1 files changed, 123 insertions, 0 deletions
diff --git a/dom/bindings/ToJSValue.cpp b/dom/bindings/ToJSValue.cpp
new file mode 100644
index 0000000000..73fc7b1e33
--- /dev/null
+++ b/dom/bindings/ToJSValue.cpp
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/Exceptions.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "nsAString.h"
+#include "nsContentUtils.h"
+#include "nsStringBuffer.h"
+#include "xpcpublic.h"
+
+namespace mozilla::dom {
+
+bool ToJSValue(JSContext* aCx, const nsAString& aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  // Make sure we're called in a compartment
+  MOZ_ASSERT(JS::CurrentGlobalOrNull(aCx));
+
+  // XXXkhuey I'd love to use xpc::NonVoidStringToJsval here, but it requires
+  // a non-const nsAString for silly reasons.
+  nsStringBuffer* sharedBuffer;
+  if (!XPCStringConvert::ReadableToJSVal(aCx, aArgument, &sharedBuffer,
+                                         aValue)) {
+    return false;
+  }
+
+  if (sharedBuffer) {
+    NS_ADDREF(sharedBuffer);
+  }
+
+  return true;
+}
+
+bool ToJSValue(JSContext* aCx, const nsACString& aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  return UTF8StringToJsval(aCx, aArgument, aValue);
+}
+
+bool ToJSValue(JSContext* aCx, nsresult aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  RefPtr<Exception> exception = CreateException(aArgument);
+  return ToJSValue(aCx, exception, aValue);
+}
+
+bool ToJSValue(JSContext* aCx, ErrorResult&& aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  MOZ_ASSERT(aArgument.Failed());
+  MOZ_ASSERT(
+      !aArgument.IsUncatchableException(),
+      "Doesn't make sense to convert uncatchable exception to a JS value!");
+  MOZ_ALWAYS_TRUE(aArgument.MaybeSetPendingException(aCx));
+  MOZ_ALWAYS_TRUE(JS_GetPendingException(aCx, aValue));
+  JS_ClearPendingException(aCx);
+  return true;
+}
+
+bool ToJSValue(JSContext* aCx, Promise& aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  aValue.setObject(*aArgument.PromiseObj());
+  return MaybeWrapObjectValue(aCx, aValue);
+}
+
+bool ToJSValue(JSContext* aCx, const WindowProxyHolder& aArgument,
+               JS::MutableHandle<JS::Value> aValue) {
+  BrowsingContext* bc = aArgument.get();
+  if (!bc) {
+    aValue.setNull();
+    return true;
+  }
+  JS::Rooted<JSObject*> windowProxy(aCx);
+  if (bc->IsInProcess()) {
+    windowProxy = bc->GetWindowProxy();
+    if (!windowProxy) {
+      nsPIDOMWindowOuter* window = bc->GetDOMWindow();
+      if (!window) {
+        // Torn down enough that we should just return null.
+        aValue.setNull();
+        return true;
+      }
+      if (!window->EnsureInnerWindow()) {
+        return Throw(aCx, NS_ERROR_UNEXPECTED);
+      }
+      windowProxy = bc->GetWindowProxy();
+    }
+    return ToJSValue(aCx, windowProxy, aValue);
+  }
+
+  if (!GetRemoteOuterWindowProxy(aCx, bc, /* aTransplantTo = */ nullptr,
+                                 &windowProxy)) {
+    return false;
+  }
+  aValue.setObjectOrNull(windowProxy);
+  return true;
+}
+
+// Static assertion tests for the `binding_detail::ScriptableInterfaceType`
+// helper template, used by `ToJSValue`.
+namespace binding_detail {
+static_assert(std::is_same_v<ScriptableInterfaceType<nsISupports>, nsISupports>,
+              "nsISupports works with ScriptableInterfaceType");
+static_assert(
+    std::is_same_v<ScriptableInterfaceType<nsIGlobalObject>, nsISupports>,
+    "non-scriptable interfaces get a fallback");
+static_assert(std::is_same_v<ScriptableInterfaceType<nsIObserver>, nsIObserver>,
+              "scriptable interfaces should get the correct type");
+static_assert(std::is_same_v<ScriptableInterfaceType<nsIRunnable>, nsIRunnable>,
+              "scriptable interfaces should get the correct type");
+class SingleScriptableInterface : public nsIObserver {};
+static_assert(
+    std::is_same_v<ScriptableInterfaceType<SingleScriptableInterface>,
+                   nsIObserver>,
+    "Concrete type with one scriptable interface picks the correct interface");
+class MultiScriptableInterface : public nsIObserver, public nsIRunnable {};
+static_assert(std::is_same_v<ScriptableInterfaceType<MultiScriptableInterface>,
+                             nsISupports>,
+              "Concrete type with multiple scriptable interfaces falls back");
+}  // namespace binding_detail
+}  // namespace mozilla::dom