feat: new option outExtension

docs/README.md

@@ -224,6 +224,37 @@ dist
 └── index.js
 ```
 
+### Output extension
+
+You can also change the output extension of the files by using `outExtension` option:
+
+```ts
+export default defineConfig({
+  outExtension({ format }) {
+    return {
+      js: `.${format}.js`,
+    }
+  },
+})
+```
+
+This will generate your files to `[name].[format].js`.
+
+The signature of `outExtension` is:
+
+```ts
+type OutExtension = (ctx: Context) => Result
+
+type Context = {
+  options: NormalizedOptions
+  format: Format
+  /** "type" field in project's package.json */
+  pkgType?: string
+}
+
+type Result = { js?: string }
+```
+
 ### Code Splitting
 
 Code splitting currently only works with the `esm` output format, and it's enabled by default. If you want code splitting for `cjs` output format as well, try using `--splitting` flag which is an experimental feature to get rid of [the limitation in esbuild](https://esbuild.github.io/api/#splitting).
@@ -319,7 +350,7 @@ export default defineConfig({
 })
 ```
 
-### Tree Shaking
+### Tree shaking
 
 esbuild has [tree shaking](https://esbuild.github.io/api/#tree-shaking) enabled by default, but sometimes it's not working very well, see [#1794](https://github.com/evanw/esbuild/issues/1794) [#1435](https://github.com/evanw/esbuild/issues/1435), so tsup offers an additional option to let you use Rollup for tree shaking instead:
 

package.json

@@ -63,7 +63,7 @@
     "svelte": "3.46.4",
     "ts-essentials": "9.1.2",
     "tsconfig-paths": "3.12.0",
-    "tsup": "5.12.5",
+    "tsup": "6.0.1",
     "typescript": "4.6.3",
     "vitest": "0.8.4",
     "wait-for-expect": "3.0.2"

src/esbuild/index.ts

@@ -18,23 +18,44 @@ import { truthy } from '../utils'
 import { swcPlugin } from './swc'
 import { nativeNodeModulesPlugin } from './native-node-module'
 import { PluginContainer } from '../plugin'
+import { OutExtensionFactory } from '../options'
 
-const getOutputExtensionMap = (
-  pkgTypeField: string | undefined,
+const defaultOutExtension = ({
+  format,
+  pkgType,
+}: {
   format: Format
-) => {
-  const isModule = pkgTypeField === 'module'
-  const map: Record<string, string> = {}
+  pkgType?: string
+}): { js: string } => {
+  let jsExtension = '.js'
+  const isModule = pkgType === 'module'
   if (isModule && format === 'cjs') {
-    map['.js'] = '.cjs'
+    jsExtension = '.cjs'
   }
   if (!isModule && format === 'esm') {
-    map['.js'] = '.mjs'
+    jsExtension = '.mjs'
   }
   if (format === 'iife') {
-    map['.js'] = '.global.js'
+    jsExtension = '.global.js'
+  }
+  return {
+    js: jsExtension,
+  }
+}
+
+const getOutputExtensionMap = (
+  options: NormalizedOptions,
+  format: Format,
+  pkgType: string | undefined
+) => {
+  const outExtension: OutExtensionFactory =
+    options.outExtension || defaultOutExtension
+
+  const defaultExtension = defaultOutExtension({ format, pkgType })
+  const extension = outExtension({ options, format, pkgType })
+  return {
+    '.js': extension.js || defaultExtension.js,
   }
-  return map
 }
 
 export async function runEsbuild(
@@ -62,7 +83,7 @@ export async function runEsbuild(
   ]
   const outDir = options.outDir
 
-  const outExtension = getOutputExtensionMap(pkg.type, format)
+  const outExtension = getOutputExtensionMap(options, format, pkg.type)
   const env: { [k: string]: string } = {
     ...options.env,
   }

src/index.ts

@@ -13,7 +13,7 @@ import execa from 'execa'
 import kill from 'tree-kill'
 import { version } from '../package.json'
 import { createLogger, setSilent } from './log'
-import { DtsConfig, Format, Options } from './options'
+import { NormalizedOptions, Format, Options } from './options'
 import { runEsbuild } from './esbuild'
 import { shebang } from './plugins/shebang'
 import { cjsSplitting } from './plugins/cjs-splitting'
@@ -22,16 +22,7 @@ import { es5 } from './plugins/es5'
 import { sizeReporter } from './plugins/size-reporter'
 import { treeShakingPlugin } from './plugins/tree-shaking'
 
-export type { Format, Options }
-
-export type NormalizedOptions = Omit<
-  MarkRequired<Options, 'entry' | 'format' | 'outDir'>,
-  'dts'
-> & {
-  dts?: DtsConfig
-  tsconfigResolvePaths: Record<string, string[]>
-  tsconfigDecoratorMetadata?: boolean
-}
+export type { Format, Options, NormalizedOptions }
 
 export const defineConfig = (
   options:

src/options.ts

@@ -1,10 +1,24 @@
 import type { BuildOptions, Plugin as EsbuildPlugin, Loader } from 'esbuild'
 import type { InputOption } from 'rollup'
-import { Plugin } from './plugin'
-import { TreeshakingStrategy } from './plugins/tree-shaking'
+import { MarkRequired } from 'ts-essentials'
+import type { Plugin } from './plugin'
+import type { TreeshakingStrategy } from './plugins/tree-shaking'
 
 export type Format = 'cjs' | 'esm' | 'iife'
 
+export type ContextForOutPathGeneration = {
+  options: NormalizedOptions
+  format: Format
+  /** "type" field in project's package.json */
+  pkgType?: string
+}
+
+export type OutExtensionObject = { js?: string }
+
+export type OutExtensionFactory = (
+  ctx: ContextForOutPathGeneration
+) => OutExtensionObject
+
 export type DtsConfig = {
   entry?: InputOption
   /** Resolve external types used in dts files from node_modules */
@@ -57,6 +71,7 @@ export type Options = {
   jsxFactory?: string
   jsxFragment?: string
   outDir?: string
+  outExtension?: OutExtensionFactory
   format?: Format[]
   globalName?: string
   env?: {
@@ -158,3 +173,12 @@ export type Options = {
    */
   treeshake?: TreeshakingStrategy
 }
+
+export type NormalizedOptions = Omit<
+  MarkRequired<Options, 'entry' | 'format' | 'outDir'>,
+  'dts'
+> & {
+  dts?: DtsConfig
+  tsconfigResolvePaths: Record<string, string[]>
+  tsconfigDecoratorMetadata?: boolean
+}

test/index.test.ts

@@ -860,3 +860,29 @@ test('use rollup for treeshaking', async () => {
     `import { inject } from 'vue'`
   )
 })
+
+test('custom output extension', async () => {
+  const { outFiles } = await run(
+    getTestName(),
+    {
+      'input.ts': `export const foo = [1,2,3]`,
+      'tsup.config.ts': `export default {
+        outExtension({ format }) {
+          return {
+            js: '.' + format + '.js'
+          }
+        }
+      }`,
+    },
+    {
+      entry: ['input.ts'],
+      flags: ['--format', 'esm,cjs'],
+    }
+  )
+  expect(outFiles).toMatchInlineSnapshot(`
+    [
+      "input.cjs.js",
+      "input.esm.js",
+    ]
+  `)
+})