feat(core): allow omitting lib config

packages/core/src/cli/init.ts

@@ -88,6 +88,10 @@ export const applyCliOptions = (
   options: BuildOptions,
   root: string,
 ): void => {
+  if (config.lib === undefined) {
+    config.lib = [{} satisfies LibConfig];
+  }
+
   if (options.root) {
     config.root = root;
   }

packages/core/src/config.ts

@@ -1963,7 +1963,7 @@ export async function composeCreateRsbuildConfig(
 ): Promise<RsbuildConfigWithLibInfo[]> {
   const constantRsbuildConfig = await createConstantRsbuildConfig();
   const {
-    lib: libConfigsArray,
+    lib: rawLibConfigsArray,
     mode: _mode,
     root,
     plugins: sharedPlugins,
@@ -1977,6 +1977,9 @@ export async function composeCreateRsbuildConfig(
     logger.level = logLevel;
   }
 
+  const libConfigsArray =
+    rawLibConfigsArray === undefined ? [{}] : rawLibConfigsArray;
+
   if (!Array.isArray(libConfigsArray) || libConfigsArray.length === 0) {
     throw new Error(
       `Expect "lib" field to be a non-empty array, but got: ${color.cyan(

packages/core/src/types/config.ts

@@ -504,7 +504,7 @@ interface RslibOutputConfig extends OutputConfig {
 }
 
 export interface RslibConfig extends RsbuildConfig {
-  lib: LibConfig[];
+  lib?: LibConfig[];
   /**
    * @inheritdoc
    */

packages/core/tests/cli.test.ts

@@ -66,6 +66,46 @@ describe('parseEntryOption', () => {
 });
 
 describe('applyCliOptions', () => {
+  test('applies CLI flags to the implicit default library', () => {
+    const config = {
+      source: {},
+      output: {},
+    } as RslibConfig;
+
+    const options = {
+      format: 'cjs',
+      entry: ['index=src/index.ts'],
+      dts: true,
+    } as CommonOptions;
+
+    applyCliOptions(config, options, '/abs/root');
+
+    expect(config.lib).toEqual([
+      {
+        dts: true,
+        format: 'cjs',
+        output: {},
+        source: {
+          entry: {
+            index: 'src/index.ts',
+          },
+        },
+      },
+    ]);
+  });
+
+  test('does not apply CLI flags to null lib field as implicit default library', () => {
+    const config = {
+      lib: null,
+    } as unknown as RslibConfig;
+
+    const options = {
+      format: 'cjs',
+    } as CommonOptions;
+
+    expect(() => applyCliOptions(config, options, '/abs/root')).toThrow();
+  });
+
   test('applies CLI flags to the config and its libraries', () => {
     const config = {
       root: '/initial',
@@ -117,15 +157,15 @@ describe('applyCliOptions', () => {
       distPath: 'dist/custom',
     } as CommonOptions;
 
-    const libBefore = config.lib[0]!;
+    const libBefore = config.lib![0]!;
     const outputBefore = libBefore.output;
 
     applyCliOptions(config, options, '/abs/custom');
 
     expect(config.root).toBe('/abs/custom');
     expect(config.logLevel).toBe('error');
 
-    const lib = config.lib[0]!;
+    const lib = config.lib![0]!;
     expect(lib.format).toBe('cjs');
     expect(lib.bundle).toBe(false);
     expect(lib.dts).toBe(true);

packages/core/tests/config.test.ts

@@ -457,6 +457,30 @@ describe('CLI options', () => {
 });
 
 describe('Should compose create Rsbuild config correctly', () => {
+  test('treats omitted lib field as default library config', async () => {
+    const rslibConfig: RslibConfig = {
+      root: join(__dirname, '..'),
+    };
+
+    const composedRsbuildConfig = await composeRsbuildEnvironments(rslibConfig);
+
+    expect(Object.keys(composedRsbuildConfig.environments))
+      .toMatchInlineSnapshot(`
+      [
+        "esm",
+      ]
+    `);
+    expect(composedRsbuildConfig.environmentWithInfos[0]?.format).toBe('esm');
+  });
+
+  test('does not treat null lib field as default library config', async () => {
+    const rslibConfig = {
+      lib: null,
+    } as unknown as RslibConfig;
+
+    await expect(composeCreateRsbuildConfig(rslibConfig)).rejects.toThrow();
+  });
+
   test('Merge Rsbuild config in each format', async () => {
     const rslibConfig: RslibConfig = {
       lib: [

packages/core/tests/exe.test.ts

@@ -16,9 +16,9 @@ import {
 
 const packageRoot = path.resolve(import.meta.dirname, '..');
 
-type TestLibConfig = Parameters<
-  typeof composeCreateRsbuildConfig
->[0]['lib'][number];
+type TestLibConfig = NonNullable<
+  Parameters<typeof composeCreateRsbuildConfig>[0]['lib']
+>[number];
 
 const composeTestRslibConfig = (lib: TestLibConfig) =>
   composeCreateRsbuildConfig({

tests/benchmark/index.bench.ts

@@ -11,10 +11,11 @@ const disableDts = (rslibConfig: RslibConfig) => {
 };
 
 const onlyEnableMF = (rslibConfig: RslibConfig) => {
-  const length = rslibConfig.lib.length;
+  const lib = rslibConfig.lib!;
+  const length = lib.length;
   for (let i = length - 1; i >= 0; i--) {
-    if (rslibConfig.lib[i] && rslibConfig.lib[i]!.format !== 'mf') {
-      rslibConfig.lib.splice(i, 1);
+    if (lib[i] && lib[i]!.format !== 'mf') {
+      lib.splice(i, 1);
     }
   }
   disableDts(rslibConfig);

tests/integration/shims/esm/rslibShimsDisabled.config.ts

@@ -3,7 +3,7 @@ import config from './rslib.config';
 
 export default defineConfig({
   ...config,
-  lib: config.lib.map((libConfig) => {
+  lib: config.lib!.map((libConfig) => {
     if (typeof libConfig.output!.distPath === 'string') {
       libConfig.output!.distPath = libConfig.output!.distPath.replace(
         './dist/enabled',

tests/scripts/shared.ts

@@ -164,15 +164,15 @@ export async function getResults(
   let mfExposeEntry: string | undefined;
   let key = '';
 
-  const formatCount: Record<Format, number> = rslibConfig.lib.reduce(
+  const formatCount: Record<Format, number> = rslibConfig.lib!.reduce(
     (acc, { format = 'esm' }) => {
       acc[format] = (acc[format] ?? 0) + 1;
       return acc;
     },
     {} as Record<Format, number>,
   );
 
-  for (const libConfig of rslibConfig.lib) {
+  for (const libConfig of rslibConfig.lib!) {
     const { format = 'esm' } = libConfig;
     const currentFormatCount = formatCount[format];
     const currentFormatIndex = formatIndex[format]++;

tests/type-tests/resolution-bundler/index.ts

@@ -5,3 +5,13 @@ import { createRslib, defineConfig } from '@rslib/core';
 createRslib({});
 
 defineConfig({ lib: [] });
+
+defineConfig({});
+
+defineConfig({
+  source: {
+    entry: {
+      index: './src/index.ts',
+    },
+  },
+});

tests/type-tests/resolution-nodenext/index.ts

@@ -5,3 +5,13 @@ import { createRslib, defineConfig } from '@rslib/core';
 createRslib({});
 
 defineConfig({ lib: [] });
+
+defineConfig({});
+
+defineConfig({
+  source: {
+    entry: {
+      index: './src/index.ts',
+    },
+  },
+});

website/docs/en/config/lib/index.mdx

@@ -26,12 +26,14 @@ interface LibConfig extends EnvironmentConfig {
 }
 
 interface RslibConfig extends RsbuildConfig {
-  lib: LibConfig[];
+  lib?: LibConfig[];
 }
 ```
 
-- **Default:** `undefined`
+- **Default:** `[{}]`
 
-- **Required:** `true`
+- **Required:** `false`
 
 The `lib` configuration is an array of objects, each representing a distinct set of configurations. These include all Rsbuild configurations as well as Rslib-specific configurations, designed to generate different outputs.
+
+If `lib` is omitted, Rslib uses a default configuration equivalent to `lib: [{}]`; if `lib` is set explicitly, it must be a non-empty array.

website/docs/en/guide/basic/configure-rslib.mdx

@@ -10,6 +10,8 @@ Rslib's configuration is based on Rsbuild, which means that you can use all of R
 
 Rslib provides the `lib` option to configure the library outputs. It is an array, and each object is used to describe a format of the output.
 
+When you only need the default single ESM output, you can omit the `lib` field. This is equivalent to setting `lib: [{}]`.
+
 For example, output ESM and CJS formats, and use `es2021` syntax:
 
 ```js title="rslib.config.mjs"

website/docs/zh/config/lib/index.mdx

@@ -26,12 +26,14 @@ interface LibConfig extends EnvironmentConfig {
 }
 
 interface RslibConfig extends RsbuildConfig {
-  lib: LibConfig[];
+  lib?: LibConfig[];
 }
 ```
 
-- **默认值:** `undefined`
+- **默认值:** `[{}]`
 
-- **必选:** `true`
+- **必选:** `false`
 
 `lib` 配置是一个对象数组，每个对象代表一组不同的配置。这些配置包括所有 Rsbuild 配置以及 Rslib 特定的配置，可以生成不同格式的产物。
+
+若省略 `lib` 字段，Rslib 会使用等价于 `lib: [{}]` 的默认配置；若显式配置 `lib`，则必须为非空数组。

website/docs/zh/guide/basic/configure-rslib.mdx

@@ -10,6 +10,8 @@ Rslib 的配置是基于 Rsbuild 扩展的，这意味着你可以使用 Rsbuild
 
 Rslib 提供了 `lib` 选项来配置库产物，它是一个数组，每个对象用于描述一种输出格式。
 
+当你只需要默认的单个 ESM 产物时，可以省略 `lib` 字段。这等价于配置 `lib: [{}]`。
+
 例如，输出 ESM 和 CJS 两种格式的产物，并使用 `es2021` 语法：
 
 ```js title="rslib.config.mjs"