feat: support custom config file with --config flag

docs/README.md

@@ -84,6 +84,8 @@ You can use any of these files:
 
 > INFO: In all the custom files you can export the options either as `tsup`, `default` or `module.exports =`
 
+You can also specify a custom filename using the `--config` flag, or passing `--no-config` to disable config files.
+
 [Check out all available options](https://paka.dev/npm/tsup#module-index-export-Options).
 
 #### TypeScript / JavaScript

src/cli-main.ts

@@ -78,6 +78,7 @@ export async function main(options: Options = {}) {
       default: 'node',
     })
     .option('--loader <ext=loader>', 'Specify the loader for a file extension')
+    .option('--config <filename>', 'Use a custom config file')
     .option('--no-config', 'Disable config file')
     .option('--shims', 'Enable cjs and esm shims')
     .option('--inject-style', 'Inject style tag to document head')

src/index.ts

@@ -115,7 +115,12 @@ const normalizeOptions = async (
 
 export async function build(_options: Options) {
   const config =
-    _options.config === false ? {} : await loadTsupConfig(process.cwd())
+    _options.config === false
+      ? {}
+      : await loadTsupConfig(
+          process.cwd(),
+          _options.config === true ? undefined : _options.config
+        )
 
   const configData =
     typeof config.data === 'function'

src/load.ts

@@ -33,18 +33,21 @@ const jsonLoader = {
 joycon.addLoader(jsonLoader)
 
 export async function loadTsupConfig(
-  cwd: string
+  cwd: string,
+  configFile?: string
 ): Promise<{ path?: string; data?: ReturnType<typeof defineConfig> }> {
   const configJoycon = new JoyCon()
   const configPath = await configJoycon.resolve({
-    files: [
-      'tsup.config.ts',
-      'tsup.config.js',
-      'tsup.config.cjs',
-      'tsup.config.mjs',
-      'tsup.config.json',
-      'package.json',
-    ],
+    files: configFile
+      ? [configFile]
+      : [
+          'tsup.config.ts',
+          'tsup.config.js',
+          'tsup.config.cjs',
+          'tsup.config.mjs',
+          'tsup.config.json',
+          'package.json',
+        ],
     cwd,
     stopDir: path.parse(cwd).root,
     packageKey: 'tsup',

src/options.ts

@@ -142,8 +142,9 @@ export type Options = {
   loader?: Record<string, Loader>
   /**
    * Disable config file with `false`
+   * Or pass a custom config filename
    */
-  config?: boolean
+  config?: boolean | string
   /**
    * Use a custom tsconfig
    */

test/index.test.ts

@@ -886,3 +886,24 @@ test('custom output extension', async () => {
     ]
   `)
 })
+
+test('custom config file', async () => {
+  const { outFiles } = await run(
+    getTestName(),
+    {
+      'input.ts': `export const foo = [1,2,3]`,
+      'custom.config.ts': `export default {
+        format: ['esm']
+      }`,
+    },
+    {
+      entry: ['input.ts'],
+      flags: ['--config', 'custom.config.ts'],
+    }
+  )
+  expect(outFiles).toMatchInlineSnapshot(`
+    [
+      "input.mjs",
+    ]
+  `)
+})

tsconfig.json

@@ -8,7 +8,8 @@
     // "allowJs": true,                       /* Allow javascript files to be compiled. */
     // "checkJs": true,                       /* Report errors in .js files. */
     // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
-    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
+    "declaration": true /* Generates corresponding '.d.ts' file. */,
+    "declarationDir": "dist",
     // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
     // "sourceMap": true,                     /* Generates corresponding '.map' file. */
     // "outFile": "./",                       /* Concatenate and emit output to single file. */