From de900a196a5a66f5363f40fd6d38b879aee96875 Mon Sep 17 00:00:00 2001
From: Hiroki Osame <hiroki.osame@gmail.com>
Date: Fri, 7 Jun 2024 09:48:31 +0900
Subject: [PATCH] fix(esm): resolve implicit ts paths in packages

---
 src/esm/hook/resolve.ts | 5 ++++-
 src/utils/path-utils.ts | 3 +++
 tests/fixtures.ts       | 2 ++
 tests/specs/smoke.ts    | 4 +++-
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/esm/hook/resolve.ts b/src/esm/hook/resolve.ts
index 167390d76..7a1959b81 100644
--- a/src/esm/hook/resolve.ts
+++ b/src/esm/hook/resolve.ts
@@ -12,6 +12,7 @@ import {
 	fileUrlPrefix,
 	tsExtensionsPattern,
 	isDirectoryPattern,
+	isBarePackageName,
 } from '../../utils/path-utils.js';
 import {
 	getFormatFromFileUrl,
@@ -160,12 +161,14 @@ export const resolve: resolve = async (
 	// If `allowJs` is set in `tsconfig.json`, then we'll apply the same resolution logic
 	// to files without a TypeScript extension.
 	if (
-		acceptsQuery // file path
+		// Ignore if it's a bare package name and there's no subpath
+		!isBarePackageName.test(specifier)
 		&& (
 			tsExtensionsPattern.test(context.parentURL!)
 			|| allowJs
 		)
 	) {
+		// TODO: When guessing the .ts extension in a package, should it guess if there's an export map?
 		const tsPaths = resolveTsPath(specifier);
 		if (tsPaths) {
 			for (const tsPath of tsPaths) {
diff --git a/src/utils/path-utils.ts b/src/utils/path-utils.ts
index 68a5a1813..1f26e5916 100644
--- a/src/utils/path-utils.ts
+++ b/src/utils/path-utils.ts
@@ -51,3 +51,6 @@ export const tsExtensionsPattern = /\.([cm]?ts|[tj]sx)($|\?)/;
 export const isJsonPattern = /\.json($|\?)/;
 
 export const isDirectoryPattern = /\/(?:$|\?)/;
+
+// Only matches packages names without subpaths (e.g. `foo` but not `foo/bar`)
+export const isBarePackageName = /^(?:@[^/]+\/)?[^/]+$/;
diff --git a/tests/fixtures.ts b/tests/fixtures.ts
index beed9c0f0..1963c3250 100644
--- a/tests/fixtures.ts
+++ b/tests/fixtures.ts
@@ -256,6 +256,7 @@ export const files = {
 				type: 'commonjs',
 			}),
 			'index.js': syntaxLowering,
+			'ts.ts': syntaxLowering,
 		},
 		'pkg-module': {
 			'package.json': createPackageJson({
@@ -263,6 +264,7 @@ export const files = {
 				main: './index.js',
 			}),
 			'index.js': `${syntaxLowering}\nexport * from "./empty-export"`,
+			'ts.ts': syntaxLowering,
 			'empty-export/index.js': 'export {}',
 		},
 	},
diff --git a/tests/specs/smoke.ts b/tests/specs/smoke.ts
index 5c7a3c900..b5b6dfeaa 100644
--- a/tests/specs/smoke.ts
+++ b/tests/specs/smoke.ts
@@ -186,7 +186,9 @@ export default testSuite(async ({ describe }, { tsx, supports }: NodeApis) => {
 						import * as pkgCommonjs from 'pkg-commonjs';
 						import * as pkgModule from 'pkg-module';
 
-						// TODO: Test resolving TS files in dependencies (e.g. implicit extensions & export maps)
+						// Resolving TS files in dependencies (e.g. implicit extensions & export maps)
+						import 'pkg-commonjs/ts.js';
+						import 'pkg-module/ts.js';
 
 						// .js
 						import * as js from './js/index.js';