fix(ngcc): ensure that path-mapped secondary entry-points are processed correctly (#35227)

The `TargetedEntryPointFinder` must work out what the
containing package is for each entry-point that it finds.

The logic for doing this was flawed in the case that the
package was in a path-mapped directory and not in a
node_modules folder. This meant that secondary entry-points
were incorrectly setting their own path as the package
path, rather than the primary entry-point path.

Fixes #35188

PR Close #35227

packages/compiler-cli/ngcc/src/entry_point_finder/targeted_entry_point_finder.ts

@@ -110,17 +110,27 @@ export class TargetedEntryPointFinder implements EntryPointFinder {
       if (entryPointPath.startsWith(basePath)) {
         let packagePath = basePath;
         const segments = this.splitPath(relative(basePath, entryPointPath));
-
-        // Start the search at the last nested `node_modules` folder if the relative
-        // `entryPointPath` contains one or more.
         let nodeModulesIndex = segments.lastIndexOf(relativeFrom('node_modules'));
+
+        // If there are no `node_modules` in the relative path between the `basePath` and the
+        // `entryPointPath` then just try the `basePath` as the `packagePath`.
+        // (This can be the case with path-mapped entry-points.)
+        if (nodeModulesIndex === -1) {
+          if (this.fs.exists(join(packagePath, 'package.json'))) {
+            return packagePath;
+          }
+        }
+
+        // Start the search at the deepest nested `node_modules` folder that is below the `basePath`
+        // but above the `entryPointPath`, if there are any.
         while (nodeModulesIndex >= 0) {
           packagePath = join(packagePath, segments.shift() !);
           nodeModulesIndex--;
         }
 
-        // Note that we skip the first `packagePath` and start looking from the first folder below
-        // it because that will be the `node_modules` folder.
+        // Note that we start at the folder below the current candidate `packagePath` because the
+        // initial candidate `packagePath` is either a `node_modules` folder or the `basePath` with
+        // no `package.json`.
         for (const segment of segments) {
           packagePath = join(packagePath, segment);
           if (this.fs.exists(join(packagePath, 'package.json'))) {
@@ -128,9 +138,9 @@ export class TargetedEntryPointFinder implements EntryPointFinder {
           }
         }
 
-        // If we got here then we couldn't find a `packagePath` for the current `basePath` but since
-        // `basePath`s are guaranteed not to be a sub-directory each other then no other `basePath`
-        // will match either.
+        // If we got here then we couldn't find a `packagePath` for the current `basePath`.
+        // Since `basePath`s are guaranteed not to be a sub-directory of each other then no other
+        // `basePath` will match either.
         break;
       }
     }

packages/compiler-cli/ngcc/test/entry_point_finder/targeted_entry_point_finder_spec.ts

@@ -203,6 +203,31 @@ runInEachFileSystem(() => {
         ]);
       });
 
+      it('should correctly compute the packagePath of secondary entry-points via pathMappings',
+         () => {
+           const basePath = _Abs('/path_mapped/node_modules');
+           const targetPath = _Abs('/path_mapped/dist/primary/secondary');
+           const pathMappings: PathMappings = {
+             baseUrl: '/path_mapped/dist',
+             paths: {'libs': ['primary'], 'extras': ['primary/*']}
+           };
+           loadTestFiles([
+             ...createPackage(_Abs('/path_mapped/dist'), 'primary'),
+             ...createPackage(_Abs('/path_mapped/dist/primary'), 'secondary'),
+           ]);
+           const srcHost = new EsmDependencyHost(fs, new ModuleResolver(fs, pathMappings));
+           const dtsHost = new DtsDependencyHost(fs, pathMappings);
+           resolver = new DependencyResolver(fs, logger, {esm2015: srcHost}, dtsHost);
+           const finder = new TargetedEntryPointFinder(
+               fs, config, logger, resolver, basePath, targetPath, pathMappings);
+           const {entryPoints} = finder.findEntryPoints();
+           expect(entryPoints.length).toEqual(1);
+           const entryPoint = entryPoints[0];
+           expect(entryPoint.name).toEqual('secondary');
+           expect(entryPoint.path).toEqual(_Abs('/path_mapped/dist/primary/secondary'));
+           expect(entryPoint.package).toEqual(_Abs('/path_mapped/dist/primary'));
+         });
+
       it('should handle pathMappings that map to files or non-existent directories', () => {
         const basePath = _Abs('/path_mapped/node_modules');
         const targetPath = _Abs('/path_mapped/node_modules/test');
@@ -451,6 +476,7 @@ runInEachFileSystem(() => {
         {
           name: _Abs(`${basePath}/${packageName}/package.json`),
           contents: JSON.stringify({
+            name: packageName,
             typings: `./${packageName}.d.ts`,
             fesm2015: `./fesm2015/${packageName}.js`,
             esm5: `./esm5/${packageName}.js`,