feat(exports)!: add legacy option, remove main & module fields if pure ESM

Author: sxzz

dts.snapshot.json

@@ -27,7 +27,7 @@
     "CopyOptionsFn": "type CopyOptionsFn = (_: ResolvedConfig) => Awaitable<CopyOptions>",
     "CssOptions": "interface CssOptions {\n splitting?: boolean\n fileName?: string\n}",
     "DevtoolsOptions": "interface DevtoolsOptions extends NonNullable<InputOptions['devtools']> {\n ui?: boolean | Partial<StartOptions>\n clean?: boolean\n}",
-    "ExportsOptions": "interface ExportsOptions {\n devExports?: boolean | string\n packageJson?: boolean\n all?: boolean\n exclude?: (RegExp | string)[]\n customExports?: (_: Record<string, any>, _: { pkg: PackageJson; chunks: ChunksByFormat; isPublish: boolean }) => Awaitable<Record<string, any>>\n}",
+    "ExportsOptions": "interface ExportsOptions {\n devExports?: boolean | string\n packageJson?: boolean\n all?: boolean\n exclude?: (RegExp | string)[]\n legacy?: boolean\n customExports?: (_: Record<string, any>, _: { pkg: PackageJson; chunks: ChunksByFormat; isPublish: boolean }) => Awaitable<Record<string, any>>\n}",
     "Format": "type Format = ModuleFormat",
     "globalLogger": "Logger",
     "InlineConfig": "interface InlineConfig extends UserConfig {\n config?: boolean | string\n configLoader?: 'auto' | 'native' | 'unrun'\n filter?: RegExp | Arrayable<string>\n}",

package.json

@@ -23,8 +23,6 @@
     "./package.json": "./package.json",
     "./client": "./client.d.ts"
   },
-  "main": "./dist/index.mjs",
-  "module": "./dist/index.mjs",
   "types": "./dist/index.d.mts",
   "typesVersions": {
     "*": {

packages/create-tsdown/package.json

@@ -20,8 +20,6 @@
     "./run": "./dist/run.mjs",
     "./package.json": "./package.json"
   },
-  "main": "./dist/index.mjs",
-  "module": "./dist/index.mjs",
   "types": "./dist/index.d.mts",
   "typesVersions": {
     "*": {

packages/migrate/package.json

@@ -20,8 +20,6 @@
     "./run": "./dist/run.mjs",
     "./package.json": "./package.json"
   },
-  "main": "./dist/index.mjs",
-  "module": "./dist/index.mjs",
   "types": "./dist/index.d.mts",
   "typesVersions": {
     "*": {

src/features/pkg/exports.test.ts

@@ -52,8 +52,8 @@ describe.concurrent('generateExports', () => {
           ".": "./main.js",
           "./package.json": "./package.json",
         },
-        "main": "./main.js",
-        "module": "./main.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -77,8 +77,8 @@ describe.concurrent('generateExports', () => {
           "./foo": "./foo.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -102,8 +102,8 @@ describe.concurrent('generateExports', () => {
           "./foo": "./foo/index.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -308,8 +308,6 @@ describe.concurrent('generateExports', () => {
     // key order matters
     expect(JSON.stringify(results, undefined, 2)).toMatchInlineSnapshot(`
       "{
-        "main": "./index.js",
-        "module": "./index.js",
         "exports": {
           ".": {
             "dev": "./SRC/index.js",
@@ -345,8 +343,8 @@ describe.concurrent('generateExports', () => {
           "./foo": "./foo.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -373,8 +371,8 @@ describe.concurrent('generateExports', () => {
           "./foo": "./foo.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -459,8 +457,8 @@ describe.concurrent('generateExports', () => {
           "./foo": "./foo/index.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": "./index.d.ts",
       }
@@ -538,8 +536,8 @@ describe.concurrent('generateExports', () => {
           "./package.json": "./package.json",
           "./style.css": "./style.css",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -564,8 +562,8 @@ describe.concurrent('generateExports', () => {
           ".": "./index.js",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -589,8 +587,8 @@ describe.concurrent('generateExports', () => {
           "./custom.css": "./custom.css",
           "./package.json": "./package.json",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -614,8 +612,8 @@ describe.concurrent('generateExports', () => {
           "./package.json": "./package.json",
           "./style.css": "./dist/style.css",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": undefined,
         "types": undefined,
       }
@@ -644,8 +642,8 @@ describe.concurrent('generateExports', () => {
           "./package.json": "./package.json",
           "./style.css": "./style.css",
         },
-        "main": "./index.js",
-        "module": "./index.js",
+        "main": undefined,
+        "module": undefined,
         "publishExports": {
           ".": "./index.js",
           "./package.json": "./package.json",

src/features/pkg/exports.ts

@@ -48,6 +48,16 @@ export interface ExportsOptions {
    */
   exclude?: (RegExp | string)[]
 
+  /**
+   * Generate legacy fields (`main` and `module`) for older Node.js and bundlers
+   * that do not support package `exports` field.
+   *
+   * Defaults to false, if only ESM builds are included, true otherwise.
+   *
+   * @see {@link https://github.com/publint/publint/issues/24}
+   */
+  legacy?: boolean
+
   customExports?: (
     exports: Record<string, any>,
     context: {
@@ -112,8 +122,15 @@ export async function generateExports(
   publishExports?: Record<string, any>
 }> {
   typeAssert(options.exports)
-  const {
-    exports: { devExports, all, packageJson = true, exclude, customExports },
+  let {
+    exports: {
+      devExports,
+      all,
+      packageJson = true,
+      exclude,
+      customExports,
+      legacy,
+    },
     css,
     logger,
   } = options
@@ -131,6 +148,9 @@ export async function generateExports(
     logger.warn(`No CJS or ESM formats found in chunks for package ${pkg.name}`)
   }
 
+  const isPureESM = formats.length === 1 && formats[0] === 'es'
+  legacy ??= !isPureESM
+
   for (const [format, chunksByFormat] of Object.entries(chunks) as [
     NormalizedFormat,
     RolldownChunk[],
@@ -239,8 +259,8 @@ export async function generateExports(
   }
 
   return {
-    main: main || module || pkg.main,
-    module: module || pkg.module,
+    main: legacy ? main || module || pkg.main : undefined,
+    module: legacy ? module || pkg.module : undefined,
     types: cjsTypes || esmTypes || pkg.types,
     exports,
     publishExports,