Merge pull request #1068 from yurikhan/violationDetails

Schema violation details

doc/schema.md

@@ -8,7 +8,7 @@ RapidJSON implemented a JSON Schema validator for [JSON Schema Draft v4](http://
 
 [TOC]
 
-# Basic Usage {#BasicUsage}
+# Basic Usage {#Basic}
 
 First of all, you need to parse a JSON Schema into `Document`, and then compile the `Document` into a `SchemaDocument`.
 
@@ -52,11 +52,11 @@ Some notes:
 * One `SchemaDocument` can be referenced by multiple `SchemaValidator`s. It will not be modified by `SchemaValidator`s.
 * A `SchemaValidator` may be reused to validate multiple documents. To run it for other documents, call `validator.Reset()` first.
 
-# Validation during parsing/serialization {#ParsingSerialization}
+# Validation during parsing/serialization {#Fused}
 
 Unlike most JSON Schema validator implementations, RapidJSON provides a SAX-based schema validator. Therefore, you can parse a JSON from a stream while validating it on the fly. If the validator encounters a JSON value that invalidates the supplied schema, the parsing will be terminated immediately. This design is especially useful for parsing large JSON files.
 
-## DOM parsing {#DomParsing}
+## DOM parsing {#DOM}
 
 For using DOM in parsing, `Document` needs some preparation and finalizing tasks, in addition to receiving SAX events, thus it needs some work to route the reader, validator and the document. `SchemaValidatingReader` is a helper class that doing such work.
 
@@ -97,7 +97,7 @@ if (!reader.GetParseResult()) {
 }
 ~~~
 
-## SAX parsing {#SaxParsing}
+## SAX parsing {#SAX}
 
 For using SAX in parsing, it is much simpler. If it only need to validate the JSON without further processing, it is simply:
 
@@ -144,7 +144,7 @@ if (!d.Accept(validator)) {
 
 Of course, if your application only needs SAX-style serialization, it can simply send SAX events to `SchemaValidator` instead of `Writer`.
 
-# Remote Schema {#RemoteSchema}
+# Remote Schema {#Remote}
 
 JSON Schema supports [`$ref` keyword](http://spacetelescope.github.io/understanding-json-schema/structuring.html), which is a [JSON pointer](doc/pointer.md) referencing to a local or remote schema. Local pointer is prefixed with `#`, while remote pointer is an relative or absolute URI. For example:
 
@@ -176,7 +176,7 @@ The failed test is "changed scope ref invalid" of "change resolution scope" in `
 
 Besides, the `format` schema keyword for string values is ignored, since it is not required by the specification.
 
-## Regular Expression {#RegEx}
+## Regular Expression {#Regex}
 
 The schema keyword `pattern` and `patternProperties` uses regular expression to match the required pattern.
 
@@ -235,3 +235,271 @@ On a Mac Book Pro (2.8 GHz Intel Core i7), the following results are collected.
 |[`jayschema`](https://github.com/natesilva/jayschema)|0.1%|21 (± 1.14%)|
 
 That is, RapidJSON is about 1.5x faster than the fastest JavaScript library (ajv). And 1400x faster than the slowest one.
+
+# Schema violation reporting {#Reporting}
+
+(Unreleased as of 2017-09-20)
+
+When validating an instance against a JSON Schema,
+it is often desirable to report not only whether the instance is valid,
+but also the ways in which it violates the schema.
+
+The `SchemaValidator` class
+collects errors encountered during validation
+into a JSON `Value`.
+This error object can then be accessed as `validator.GetError()`.
+
+The structure of the error object is subject to change
+in future versions of RapidJSON,
+as there is no standard schema for violations.
+The details below this point are provisional only.
+
+## General provisions {#ReportingGeneral}
+
+Validation of an instance value against a schema
+produces an error value.
+The error value is always an object.
+An empty object `{}` indicates the instance is valid.
+
+* The name of each member
+  corresponds to the JSON Schema keyword that is violated.
+* The value is either an object describing a single violation,
+  or an array of such objects.
+
+Each violation object contains two string-valued members
+named `instanceRef` and `schemaRef`.
+`instanceRef` contains the URI fragment serialization
+of a JSON Pointer to the instance subobject
+in which the violation was detected.
+`schemaRef` contains the URI of the schema
+and the fragment serialization of a JSON Pointer
+to the subschema that was violated.
+
+Individual violation objects can contain other keyword-specific members.
+These are detailed further.
+
+For example, validating this instance:
+
+~~~json
+{"numbers": [1, 2, "3", 4, 5]}
+~~~
+
+against this schema:
+
+~~~json
+{
+  "type": "object",
+  "properties": {
+    "numbers": {"$ref": "numbers.schema.json"}
+  }
+}
+~~~
+
+where `numbers.schema.json` refers
+(via a suitable `IRemoteSchemaDocumentProvider`)
+to this schema:
+
+~~~json
+{
+  "type": "array",
+  "items": {"type": "number"}
+}
+~~~
+
+produces the following error object:
+
+~~~json
+{
+  "type": {
+    "instanceRef": "#/numbers/2",
+    "schemaRef": "numbers.schema.json#/items",
+    "expected": ["number"],
+    "actual": "string"
+  }
+}
+~~~
+
+## Validation keywords for numbers {#Numbers}
+
+### multipleOf {#multipleof}
+
+* `expected`: required number strictly greater than 0.
+  The value of the `multipleOf` keyword specified in the schema.
+* `actual`: required number.
+  The instance value.
+
+### maximum {#maximum}
+
+* `expected`: required number.
+  The value of the `maximum` keyword specified in the schema.
+* `exclusiveMaximum`: optional boolean.
+  This will be true if the schema specified `"exclusiveMaximum": true`,
+  and will be omitted otherwise.
+* `actual`: required number.
+  The instance value.
+
+### minimum {#minimum}
+
+* `expected`: required number.
+  The value of the `minimum` keyword specified in the schema.
+* `exclusiveMinimum`: optional boolean.
+  This will be true if the schema specified `"exclusiveMinimum": true`,
+  and will be omitted otherwise.
+* `actual`: required number.
+  The instance value.
+
+## Validation keywords for strings {#Strings}
+
+### maxLength {#maxLength}
+
+* `expected`: required number greater than or equal to 0.
+  The value of the `maxLength` keyword specified in the schema.
+* `actual`: required string.
+  The instance value.
+
+### minLength {#minLength}
+
+* `expected`: required number greater than or equal to 0.
+  The value of the `minLength` keyword specified in the schema.
+* `actual`: required string.
+  The instance value.
+
+### pattern {#pattern}
+
+* `actual`: required string.
+  The instance value.
+
+(The expected pattern is not reported
+because the internal representation in `SchemaDocument`
+does not store the pattern in original string form.)
+
+## Validation keywords for arrays {#Arrays}
+
+### additionalItems {#additionalItems}
+
+This keyword is reported
+when the value of `items` schema keyword is an array,
+the value of `additionalItems` is `false`,
+and the instance is an array
+with more items than specified in the `items` array.
+
+* `disallowed`: required integer greater than or equal to 0.
+  The index of the first item that has no corresponding schema.
+
+### maxItems and minItems {#maxItems-minItems}
+
+* `expected`: required integer greater than or equal to 0.
+  The value of `maxItems` (respectively, `minItems`)
+  specified in the schema.
+* `actual`: required integer greater than or equal to 0.
+  Number of items in the instance array.
+
+### uniqueItems {#uniqueItems}
+
+* `duplicates`: required array
+  whose items are integers greater than or equal to 0.
+  Indices of items of the instance that are equal.
+
+(RapidJSON only reports the first two equal items,
+for performance reasons.)
+
+## Validation keywords for objects
+
+### maxProperties and minProperties {#maxProperties-minProperties}
+
+* `expected`: required integer greater than or equal to 0.
+  The value of `maxProperties` (respectively, `minProperties`)
+  specified in the schema.
+* `actual`: required integer greater than or equal to 0.
+  Number of properties in the instance object.
+
+### required {#required}
+
+* `missing`: required array of one or more unique strings.
+  The names of properties
+  that are listed in the value of the `required` schema keyword
+  but not present in the instance object.
+
+### additionalProperties {#additionalProperties}
+
+This keyword is reported
+when the schema specifies `additionalProperties: false`
+and the name of a property of the instance is
+neither listed in the `properties` keyword
+nor matches any regular expression in the `patternProperties` keyword.
+
+* `disallowed`: required string.
+  Name of the offending property of the instance.
+
+(For performance reasons,
+RapidJSON only reports the first such property encountered.)
+
+### dependencies {#dependencies}
+
+* `errors`: required object with one or more properties.
+  Names and values of its properties are described below.
+
+Recall that JSON Schema Draft 04 supports
+*schema dependencies*,
+where presence of a named *controlling* property
+requires the instance object to be valid against a subschema,
+and *property dependencies*,
+where presence of a controlling property
+requires other *dependent* properties to be also present.
+
+For a violated schema dependency,
+`errors` will contain a property
+with the name of the controlling property
+and its value will be the error object
+produced by validating the instance object
+against the dependent schema.
+
+For a violated property dependency,
+`errors` will contain a property
+with the name of the controlling property
+and its value will be an array of one or more unique strings
+listing the missing dependent properties.
+
+## Validation keywords for any instance type {#AnyTypes}
+
+### enum {#enum}
+
+This keyword has no additional properties
+beyond `instanceRef` and `schemaRef`.
+
+* The allowed values are not listed
+  because `SchemaDocument` does not store them in original form.
+* The violating value is not reported
+  because it might be unwieldy.
+
+If you need to report these details to your users,
+you can access the necessary information
+by following `instanceRef` and `schemaRef`.
+
+### type {#type}
+
+* `expected`: required array of one or more unique strings,
+  each of which is one of the seven primitive types
+  defined by the JSON Schema Draft 04 Core specification.
+  Lists the types allowed by the `type` schema keyword.
+* `actual`: required string, also one of seven primitive types.
+  The primitive type of the instance.
+
+### allOf, anyOf, and oneOf {#allOf-anyOf-oneOf}
+
+* `errors`: required array of at least one object.
+  There will be as many items as there are subschemas
+  in the `allOf`, `anyOf` or `oneOf` schema keyword, respectively.
+  Each item will be the error value
+  produced by validating the instance
+  against the corresponding subschema.
+
+For `allOf`, at least one error value will be non-empty.
+For `anyOf`, all error values will be non-empty.
+For `oneOf`, either all error values will be non-empty,
+or more than one will be empty.
+
+### not {#not}
+
+This keyword has no additional properties
+apart from `instanceRef` and `schemaRef`.

example/schemavalidator/schemavalidator.cpp

@@ -6,6 +6,7 @@
 #include "rapidjson/filereadstream.h"
 #include "rapidjson/schema.h"
 #include "rapidjson/stringbuffer.h"
+#include "rapidjson/prettywriter.h"
 
 using namespace rapidjson;
 
@@ -67,6 +68,11 @@ int main(int argc, char *argv[]) {
         sb.Clear();
         validator.GetInvalidDocumentPointer().StringifyUriFragment(sb);
         fprintf(stderr, "Invalid document: %s\n", sb.GetString());
+        // Detailed violation report is available as a JSON value
+        sb.Clear();
+        PrettyWriter<StringBuffer> w(sb);
+        validator.GetError().Accept(w);
+        fprintf(stderr, "Error report:\n%s\n", sb.GetString());
         return EXIT_FAILURE;
     }
 }