fixup! fix(ngcc): cope with packages following APF v14+

packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts

@@ -137,7 +137,7 @@ export class ModuleResolver {
    *
    * This is achieved by checking for the existence of `${modulePath}/package.json`.
    * If there is no `package.json`, we check whether this is an APF v14+ secondary entry-point,
-   * which does not have each own `package.json` but has an `exports` entry in the package's primary
+   * which does not have its own `package.json` but has an `exports` entry in the package's primary
    * `package.json`.
    */
   private isEntryPoint(modulePath: AbsoluteFsPath): boolean {

packages/compiler-cli/ngcc/src/utils.ts

@@ -201,18 +201,42 @@ export function loadJson<T extends JsonObject = JsonObject>(
 export function loadSecondaryEntryPointInfoForApfV14(
     fs: ReadonlyFileSystem, primaryPackageJson: JsonObject|null, packagePath: AbsoluteFsPath,
     entryPointPath: AbsoluteFsPath): JsonObject|null {
-  // Check if primary `package.json` has been loaded and has an `exports` property.
-  if (primaryPackageJson?.exports === undefined) {
+  // Check if primary `package.json` has been loaded and has an `exports` property that is an
+  // object.
+  const exportMap = primaryPackageJson?.exports;
+  if (!isExportObject(exportMap)) {
     return null;
   }
 
   // Find the `exports` key for the secondary entry-point.
   const relativeEntryPointPath = fs.relative(packagePath, entryPointPath);
-  const exportsKey = `./${relativeEntryPointPath}`;
+  const entryPointExportKey = `./${relativeEntryPointPath}`;
 
-  // Read the data (if it exists).
-  const exportsData =
-      (primaryPackageJson.exports as JsonObject)[exportsKey] as JsonObject | undefined;
+  // Read the info for the entry-point.
+  const entryPointInfo = exportMap[entryPointExportKey];
 
-  return exportsData ?? null;
+  // Check whether the entry-point info exists and is an export map.
+  return isExportObject(entryPointInfo) ? entryPointInfo : null;
+}
+
+/**
+ * Check whether a value read from a JSON file is a Node.js export map (either the top-level one or
+ * one for a subpath).
+ *
+ * In `package.json` files, the `exports` field can be of type `Object | string | string[]`, but APF
+ * v14+ uses an object with subpath exports for each entry-point, which in turn are conditional
+ * exports (see references below). This function verifies that a value read from the top-level
+ * `exports` field or a subpath is of type `Object` (and not `string` or `string[]`).
+ *
+ * References:
+ * - https://nodejs.org/api/packages.html#exports
+ * - https://nodejs.org/api/packages.html#subpath-exports
+ * - https://nodejs.org/api/packages.html#conditional-exports
+ * - https://v14.angular.io/guide/angular-package-format#exports
+ *
+ * @param thing The value read from the JSON file
+ * @returns True if the value is an `Object` (and not an `Array`).
+ */
+function isExportObject(thing: JsonValue): thing is JsonObject {
+  return (typeof thing === 'object') && (thing !== null) && !Array.isArray(thing);
 }

packages/compiler-cli/ngcc/test/utils_spec.ts

@@ -283,7 +283,7 @@ runInEachFileSystem(() => {
   beforeEach(() => fs = getFileSystem());
 
   describe('loadSecondaryEntryPointInfoForApfV14()', () => {
-    it('should return `null` of the primary `package.json` failed to be loaded', () => {
+    it('should return `null` if the primary `package.json` failed to be loaded', () => {
       expect(loadSecondaryEntryPointInfoForApfV14(fs, null, _abs('/foo'), _abs('/foo/bar')))
           .toBe(null);
     });
@@ -300,12 +300,39 @@ runInEachFileSystem(() => {
           .toBe(null);
     });
 
+    it('should return `null` if the primary `package.json`\'s `exports` property is a string',
+       () => {
+         const primaryPackageJson = {
+           name: 'some-package',
+           exports: './index.js',
+         };
+
+         expect(loadSecondaryEntryPointInfoForApfV14(
+                    fs, primaryPackageJson, _abs('/foo'), _abs('/foo/bar')))
+             .toBe(null);
+       });
+
+    it('should return `null` if the primary `package.json`\'s `exports` property is a string array',
+       () => {
+         const primaryPackageJson = {
+           name: 'some-package',
+           exports: [
+             './foo.js',
+             './bar.js',
+           ],
+         };
+
+         expect(loadSecondaryEntryPointInfoForApfV14(
+                    fs, primaryPackageJson, _abs('/foo'), _abs('/foo/bar')))
+             .toBe(null);
+       });
+
     it('should return `null` if there is no info for the specified entry-point', () => {
       const primaryPackageJson = {
         name: 'some-package',
         exports: {
           './baz': {
-            isBar: false,
+            main: './baz/index.js',
           },
         },
       };
@@ -315,19 +342,48 @@ runInEachFileSystem(() => {
           .toBe(null);
     });
 
-    it('should return the entry-point info if it exists', () => {
+    it('should return `null` if the entry-point info is a string', () => {
+      const primaryPackageJson = {
+        name: 'some-package',
+        exports: {
+          './bar': './bar/index.js',
+        },
+      };
+
+      expect(loadSecondaryEntryPointInfoForApfV14(
+                 fs, primaryPackageJson, _abs('/foo'), _abs('/foo/bar')))
+          .toBe(null);
+    });
+
+    it('should return `null` if the entry-point info is a string array', () => {
+      const primaryPackageJson = {
+        name: 'some-package',
+        exports: {
+          './bar': [
+            './bar/a.js',
+            './bar/b.js',
+          ],
+        },
+      };
+
+      expect(loadSecondaryEntryPointInfoForApfV14(
+                 fs, primaryPackageJson, _abs('/foo'), _abs('/foo/bar')))
+          .toBe(null);
+    });
+
+    it('should return the entry-point info if it exists and is an object', () => {
       const primaryPackageJson = {
         name: 'some-package',
         exports: {
           './bar': {
-            isBar: true,
+            main: './bar/index.js',
           },
         },
       };
 
       expect(loadSecondaryEntryPointInfoForApfV14(
                  fs, primaryPackageJson, _abs('/foo'), _abs('/foo/bar')))
-          .toEqual({isBar: true});
+          .toEqual({main: './bar/index.js'});
     });
   });
 });