[dart2js_info] deduplicate holdings in JSON serialization

Reduces file size and makes scanning easier

Change-Id: I50af1bcc58670c25b77af4310c7455952778198e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/419781
Reviewed-by: Srujan Gaddam <[email protected]>
Auto-Submit: Kevin Moore <[email protected]>
Commit-Queue: Kevin Moore <[email protected]>

Author: kevmoo

pkg/dart2js_info/lib/json_info_codec.dart

@@ -440,29 +440,20 @@ class AllInfoToJsonConverter extends Converter<AllInfo, Map>
     };
   }
 
-  Map visitDependencyInfo(DependencyInfo info) => {
-    'id': idFor(info.target).serializedId,
-    if (info.mask != null) 'mask': info.mask,
-  };
+  Map visitDependencyInfo(DependencyInfo info) =>
+      _createFromDepInfo(info).toJson();
+
+  _InfoClass _createFromDepInfo(DependencyInfo info) =>
+      _InfoClass._(idFor(info.target).serializedId, info.mask);
 
   Map _visitAllInfoHolding(AllInfo allInfo) {
-    var map = SplayTreeMap<String, List>(compareNatural);
+    var map = SplayTreeMap<String, List<Map<String, dynamic>>>(compareNatural);
     void helper(CodeInfo info) {
       if (info.uses.isEmpty) return;
       map[idFor(info).serializedId] =
-          info.uses.map(visitDependencyInfo).toList()..sort((a, b) {
-            final value = a['id'].compareTo(b['id']);
-            if (value != 0) return value;
-            final aMask = a['mask'] as String?;
-            final bMask = b['mask'] as String?;
-            if (aMask == null) {
-              return bMask == null ? 0 : 1;
-            }
-            if (bMask == null) {
-              return -1;
-            }
-            return aMask.compareTo(bMask);
-          });
+          SplayTreeSet.of(
+            info.uses.map(_createFromDepInfo),
+          ).map((e) => e.toJson()).toList();
     }
 
     allInfo.functions.forEach(helper);
@@ -675,3 +666,33 @@ class Id {
 
   String get serializedId => '${kindToString(kind)}/$id';
 }
+
+/// Represents the serialization information of [DependencyInfo] with equality
+/// and comparison implemented.
+final class _InfoClass implements Comparable<_InfoClass> {
+  final String id;
+  final String? mask;
+
+  _InfoClass._(this.id, this.mask);
+
+  Map<String, dynamic> toJson() => {'id': id, if (mask != null) 'mask': mask};
+
+  @override
+  int compareTo(_InfoClass other) {
+    final value = id.compareTo(other.id);
+    if (value != 0) {
+      return value;
+    }
+
+    final myMask = mask, otherMask = other.mask;
+
+    if (myMask == null) {
+      return otherMask == null ? 0 : 1;
+    }
+    if (otherMask == null) {
+      return -1;
+    }
+
+    return myMask.compareTo(otherMask);
+  }
+}