Revert "[dart:html] Throw exception if Window.open opens null window"

This reverts commit a356f71b71.

Reason for revert: This should be handled by throwing an exception when
the methods of the returned window are called, not when it is opened.
This would be a noisy breaking change that we don't want for 3.1. For
now, revert until the change that affects the individual methods is
landed.

Original change's description:
> [dart:html] Throw exception if Window.open opens null window
>
> Window.open silently allows a null window to be opened, and
> issues arise later when users try to use the non-null wrapper.
> This CL changes that to throw an exception if the window is null.
> This exception can be caught and recovered from. This avoids the
> larger breaking change of making this API nullable.
>
> CoreLibraryReviewExempt: Backend-specific library.
> Change-Id: I9a53a477cb370c3bc6bc26b2162ce66c5af166aa
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/306910
> Reviewed-by: Sigmund Cherem <sigmund@google.com>
> Commit-Queue: Srujan Gaddam <srujzs@google.com>

CoreLibraryReviewExempt: Revert in backend-specific library.
Change-Id: I5007b7d7aa608bfc8e5827b5f967af5573d0b758
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/309000
Commit-Queue: Srujan Gaddam <srujzs@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>

CHANGELOG.md

@@ -36,14 +36,6 @@
 [#51486]: https://github.com/dart-lang/sdk/issues/51486
 [#52027]: https://github.com/dart-lang/sdk/issues/52027
 
-#### `dart:html`
-
-- **Breaking change to Window.open**:
-  `Window.open` will now throw an exception that can be caught
-  (`NullWindowException`) if the opened window is null. Previously, this null
-  window would be wrapped, and there would be surprising runtime errors when any
-  member is used on the wrapper.
-
 #### `dart:js_interop`
 
 - **Object literal constructors**:

sdk/lib/html/dart2js/html_dart2js.dart

@@ -32154,18 +32154,17 @@ class Window extends EventTarget
   /**
    * Opens a new window.
    *
-   * Throws a NullWindowException if the opened window is null.
-   *
    * ## Other resources
    *
    * * [Window.open](https://developer.mozilla.org/en-US/docs/Web/API/Window.open)
    *   from MDN.
    */
   WindowBase open(String url, String name, [String? options]) {
-    final win =
-        options == null ? _open2(url, name) : _open3(url, name, options);
-    if (win == null) throw new NullWindowException();
-    return _DOMWindowCrossFrame._createSafe(win);
+    if (options == null) {
+      return _DOMWindowCrossFrame._createSafe(_open2(url, name));
+    } else {
+      return _DOMWindowCrossFrame._createSafe(_open3(url, name, options));
+    }
   }
 
   // API level getter and setter for Location.
@@ -33778,13 +33777,6 @@ class Window extends EventTarget
       ? JS<num>('num', '#.scrollY', this).round()
       : document.documentElement!.scrollTop;
 }
-
-class NullWindowException implements Exception {
-  @override
-  String toString() {
-    return 'Attempted to call Window.open with a null window.';
-  }
-}
 // Copyright (c) 2012, 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.
@@ -40025,7 +40017,7 @@ EventTarget? _convertNativeToDart_EventTarget(e) {
     return e;
 }
 
-_convertDartToNative_EventTarget(e) {
+EventTarget? _convertDartToNative_EventTarget(e) {
   if (e is _DOMWindowCrossFrame) {
     return e._window;
   } else {
@@ -40124,7 +40116,7 @@ class _DOMWindowCrossFrame implements WindowBase {
   // Private window.  Note, this is a window in another frame, so it
   // cannot be typed as "Window" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
-  final Object _window;
+  final _window;
 
   // Fields.
   HistoryBase get history =>

tests/lib/html/window_test.dart

@@ -11,13 +11,4 @@ main() {
     expect(window.scrollX, 0);
     expect(window.scrollY, 0);
   });
-  test('open', () {
-    window.open('', 'blank');
-    try {
-      // A blank page with no access to the original window (noopener) should
-      // result in null.
-      window.open('', 'invalid', 'noopener=true');
-      fail('Expected Window.open to throw.');
-    } on NullWindowException {}
-  });
 }

tools/dom/src/dart2js_Conversions.dart

@@ -33,7 +33,7 @@ EventTarget? _convertNativeToDart_EventTarget(e) {
     return e;
 }
 
-_convertDartToNative_EventTarget(e) {
+EventTarget? _convertDartToNative_EventTarget(e) {
   if (e is _DOMWindowCrossFrame) {
     return e._window;
   } else {

tools/dom/src/dart2js_DOMImplementation.dart

@@ -9,7 +9,7 @@ class _DOMWindowCrossFrame implements WindowBase {
   // Private window.  Note, this is a window in another frame, so it
   // cannot be typed as "Window" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
-  final Object _window;
+  final _window;
 
   // Fields.
   HistoryBase get history =>

tools/dom/templates/html/impl/impl_Window.darttemplate

@@ -50,18 +50,17 @@ $(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
   /**
    * Opens a new window.
    *
-   * Throws a NullWindowException if the opened window is null.
-   *
    * ## Other resources
    *
    * * [Window.open](https://developer.mozilla.org/en-US/docs/Web/API/Window.open)
    *   from MDN.
    */
   WindowBase open(String url, String name, [String$NULLABLE options]) {
-    final win =
-        options == null ? _open2(url, name) : _open3(url, name, options);
-    if (win == null) throw new NullWindowException();
-    return _DOMWindowCrossFrame._createSafe(win);
+    if (options == null) {
+      return _DOMWindowCrossFrame._createSafe(_open2(url, name));
+    } else {
+      return _DOMWindowCrossFrame._createSafe(_open3(url, name, options));
+    }
   }
 
   // API level getter and setter for Location.
@@ -255,10 +254,3 @@ $!MEMBERS
       JS<num>('num', '#.scrollY', this).round() :
       document.documentElement$NULLASSERT.scrollTop;
 }
-
-class NullWindowException implements Exception {
-  @override
-  String toString() {
-    return 'Attempted to call Window.open with a null window.';
-  }
-}

tools/dom/web_library_bindings.dart

@@ -9581,7 +9581,6 @@ final Map<String, Set<String>> dartTypeToNativeTypes = {
   'NoncedElement': {'NoncedElement'},
   'Notification': {'Notification'},
   'NotificationEvent': {'NotificationEvent'},
-  'NullWindowException': {'NullWindowException'},
   'Number': {'SVGNumber'},
   'NumberInputElement': {'NumberInputElement'},
   'NumberList': {'SVGNumberList'},