Added new policy Schema classes.

components/policy/core/common/schema.cc

Index: components/policy/core/common/schema.cc
diff --git a/components/policy/core/common/schema.cc b/components/policy/core/common/schema.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d897228552da876cce4ee6cfd6a6fbebd6ce88c5
--- /dev/null
+++ b/components/policy/core/common/schema.cc
@@ -0,0 +1,332 @@
+// Copyright 2013 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 "components/policy/core/common/schema.h"
+
+#include <algorithm>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/memory/scoped_vector.h"
+#include "components/json_schema/json_schema_constants.h"
+#include "components/json_schema/json_schema_validator.h"
+#include "components/policy/core/common/schema_internal.h"
+
+namespace policy {
+
+namespace schema {
+
+namespace {
+
+const char kJSONSchemaVersion[] = "http://json-schema.org/draft-03/schema#";
+
+class PolicySchemaImpl : public PolicySchema {

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

If PolicySchema has only one implementation, why make it pure-virtual?

[Joao da Silva, 2013/09/13 14:02:54]

Right. There were 2 implementations but in the end one was enough, so this can
be simplified. Done.

+ public:
+  explicit PolicySchemaImpl(const internal::SchemaNode* root)
+      : root_(root) {}
+
+  virtual ~PolicySchemaImpl();
+
+  static scoped_ptr<PolicySchema> Parse(const std::string& schema,
+                                        std::string* error);
+
+  virtual Schema schema() const OVERRIDE {
+    return Schema(root_);
+  }
+
+ private:
+  PolicySchemaImpl() : root_(NULL) {}
+
+  const internal::SchemaNode* Parse(const base::DictionaryValue& schema,
+                                    std::string* error);
+  const internal::SchemaNode* ParseDictionary(
+      const base::DictionaryValue& schema,
+      std::string* error);
+  const internal::SchemaNode* ParseList(const base::DictionaryValue& schema,
+                                        std::string* error);
+
+  const internal::SchemaNode* root_;
+  ScopedVector<internal::SchemaNode> schema_nodes_;
+  // Note: |property_nodes_| contains PropertyNode[] and must be cleared
+  // manually to properly use delete[].
+  std::vector<internal::PropertyNode*> property_nodes_;
+  ScopedVector<internal::PropertiesNode> properties_nodes_;
+  ScopedVector<std::string> keys_;
+
+  DISALLOW_COPY_AND_ASSIGN(PolicySchemaImpl);
+};
+
+bool SchemaTypeToValueType(const std::string& type_string,
+                           base::Value::Type* type) {
+  // Note: "any" is not an accepted type.
+  static const struct {
+    const char* schema_type;
+    base::Value::Type value_type;
+  } kSchemaToValueTypeMap[] = {
+    { json_schema_constants::kArray,        base::Value::TYPE_LIST       },
+    { json_schema_constants::kBoolean,      base::Value::TYPE_BOOLEAN    },
+    { json_schema_constants::kInteger,      base::Value::TYPE_INTEGER    },
+    { json_schema_constants::kNull,         base::Value::TYPE_NULL       },
+    { json_schema_constants::kNumber,       base::Value::TYPE_DOUBLE     },
+    { json_schema_constants::kObject,       base::Value::TYPE_DICTIONARY },
+    { json_schema_constants::kString,       base::Value::TYPE_STRING     },
+  };
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(kSchemaToValueTypeMap); ++i) {
+    if (kSchemaToValueTypeMap[i].schema_type == type_string) {
+      *type = kSchemaToValueTypeMap[i].value_type;
+      return true;
+    }
+  }
+  return false;
+}
+
+PolicySchemaImpl::~PolicySchemaImpl() {
+  for (size_t i = 0; i < property_nodes_.size(); ++i)
+    delete[] property_nodes_[i];
+}
+
+// static
+scoped_ptr<PolicySchema> PolicySchemaImpl::Parse(const std::string& content,
+                                                 std::string* error) {
+  // Validate as a generic JSON schema.
+  scoped_ptr<base::DictionaryValue> dict =
+      JSONSchemaValidator::IsValidSchema(content, error);
+  if (!dict)
+    return scoped_ptr<PolicySchema>();
+
+  // Validate the schema version.

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

That means we can never migrate to newer schema versions if we want to keep old
Chrome builds working. Is that intentional?

[Joao da Silva, 2013/09/13 14:02:54]

What can we possibly do for old builds?

We'll have to support both versions for a while, wait until extensions also
update to the new version (this may be 6 months to even a year), and then the
old version is removed when the metrics show that there are no more users.

Is there something you'd like to add at this stage?

[Mattias Nissler (ping if slow), 2013/09/13 14:55:17]

I'm worried about the fact that extension authors can't switch to the new
version as long as the old browser version is still around. It might be simpler
to just drop the check here if the assumption is that  new schema versions are
backward-compatible (so the browser is forward-compatible with new browser
versions).

[Joao da Silva, 2013/09/13 15:15:47]

I see where you're coming from. The latest draft is indeed quite similar to v3,
so it makes sense to accept later versions.

That means that we also have to modify the JSONSchemaValidator to ignore unknown
attributes. I'll do that change later, and update these unittests.

+  std::string string_value;
+  if (!dict->GetString(json_schema_constants::kSchema, &string_value) ||
+      string_value != kJSONSchemaVersion) {
+    *error = "Must declare JSON Schema v3 version in \"$schema\".";
+    return scoped_ptr<PolicySchema>();
+  }
+
+  // Validate the main type.
+  if (!dict->GetString(json_schema_constants::kType, &string_value) ||
+      string_value != json_schema_constants::kObject) {
+    *error =
+        "The main schema must have a type attribute with \"object\" value.";
+    return scoped_ptr<PolicySchema>();
+  }
+
+  // Checks for invalid attributes at the top-level.

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

Any good reason? They'd just be ignored.

[Joao da Silva, 2013/09/13 14:02:54]

So that extension authors see the error.

These could be warnings for now so that we could lift the restriction in the
future, but I don't see how we can have top-level policies with any name. If you
feel strongly about being open to this future change then I'll turn these into
LOG(WARNING)s.

[Mattias Nissler (ping if slow), 2013/09/13 14:55:17]

Right, makes sense. Let's leave the check in then.

+  if (dict->HasKey(json_schema_constants::kAdditionalProperties) ||
+      dict->HasKey(json_schema_constants::kPatternProperties)) {
+    *error = "\"additionalProperties\" and \"patternProperties\" are not "
+             "supported at the main schema.";
+    return scoped_ptr<PolicySchema>();
+  }
+
+  scoped_ptr<PolicySchemaImpl> impl(new PolicySchemaImpl());
+  impl->root_ = impl->Parse(*dict, error);
+  if (!impl->root_)
+    impl.reset();
+  return impl.PassAs<PolicySchema>();
+}
+
+const internal::SchemaNode* PolicySchemaImpl::Parse(
+    const base::DictionaryValue& schema,
+    std::string* error) {
+  std::string type_string;
+  if (!schema.GetString(json_schema_constants::kType, &type_string)) {
+    *error = "The schema type must be declared.";
+    return NULL;
+  }
+
+  base::Value::Type type = base::Value::TYPE_NULL;
+  if (!SchemaTypeToValueType(type_string, &type)) {
+    *error = "The \"any\" type can't be used.";

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

I think you should just say "Type not supported: " << type_string

[Joao da Silva, 2013/09/13 14:02:54]

Done. The "any" type was assumed because the JSONSchemaValidator rejects unknown
types, and only "any" is missing from SchemaTypeToValueType.

+    return NULL;
+  }
+
+  if (type == base::Value::TYPE_DICTIONARY)
+    return ParseDictionary(schema, error);
+  if (type == base::Value::TYPE_LIST)
+    return ParseList(schema, error);
+
+  internal::SchemaNode* node = new internal::SchemaNode;
+  node->type = type;
+  node->extra = NULL;
+  schema_nodes_.push_back(node);
+  return node;
+}
+
+const internal::SchemaNode* PolicySchemaImpl::ParseDictionary(
+    const base::DictionaryValue& schema,
+    std::string* error) {
+  internal::PropertiesNode* properties_node = new internal::PropertiesNode;
+  properties_node->begin = NULL;
+  properties_node->end = NULL;
+  properties_node->additional = NULL;
+  properties_nodes_.push_back(properties_node);
+
+  const base::DictionaryValue* dict = NULL;
+  const base::DictionaryValue* properties = NULL;
+  if (schema.GetDictionary(json_schema_constants::kProperties, &properties)) {
+    internal::PropertyNode* property_nodes =
+        new internal::PropertyNode[properties->size()];
+    property_nodes_.push_back(property_nodes);
+
+    size_t index = 0;
+    for (base::DictionaryValue::Iterator it(*properties);
+         !it.IsAtEnd(); it.Advance(), ++index) {
+      // This should have been verified by the JSONSchemaValidator.
+      CHECK(it.value().GetAsDictionary(&dict));
+      const internal::SchemaNode* sub_schema = Parse(*dict, error);
+      if (!sub_schema)
+        return NULL;
+      std::string* key = new std::string(it.key());
+      keys_.push_back(key);
+      property_nodes[index].key = key->c_str();
+      property_nodes[index].schema = sub_schema;
+    }
+    CHECK_EQ(properties->size(), index);
+    properties_node->begin = property_nodes;
+    properties_node->end = property_nodes + index;
+  }
+
+  if (schema.GetDictionary(json_schema_constants::kAdditionalProperties,
+                           &dict)) {
+    const internal::SchemaNode* sub_schema = Parse(*dict, error);
+    if (!sub_schema)
+      return NULL;
+    properties_node->additional = sub_schema;
+  }
+
+  internal::SchemaNode* schema_node = new internal::SchemaNode;
+  schema_node->type = base::Value::TYPE_DICTIONARY;
+  schema_node->extra = properties_node;
+  schema_nodes_.push_back(schema_node);
+  return schema_node;
+}
+
+const internal::SchemaNode* PolicySchemaImpl::ParseList(
+    const base::DictionaryValue& schema,
+    std::string* error) {
+  const base::DictionaryValue* dict = NULL;
+  if (!schema.GetDictionary(json_schema_constants::kItems, &dict)) {
+    *error = "Arrays must declare a single schema for their items.";
+    return NULL;
+  }
+  const internal::SchemaNode* items_schema_node = Parse(*dict, error);
+  if (!items_schema_node)
+    return NULL;
+
+  internal::SchemaNode* schema_node = new internal::SchemaNode;
+  schema_node->type = base::Value::TYPE_LIST;
+  schema_node->extra = items_schema_node;
+  schema_nodes_.push_back(schema_node);
+  return schema_node;
+}
+
+}  // namespace
+
+Schema::Iterator::Iterator(const internal::PropertiesNode* properties)
+    : it_(properties->begin),
+      end_(properties->end) {}
+
+Schema::Iterator::Iterator(const Iterator& iterator)
+    : it_(iterator.it_),
+      end_(iterator.end_) {}
+
+Schema::Iterator::~Iterator() {}
+
+Schema::Iterator& Schema::Iterator::operator=(const Iterator& iterator) {
+  it_ = iterator.it_;
+  end_ = iterator.end_;
+  return *this;
+}
+
+bool Schema::Iterator::IsAtEnd() const {
+  return it_ == end_;
+}
+
+void Schema::Iterator::Advance() {
+  ++it_;
+}
+
+const char* Schema::Iterator::key() const {
+  return it_->key;
+}
+
+Schema Schema::Iterator::schema() const {
+  return Schema(it_->schema);
+}
+
+Schema::Schema(const internal::SchemaNode* schema) : schema_(schema) {}
+
+Schema::Schema(const Schema& schema) : schema_(schema.schema_) {}
+
+Schema& Schema::operator=(const Schema& schema) {
+  schema_ = schema.schema_;
+  return *this;
+}
+
+base::Value::Type Schema::type() const {
+  CHECK(valid());
+  return schema_->type;
+}
+
+Schema::Iterator Schema::GetPropertiesIterator() const {
+  CHECK(valid());
+  CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
+  return Iterator(
+      static_cast<const internal::PropertiesNode*>(schema_->extra));
+}
+
+namespace {
+
+bool CompareKeys(const internal::PropertyNode& node, const std::string& key) {
+  return node.key < key;
+}
+
+}  // namespace
+
+Schema Schema::GetKnownProperty(const std::string& key) const {
+  CHECK(valid());
+  CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
+  const internal::PropertiesNode* properties_node =
+      static_cast<const internal::PropertiesNode*>(schema_->extra);
+  const internal::PropertyNode* it = std::lower_bound(
+      properties_node->begin, properties_node->end, key, CompareKeys);
+  if (it != properties_node->end && it->key == key)
+    return Schema(it->schema);
+  return Schema(NULL);
+}
+
+Schema Schema::GetAdditionalProperties() const {
+  CHECK(valid());
+  CHECK_EQ(base::Value::TYPE_DICTIONARY, type());
+  return Schema(
+      static_cast<const internal::PropertiesNode*>(schema_->extra)->additional);

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

Hm, casts. Maybe use a union? That's still easier to read.

[Joao da Silva, 2013/09/13 14:02:54]

I don't mind these casts *at all* :-)

I did want to use a union at first, but only the first element of a union can be
statically initialized.

I find this better than having 2 pointers. Do you have other ideas, or is that
cast fine for now?

[Mattias Nissler (ping if slow), 2013/09/13 14:55:17]

Fine to go with the cast then.

+}
+
+Schema Schema::GetProperty(const std::string& key) const {
+  Schema schema = GetKnownProperty(key);
+  return schema.valid() ? schema : GetAdditionalProperties();

[Mattias Nissler (ping if slow), 2013/09/13 12:56:48]

Shouldn't this return Schema(NULL) for the error case?

[Joao da Silva, 2013/09/13 14:02:54]

GetAdditionalProperties returns Schema(NULL) if the PropertiesNode->additional
field is NULL.

[Mattias Nissler (ping if slow), 2013/09/13 14:55:17]

Right, sorry, I was confused.

+}
+
+Schema Schema::GetItems() const {
+  CHECK(valid());
+  CHECK_EQ(base::Value::TYPE_LIST, type());
+  return Schema(static_cast<const internal::SchemaNode*>(schema_->extra));
+}
+
+// static
+scoped_ptr<PolicySchema> PolicySchema::Wrap(
+    const internal::SchemaNode* schema) {
+  return scoped_ptr<PolicySchema>(new PolicySchemaImpl(schema));
+}
+
+// static
+scoped_ptr<PolicySchema> PolicySchema::Parse(const std::string& schema,
+                                             std::string* error) {
+  return PolicySchemaImpl::Parse(schema, error);
+}
+
+}  // namespace schema
+
+}  // namespace policy