[dart2js] Remove '--no-sound-null-safety' flag and make '--sound-null-safety' flag a no-op with warning.

Change-Id: I0225f9306aa2a84494f3fc17c9f7191214404249
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406081
Reviewed-by: Ivan Inozemtsev <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Bob Nystrom <[email protected]>
Reviewed-by: Mayank Patke <[email protected]>

Author: natebiggs

pkg/compiler/lib/src/commandline_options.dart

@@ -134,7 +134,7 @@ class Flags {
   static const String serverMode = '--server-mode';
 
   static const String soundNullSafety = '--sound-null-safety';
-  static const String noSoundNullSafety = '--no-sound-null-safety';
+
   static const String mergeFragmentsThreshold = '--merge-fragments-threshold';
 
   static const String writeResources = '--write-resources';

pkg/compiler/lib/src/dart2js.dart

@@ -359,15 +359,6 @@ Future<api.CompilationResult> compile(
     );
   }
 
-  String? nullSafetyMode;
-  void setNullSafetyMode(String argument) {
-    if (nullSafetyMode != null && nullSafetyMode != argument) {
-      _helpAndFail("Cannot specify both $nullSafetyMode and $argument.");
-    }
-    nullSafetyMode = argument;
-    passThrough(argument);
-  }
-
   void setInvoker(String argument) {
     invoker = extractParameter(argument);
   }
@@ -525,8 +516,7 @@ Future<api.CompilationResult> compile(
     _OneOption(Flags.enableProtoShaking, passThrough),
     _OneOption(Flags.benchmarkingProduction, passThrough),
     _OneOption(Flags.benchmarkingExperiment, passThrough),
-    _OneOption(Flags.soundNullSafety, setNullSafetyMode),
-    _OneOption(Flags.noSoundNullSafety, setNullSafetyMode),
+    _OneOption(Flags.soundNullSafety, passThrough),
     _OneOption(Flags.dumpUnusedLibraries, passThrough),
     _OneOption(Flags.writeResources, passThrough),
 
@@ -597,18 +587,6 @@ Future<api.CompilationResult> compile(
 
   parseCommandLine(handlers, argv);
 
-  if (nullSafetyMode == Flags.noSoundNullSafety && platformBinaries == null) {
-    // Compiling without sound null safety is no longer allowed except in the
-    // cases where an unsound platform .dill file is manually provided.
-    // The unsound .dills are no longer packaged in the SDK release so any
-    // compile initiated through `dart compile js --no-sound-null-safety`
-    // will not find a .dill in the default location and should be prevented
-    // from executing.
-    _fail(
-      'the flag --no-sound-null-safety is not supported in Dart 3.\n'
-      'See: https://dart.dev/null-safety.',
-    );
-  }
   final diagnostic = diagnosticHandler = FormattingDiagnosticHandler();
   if (verbose != null) {
     diagnostic.verbose = verbose!;
@@ -644,6 +622,14 @@ Future<api.CompilationResult> compile(
     );
   }
 
+  if (options.contains(Flags.soundNullSafety)) {
+    warning(
+      "Option '${Flags.soundNullSafety}' is deprecated. As of Dart 3, Dart "
+      "only supports sound null safety. This flag will be removed in a future "
+      "version of Dart.",
+    );
+  }
+
   for (String hint in hints) {
     diagnostic.info(hint, api.Diagnostic.hint);
   }

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart

@@ -401,7 +401,6 @@ class ModelEmitter {
   /// Generates a simple header that provides the compiler's build id.
   js.Comment buildGeneratedBy() {
     final flavor = StringBuffer();
-    flavor.write(_options.nullSafetyMode);
     if (_options.trustPrimitives) flavor.write(', trust primitives');
     if (_options.omitImplicitChecks) flavor.write(', omit checks');
     if (_options.laxRuntimeTypeToString) {

pkg/compiler/lib/src/options.dart

@@ -11,8 +11,6 @@ import 'package:front_end/src/api_unstable/dart2js.dart' as fe;
 import 'commandline_options.dart' show Flags;
 import 'util/util.dart';
 
-enum NullSafetyMode { unsound, sound }
-
 enum FeatureStatus { shipped, shipping, canary }
 
 enum CompilerPhase {
@@ -534,13 +532,6 @@ class CompilerOptions implements DiagnosticOptions {
   /// Whether to generate code containing user's `assert` statements.
   bool enableUserAssertions = false;
 
-  /// Whether to generate code asserting that non-nullable parameters in opt-in
-  /// code are not null. In mixed mode code (some opting into non-nullable, some
-  /// not), null-safety is unsound, allowing `null` values to be assigned to
-  /// variables with non-nullable types. This assertion lets the opt-in code
-  /// operate with a stronger guarantee.
-  bool enableNullAssertions = false;
-
   /// Whether to generate code asserting that non-nullable return values of
   /// `@Native` methods or `JS()` invocations are checked for being non-null.
   /// Emits checks only in sound null-safety.
@@ -678,22 +669,10 @@ class CompilerOptions implements DiagnosticOptions {
   /// migrated to null safety (but before sound null safety is enabled).
   bool experimentNullSafetyChecks = false;
 
-  /// Whether the compiler should emit code with unsound or sound semantics.
-  /// Since Dart 3.0 this is no longer inferred from sources, but defaults to
-  /// sound semantics.
-  ///
-  /// This option should rarely need to be accessed directly. Consider using
-  /// [useLegacySubtyping] instead.
-  NullSafetyMode nullSafetyMode = NullSafetyMode.sound;
-  bool _soundNullSafety = false;
-  bool _noSoundNullSafety = false;
-
   /// Whether to use legacy subtype semantics rather than null-safe semantics.
   /// This is `true` if unsound null-safety semantics are being used, since
   /// dart2js does not emit warnings for unsound null-safety.
-  bool get useLegacySubtyping {
-    return nullSafetyMode == NullSafetyMode.unsound;
-  }
+  bool get useLegacySubtyping => false;
 
   /// If specified, a bundle of optimizations to enable (or disable).
   int? optimizationLevel;
@@ -937,9 +916,6 @@ class CompilerOptions implements DiagnosticOptions {
       ..enableUserAssertions =
           _hasOption(options, Flags.enableCheckedMode) ||
           _hasOption(options, Flags.enableAsserts)
-      ..enableNullAssertions =
-          _hasOption(options, Flags.enableCheckedMode) ||
-          _hasOption(options, Flags.enableNullAssertions)
       ..nativeNullAssertions = _hasOption(options, Flags.nativeNullAssertions)
       .._noNativeNullAssertions = _hasOption(
         options,
@@ -1014,8 +990,6 @@ class CompilerOptions implements DiagnosticOptions {
       .._cfeOnly = _hasOption(options, Flags.cfeOnly)
       .._stageFlag = _extractStringOption(options, '${Flags.stage}=', null)
       ..debugGlobalInference = _hasOption(options, Flags.debugGlobalInference)
-      .._soundNullSafety = _hasOption(options, Flags.soundNullSafety)
-      .._noSoundNullSafety = _hasOption(options, Flags.noSoundNullSafety)
       .._mergeFragmentsThreshold = _extractIntOption(
         options,
         '${Flags.mergeFragmentsThreshold}=',
@@ -1094,12 +1068,6 @@ class CompilerOptions implements DiagnosticOptions {
         equalMaps(experimentalFlags, fe.defaultExperimentalFlags)) {
       throw ArgumentError("Missing required ${Flags.platformBinaries}");
     }
-    if (_soundNullSafety && _noSoundNullSafety) {
-      throw ArgumentError(
-        "'${Flags.soundNullSafety}' is incompatible with "
-        "'${Flags.noSoundNullSafety}'",
-      );
-    }
     if (nativeNullAssertions && _noNativeNullAssertions) {
       throw ArgumentError(
         "'${Flags.nativeNullAssertions}' is incompatible with "
@@ -1112,7 +1080,7 @@ class CompilerOptions implements DiagnosticOptions {
         "'${Flags.noInteropNullAssertions}'",
       );
     }
-    if (nullSafetyMode == NullSafetyMode.sound && experimentNullSafetyChecks) {
+    if (experimentNullSafetyChecks) {
       throw ArgumentError(
         '${Flags.experimentNullSafetyChecks} is incompatible '
         'with sound null safety.',
@@ -1135,9 +1103,6 @@ class CompilerOptions implements DiagnosticOptions {
       features.forceCanary();
     }
 
-    if (_soundNullSafety) nullSafetyMode = NullSafetyMode.sound;
-    if (_noSoundNullSafety) nullSafetyMode = NullSafetyMode.unsound;
-
     if (optimizationLevel != null) {
       if (optimizationLevel == 0) {
         disableInlining = true;
@@ -1187,12 +1152,7 @@ class CompilerOptions implements DiagnosticOptions {
       omitLateNames = false;
     }
 
-    if (nullSafetyMode != NullSafetyMode.sound) {
-      // Technically, we should still assert if the user passed in a flag to
-      // assert, but this was not the behavior before, so to avoid a breaking
-      // change, we don't assert in unsound mode.
-      nativeNullAssertions = false;
-    } else if (_noNativeNullAssertions) {
+    if (_noNativeNullAssertions) {
       // Never assert if the user tells us not to.
       nativeNullAssertions = false;
     } else if (!nativeNullAssertions &&

pkg/compiler/lib/src/phase/load_kernel.dart

@@ -234,19 +234,6 @@ Future<_LoadFromKernelResult> _loadFromKernel(
 
   await read(resolvedUri);
 
-  var isStrongDill =
-      component.mode == ir.NonNullableByDefaultCompiledMode.Strong;
-  var incompatibleNullSafetyMode =
-      isStrongDill ? NullSafetyMode.unsound : NullSafetyMode.sound;
-  if (options.nullSafetyMode == incompatibleNullSafetyMode) {
-    var dillMode = isStrongDill ? 'sound' : 'unsound';
-    var option = isStrongDill ? Flags.noSoundNullSafety : Flags.soundNullSafety;
-    throw ArgumentError(
-      "$resolvedUri was compiled with $dillMode null "
-      "safety and is incompatible with the '$option' option",
-    );
-  }
-
   if (options.platformBinaries != null &&
       options.stage.shouldReadPlatformBinaries) {
     var platformUri = options.platformBinaries?.resolve(
@@ -294,9 +281,7 @@ Future<_LoadFromSourceResult> _loadFromSource(
   Map<String, String>? environment = cfeConstants ? options.environment : null;
   Target target = Dart2jsTarget(
     targetName,
-    TargetFlags(
-      soundNullSafety: options.nullSafetyMode == NullSafetyMode.sound,
-    ),
+    TargetFlags(),
     options: options,
     supportsUnevaluatedConstants: !cfeConstants,
   );
@@ -333,14 +318,12 @@ Future<_LoadFromSourceResult> _loadFromSource(
           '${Flags.experimentNullSafetyChecks}.',
     });
   }
-  if (isLegacy && options.nullSafetyMode == NullSafetyMode.sound) {
+  if (isLegacy) {
     reporter.reportErrorMessage(noLocationSpannable, MessageKind.generic, {
       'text':
           "Starting with Dart 3.0, `dart compile js` expects programs to "
           "be null-safe by default. Some libraries reached from $resolvedUri "
-          "are opted out of null safety. You can temporarily compile this "
-          "application using the deprecated '${Flags.noSoundNullSafety}' "
-          "option.",
+          "are opted out of null safety.",
     });
   }
 

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

@@ -10,7 +10,6 @@ import 'package:kernel/binary/ast_from_binary.dart' as ir;
 import 'package:kernel/binary/ast_to_binary.dart' as ir;
 
 import '../../compiler_api.dart' as api;
-import '../commandline_options.dart' show Flags;
 import '../common/codegen.dart';
 import '../common/tasks.dart';
 import '../deferred_load/output_unit.dart';
@@ -97,31 +96,8 @@ class SerializationTask extends CompilerTask {
     });
   }
 
-  void updateOptionsFromComponent(ir.Component component) {
-    var isStrongDill =
-        component.mode == ir.NonNullableByDefaultCompiledMode.Strong;
-    var incompatibleNullSafetyMode =
-        isStrongDill ? NullSafetyMode.unsound : NullSafetyMode.sound;
-    if (_options.nullSafetyMode == incompatibleNullSafetyMode) {
-      var dillMode = isStrongDill ? 'sound' : 'unsound';
-      var option =
-          isStrongDill ? Flags.noSoundNullSafety : Flags.soundNullSafety;
-      throw ArgumentError(
-        "${_options.inputDillUri} was compiled with "
-        "$dillMode null safety and is incompatible with the '$option' "
-        "option",
-      );
-    }
-
-    _options.nullSafetyMode =
-        component.mode == ir.NonNullableByDefaultCompiledMode.Strong
-            ? NullSafetyMode.sound
-            : NullSafetyMode.unsound;
-  }
-
   Future<ir.Component> deserializeComponentAndUpdateOptions() async {
     ir.Component component = await deserializeComponent();
-    updateOptionsFromComponent(component);
     return component;
   }
 

pkg/compiler/lib/src/ssa/builder.dart

@@ -2065,7 +2065,6 @@ class KernelSsaGraphBuilder extends ir.VisitorDefault<void>
     HInstruction value,
     DartType type,
   ) {
-    if (!options.enableNullAssertions) return value;
     if (!dartTypes.isNonNullableIfSound(type)) return value;
 
     // `operator==` is usually augmented to handle a `null`-argument before this

pkg/compiler/test/dump_info/data/deferred/main.dart

@@ -105,7 +105,7 @@
   "id": "outputUnit/1",
   "kind": "outputUnit",
   "name": "1",
-  "size": 1204,
+  "size": 1184,
   "filename": "out_1.part.js",
   "imports": [
     "lib"
@@ -223,7 +223,7 @@
   "id": "outputUnit/1",
   "kind": "outputUnit",
   "name": "1",
-  "size": 1204,
+  "size": 1184,
   "filename": "out_1.part.js",
   "imports": [
     "lib"

pkg/compiler/test/dump_info/data/deferred_future/main.dart

@@ -113,7 +113,7 @@
   "id": "outputUnit/1",
   "kind": "outputUnit",
   "name": "1",
-  "size": 928,
+  "size": 908,
   "filename": "out_1.part.js",
   "imports": [
     "lib1"

pkg/compiler/test/end_to_end/modular_loader_test.dart

@@ -48,7 +48,6 @@ main() {
       options: [
         '--input-dill=memory:c.dill',
         '--dill-dependencies=memory:a.dill,memory:b.dill,memory:unused.dill',
-        '--sound-null-safety',
       ],
       memorySourceFiles: {
         'a.dill': aDill,