Support for enhanced parts (#3892)

There isn't _much_ for dartdoc to be concerned with. Dartdoc basically must be
aware of an exports foud in a part, and there might be reasons to be concerned
with imports coming from a part. In particular, dartdoc used to skip resolving
all part files when searching for libraries, just as an optimization. Can't do
that any more.

This might not be a full implementation of enhanced parts support, but it sets
up the basics.

lib/src/model/package_builder.dart

@@ -283,6 +283,9 @@ class PubPackageBuilder implements PackageBuilder {
           continue;
         }
         newFiles.addFilesReferencedBy(resolvedLibrary.element);
+        for (var unit in resolvedLibrary.units) {
+          newFiles.addFilesReferencedBy(unit.declaredElement);
+        }
         if (processedLibraries.contains(resolvedLibrary.element)) {
           continue;
         }
@@ -548,24 +551,37 @@ class DartDocResolvedLibrary {
 extension on Set<String> {
   /// Adds [element]'s path and all of its part files' paths to `this`, and
   /// recursively adds the paths of all imported and exported libraries.
-  void addFilesReferencedBy(LibraryOrAugmentationElement? element) {
+  ///
+  /// [element] must be a [LibraryElement] or [CompilationUnitElement].
+  void addFilesReferencedBy(Element? element) {
     if (element == null) return;
 
     var path = element.source?.fullName;
     if (path == null) return;
 
     if (add(path)) {
-      for (var import in element.libraryImports) {
+      var libraryImports = switch (element) {
+        LibraryElement(:var libraryImports) ||
+        CompilationUnitElement(:var libraryImports) =>
+          libraryImports,
+        _ => const <LibraryImportElement>[],
+      };
+      for (var import in libraryImports) {
         addFilesReferencedBy(import.importedLibrary);
       }
-      for (var export in element.libraryExports) {
+
+      var libraryExports = switch (element) {
+        LibraryElement(:var libraryExports) ||
+        CompilationUnitElement(:var libraryExports) =>
+          libraryExports,
+        _ => const <LibraryExportElement>[],
+      };
+      for (var export in libraryExports) {
         addFilesReferencedBy(export.exportedLibrary);
       }
       if (element is LibraryElement) {
-        for (var part in element.parts
-            .map((e) => e.uri)
-            .whereType<DirectiveUriWithUnit>()) {
-          add(part.source.fullName);
+        for (var unit in element.units) {
+          addFilesReferencedBy(unit);
         }
       }
     }

test/dartdoc_test_base.dart

@@ -43,7 +43,7 @@ abstract class DartdocTestBase {
 
   String get sdkConstraint => '>=3.6.0 <4.0.0';
 
-  List<String> get experiments => ['wildcard-variables'];
+  List<String> get experiments => ['enhanced-parts', 'wildcard-variables'];
 
   bool get skipUnreachableSdkLibraries => true;
 

test/packages_test.dart

@@ -5,16 +5,26 @@
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:dartdoc/src/dartdoc_options.dart';
+import 'package:dartdoc/src/model/class.dart';
 import 'package:dartdoc/src/model/documentable.dart';
 import 'package:dartdoc/src/model/kind.dart';
 import 'package:dartdoc/src/package_config_provider.dart';
 import 'package:dartdoc/src/package_meta.dart';
 import 'package:dartdoc/src/special_elements.dart';
 import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
 
+import 'dartdoc_test_base.dart';
+import 'src/test_descriptor_utils.dart' as d;
 import 'src/utils.dart' as utils;
 
 void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(PackagesTest);
+  });
+
+  // TODO(srawlins): Migrate to test_reflective_loader tests.
+
   late MemoryResourceProvider resourceProvider;
   late PackageMetaProvider packageMetaProvider;
   late FakePackageConfigProvider packageConfigProvider;
@@ -103,6 +113,8 @@ int x;
             projectPath, packageMetaProvider, packageConfigProvider);
 
         expect(packageGraph.localPublicLibraries, hasLength(1));
+        var library = packageGraph.libraries.named('a');
+        expect(library.isDocumented, true);
       });
 
       test('has private libraries', () async {
@@ -489,3 +501,88 @@ int x;
     });
   });
 }
+
+@reflectiveTest
+class PackagesTest extends DartdocTestBase {
+  @override
+  String get libraryName => 'lib';
+
+  void test_exportedElements() async {
+    var graph = await bootPackageFromFiles(
+      [
+        d.dir('lib', [
+          d.file('lib.dart', "export 'src/impl.dart';"),
+          d.dir('src', [
+            d.file('impl.dart', 'class C {}'),
+          ]),
+        ]),
+      ],
+    );
+    var library = graph.libraries.named('lib');
+    expect(library.classes.single.name, 'C');
+  }
+
+  void test_exportedElements_indirectlyExported() async {
+    var graph = await bootPackageFromFiles(
+      [
+        d.dir('lib', [
+          d.file('lib.dart', "export 'src/impl.dart';"),
+          d.dir('src', [
+            d.file('impl.dart', "export 'impl2.dart';"),
+            d.file('impl2.dart', 'class C {}'),
+          ]),
+        ]),
+      ],
+    );
+    var library = graph.libraries.named('lib');
+    expect(library.classes.single.name, 'C');
+  }
+
+  void test_exportedElements_fromPart() async {
+    var graph = await bootPackageFromFiles(
+      [
+        d.dir('lib', [
+          d.file('lib.dart', "part 'part.dart';"),
+          d.file('part.dart', '''
+part of 'lib.dart';
+export 'src/impl.dart';
+'''),
+          d.dir('src', [
+            d.file('impl.dart', 'class C {}'),
+          ]),
+        ]),
+      ],
+    );
+    var library = graph.libraries.named('lib');
+    expect(library.qualifiedName, 'lib');
+    expect(library.classes, isNotEmpty);
+    expect(library.classes.single,
+        isA<Class>().having((c) => c.name, 'name', 'C'));
+  }
+
+  void test_exportedElements_fromPartOfPart() async {
+    var graph = await bootPackageFromFiles(
+      [
+        d.dir('lib', [
+          d.file('lib.dart', "part 'part1.dart';"),
+          d.file('part1.dart', '''
+part of 'lib.dart';
+part 'part2.dart';
+'''),
+          d.file('part2.dart', '''
+part of 'part1.dart';
+export 'src/impl.dart';
+'''),
+          d.dir('src', [
+            d.file('impl.dart', 'class C {}'),
+          ]),
+        ]),
+      ],
+    );
+    var library = graph.libraries.named('lib');
+    expect(library.qualifiedName, 'lib');
+    expect(library.classes, isNotEmpty);
+    expect(library.classes.single,
+        isA<Class>().having((c) => c.name, 'name', 'C'));
+  }
+}