Allow searching and filtering on packages that are provided in the query

app/lib/search/mem_index.dart

@@ -207,6 +207,7 @@ class InMemoryPackageIndex {
     BitArray packages,
     IndexedScore<String> Function() scoreFn,
   ) {
+    _resetBitArray(packages, query.packages);
     final predicateFilterCount = _filterOnPredicates(query, packages);
     if (predicateFilterCount <= query.offset) {
       return PackageSearchResult.empty();
@@ -333,6 +334,21 @@ class InMemoryPackageIndex {
     );
   }
 
+  /// The [BitArrayPool] does not resets the reused pool items, because initialization
+  /// depends on the presence of the [filterOnPackages] list.
+  void _resetBitArray(BitArray selected, List<String>? filterOnPackages) {
+    if (filterOnPackages != null && filterOnPackages.isNotEmpty) {
+      selected.clearAll();
+      for (final package in filterOnPackages) {
+        final index = _nameToIndex[package];
+        if (index == null) continue;
+        selected.setBit(index);
+      }
+    } else {
+      selected.setRange(0, _documents.length);
+    }
+  }
+
   /// Returns the package name that is considered as the best name match
   /// for the [query], or `null` if there is no such package name, or the
   /// match is not enabled for the given context (e.g. non-default ordering).

app/lib/search/search_service.dart

@@ -211,6 +211,7 @@ class ServiceSearchQuery {
   int get offset => max(0, _data.offset ?? 0);
   int get limit => max(_minSearchLimit, _data.limit ?? 10);
   TextMatchExtent? get textMatchExtent => _data.textMatchExtent;
+  List<String>? get packages => _data.packages;
 
   Map<String, dynamic> toUriQueryParameters() {
     return _data.toUriQueryParameters();

app/lib/search/token_index.dart

@@ -249,10 +249,8 @@ class ScorePool<K> extends _AllocationPool<IndexedScore<K>> {
 class BitArrayPool extends _AllocationPool<BitArray> {
   BitArrayPool(int length)
       : super(
-          // sets all bits to 1
-          () => BitArray(length)..setRange(0, length),
-          // sets all bits to 1
-          (array) => array.setRange(0, length),
+          () => BitArray(length),
+          (array) {}, // keeping the array as-is, reset happens at the beginning of the processing
         );
 }
 

app/test/search/mem_index_test.dart

@@ -5,6 +5,7 @@
 import 'dart:convert';
 
 import 'package:_pub_shared/search/search_form.dart';
+import 'package:_pub_shared/search/search_request_data.dart';
 import 'package:clock/clock.dart';
 import 'package:pub_dev/search/mem_index.dart';
 import 'package:pub_dev/search/search_service.dart';
@@ -543,6 +544,27 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
           ServiceSearchQuery.parse(query: '=', order: SearchOrder.text));
       expect(rs.isEmpty, isTrue);
     });
+
+    test('only packages list filter', () {
+      final rs = index
+          .search(ServiceSearchQuery(SearchRequestData(packages: ['http'])));
+      expect(rs.packageHits.map((e) => e.package).toList(), ['http']);
+    });
+
+    test('query + packages list filter', () {
+      // library itself would return `http` too
+      final rs = index.search(ServiceSearchQuery(SearchRequestData(
+        query: 'library',
+        packages: ['async'],
+      )));
+      expect(rs.packageHits.map((e) => e.package).toList(), ['async']);
+    });
+
+    test('non-existent package name', () {
+      final rs = index.search(
+          ServiceSearchQuery(SearchRequestData(packages: ['not-a-package'])));
+      expect(rs.packageHits, isEmpty);
+    });
   });
 
   group('special cases', () {

pkg/_pub_shared/lib/search/search_request_data.dart

@@ -17,6 +17,7 @@ class SearchRequestData {
   final int? offset;
   final int? limit;
   final TextMatchExtent? textMatchExtent;
+  final List<String>? packages;
 
   SearchRequestData({
     String? query,
@@ -27,8 +28,10 @@ class SearchRequestData {
     this.offset,
     this.limit,
     this.textMatchExtent,
+    List<String>? packages,
   })  : query = _trimToNull(query),
-        publisherId = _trimToNull(publisherId);
+        publisherId = _trimToNull(publisherId),
+        packages = packages != null && packages.isNotEmpty ? packages : null;
 
   factory SearchRequestData.fromJson(Map<String, dynamic> json) =>
       _$SearchRequestDataFromJson(json);
@@ -54,6 +57,7 @@ class SearchRequestData {
         break;
       }
     }
+    final packages = uri.queryParametersAll['packages'];
 
     return SearchRequestData(
       query: q,
@@ -64,6 +68,7 @@ class SearchRequestData {
       offset: offset,
       limit: limit,
       textMatchExtent: textMatchExtent,
+      packages: packages,
     );
   }
 
@@ -78,6 +83,7 @@ class SearchRequestData {
       'limit': (limit ?? 10).toString(),
       'order': order?.name,
       if (textMatchExtent != null) 'textMatchExtent': textMatchExtent!.name,
+      if (packages != null && packages!.isNotEmpty) 'packages': packages,
     };
     map.removeWhere((k, v) => v == null);
     return map;