[ddc] Add option to throw null safety violations

Allows sound-like null safety when running mixed applications in weak
mode.

This is not a specified option and is only intended to assist large
scale migration efforts.

Change-Id: Icd0abb0e876d16e719a01e8381eef55a2b511051
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/171821
Commit-Queue: Nicholas Shahan <nshahan@google.com>
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Reviewed-by: Mark Zhou <markzipan@google.com>

pkg/dev_compiler/tool/ddb

@@ -49,18 +49,18 @@ void main(List<String> args) async {
     ..addFlag('sound-null-safety',
         help: 'Compile for sound null safety at runtime. Passed through to the '
             'DDC binary. Defaults to false.',
-        defaultsTo: false,
-        negatable: true)
+        defaultsTo: false)
     ..addFlag('null-assertions',
         help: 'Run with assertions that values passed to non-nullable method '
             'parameters are not null.',
-        defaultsTo: false,
-        negatable: true)
+        defaultsTo: false)
     ..addFlag('native-null-assertions',
         help: 'Run with assertions on non-nullable values returned from native '
             'APIs.',
         defaultsTo: true,
         negatable: true)
+    ..addFlag('weak-null-safety-errors',
+        help: 'Treat weak null safety warnings as errors.', defaultsTo: false)
     ..addFlag('observe',
         help:
             'Run the compiler in the Dart VM with --observe. Implies --debug.',
@@ -86,7 +86,6 @@ void main(List<String> args) async {
         abbr: 'v',
         help: 'Echos the commands, arguments, and environment this script is '
             'running.',
-        negatable: false,
         defaultsTo: false)
     ..addOption('vm-service-port',
         help: 'Specify the observatory port. Implied --observe.');
@@ -115,19 +114,10 @@ void main(List<String> args) async {
   var compile = mode == 'compile' || mode == 'all';
   var run = mode == 'run' || mode == 'all';
   var verbose = options['verbose'] as bool;
+  var soundNullSafety = options['sound-null-safety'] as bool;
   var nonNullAsserts = options['null-assertions'] as bool;
   var nativeNonNullAsserts = options['null-assertions'] as bool;
-
-  var soundNullSafety = options['sound-null-safety'] as bool;
-  // Enable null safety either by passing the `non-nullable` experiment flag or
-  // `sound-null-safety`.
-  var nnbd = experiments.contains('non-nullable') || soundNullSafety;
-
-  // Ensure non-nullable is passed as a flag.
-  if (soundNullSafety && !experiments.contains('non-nullable')) {
-    experiments.add('non-nullable');
-  }
-
+  var weakNullSafetyErrors = options['weak-null-safety-errors'] as bool;
   var entry = p.canonicalize(options.rest.first);
   var out = (options['out'] as String) ?? p.setExtension(entry, '.js');
   var libRoot = p.dirname(entry);
@@ -275,11 +265,12 @@ void main(List<String> args) async {
   require(['dart_sdk', '$basename'],
         function(sdk, app) {
     'use strict';
-    if ($nnbd) {
-      sdk.dart.weakNullSafetyWarnings(!$soundNullSafety);
-      sdk.dart.nonNullAsserts($nonNullAsserts);
-      sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
-    }
+
+    sdk.dart.weakNullSafetyWarnings(
+        !($weakNullSafetyErrors || $soundNullSafety));
+    sdk.dart.weakNullSafetyErrors($weakNullSafetyErrors);
+    sdk.dart.nonNullAsserts($nonNullAsserts);
+    sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
     sdk._debugger.registerDevtoolsFormatter();
     app.$libname.main([]);
   });
@@ -311,11 +302,11 @@ let sdk = require(\"dart_sdk\");
 sdk.dart.global.self = sdk.dart.global;
 let main = require(\"./$basename\").$libname.main;
 try {
-  if ($nnbd) {
-    sdk.dart.weakNullSafetyWarnings(!$soundNullSafety);
-    sdk.dart.nonNullAsserts($nonNullAsserts);
-    sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
-  }
+  sdk.dart.weakNullSafetyWarnings(
+      !($weakNullSafetyErrors || $soundNullSafety));
+  sdk.dart.weakNullSafetyErrors($weakNullSafetyErrors);
+  sdk.dart.nonNullAsserts($nonNullAsserts);
+  sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
   sdk._isolate_helper.startRootIsolate(main, []);
 } catch(e) {
   if (!source_maps) {
@@ -346,14 +337,14 @@ load("$ddcPath/lib/js/legacy/dart_library.js");
 load("$sdkJsPath/dart_sdk.js");
 load("$out");
 
-let dart_sdk = dart_library.import('dart_sdk');
+let sdk = dart_library.import('dart_sdk');
 // Create a self reference for JS interop tests that set fields on self.
-dart_sdk.dart.global.self = dart_sdk.dart.global;
-if ($nnbd) {
-  dart_sdk.dart.weakNullSafetyWarnings(!$soundNullSafety);
-  dart_sdk.dart.nonNullAsserts($nonNullAsserts);
-  dart_sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
-}
+sdk.dart.global.self = sdk.dart.global;
+sdk.dart.weakNullSafetyWarnings(
+    !($weakNullSafetyErrors || $soundNullSafety));
+sdk.dart.weakNullSafetyErrors($weakNullSafetyErrors);
+sdk.dart.nonNullAsserts($nonNullAsserts);
+sdk.dart.nativeNonNullAsserts($nativeNonNullAsserts);
 dart_library.start('$basename', '$libname');
 ''';
       var d8File = p.setExtension(out, '.d8.js');

pkg/test_runner/lib/src/browser.dart

@@ -147,9 +147,16 @@ bool _invalidVariableName(String keyword, {bool strictMode = true}) {
 /// [testJSDir] is the relative path to the build directory where the
 /// dartdevc-generated JS file is stored. [nonNullAsserts] enables non-null
 /// assertions for non-nullable method parameters when running with weak null
-/// safety.
-String dartdevcHtml(String testName, String testNameAlias, String testJSDir,
-    Compiler compiler, NnbdMode mode, bool nonNullAsserts) {
+/// safety. [weakNullSafetyErrors] enables null safety type violations to throw
+/// when running in weak mode.
+String dartdevcHtml(
+    String testName,
+    String testNameAlias,
+    String testJSDir,
+    Compiler compiler,
+    NnbdMode mode,
+    bool nonNullAsserts,
+    bool weakNullSafetyErrors) {
   var testId = pathToJSIdentifier(testName);
   var testIdAlias = pathToJSIdentifier(testNameAlias);
   var isNnbd = mode != NnbdMode.legacy;
@@ -233,7 +240,8 @@ requirejs(["$testName", "dart_sdk", "async_helper"],
   };
 
   if ($isNnbd) {
-    sdk.dart.weakNullSafetyWarnings(!$isNnbdStrong);
+    sdk.dart.weakNullSafetyWarnings(!($weakNullSafetyErrors || $isNnbdStrong));
+    sdk.dart.weakNullSafetyErrors($weakNullSafetyErrors);
     sdk.dart.nonNullAsserts($nonNullAsserts);
   }
 

pkg/test_runner/lib/src/test_suite.dart

@@ -925,8 +925,16 @@ class StandardTestSuite extends TestSuite {
             Path(compilationTempDir).relativeTo(Repository.dir).toString();
         var nullAssertions =
             testFile.sharedOptions.contains('--null-assertions');
-        content = dartdevcHtml(nameNoExt, nameFromModuleRootNoExt, jsDir,
-            configuration.compiler, configuration.nnbdMode, nullAssertions);
+        var weakNullSafetyErrors =
+            testFile.ddcOptions.contains('--weak-null-safety-errors');
+        content = dartdevcHtml(
+            nameNoExt,
+            nameFromModuleRootNoExt,
+            jsDir,
+            configuration.compiler,
+            configuration.nnbdMode,
+            nullAssertions,
+            weakNullSafetyErrors);
       }
     }
 

sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart

@@ -12,26 +12,49 @@ part of dart._runtime;
 @notNull
 external bool compileTimeFlag(String flag);
 
-_throwNullSafetyWarningError() => throw UnsupportedError(
-    'Null safety errors cannot be shown as warnings when running with sound '
-    'null safety.');
+_throwInvalidFlagError(String message) =>
+    throw UnsupportedError('Invalid flag combination.\n$message');
 
 @notNull
 bool _weakNullSafetyWarnings = false;
 
-/// Sets the runtime mode to show warnings when running with weak null safety.
+/// Sets the runtime mode to show warnings when types violate sound null safety.
 ///
-/// These are warnings for issues that will become errors when sound null safety
-/// is enabled. Showing warnings while running with sound null safety is not
-/// supported (they will be errors).
+/// This option is not compatible with weak null safety errors or sound null
+/// safety (the warnings will be errors).
 void weakNullSafetyWarnings(bool showWarnings) {
   if (showWarnings && compileTimeFlag('soundNullSafety')) {
-    _throwNullSafetyWarningError();
+    _throwInvalidFlagError(
+        'Null safety violations cannot be shown as warnings when running with '
+        'sound null safety.');
   }
 
   _weakNullSafetyWarnings = showWarnings;
 }
 
+@notNull
+bool _weakNullSafetyErrors = false;
+
+/// Sets the runtime mode to throw errors when types violate sound null safety.
+///
+/// This option is not compatible with weak null safety warnings (the warnings
+/// are now errors) or sound null safety (the errors are already errors).
+void weakNullSafetyErrors(bool showErrors) {
+  if (showErrors && compileTimeFlag('soundNullSafety')) {
+    _throwInvalidFlagError(
+        'Null safety violations are already thrown as errors when running with '
+        'sound null safety.');
+  }
+
+  if (showErrors && _weakNullSafetyWarnings) {
+    _throwInvalidFlagError(
+        'Null safety violations can be shown as warnings or thrown as errors, '
+        'not both.');
+  }
+
+  _weakNullSafetyErrors = showErrors;
+}
+
 @notNull
 bool _nonNullAsserts = false;
 
@@ -250,10 +273,12 @@ void _warn(arg) {
   JS('void', 'console.warn(#)', arg);
 }
 
-void _nullWarn(arg) {
+void _nullWarn(message) {
   if (_weakNullSafetyWarnings) {
-    _warn('$arg\n'
+    _warn('$message\n'
         'This will become a failure when runtime null safety is enabled.');
+  } else if (_weakNullSafetyErrors) {
+    throw TypeErrorImpl(message);
   }
 }
 

tests/dartdevc/weak_null_safety_errors_test.dart

@@ -0,0 +1,17 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Requirements=nnbd-weak
+
+// dartdevcOptions=--weak-null-safety-errors
+
+import 'package:expect/expect.dart';
+
+void main() {
+  Expect.throwsTypeError(() => null as int);
+  dynamic dynamicNull = null;
+  Expect.throwsTypeError(() => fn(dynamicNull));
+}
+
+void fn(StringBuffer arg) {}