Create a mechanism define declarative rules via the extension manifest.

extensions/common/api/declarative/declarative_manifest_data.cc

Index: extensions/common/api/declarative/declarative_manifest_data.cc
diff --git a/extensions/common/api/declarative/declarative_manifest_data.cc b/extensions/common/api/declarative/declarative_manifest_data.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a5a3de2317083be44cf6c88d56ad81bf9317c919
--- /dev/null
+++ b/extensions/common/api/declarative/declarative_manifest_data.cc
@@ -0,0 +1,176 @@
+// Copyright 2015 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/common/api/declarative/declarative_manifest_data.h"
+
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "extensions/common/manifest_constants.h"
+
+using base::UTF8ToUTF16;
+using base::StringPrintf;
+
+namespace extensions {
+
+namespace {
+
+const char* ValueTypeToString(const base::Value* value) {
+  const base::Value::Type type = value->GetType();
+  static const char* strings[] = {"null",
+                                  "boolean",
+                                  "integer",
+                                  "double",
+                                  "string",
+                                  "binary",
+                                  "dictionary",
+                                  "list"};
+  CHECK(static_cast<size_t>(type) < arraysize(strings));
+  return strings[type];
+}
+
+class ErrorBuilder {
+ public:
+  ErrorBuilder(base::string16* error) : error_(error) {}

[not at google - send to devlin, 2015/06/09 20:55:41]

explicit

[danduong, 2015/06/10 00:17:16]

Done.

+
+  // Appends a literal string |error|.
+  void Append(const char* error) {
+    if (error_->length())
+      error_->append(UTF8ToUTF16("; "));
+    error_->append(UTF8ToUTF16(error));
+  }
+
+  // Appends a string |error| with the first %s replaced by |sub|.
+  void Append(const char* error, const char* sub) {
+    Append(base::StringPrintf(error, sub).c_str());
+  }
+
+ private:
+  base::string16* error_;
+  DISALLOW_COPY_AND_ASSIGN(ErrorBuilder);
+};
+
+// Converts a rule defined in the manifest into a JSON internal format. The
+// difference is that actions and conditions use a "type" key to define the
+// type of rule/condition, while the internal format uses a "instanceType" key
+// for this. This function walks through all the conditions and rules to swap
+// the manifest key for the internal key.
+bool ConvertManifestRule(const linked_ptr<DeclarativeManifestData::Rule>& rule,
+                         ErrorBuilder* error_builder) {
+  auto convert_list =
+      [error_builder](std::vector<linked_ptr<base::Value>>& list) {
+        for (const linked_ptr<base::Value>& value : list) {
+          base::DictionaryValue* dictionary = nullptr;
+          if (!value->GetAsDictionary(&dictionary)) {
+            error_builder->Append("expected dictionary, got %s",
+                                  ValueTypeToString(value.get()));
+            return false;
+          }
+          std::string type;
+          if (!dictionary->GetString("type", &type)) {
+            error_builder->Append("'type' is required");

[not at google - send to devlin, 2015/06/09 20:55:40]

this will also fail if "type" is set but isn't a string, so you might want to
say "'type' is required, and must be a string".

[danduong, 2015/06/10 00:17:16]

Done.

+            return false;
+          }
+          dictionary->Remove("type", nullptr);
+          dictionary->SetString("instanceType", type);
+        }
+        return true;
+      };
+  return convert_list(rule->actions) && convert_list(rule->conditions);
+}
+
+}  // namespace
+
+DeclarativeManifestData::DeclarativeManifestData() {
+}
+
+DeclarativeManifestData::~DeclarativeManifestData() {
+}
+
+// static
+DeclarativeManifestData* DeclarativeManifestData::Get(
+    const Extension* extension) {
+  return static_cast<DeclarativeManifestData*>(
+      extension->GetManifestData(manifest_keys::kEventRules));
+}
+
+// static
+scoped_ptr<DeclarativeManifestData> DeclarativeManifestData::FromValue(
+    const base::Value& value,
+    base::string16* error) {
+  //  The following is an example of how an event programmatic rule definition
+  //  translates to a manifest definition.
+  //
+  //  From javascript:
+  //
+  //  chrome.declarativeContent.onPageChanged.addRules([{
+  //    actions: [
+  //      new chrome.declarativeContent.ShowPageAction()
+  //    ],
+  //    conditions: [
+  //      new chrome.declarativeContent.PageStateMatcher({css: ["video"]})
+  //    ]
+  //  }]);
+  //
+  //  In manifest:
+  //
+  //  "event_rules": [{
+  //    "event" : "declarativeContent.onPageChanged",
+  //    "actions" : [{
+  //      "type": "declarativeContent.ShowPageAction"
+  //    }],
+  //    "conditions" : [{
+  //      "css": ["video"],
+  //      "type" : "declarativeContent.PageStateMatcher"
+  //    }]
+  //  }]
+  //
+  //  The javascript objects get translated into JSON objects with a "type"
+  //  field to indicate the instance type. Instead of adding rules to a
+  //  specific event list, each rule has an "event" field to indicate which
+  //  event it applies to.
+  //
+  ErrorBuilder error_builder(error);
+  scoped_ptr<DeclarativeManifestData> result(new DeclarativeManifestData());
+  const base::ListValue* list = nullptr;
+  if (!value.GetAsList(&list)) {
+    error_builder.Append("'event_rules' expected list, got %s",
+                         ValueTypeToString(&value));
+    return scoped_ptr<DeclarativeManifestData>();
+  }
+
+  for (size_t i = 0; i < list->GetSize(); ++i) {
+    const base::DictionaryValue* dict = nullptr;
+    if (!list->GetDictionary(i, &dict)) {
+      const base::Value* value = nullptr;
+      if (list->Get(i, &value))
+        error_builder.Append("expected dictionary, got %s",
+                             ValueTypeToString(value));
+      else
+        error_builder.Append("expected dictionary");
+      return scoped_ptr<DeclarativeManifestData>();
+    }
+    std::string event;
+    if (!dict->GetString("event", &event)) {
+      error_builder.Append("'event' is required");
+      return scoped_ptr<DeclarativeManifestData>();
+    }
+
+    linked_ptr<Rule> rule(new Rule());
+    if (Rule::Populate(*dict, rule.get()) &&
+        ConvertManifestRule(rule, &error_builder)) {
+      result->event_rules_map_[event].push_back(rule);
+    } else {
+      error_builder.Append("rule failed to populate");

[not at google - send to devlin, 2015/06/09 20:55:40]

I think that, now, the Populate and the ConvertManifestRule should be different
steps, because "rule failed to populate" may not actually be true, in the case
that it was actually ConvertManifestRule which failed (in which case the error
will have already been populated).

+      return scoped_ptr<DeclarativeManifestData>();
+    }
+  }
+  return result.Pass();
+}
+
+std::vector<linked_ptr<DeclarativeManifestData::Rule>>&
+DeclarativeManifestData::RulesForEvent(const std::string& event) {
+  return event_rules_map_[event];
+}
+
+}  // namespace extensions