Fix issue where excluded packages can sometimes default to remote linking

lib/src/model/class.dart

@@ -179,12 +179,12 @@ class Class extends Container
     var result = <Class>{};
     var seen = <Class>{};
 
-    // Recursively adds [implementor] if public, or the impelentors of
+    // Recursively adds [implementor] if public, or the implementors of
     // [implementor] if not.
     void addToResult(Class implementor) {
       if (seen.contains(implementor)) return;
       seen.add(implementor);
-      if (implementor.isPublic) {
+      if (implementor.isPublicAndPackageDocumented) {
         result.add(implementor);
       } else {
         model_utils

lib/src/model/model_element.dart

@@ -1036,8 +1036,7 @@ abstract class ModelElement extends Canonicalization
   @override
   Package get package => library?.package;
 
-  bool get isPublicAndPackageDocumented =>
-      isPublic && library.packageGraph.packageDocumentedFor(this);
+  bool get isPublicAndPackageDocumented => isPublic && package.isDocumented;
 
   List<Parameter> _allParameters;
 

lib/src/model/package.dart

@@ -188,7 +188,10 @@ class Package extends LibraryContainer
           _documentedWhere = DocumentLocation.local;
         }
       } else {
-        if (config.linkToRemote && config.linkToUrl.isNotEmpty && isPublic) {
+        if (config.linkToRemote &&
+            config.linkToUrl.isNotEmpty &&
+            isPublic &&
+            !packageGraph.config.isPackageExcluded(name)) {
           _documentedWhere = DocumentLocation.remote;
         } else {
           _documentedWhere = DocumentLocation.missing;

lib/src/model/package_graph.dart

@@ -277,20 +277,6 @@ class PackageGraph {
   bool allLibrariesAdded = false;
   bool _localDocumentationBuilt = false;
 
-  Set<String> _allRootDirs;
-
-  /// Returns true if there's at least one library documented in the package
-  /// that has the same package path as the library for the given element.
-  ///
-  /// Usable as a cross-check for dartdoc's canonicalization to generate
-  /// warnings for ModelElement.isPublicAndPackageDocumented.
-  bool packageDocumentedFor(ModelElement element) {
-    _allRootDirs ??= {
-      ...(publicLibraries.map((l) => l.packageMeta?.resolvedDir))
-    };
-    return _allRootDirs.contains(element.library.packageMeta?.resolvedDir);
-  }
-
   PackageWarningCounter get packageWarningCounter => _packageWarningCounter;
 
   final Set<Tuple3<Element, PackageWarning, String>> _warnAlreadySeen = {};

test/end2end/dartdoc_test.dart

@@ -206,10 +206,12 @@ void main() {
     });
 
     test('basic interlinking test', () async {
-      var dartdoc = await buildDartdoc([], _testPackageDir, tempDir);
+      var dartdoc = await buildDartdoc(
+          ['--exclude-packages=args'], _testPackageDir, tempDir);
       var results = await dartdoc.generateDocs();
       var p = results.packageGraph;
       var meta = p.publicPackages.firstWhere((p) => p.name == 'meta');
+      var args = p.publicPackages.firstWhere((p) => p.name == 'args');
       var useSomethingInAnotherPackage = p.publicLibraries
           .firstWhere((l) => l.name == 'fake')
           .properties
@@ -219,6 +221,7 @@ void main() {
           .properties
           .firstWhere((p) => p.name == 'useSomethingInTheSdk');
       expect(meta.documentedWhere, equals(DocumentLocation.remote));
+      expect(args.documentedWhere, equals(DocumentLocation.missing));
       expect(
           useSomethingInAnotherPackage.modelType.linkedName,
           matches(

test/end2end/model_test.dart

@@ -1513,7 +1513,7 @@ void main() {
     });
 
     test('correctly finds all the classes', () {
-      expect(classes, hasLength(37));
+      expect(classes, hasLength(38));
     });
 
     test('abstract', () {

testing/test_package/lib/example.dart

@@ -8,6 +8,7 @@ import 'dart:math';
 import 'src/mylib.dart' show Helper;
 import 'package:test_package_imported/main.dart';
 
+export 'package:args/args.dart' show ArgParser;
 export 'dart:core' show deprecated, Deprecated;
 import 'package:meta/meta.dart' show protected, factory;
 

tool/grind.dart

@@ -1106,8 +1106,6 @@ Future<WarningsCollection> _buildDartdocFlutterPluginDocs() async {
           [
             '--enable-asserts',
             path.join(Directory.current.path, 'bin', 'dartdoc.dart'),
-            '--exclude-packages',
-            'Dart', // TODO(jcollins-g): dart-lang/dartdoc#1431
             '--json',
             '--link-to-remote',
             '--output',