feat: add support for package.json exports

With this change exports field will be included in the package.json of the library.

integration/samples/apf/specs/package.ts

@@ -42,6 +42,30 @@ describe(`@sample/apf`, () => {
     it(`should apply the 'sideEffects: false' flag by default`, () => {
       expect(PACKAGE['sideEffects']).to.be.false;
     });
+
+    it(`should add package 'exports'`, () => {
+      expect(PACKAGE['exports']).to.deep.equal({
+        './package.json': {
+          default: './package.json',
+        },
+        '.': {
+          types: './sample-apf.d.ts',
+          default: './fesm2020/sample-apf.js',
+        },
+        './secondary': {
+          types: './secondary/sample-apf-secondary.d.ts',
+          default: './fesm2020/sample-apf-secondary.js',
+        },
+        './secondary/testing': {
+          types: './secondary/testing/sample-apf-secondary-testing.d.ts',
+          default: './fesm2020/sample-apf-secondary-testing.js',
+        },
+        './testing': {
+          types: './testing/sample-apf-testing.d.ts',
+          default: './fesm2020/sample-apf-testing.js',
+        },
+      });
+    });
   });
 
   describe(`secondary/package.json`, () => {
@@ -86,6 +110,10 @@ describe(`@sample/apf`, () => {
     it(`should apply the 'sideEffects: false' flag by default`, () => {
       expect(PACKAGE['sideEffects']).to.be.false;
     });
+
+    it(`should not add package 'exports'`, () => {
+      expect(PACKAGE['exports']).to.be.undefined;
+    });
   });
 
   describe(`secondary/testing/package.json`, () => {
@@ -173,5 +201,9 @@ describe(`@sample/apf`, () => {
     it(`should apply the 'sideEffects: false' flag by default`, () => {
       expect(PACKAGE['sideEffects']).to.be.false;
     });
+
+    it(`should not add package 'exports'`, () => {
+      expect(PACKAGE['exports']).to.be.undefined;
+    });
   });
 });

src/lib/ng-package/entry-point/entry-point.spec.ts

@@ -34,7 +34,6 @@ describe(`NgEntryPoint`, () => {
     expect(primaryEntryPoint.entryFilePath).to.equal(resolve(testSourcePath, 'public-api.ts'));
     expect(primaryEntryPoint.isSecondaryEntryPoint).to.be.false;
     expect(primaryEntryPoint.destinationPath).to.equal(resolve(testDestinationPath));
-    expect(Object.keys(primaryEntryPoint.destinationFiles).length).to.equal(4);
     expect(primaryEntryPoint.entryFile).to.equal('public-api.ts');
     expect(primaryEntryPoint.cssUrl).to.be.undefined; // TODO: should default to 'inline'.
     expect(primaryEntryPoint.flatModuleFile).to.equal('example-test-entry-point');
@@ -104,7 +103,6 @@ describe(`NgEntryPoint`, () => {
     expect(secondaryEntryPoint.entryFilePath).to.equal(resolve(secondaryEntryPointBasePath, 'public-api.ts'));
     expect(secondaryEntryPoint.isSecondaryEntryPoint).to.be.true;
     expect(secondaryEntryPoint.destinationPath).to.equal(resolve(secondaryData.destinationPath));
-    expect(Object.keys(secondaryEntryPoint.destinationFiles).length).to.equal(4);
     expect(secondaryEntryPoint.entryFile).to.equal('public-api.ts');
     expect(secondaryEntryPoint.cssUrl).to.be.undefined; // TODO: should default to 'inline'.
     expect(secondaryEntryPoint.flatModuleFile).to.equal('example-test-entry-point-extra');

src/lib/ng-package/entry-point/entry-point.ts

@@ -1,6 +1,7 @@
 import * as path from 'path';
 import { NgPackageConfig } from '../../../ng-package.schema';
 import { CssUrl } from '../../styles/stylesheet-processor';
+import { ensureUnixPath } from '../../utils/path';
 
 /** A list of output absolute paths for various formats */
 export interface DestinationFiles {
@@ -12,6 +13,8 @@ export interface DestinationFiles {
   fesm2015: string;
   /** Absolute path of this entry point `ESM2020` module */
   esm2020: string;
+  /** Sub path of entrypoint distributable. */
+  directory: string;
 }
 
 /**
@@ -87,6 +90,7 @@ export class NgEntryPoint {
     const pathJoinWithDest = (...paths: string[]) => path.join(primaryDestPath, ...paths);
 
     return {
+      directory: ensureUnixPath(secondaryDir),
       declarations: pathJoinWithDest(secondaryDir, `${flatModuleFile}.d.ts`),
       esm2020: pathJoinWithDest('esm2020', secondaryDir, `${flatModuleFile}.js`),
       fesm2020: pathJoinWithDest('fesm2020', `${flatModuleFile}.js`),

src/lib/ng-package/entry-point/write-package.transform.ts

@@ -8,9 +8,10 @@ import { ensureUnixPath } from '../../utils/path';
 import { copyFile, exists, stat, rmdir, writeFile } from '../../utils/fs';
 import * as log from '../../utils/log';
 import { globFiles } from '../../utils/glob';
-import { EntryPointNode, isEntryPointInProgress, isPackage, PackageNode, fileUrl } from '../nodes';
+import { EntryPointNode, isEntryPointInProgress, isPackage, PackageNode, fileUrl, isEntryPoint } from '../nodes';
 import { Node } from '../../graph/node';
 import { NgPackagrOptions } from '../options.di';
+import { BuildGraph } from '../../graph/build-graph';
 
 type CompilationMode = 'partial' | 'full' | undefined;
 
@@ -99,12 +100,14 @@ export const writePackageTransform = (options: NgPackagrOptions) =>
         ngEntryPoint,
         ngPackage,
         {
+          type: 'module',
           module: relativeUnixFromDestPath(destinationFiles.fesm2015),
           es2020: relativeUnixFromDestPath(destinationFiles.fesm2020),
           esm2020: relativeUnixFromDestPath(destinationFiles.esm2020),
           fesm2020: relativeUnixFromDestPath(destinationFiles.fesm2020),
           fesm2015: relativeUnixFromDestPath(destinationFiles.fesm2015),
           typings: relativeUnixFromDestPath(destinationFiles.declarations),
+          exports: ngEntryPoint.packageJson.exports || generatePackageExports(ngEntryPoint, graph),
           // webpack v4+ specific flag to enable advanced optimizations and code splitting
           sideEffects: ngEntryPoint.sideEffects,
         },
@@ -271,3 +274,34 @@ function checkNonPeerDependencies(
     }
   }
 }
+
+type PackageExports = Record<string, { default: string; types?: string }>;
+function generatePackageExports(
+  { isSecondaryEntryPoint, destinationPath }: NgEntryPoint,
+  graph: BuildGraph,
+): PackageExports | undefined {
+  if (isSecondaryEntryPoint) {
+    // Package exports are only available in the primary entrypoint.
+    return undefined;
+  }
+
+  const entryPoints = graph.filter(isEntryPoint);
+  const exports: PackageExports = {
+    './package.json': {
+      default: './package.json',
+    },
+  };
+
+  const relativeUnixFromDestPath = (filePath: string) =>
+    './' + ensureUnixPath(path.relative(destinationPath, filePath));
+
+  for (const entryPoint of entryPoints) {
+    const { destinationFiles, isSecondaryEntryPoint } = entryPoint.data.entryPoint;
+    exports[isSecondaryEntryPoint ? `./${destinationFiles.directory}` : '.'] = {
+      types: relativeUnixFromDestPath(destinationFiles.declarations),
+      default: relativeUnixFromDestPath(destinationFiles.fesm2020),
+    };
+  }
+
+  return exports;
+}