[Extensions Bindings] Add chrome.runtime.lastError support

extensions/renderer/api_last_error.cc

Index: extensions/renderer/api_last_error.cc
diff --git a/extensions/renderer/api_last_error.cc b/extensions/renderer/api_last_error.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3b527f96dc7119d3fdc436864c49951de3851ecf
--- /dev/null
+++ b/extensions/renderer/api_last_error.cc
@@ -0,0 +1,149 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "extensions/renderer/api_last_error.h"
+
+#include "gin/converter.h"
+#include "gin/handle.h"
+#include "gin/object_template_builder.h"
+#include "gin/wrappable.h"
+
+namespace extensions {
+
+namespace {
+
+const char kLastErrorProperty[] = "lastError";
+
+class LastErrorObject final : public gin::Wrappable<LastErrorObject> {
+ public:
+  explicit LastErrorObject(const std::string& error) : error_(error) {}
+
+  static gin::WrapperInfo kWrapperInfo;
+
+  // gin::Wrappable:
+  gin::ObjectTemplateBuilder GetObjectTemplateBuilder(
+      v8::Isolate* isolate) override {
+    DCHECK(isolate);
+    return Wrappable<LastErrorObject>::GetObjectTemplateBuilder(isolate)
+        .SetProperty("message", &LastErrorObject::GetLastError);
+  }
+
+  void Reset(const std::string& error) {
+    error_ = error;
+    accessed_ = false;
+  }
+
+  const std::string& error() const { return error_; }
+  bool accessed() const { return accessed_; }
+
+ private:
+  std::string GetLastError() {
+    accessed_ = true;
+    return error_;
+  }
+
+  std::string error_;
+  bool accessed_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(LastErrorObject);
+};
+
+gin::WrapperInfo LastErrorObject::kWrapperInfo = {gin::kEmbedderNativeGin};
+
+}  // namespace
+
+APILastError::APILastError(const GetParent& get_parent)
+    : get_parent_(get_parent) {}
+APILastError::APILastError(APILastError&& other) = default;
+APILastError::~APILastError() = default;
+
+void APILastError::SetError(v8::Local<v8::Context> context,
+                            const std::string& error) {
+  v8::Isolate* isolate = context->GetIsolate();
+  DCHECK(isolate);
+  v8::HandleScope handle_scope(isolate);
+
+  // The various accesses/sets on an object could potentially fail if script has
+  // set any crazy interceptors. For the most part, we don't care about behaving
+  // perfectly in these circumstances, but we eat the exception so callers don't
+  // have to worry about it. We also SetVerbose() so that developers will have a
+  // clue what happened if this does arise.
+  // TODO(devlin): Whether or not this needs to be verbose is debatable.
+  v8::TryCatch try_catch(isolate);
+  try_catch.SetVerbose(true);
+
+  v8::Local<v8::Object> parent = get_parent_.Run(context);
+  if (parent.IsEmpty())
+    return;
+  v8::Local<v8::String> key = gin::StringToSymbol(isolate, kLastErrorProperty);
+  v8::MaybeLocal<v8::Value> maybe_error = parent->Get(context, key);
+  v8::Local<v8::Value> local_error;
+  if (!maybe_error.ToLocal(&local_error))

[jbroman, 2017/02/13 19:41:27]

nit: Don't have to, but it's usual to do the ToLocal inline with the thing that
could fail, like:

v8::Local<v8::Value> local_error;
if (!parent->Get(context, key).ToLocal(&local_error))
  return;

[Devlin, 2017/02/14 04:57:08]

Whoops, been trying to do that more, but didn't here.  Done.

+    return;
+
+  if (!local_error->IsUndefined()) {
+    // There may be an existing last error to overwrite.
+    LastErrorObject* last_error = nullptr;
+    if (!gin::Converter<LastErrorObject*>::FromV8(context->GetIsolate(),
+                                                  local_error, &last_error)) {
+      // If it's not a real lastError (e.g. if a script manually set it), don't
+      // do anything.
+      return;
+    }
+    last_error->Reset(error);
+  } else {
+    DCHECK(context->GetIsolate());
+    v8::Local<v8::Value> last_error =
+        gin::CreateHandle(context->GetIsolate(), new LastErrorObject(error))
+            .ToV8();
+    DCHECK(!last_error.IsEmpty());
+    // This Set() can fail, but there's nothing to do if it does (the exception
+    // will be caught by the TryCatch above).
+    ignore_result(parent->Set(
+        context, gin::StringToSymbol(isolate, kLastErrorProperty), last_error));
+  }
+}
+
+void APILastError::ClearError(v8::Local<v8::Context> context,
+                              bool report_if_unchecked) {
+  v8::Isolate* isolate = context->GetIsolate();
+  v8::HandleScope handle_scope(isolate);
+
+  v8::Local<v8::Object> parent;
+  LastErrorObject* last_error = nullptr;
+  v8::Local<v8::String> key;
+  {
+    // See comment in SetError().
+    v8::TryCatch try_catch(isolate);
+    try_catch.SetVerbose(true);
+
+    parent = get_parent_.Run(context);
+    if (parent.IsEmpty())
+      return;
+    key = gin::StringToSymbol(isolate, kLastErrorProperty);
+    v8::MaybeLocal<v8::Value> maybe_error = parent->Get(context, key);

[jbroman, 2017/02/13 19:41:27]

ditto here about ToLocal

[Devlin, 2017/02/14 04:57:08]

Done.

+    v8::Local<v8::Value> local_error;
+    if (!maybe_error.ToLocal(&local_error))
+      return;
+    if (!gin::Converter<LastErrorObject*>::FromV8(context->GetIsolate(),
+                                                  local_error, &last_error)) {
+      return;
+    }
+  }
+
+  if (report_if_unchecked && !last_error->accessed()) {
+    isolate->ThrowException(
+        v8::Exception::Error(gin::StringToV8(isolate, last_error->error())));
+  }
+
+  // See comment in SetError().
+  v8::TryCatch try_catch(isolate);
+  try_catch.SetVerbose(true);
+
+  // This Delete() can fail, but there's nothing to do if it does (the exception
+  // will be caught by the TryCatch above).
+  parent->Delete(context, key);
+}
+
+}  // namespace extensions