Implements a C++ version of JSONSchemaValidator.

chrome/common/json_schema_validator.h

+// Copyright (c) 2010 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.
+
+#ifndef CHROME_COMMON_JSON_SCHEMA_VALIDATOR_H_
+#define CHROME_COMMON_JSON_SCHEMA_VALIDATOR_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+
+class DictionaryValue;
+class FundamentalValue;
+class ListValue;
+class StringValue;
+class Value;
+
+//==============================================================================
+// This class implements a subset of JSON Schema.
+// See: http://www.json.com/json-schema-proposal/ for more details.
+//
+// There is also an older JavaScript implementation of the same functionality in
+// chrome/renderer/resources/json_schema.js.
+//
+// The following features of JSON Schema are not implemented:
+// - requires
+// - unique
+// - disallow
+// - union types (but replaced with 'choices')
+// - number.maxDecimal
+// - string.pattern
+//
+// The following properties are not applicable to the interface exposed by
+// this class:
+// - options
+// - readonly
+// - title
+// - description
+// - format
+// - default
+// - transient
+// - hidden
+//
+// There are also these departures from the JSON Schema proposal:
+// - null counts as 'unspecified' for optional values
+// - added the 'choices' property, to allow specifying a list of possible types
+//   for a value
+// - by default an "object" typed schema does not allow additional properties.
+//   if present, "additionalProperties" is to be a schema against which all
+//   additional properties will be validated.
+//==============================================================================
+class JSONSchemaValidator {
+ public:
+  // Details about a validation error.
+  struct Error {
+    Error();
+
+    explicit Error(const std::string& message);
+
+    Error(const std::string& path, const std::string& message);
+
+    // The path to the location of the error in the JSON structure.
+    std::string path;
+
+    // An english message describing the error.
+    std::string message;
+  };
+
+  // Error messages.
+  static const char kUnknownTypeReference[];
+  static const char kInvalidChoice[];
+  static const char kInvalidEnum[];
+  static const char kObjectPropertyIsRequired[];
+  static const char kUnexpectedProperty[];
+  static const char kArrayMinItems[];
+  static const char kArrayMaxItems[];
+  static const char kArrayItemRequired[];
+  static const char kStringMinLength[];
+  static const char kStringMaxLength[];
+  static const char kStringPattern[];
+  static const char kInfinityNaNNotSupported[];
+  static const char kNumberMinimum[];
+  static const char kNumberMaximum[];
+  static const char kInvalidType[];
+
+  // Classifies a Value as one of the JSON schema primitive types.
+  static std::string GetJSONSchemaType(Value* value);
+
+  // Utility methods to format error messages. The first method can have one
+  // wildcard represented by '*', which is replaced with s1. The second method
+  // can have two, which are replaced by s1 and s2.
+  static std::string FormatErrorMessage(const std::string& format,
+                                        const std::string& s1);
+  static std::string FormatErrorMessage(const std::string& format,
+                                        const std::string& s1,
+                                        const std::string& s2);
+
+  // Creates a validator for the specified schema.
+  //
+  // NOTE: This constructor assumes that |schema| is well formed and valid.
+  // Errors will result in CHECK at runtime; this constructor should not be used
+  // with untrusted schemas.
+  explicit JSONSchemaValidator(DictionaryValue* schema);
+
+  // Creates a validator for the specified schema and user-defined types. Each
+  // type must be a valid JSONSchema type description with an additional "id"
+  // field. Schema objects in |schema| can refer to these types with the "$ref"
+  // property.
+  //
+  // NOTE: This constructor assumes that |schema| and |types| are well-formed
+  // and valid. Errors will result in CHECK at runtime; this constructor should
+  // not be used with untrusted schemas.
+  JSONSchemaValidator(DictionaryValue* schema, ListValue* types);
+
+  // Whether the validator allows additional items for objects and lists, beyond
+  // those defined by their schema, by default.
+  //
+  // This setting defaults to false: all items in an instance list or object
+  // must be defined by the corresponding schema.
+  //
+  // This setting can be overridden on individual object and list schemas by
+  // setting the "additionalProperties" field.
+  bool default_allow_additional_properties() const {
+    return default_allow_additional_properties_;
+  }
+
+  void set_default_allow_additional_properties(bool val) {
+    default_allow_additional_properties_ = val;
+  }
+
+  // Returns any errors from the last call to to Validate().
+  const std::vector<Error>& errors() const {
+    return errors_;
+  }
+
+  // Validates a JSON value. Returns true if the instance is valid, false
+  // otherwise. If false is returned any errors are available from the errors()
+  // getter.
+  bool Validate(Value* instance);
+
+ private:
+  typedef std::map<std::string, DictionaryValue*> TypeMap;
+
+  // Each of the below methods handle a subset of the validation process. The
+  // path paramater is the path to |instance| from the root of the instance tree
+  // and is used in error messages.
+
+  // Validates any instance node against any schema node. This is called for
+  // every node in the instance tree, and it just decides which of the more
+  // detailed methods to call.
+  void Validate(Value* instance, DictionaryValue* schema,
+                const std::string& path);
+
+  // Validates a node against a list of possible schemas. If any one of the
+  // schemas match, the node is valid.
+  void ValidateChoices(Value* instance, ListValue* choices,
+                       const std::string& path);
+
+  // Validates a node against a list of exact primitive values, eg 42, "foobar".
+  void ValidateEnum(Value* instance, ListValue* choices,
+                    const std::string& path);
+
+  // Validates a JSON object against an object schema node.
+  void ValidateObject(DictionaryValue* instance, DictionaryValue* schema,
+                      const std::string& path);
+
+  // Validates a JSON array against an array schema node.
+  void ValidateArray(ListValue* instance, DictionaryValue* schema,
+                     const std::string& path);
+
+  // Validates a JSON array against an array schema node configured to be a
+  // tuple. In a tuple, there is one schema node for each item expected in the
+  // array.
+  void ValidateTuple(ListValue* instance, DictionaryValue* schema,
+                     const std::string& path);
+
+  // Validate a JSON string against a string schema node.
+  void ValidateString(StringValue* instance, DictionaryValue* schema,
+                      const std::string& path);
+
+  // Validate a JSON number against a number schema node.
+  void ValidateNumber(Value* instance, DictionaryValue* schema,
+                      const std::string& path);
+
+  // Validates that the JSON node |instance| has |expected_type|.
+  bool ValidateType(Value* instance, const std::string& expected_type,
+                    const std::string& path);
+
+  // Returns true if |schema| will allow additional items of any type.
+  bool SchemaAllowsAnyAdditionalItems(
+      DictionaryValue* schema, DictionaryValue** addition_items_schema);
+
+  // The root schema node.
+  DictionaryValue* schema_root_;
+
+  // Map of user-defined name to type.
+  TypeMap types_;
+
+  // Whether we allow additional properties on objects by default. This can be
+  // overridden by the allow_additional_properties flag on an Object schema.
+  bool default_allow_additional_properties_;
+
+  // Errors accumulated since the last call to Validate().
+  std::vector<Error> errors_;
+
+
+  DISALLOW_COPY_AND_ASSIGN(JSONSchemaValidator);
+};
+
+#endif  // CHROME_COMMON_JSON_SCHEMA_VALIDATOR_H_