[dart2js] Remove deserializer 'emptyAsNull' pattern.

Change-Id: I5b5e668fa6c1c261503de55f70aab966ca9df66f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/338300
Reviewed-by: Mayank Patke <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>

Author: natebiggs

pkg/compiler/lib/src/common/codegen.dart

@@ -118,7 +118,7 @@ class _CodegenImpact extends WorldImpactBuilderImpl implements CodegenImpact {
     final typeVariableBoundsSubtypeChecks = source.readListOrNull(() {
       return Pair(source.readDartType(), source.readDartType());
     })?.toSet();
-    final constSymbols = source.readStrings(emptyAsNull: true)?.toSet();
+    final constSymbols = source.readStringsOrNull()?.toSet();
     final specializedGetInterceptors = source.readListOrNull(() {
       return source.readClasses().toSet();
     });

pkg/compiler/lib/src/elements/entities.dart

@@ -360,9 +360,9 @@ class ParameterStructure {
     source.begin(tag);
     int requiredPositionalParameters = source.readInt();
     int positionalParameters = source.readInt();
-    List<String> namedParameters = source.readStrings()!;
+    List<String> namedParameters = source.readStrings();
     Set<String> requiredNamedParameters =
-        source.readStrings(emptyAsNull: true)?.toSet() ?? const <String>{};
+        source.readStringsOrNull()?.toSet() ?? const <String>{};
     int typeParameters = source.readInt();
     source.end(tag);
     return ParameterStructure(

pkg/compiler/lib/src/ir/impact_data.dart

@@ -1562,7 +1562,7 @@ class _CallStructure {
     source.begin(tag);
     List<ir.DartType> typeArguments = source.readDartTypeNodes();
     int positionalArguments = source.readInt();
-    List<String> namedArguments = source.readStrings() ?? const [];
+    List<String> namedArguments = source.readStrings();
     source.end(tag);
     return _CallStructure.internal(
         typeArguments, positionalArguments, namedArguments);

pkg/compiler/lib/src/js_backend/native_data.dart

@@ -233,7 +233,7 @@ class NativeBasicData {
     bool isAllowInteropUsed = source.readBool();
     Map<ClassEntity, NativeClassTag> nativeClassTagInfo =
         source.readClassMap(() {
-      final names = source.readStrings()!;
+      final names = source.readStrings();
       bool isNonLeaf = source.readBool();
       return NativeClassTag.internal(names, isNonLeaf);
     });

pkg/compiler/lib/src/js_model/env.dart

@@ -258,7 +258,7 @@ class JClassEnvImpl implements JClassEnv {
     ir.Class cls = source.readClassNode();
     Map<String, ir.Member> constructorMap =
         source.readStringMap(source.readMemberNode);
-    Map<Name, ir.Member> memberMap = source.readNameMap(source.readMemberNode)!;
+    Map<Name, ir.Member> memberMap = source.readNameMap(source.readMemberNode);
     List<ir.Member> members = source.readMemberNodes();
     bool isSuperMixinApplication = source.readBool();
     source.end(tag);
@@ -330,7 +330,7 @@ class ContextEnv implements JClassEnv {
   factory ContextEnv.readFromDataSource(DataSourceReader source) {
     source.begin(tag);
     Map<Name, MemberEntity> _memberMap =
-        source.readNameMap(() => source.readMember())!;
+        source.readNameMap(() => source.readMember());
     source.end(tag);
     return ContextEnv(_memberMap);
   }
@@ -390,7 +390,7 @@ class ClosureClassEnv extends ContextEnv {
   factory ClosureClassEnv.readFromDataSource(DataSourceReader source) {
     source.begin(tag);
     Map<Name, MemberEntity> _memberMap =
-        source.readNameMap(() => source.readMember())!;
+        source.readNameMap(() => source.readMember());
     source.end(tag);
     return ClosureClassEnv(_memberMap);
   }
@@ -416,7 +416,7 @@ class RecordClassEnv implements JClassEnv {
   factory RecordClassEnv.readFromDataSource(DataSourceReader source) {
     source.begin(tag);
     Map<Name, MemberEntity> _memberMap =
-        source.readNameMap(() => source.readMember())!;
+        source.readNameMap(() => source.readMember());
     source.end(tag);
     return RecordClassEnv(_memberMap);
   }

pkg/compiler/lib/src/serialization/source.dart

@@ -271,12 +271,7 @@ class DataSourceReader {
   List<E>? readListOrNull<E>(E f()) {
     int count = readInt();
     if (count == 0) return null;
-    final first = f();
-    List<E> list = List<E>.filled(count, first);
-    for (int i = 1; i < count; i++) {
-      list[i] = f();
-    }
-    return list;
+    return List<E>.generate(count, (_) => f(), growable: false);
   }
 
   bool readBool() {
@@ -334,30 +329,32 @@ class DataSourceReader {
     return null;
   }
 
-  /// Reads a list of string values from this data source. If [emptyAsNull] is
-  /// `true`, `null` is returned instead of an empty list.
+  /// Reads a list of string values from this data source.
+  ///
+  /// This is a convenience method to be used together with
+  /// [DataSinkWriter.writeStrings].
+  List<String> readStrings() {
+    return readStringsOrNull() ?? const <String>[];
+  }
+
+  /// Reads a list of string values from this data source. If the list would be
+  /// empty returns `null` instead.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeStrings].
-  List<String>? readStrings({bool emptyAsNull = false}) {
+  List<String>? readStringsOrNull() {
     int count = readInt();
-    if (count == 0 && emptyAsNull) return null;
-    List<String> list = List<String>.filled(count, '');
-    for (int i = 0; i < count; i++) {
-      list[i] = readString();
-    }
-    return list;
+    if (count == 0) return null;
+    return List.generate(count, (_) => readString(), growable: false);
   }
 
   /// Reads a map from [Name] values to [V] values from this data source,
-  /// calling [f] to read each value from the data source. If [emptyAsNull] is
-  /// `true`, `null` is returned instead of an empty map.
+  /// calling [f] to read each value from the data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeNameMap].
-  Map<Name, V>? readNameMap<V>(V f(), {bool emptyAsNull = false}) {
+  Map<Name, V> readNameMap<V>(V f()) {
     int count = readInt();
-    if (count == 0 && emptyAsNull) return null;
     Map<Name, V> map = {};
     for (int i = 0; i < count; i++) {
       Name key = readMemberName();
@@ -368,8 +365,7 @@ class DataSourceReader {
   }
 
   /// Reads a map from string values to [V] values from this data source,
-  /// calling [f] to read each value from the data source. If [emptyAsNull] is
-  /// `true`, `null` is returned instead of an empty map.
+  /// calling [f] to read each value from the data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeStringMap].
@@ -625,8 +621,7 @@ class DataSourceReader {
   }
 
   /// Reads a map from kernel tree nodes to [V] values from this data source,
-  /// calling [f] to read each value from the data source. If [emptyAsNull] is
-  /// `true`, `null` is returned instead of an empty map.
+  /// calling [f] to read each value from the data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeTreeNodeMap].
@@ -667,21 +662,6 @@ class DataSourceReader {
     return null;
   }
 
-  /// Reads a list of references to kernel tree nodes in the known [context]
-  /// from this data source. If [emptyAsNull] is `true`, `null` is returned
-  /// instead of an empty list.
-  ///
-  /// This is a convenience method to be used together with
-  /// [DataSinkWriter.writeTreeNodesInContext].
-  List<E>? readTreeNodesInContext<E extends ir.TreeNode>(
-      {bool emptyAsNull = false}) {
-    int count = readInt();
-    if (count == 0 && emptyAsNull) return null;
-    return List<E>.generate(
-        count, (index) => readTreeNodeInContextInternal(currentMemberData) as E,
-        growable: false);
-  }
-
   /// Reads a map from kernel tree nodes to [V] values in the known [context]
   /// from this data source, calling [f] to read each value from the data
   /// source.
@@ -729,8 +709,7 @@ class DataSourceReader {
   }
 
   /// Reads a list of references to kernel type parameter nodes from this data
-  /// source. If [emptyAsNull] is `true`, `null` is returned instead of an empty
-  /// list.
+  /// source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeTypeParameterNodes].
@@ -1131,8 +1110,7 @@ class DataSourceReader {
   }
 
   /// Reads a map from type variable entities to [V] values from this data
-  /// source, calling [f] to read each value from the data source. If
-  /// [emptyAsNull] is `true`, `null` is returned instead of an empty map.
+  /// source, calling [f] to read each value from the data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeTypeVariableMap].
@@ -1178,8 +1156,7 @@ class DataSourceReader {
   }
 
   /// Reads a map from locals to [V] values from this data source, calling [f]
-  /// to read each value from the data source. If [emptyAsNull] is `true`,
-  /// `null` is returned instead of an empty map.
+  /// to read each value from the data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeLocalMap].
@@ -1295,8 +1272,7 @@ class DataSourceReader {
     return null;
   }
 
-  /// Reads a list of constant values from this data source. If [emptyAsNull] is
-  /// `true`, `null` is returned instead of an empty list.
+  /// Reads a list of constant values from this data source.
   ///
   /// This is a convenience method to be used together with
   /// [DataSinkWriter.writeConstants].

pkg/compiler/lib/src/universe/call_structure.dart

@@ -85,7 +85,7 @@ class CallStructure {
   factory CallStructure.readFromDataSource(DataSourceReader source) {
     source.begin(tag);
     int argumentCount = source.readInt();
-    List<String> namedArguments = source.readStrings()!;
+    List<String> namedArguments = source.readStrings();
     int typeArgumentCount = source.readInt();
     source.end(tag);
     return CallStructure(argumentCount, namedArguments, typeArgumentCount);

pkg/compiler/lib/src/universe/record_shape.dart

@@ -66,7 +66,7 @@ class RecordShape {
   factory RecordShape.readFromDataSource(DataSourceReader source) {
     source.begin(tag);
     int positionals = source.readInt();
-    List<String> names = source.readStrings()!;
+    List<String> names = source.readStrings();
     source.end(tag);
     return RecordShape(positionals, names);
   }