feat: new nonRelative option for resolving non-relative paths (#13)

If enabled, the plugin will resolve non-relative paths based on tsconfig's `baseUrl`, even if none of the `paths` are matched.

Closes #12.

Author: simonhaenisch

index.ts

@@ -3,28 +3,37 @@ import { Plugin } from 'rollup';
 import { CompilerOptions, findConfigFile, nodeModuleNameResolver, parseConfigFileTextToJson, sys } from 'typescript';
 
 export const typescriptPaths = ({
-	tsConfigPath = findConfigFile('./', sys.fileExists),
 	absolute = true,
-	transform,
+	nonRelative = false,
 	preserveExtensions = false,
+	tsConfigPath = findConfigFile('./', sys.fileExists),
+	transform,
 }: Options = {}): Plugin => {
 	const { compilerOptions, outDir } = getTsConfig(tsConfigPath);
 
 	return {
 		name: 'resolve-typescript-paths',
 		resolveId: (importee: string, importer?: string) => {
-			if (typeof importer === 'undefined' || importee.startsWith('\0') || !compilerOptions.paths) {
+			const enabled = Boolean(compilerOptions.paths || (compilerOptions.baseUrl && nonRelative));
+
+			if (typeof importer === 'undefined' || importee.startsWith('\0') || !enabled) {
 				return null;
 			}
 
-			const hasMatchingPath = Object.keys(compilerOptions.paths).some((path) =>
-				new RegExp('^' + path.replace('*', '.+') + '$').test(importee),
-			);
+			const hasMatchingPath =
+				!!compilerOptions.paths &&
+				Object.keys(compilerOptions.paths).some((path) =>
+					new RegExp('^' + path.replace('*', '.+') + '$').test(importee),
+				);
 
-			if (!hasMatchingPath) {
+			if (!hasMatchingPath && !nonRelative) {
 				return null;
 			}
 
+			if (importee.startsWith('.')) {
+				return null; // never resolve relative modules, only non-relative
+			}
+
 			const { resolvedModule } = nodeModuleNameResolver(importee, importer, compilerOptions, sys);
 
 			if (!resolvedModule) {
@@ -73,6 +82,15 @@ export interface Options {
 	 */
 	absolute?: boolean;
 
+	/**
+	 * Whether to resolve non-relative paths based on tsconfig's `baseUrl`, even
+	 * if none of the `paths` are matched; defaults to `false`.
+	 *
+	 * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#relative-vs-non-relative-module-imports
+	 * @see https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url
+	 */
+	nonRelative?: boolean;
+
 	/**
 	 * Whether to preserve `.ts` and `.tsx` file extensions instead of having them
 	 * changed to `.js`; defaults to `false`.

test/index.js

@@ -10,6 +10,8 @@ const plugin = typescriptPaths({ tsConfigPath: resolve(__dirname, 'tsconfig.json
 
 const pluginNonAbs = typescriptPaths({ tsConfigPath: resolve(__dirname, 'tsconfig.json'), absolute: false });
 
+const pluginNonRelative = typescriptPaths({ tsConfigPath: resolve(__dirname, 'tsconfig.json'), nonRelative: true });
+
 const pluginTransform = typescriptPaths({ tsConfigPath: resolve(__dirname, 'tsconfig.json'), transform });
 
 const pluginPreserveExtensions = typescriptPaths({
@@ -46,6 +48,12 @@ try {
 	// doesn't accidentally resolve relative paths that also have an alias
 	strictEqual(plugin.resolveId('../bar/foo', join(__dirname, 'foo', 'bar.ts')), null);
 
+	// skips non-relative paths unless enabled
+	strictEqual(plugin.resolveId('foo/bar', ''), null);
+
+	// resolves non-relative from baseUrl even if no path is matched
+	strictEqual(pluginNonRelative.resolveId('foo/bar', ''), join(__dirname, 'foo', 'bar.js'));
+
 	// resolves as a relative path with option `absolute: false`
 	strictEqual(pluginNonAbs.resolveId('@foobar', ''), join('test', 'foo', 'bar.js'));