io: Tidy fields in network_profiling to be final and non-nullable

The fields for `_SocketStatistic` were added one-by-one, but AFAICT,
the object is always created with an id, startTime, socketType, address, and port, all in one go. We can set those in the constructor (making
the fields non-null, and making them final); they don't need to go
through `collectStatistic`.

This has another benefit of allowing us to collect the fields in
`toMap` without checking nullability.

This change is a no-op.

Change-Id: Ic9ae2972ed3abb4c0bfe38f4a3c02c7f5f4175b9
CoreLibraryReviewExempt: No API changes.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/408402
Reviewed-by: Ben Konyi <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

sdk/lib/io/network_profiling.dart

@@ -244,51 +244,43 @@ abstract class _SocketProfile {
     InternetAddress addr,
     int port,
   ) {
-    _SocketProfile.collectStatistic(id, _SocketProfileType.startTime);
-    _SocketProfile.collectStatistic(id, _SocketProfileType.socketType, type);
-    _SocketProfile.collectStatistic(id, _SocketProfileType.address, addr);
-    _SocketProfile.collectStatistic(id, _SocketProfileType.port, port);
+    if (!_enableSocketProfiling) {
+      return;
+    }
+    // TODO(srawlins): Assert that `_idToSocketStatistic` does not contain
+    // `id.toString()`?
+    final address =
+        (addr.type == InternetAddress.anyIPv6 ||
+                addr.type == InternetAddress.loopbackIPv6)
+            ? '[${addr.address}]'
+            : addr.address;
+    _SocketStatistic(
+      id.toString(),
+      startTime: Timeline.now,
+      socketType: type,
+      address: address,
+      port: port,
+    );
   }
 
   static void collectStatistic(
     int id,
     _SocketProfileType type, [
-    dynamic object,
+    Object? object,
   ]) {
     final idKey = id.toString();
     if (!_enableSocketProfiling) {
       return;
     }
-    // Skip socket that started before _enableSocketProfiling turned on.
-    if (!_idToSocketStatistic.containsKey(idKey) &&
-        type != _SocketProfileType.startTime)
-      return;
-    _SocketStatistic stats =
-        _idToSocketStatistic[idKey] ??= _SocketStatistic(idKey);
+    // Skip any socket that started before `_enableSocketProfiling` was turned
+    // on.
+    final stats = _idToSocketStatistic[idKey];
+    assert(stats != null, '"$idKey" not found in "_idToSocketStatistic" map');
+    if (stats == null) return;
     switch (type) {
-      case _SocketProfileType.startTime:
-        stats.startTime = Timeline.now;
-        break;
       case _SocketProfileType.endTime:
         stats.endTime = Timeline.now;
         break;
-      case _SocketProfileType.address:
-        assert(object is InternetAddress);
-        final internetAddress = object as InternetAddress;
-        stats.address =
-            (internetAddress.type == InternetAddress.anyIPv6 ||
-                    internetAddress.type == InternetAddress.loopbackIPv6)
-                ? '[${internetAddress.address}]'
-                : internetAddress.address;
-        break;
-      case _SocketProfileType.port:
-        assert(object is int);
-        stats.port = object;
-        break;
-      case _SocketProfileType.socketType:
-        assert(object is String);
-        stats.socketType = object;
-        break;
       case _SocketProfileType.readBytes:
         if (object == null) return;
         stats.readBytes += object as int;
@@ -299,8 +291,13 @@ abstract class _SocketProfile {
         stats.writeBytes += object as int;
         stats.lastWriteTime = Timeline.now;
         break;
-      default:
-        throw ArgumentError('type ${type} does not exist');
+      case _SocketProfileType.startTime:
+      case _SocketProfileType.socketType:
+      case _SocketProfileType.address:
+      case _SocketProfileType.port:
+        throw ArgumentError(
+          'The "${type}" type can only be set on initialization',
+        );
     }
   }
 
@@ -336,25 +333,34 @@ enum _SocketProfileType {
 /// Socket statistic
 class _SocketStatistic {
   final String id;
-  int? startTime;
+  final int startTime;
   int? endTime;
-  String? address;
-  int? port;
-  String? socketType;
+  final String address;
+  final int port;
+  final String socketType;
   int readBytes = 0;
   int writeBytes = 0;
   int? lastWriteTime;
   int? lastReadTime;
 
-  _SocketStatistic(this.id);
+  _SocketStatistic(
+    this.id, {
+    required this.startTime,
+    required this.socketType,
+    required this.address,
+    required this.port,
+  });
 
   Map<String, dynamic> toMap() {
-    final map = <String, dynamic>{'id': id};
-    _setIfNotNull(map, 'startTime', startTime);
+    final map = <String, Object>{
+      'id': id,
+      'startTime': startTime,
+      'address': address,
+      'port': port,
+      'socketType': socketType,
+    };
+    // TODO(srawlins): Replace with null-aware elements.
     _setIfNotNull(map, 'endTime', endTime);
-    _setIfNotNull(map, 'address', address);
-    _setIfNotNull(map, 'port', port);
-    _setIfNotNull(map, 'socketType', socketType);
     _setIfNotNull(map, 'readBytes', readBytes);
     _setIfNotNull(map, 'writeBytes', writeBytes);
     _setIfNotNull(map, 'lastWriteTime', lastWriteTime);