPath, pathToFileURL} from "node:url";
 import {FilePattern} from "../linter/LinterContext.js";
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
@@ -28,22 +28,16 @@ export default class ConfigManager {
 	}
 
 	#resolveModulePaths(fileName: string): string {
-		// Node on Windows behaves strange, does not work with absolute paths
-		// and modifies files extensions in tests i.e. js -> ts, mjs -> tjs
-		// Keeping the relative path in POSIX format resolves those issues.
-		return path.posix.join(
-			path.relative(__dirname, this.#projectRootDir).replaceAll(path.win32.sep, path.posix.sep),
-			fileName);
+		const resolvedPath = path.join(this.#projectRootDir, fileName);
+		return pathToFileURL(resolvedPath).toString();
 	}
 
 	async getConfiguration(): Promise<UI5LintConfigType> {
 		let config = {} as UI5LintConfigType;
 
 		if (this.#configFile) {
 			// If it's an relative path, transform to POSIX format
-			const configFilePath = path.isAbsolute(this.#configFile) ?
-				this.#configFile :
-					this.#resolveModulePaths(this.#configFile);
+			const configFilePath = this.#resolveModulePaths(this.#configFile);
 
 			({default: config} = await import(configFilePath) as {default: UI5LintConfigType});
 		} else {

test/lib/linter/linter.ts

@@ -424,3 +424,18 @@ test.serial("lint: getProjectGraph with different directory structures", async (
 		},
 	});
 });
+
+// Test project fixtures individually
+test.serial("lint: Relative rootDir path throws an exception", async (t) => {
+	const projectPath = path.join(fixturesProjectsPath, "com.ui5.troublesome.app");
+	const {lintProject} = t.context;
+
+	await t.throwsAsync(() => {
+		return lintProject({
+			rootDir: path.relative(__dirname, projectPath),
+			filePatterns: [],
+			coverage: true,
+			details: true,
+		});
+	});
+});

test/lib/utils/configManager.ts → test/lib/utils/ConfigManager.ts

@@ -9,7 +9,8 @@ const fixturesBasePath = path.join(__dirname, "..", "..", "fixtures", "linter");
 const fixturesProjectsPath = path.join(fixturesBasePath, "projects");
 
 test("Check config file", async (t) => {
-	const confManager = new ConfigManager("./test/fixtures/linter/projects/com.ui5.troublesome.app/",
+	const confManager = new ConfigManager(
+		path.join(fixturesProjectsPath, "com.ui5.troublesome.app"),
 		"ui5lint-custom.config.cjs");
 
 	const config = await confManager.getConfiguration();
@@ -24,7 +25,8 @@ test("Check config file", async (t) => {
 });
 
 test("Check config file auto discovery", async (t) => {
-	const confManager = new ConfigManager("./test/fixtures/linter/projects/com.ui5.troublesome.app/");
+	const confManager = new ConfigManager(
+		path.join(fixturesProjectsPath, "com.ui5.troublesome.app"));
 
 	const config = await confManager.getConfiguration();
 
@@ -48,7 +50,7 @@ test("Throws an error if config file has Syntax errors", async (t) => {
 
 test("Resolves to an empty config if default module is not found", async (t) => {
 	const confManager = new ConfigManager(
-		"./test/fixtures/linter/projects/library.with.custom.paths/");
+		path.join(fixturesProjectsPath, "library.with.custom.paths/"));
 
 	const config = await confManager.getConfiguration();