feat(compiler): generate export maps on build

src/compiler/build/test/write-export-maps.spec.ts

@@ -0,0 +1,143 @@
+import { mockBuildCtx, mockValidatedConfig } from '@stencil/core/testing';
+import childProcess from 'child_process';
+
+import * as d from '../../../declarations';
+import { stubComponentCompilerMeta } from '../../types/tests/ComponentCompilerMeta.stub';
+import { writeExportMaps } from '../write-export-maps';
+
+describe('writeExportMaps', () => {
+  let config: d.ValidatedConfig;
+  let buildCtx: d.BuildCtx;
+  let execSyncSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    config = mockValidatedConfig();
+    buildCtx = mockBuildCtx(config);
+
+    execSyncSpy = jest.spyOn(childProcess, 'execSync').mockImplementation(() => '');
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should not generate any exports if there are no output targets', () => {
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(0);
+  });
+
+  it('should generate the default exports for the lazy build if present', () => {
+    config.outputTargets = [
+      {
+        type: 'dist',
+        dir: '/dist',
+        typesDir: '/dist/types',
+      },
+    ];
+
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(3);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[.][import]"="./dist/index.js"`);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[.][require]"="./dist/index.cjs.js"`);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[.][types]"="./dist/types/index.d.ts"`);
+  });
+
+  it('should generate the default exports for the custom elements build if present', () => {
+    config.outputTargets = [
+      {
+        type: 'dist-custom-elements',
+        dir: '/dist/components',
+        generateTypeDeclarations: true,
+      },
+    ];
+
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(2);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[.][import]"="./dist/components/index.js"`);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[.][types]"="./dist/components/index.d.ts"`);
+  });
+
+  it('should generate the lazy loader exports if the output target is present', () => {
+    config.rootDir = '/';
+    config.outputTargets.push({
+      type: 'dist-lazy-loader',
+      dir: '/dist/lazy-loader',
+      empty: true,
+      esmDir: '/dist/esm',
+      cjsDir: '/dist/cjs',
+      componentDts: '/dist/components.d.ts',
+    });
+
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(3);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[./loader][import]"="./dist/lazy-loader/index.js"`);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[./loader][require]"="./dist/lazy-loader/index.cjs"`);
+    expect(execSyncSpy).toHaveBeenCalledWith(`npm pkg set "exports[./loader][types]"="./dist/lazy-loader/index.d.ts"`);
+  });
+
+  it('should generate the custom elements exports if the output target is present', () => {
+    config.rootDir = '/';
+    config.outputTargets.push({
+      type: 'dist-custom-elements',
+      dir: '/dist/components',
+      generateTypeDeclarations: true,
+    });
+
+    buildCtx.components = [
+      stubComponentCompilerMeta({
+        tagName: 'my-component',
+        componentClassName: 'MyComponent',
+      }),
+    ];
+
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(4);
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-component][import]"="./dist/components/my-component.js"`,
+    );
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-component][types]"="./dist/components/my-component.d.ts"`,
+    );
+  });
+
+  it('should generate the custom elements exports for multiple components', () => {
+    config.rootDir = '/';
+    config.outputTargets.push({
+      type: 'dist-custom-elements',
+      dir: '/dist/components',
+      generateTypeDeclarations: true,
+    });
+
+    buildCtx.components = [
+      stubComponentCompilerMeta({
+        tagName: 'my-component',
+        componentClassName: 'MyComponent',
+      }),
+      stubComponentCompilerMeta({
+        tagName: 'my-other-component',
+        componentClassName: 'MyOtherComponent',
+      }),
+    ];
+
+    writeExportMaps(config, buildCtx);
+
+    expect(execSyncSpy).toHaveBeenCalledTimes(6);
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-component][import]"="./dist/components/my-component.js"`,
+    );
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-component][types]"="./dist/components/my-component.d.ts"`,
+    );
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-other-component][import]"="./dist/components/my-other-component.js"`,
+    );
+    expect(execSyncSpy).toHaveBeenCalledWith(
+      `npm pkg set "exports[./my-other-component][types]"="./dist/components/my-other-component.d.ts"`,
+    );
+  });
+});

src/compiler/build/write-build.ts

@@ -1,8 +1,9 @@
 import { catchError } from '@utils';
 
-import type * as d from '../../declarations';
+import * as d from '../../declarations';
 import { outputServiceWorkers } from '../output-targets/output-service-workers';
 import { validateBuildFiles } from './validate-files';
+import { writeExportMaps } from './write-export-maps';
 
 /**
  * Writes files to disk as a result of compilation
@@ -36,6 +37,10 @@ export const writeBuild = async (
     buildCtx.debug(`in-memory-fs: ${compilerCtx.fs.getMemoryStats()}`);
     buildCtx.debug(`cache: ${compilerCtx.cache.getMemoryStats()}`);
 
+    if (config.generateExportMaps) {
+      writeExportMaps(config, buildCtx);
+    }
+
     await outputServiceWorkers(config, buildCtx);
     await validateBuildFiles(config, compilerCtx, buildCtx);
   } catch (e: any) {

src/compiler/build/write-export-maps.ts

@@ -0,0 +1,81 @@
+import {
+  isEligiblePrimaryPackageOutputTarget,
+  isOutputTargetDistCustomElements,
+  isOutputTargetDistLazyLoader,
+} from '@utils';
+import { relative } from '@utils';
+import { execSync } from 'child_process';
+
+import * as d from '../../declarations';
+import { PRIMARY_PACKAGE_TARGET_CONFIGS } from '../types/validate-primary-package-output-target';
+
+/**
+ * Create export map entry point definitions for the `package.json` file using the npm CLI.
+ * This will generate a root entry point for the package, as well as entry points for each component and
+ * the lazy loader (if applicable).
+ *
+ * @param config The validated Stencil config
+ * @param buildCtx The build context containing the components to generate export maps for
+ */
+export const writeExportMaps = (config: d.ValidatedConfig, buildCtx: d.BuildCtx) => {
+  const eligiblePrimaryTargets = config.outputTargets.filter(isEligiblePrimaryPackageOutputTarget);
+  if (eligiblePrimaryTargets.length > 0) {
+    const primaryTarget =
+      eligiblePrimaryTargets.find((o) => o.isPrimaryPackageOutputTarget) ?? eligiblePrimaryTargets[0];
+    const outputTargetConfig = PRIMARY_PACKAGE_TARGET_CONFIGS[primaryTarget.type];
+
+    if (outputTargetConfig.getModulePath) {
+      const importPath = outputTargetConfig.getModulePath(config.rootDir, primaryTarget.dir!);
+
+      if (importPath) {
+        execSync(`npm pkg set "exports[.][import]"="${importPath}"`);
+      }
+    }
+
+    if (outputTargetConfig.getMainPath) {
+      const requirePath = outputTargetConfig.getMainPath(config.rootDir, primaryTarget.dir!);
+
+      if (requirePath) {
+        execSync(`npm pkg set "exports[.][require]"="${requirePath}"`);
+      }
+    }
+
+    if (outputTargetConfig.getTypesPath) {
+      const typesPath = outputTargetConfig.getTypesPath(config.rootDir, primaryTarget);
+
+      if (typesPath) {
+        execSync(`npm pkg set "exports[.][types]"="${typesPath}"`);
+      }
+    }
+  }
+
+  const distLazyLoader = config.outputTargets.find(isOutputTargetDistLazyLoader);
+  if (distLazyLoader != null) {
+    // Calculate relative path from project root to lazy-loader output directory
+    let outDir = relative(config.rootDir, distLazyLoader.dir);
+    if (!outDir.startsWith('.')) {
+      outDir = './' + outDir;
+    }
+
+    execSync(`npm pkg set "exports[./loader][import]"="${outDir}/index.js"`);
+    execSync(`npm pkg set "exports[./loader][require]"="${outDir}/index.cjs"`);
+    execSync(`npm pkg set "exports[./loader][types]"="${outDir}/index.d.ts"`);
+  }
+
+  const distCustomElements = config.outputTargets.find(isOutputTargetDistCustomElements);
+  if (distCustomElements != null) {
+    // Calculate relative path from project root to custom elements output directory
+    let outDir = relative(config.rootDir, distCustomElements.dir!);
+    if (!outDir.startsWith('.')) {
+      outDir = './' + outDir;
+    }
+
+    buildCtx.components.forEach((cmp) => {
+      execSync(`npm pkg set "exports[./${cmp.tagName}][import]"="${outDir}/${cmp.tagName}.js"`);
+
+      if (distCustomElements.generateTypeDeclarations) {
+        execSync(`npm pkg set "exports[./${cmp.tagName}][types]"="${outDir}/${cmp.tagName}.d.ts"`);
+      }
+    });
+  }
+};

src/compiler/config/validate-config.ts

@@ -124,6 +124,7 @@ export const validateConfig = (
     devMode,
     extras: config.extras || {},
     flags,
+    generateExportMaps: isBoolean(config.generateExportMaps) ? config.generateExportMaps : false,
     hashFileNames,
     hashedFileNameLength: config.hashedFileNameLength ?? DEFAULT_HASHED_FILENAME_LENGTH,
     hydratedFlag: validateHydrated(config),

src/compiler/types/validate-primary-package-output-target.ts

@@ -17,16 +17,30 @@ export type PrimaryPackageOutputTargetRecommendedConfig = {
    * @param outputTargetDir The output directory for the output target's compiled code.
    * @returns The recommended path for the `module` property in a project's `package.json`
    */
-  getModulePath?: (rootDir: string, outputTargetDir: string) => string | null;
+  getModulePath: (rootDir: string, outputTargetDir: string) => string | null;
   /**
    * Generates the recommended path for the `types` property based on the output target type,
    * the project's root directory, and the output target's configuration.
    *
+   * `outputTargetConfig` is typed as `any` because downstream consumers may run into type conflicts
+   * with the `type` property of all the different "eligible" output targets.
+   *
    * @param rootDir The Stencil project's root directory pulled from the validated config.
    * @param outputTargetConfig The output target's config.
    * @returns The recommended path for the `types` property in a project's `package.json`
    */
-  getTypesPath?: (rootDir: string, outputTargetConfig: any) => string | null;
+  getTypesPath: (rootDir: string, outputTargetConfig: any) => string | null;
+  /**
+   * Generates the recommended path for the `main` property based on the output target type,
+   * the project's root directory, and the output target's designated output location.
+   *
+   * Only used for generate export maps.
+   *
+   * @param rootDir The Stencil project's root directory pulled from the validated config.
+   * @param outputTargetDir The output directory for the output target's compiled code.
+   * @returns The recommended path for the `main` property in a project's `package.json`
+   */
+  getMainPath: (rootDir: string, outputTargetDir: string) => string | null;
 };
 
 /**
@@ -38,25 +52,32 @@ export const PRIMARY_PACKAGE_TARGET_CONFIGS = {
   dist: {
     getModulePath: (rootDir: string, outputTargetDir: string) =>
       normalizePath(relative(rootDir, join(outputTargetDir, 'index.js'))),
-    getTypesPath: (rootDir: string, outputTargetConfig: d.OutputTargetDist) =>
+    getTypesPath: (rootDir: string, outputTargetConfig: any) =>
       normalizePath(relative(rootDir, join(outputTargetConfig.typesDir!, 'index.d.ts'))),
+    getMainPath: (rootDir: string, outputTargetDir: string) =>
+      normalizePath(relative(rootDir, join(outputTargetDir, 'index.cjs.js'))),
   },
   'dist-collection': {
     getModulePath: (rootDir: string, outputTargetDir: string) =>
       normalizePath(relative(rootDir, join(outputTargetDir, 'index.js'))),
+    getTypesPath: () => null,
+    getMainPath: () => null,
   },
   'dist-custom-elements': {
     getModulePath: (rootDir: string, outputTargetDir: string) =>
       normalizePath(relative(rootDir, join(outputTargetDir, 'index.js'))),
-    getTypesPath: (rootDir: string, outputTargetConfig: d.OutputTargetDistCustomElements) => {
+    getTypesPath: (rootDir: string, outputTargetConfig: any) => {
       return outputTargetConfig.generateTypeDeclarations
         ? normalizePath(relative(rootDir, join(outputTargetConfig.dir!, 'index.d.ts')))
         : null;
     },
+    getMainPath: () => null,
   },
   'dist-types': {
-    getTypesPath: (rootDir: string, outputTargetConfig: d.OutputTargetDistTypes) =>
+    getModulePath: () => null,
+    getTypesPath: (rootDir: string, outputTargetConfig: any) =>
       normalizePath(relative(rootDir, join(outputTargetConfig.typesDir, 'index.d.ts'))),
+    getMainPath: () => null,
   },
 } satisfies Record<d.EligiblePrimaryPackageOutputTarget['type'], PrimaryPackageOutputTargetRecommendedConfig>;
 

src/declarations/stencil-public-compiler.ts

@@ -84,6 +84,14 @@ export interface StencilConfig {
    */
   globalStyle?: string;
 
+  /**
+   * Will generate {@link https://nodejs.org/api/packages.html#packages_exports export map} entry points
+   * for each component in the build when `true`.
+   *
+   * @default false
+   */
+  generateExportMaps?: boolean;
+
   /**
    * When the hashFileNames config is set to true, and it is a production build,
    * the hashedFileNameLength config is used to determine how many characters the file name's hash should be.