fix: fallback directory resolution to module extensions

src/loaders.ts

@@ -69,11 +69,18 @@ async function tryDirectory(
 	context: Context,
 	defaultResolve: resolve,
 ) {
-	const appendIndex = specifier.endsWith('/') ? 'index' : '/index';
+	const isExplicitDirectory = specifier.endsWith('/');
+	const appendIndex = isExplicitDirectory ? 'index' : '/index';
 
 	try {
 		return await tryExtensions(specifier + appendIndex, context, defaultResolve);
 	} catch (error: any) {
+		if (!isExplicitDirectory) {
+			try {
+				return await tryExtensions(specifier, context, defaultResolve);
+			} catch {}
+		}
+
 		const { message } = error;
 		error.message = error.message.replace(`${appendIndex.replace('/', path.sep)}'`, "'");
 		error.stack = error.stack.replace(message, error.message);

tests/fixtures/package-module/lib/esm-ext-js/index/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

tests/fixtures/package-module/lib/json/index/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

tests/fixtures/package-module/lib/ts-ext-jsx/index/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

tests/fixtures/package-module/lib/ts-ext-ts/index/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

tests/fixtures/package-module/lib/ts-ext-tsx/index/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

tests/specs/javascript/esm.ts

@@ -131,6 +131,30 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 					expect(nodeProcess.stdout).toMatch('{"default":1234}');
 				});
 			});
+
+			describe('empty directory should fallback to file', ({ test }) => {
+				const importPath = './lib/esm-ext-js/index';
+
+				test('Load', async () => {
+					const nodeProcess = await node.load(importPath);
+					assertResults(nodeProcess);
+				});
+
+				test('Import', async () => {
+					const nodeProcess = await node.import(importPath);
+					assertResults(nodeProcess);
+					expect(nodeProcess.stdout).toMatch('{"default":1234}');
+				});
+			});
+
+			describe('empty but explicit directory should not fallback to file', ({ test }) => {
+				const importPath = './lib/esm-ext-js/index/';
+
+				test('Import', async () => {
+					const nodeProcess = await node.import(importPath);
+					expect(nodeProcess.stderr).toMatch('ERR_MODULE_NOT_FOUND');
+				});
+			});
 		});
 	});
 });

tests/specs/json.ts

@@ -47,5 +47,29 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 				expect(nodeProcess.stdout).toMatch('{"default":{"loaded":"json"},"loaded":"json"}');
 			});
 		});
+
+		describe('empty directory should fallback to file', ({ test }) => {
+			const importPath = './lib/json/index';
+
+			test('Load', async () => {
+				const nodeProcess = await node.load(importPath);
+				expect(nodeProcess.exitCode).toBe(0);
+				expect(nodeProcess.stdout).toBe('');
+			});
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				expect(nodeProcess.stdout).toMatch('{"default":{"loaded":"json"},"loaded":"json"}');
+			});
+		});
+
+		describe('empty but explicit directory should not fallback to file', ({ test }) => {
+			const importPath = './lib/json/index/';
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				expect(nodeProcess.stderr).toMatch('ERR_MODULE_NOT_FOUND');
+			});
+		});
 	});
 });

tests/specs/typescript/jsx.ts

@@ -63,5 +63,29 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 				expect(nodeProcess.stdout).toMatch('{"default":["div",null,"hello world"]}');
 			});
 		});
+
+		describe('empty directory should fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-jsx/index';
+
+			test('Load', async () => {
+				const nodeProcess = await node.load(importPath);
+				assertResults(nodeProcess.stdout);
+			});
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				assertResults(nodeProcess.stdout);
+				expect(nodeProcess.stdout).toMatch('{"default":["div",null,"hello world"]}');
+			});
+		});
+
+		describe('empty but explicit directory should not fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-jsx/index/';
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				expect(nodeProcess.stderr).toMatch('ERR_MODULE_NOT_FOUND');
+			});
+		});
 	});
 });

tests/specs/typescript/ts.ts

@@ -103,5 +103,29 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 				expect(nodeProcess.stdout).toMatch('{"default":1234}');
 			});
 		});
+
+		describe('empty directory should fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-ts/index';
+
+			test('Load', async () => {
+				const nodeProcess = await node.load(importPath);
+				assertResults(nodeProcess.stdout);
+			});
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				assertResults(nodeProcess.stdout);
+				expect(nodeProcess.stdout).toMatch('{"default":1234}');
+			});
+		});
+
+		describe('empty but explicit directory should not fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-ts/index/';
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				expect(nodeProcess.stderr).toMatch('ERR_MODULE_NOT_FOUND');
+			});
+		});
 	});
 });

tests/specs/typescript/tsx.ts

@@ -63,5 +63,29 @@ export default testSuite(async ({ describe }, node: NodeApis) => {
 				expect(nodeProcess.stdout).toMatch('{"default":["div",null,"hello world"]}');
 			});
 		});
+
+		describe('empty directory should fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-tsx/index';
+
+			test('Load', async () => {
+				const nodeProcess = await node.load(importPath);
+				assertResults(nodeProcess.stdout);
+			});
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				assertResults(nodeProcess.stdout);
+				expect(nodeProcess.stdout).toMatch('{"default":["div",null,"hello world"]}');
+			});
+		});
+
+		describe('empty but explicit directory should not fallback to file', ({ test }) => {
+			const importPath = './lib/ts-ext-tsx/index/';
+
+			test('Import', async () => {
+				const nodeProcess = await node.import(importPath);
+				expect(nodeProcess.stderr).toMatch('ERR_MODULE_NOT_FOUND');
+			});
+		});
 	});
 });