From edf5464e576ba80884beb956d61dd5c1c347224c Mon Sep 17 00:00:00 2001
From: Jiachi Liu <inbox@huozhi.im>
Date: Sat, 7 Oct 2023 01:06:46 +0200
Subject: [PATCH] Error on invalid main field export (#271)

---
 src/exports.ts                                        | 6 +++++-
 src/lib/wildcard.ts                                   | 3 ++-
 src/utils.ts                                          | 3 +++
 test/integration.test.ts                              | 9 +++++++++
 test/integration/esm-pkg-cjs-main-field/package.json  | 4 ++++
 test/integration/esm-pkg-cjs-main-field/src/index.cjs | 1 +
 6 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 test/integration/esm-pkg-cjs-main-field/package.json
 create mode 100644 test/integration/esm-pkg-cjs-main-field/src/index.cjs

diff --git a/src/exports.ts b/src/exports.ts
index f803af5c..04539cae 100644
--- a/src/exports.ts
+++ b/src/exports.ts
@@ -6,7 +6,7 @@ import type {
   PackageType,
   ParsedExportCondition,
 } from './types'
-import { filenameWithoutExtension } from './utils'
+import { exit, filenameWithoutExtension, hasCjsExtension } from './utils'
 
 export function getTypings(pkg: PackageMetadata) {
   return pkg.types || pkg.typings
@@ -185,6 +185,10 @@ export function getExportPaths(
     Object.assign(pathsMap, paths)
   }
 
+  if (!isCjsPackage && pkg.main && hasCjsExtension(pkg.main)) {
+    exit('Cannot export main field with .cjs extension in ESM package, only .mjs and .js extensions are allowed')
+  }
+
   // main export '.' from main/module/typings
   const defaultMainExport = constructFullExportCondition(
     {
diff --git a/src/lib/wildcard.ts b/src/lib/wildcard.ts
index 43aa8f8f..ddeba9e8 100644
--- a/src/lib/wildcard.ts
+++ b/src/lib/wildcard.ts
@@ -8,6 +8,7 @@ import {
   hasAvailableExtension,
   nonNullable,
 } from '../utils'
+import { logger } from '../logger'
 
 // TODO: support nested wildcard exportsCondition (e.g. './foo/*')
 const getWildcardExports = (
@@ -84,7 +85,7 @@ export async function resolveWildcardExports(
   const hasWildcard = !!exportsCondition['./*']
 
   if (hasWildcard) {
-    console.warn(
+    logger.warn(
       `The wildcard export "./*" is experimental and may change or be removed at any time.\n` +
         'To open an issue, please visit https://github.com/huozhi/bunchee/issues' +
         '.\n',
diff --git a/src/utils.ts b/src/utils.ts
index 98de707c..c2cc78ae 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -139,3 +139,6 @@ export const fileExtension = (file: string | undefined) =>
 
 export const hasAvailableExtension = (filename: string): boolean =>
   availableExtensions.includes(path.extname(filename).slice(1))
+
+export const hasCjsExtension = (filename: string): boolean =>
+  path.extname(filename) === '.cjs'
\ No newline at end of file
diff --git a/test/integration.test.ts b/test/integration.test.ts
index 3e1ceaf5..5a2175ee 100644
--- a/test/integration.test.ts
+++ b/test/integration.test.ts
@@ -284,6 +284,15 @@ const testCases: {
       expect(stderr).toContain(log)
     },
   },
+  {
+    name: 'esm-pkg-cjs-main-field',
+    args: [],
+    async expected(_, { stderr }) {
+      expect(stderr).toContain(
+        'Cannot export main field with .cjs extension in ESM package, only .mjs and .js extensions are allowed',
+      )
+    }
+  }
 ]
 
 async function runBundle(
diff --git a/test/integration/esm-pkg-cjs-main-field/package.json b/test/integration/esm-pkg-cjs-main-field/package.json
new file mode 100644
index 00000000..1bd141ab
--- /dev/null
+++ b/test/integration/esm-pkg-cjs-main-field/package.json
@@ -0,0 +1,4 @@
+{
+  "type": "module",
+  "main": "./dist/index.cjs"
+}
\ No newline at end of file
diff --git a/test/integration/esm-pkg-cjs-main-field/src/index.cjs b/test/integration/esm-pkg-cjs-main-field/src/index.cjs
new file mode 100644
index 00000000..41984bc0
--- /dev/null
+++ b/test/integration/esm-pkg-cjs-main-field/src/index.cjs
@@ -0,0 +1 @@
+exports.value = 'cjs'