Fixes for discriminator (#971)

* Fix discriminator

* Fix oneOf

* Filter messages for oneOf discriminator

* Support discriminator in oneOf sibling

* Fix

* Fix

* Fix

* Support mappings

* Refactor

* Update doc

doc/openapi-discriminators.md

@@ -2,28 +2,32 @@
 
 ## OpenAPI 3.x discriminator support
 
-Starting with `1.0.51`, `json-schema-validator` partly supports the use of discriminators as described under
-https://github.com/OAI/OpenAPI-Specification/blame/master/versions/3.0.3.md#L2693 and following.
+Starting with `1.0.51`, `json-schema-validator` partly supports the use of the [`discriminator`](https://github.com/OAI/OpenAPI-Specification/blob/7cc8f4c4e742a20687fa65ace54ed32fcb8c6df0/versions/3.1.0.md#discriminator-object) keyword.
+
+Note that the use of the `discriminator` keyword does not affect the validation of `anyOf` or `oneOf`. The use of `discriminator` is not equivalent to having a `if`/`then` with the `discriminator` propertyName. 
+
+When a `discriminator` is used, the assertions generated by `anyOf` or `oneOf` will only be the assertions generated from the schema that the discriminator applies to. An assertion will be generated if a `discriminator` is used but there is no matching schema that maps to the value in the `propertyName`.
 
 ## How to use
 
 1. Configure `SchemaValidatorsConfig` accordingly:
    ```java
    class Demo{ 
-    void demo() {
+     void demo() {
         SchemaValidatorsConfig config = new SchemaValidatorsConfig();
         config.setOpenAPI3StyleDiscriminators(true); // defaults to false
-    }
+     }
    }
    ```
-2. Use the configured `SchemaValidatorsConfig` with the `JSONSchemaFactory` when creating the `JSONSchema`
+2. Use the configured `SchemaValidatorsConfig` with the `JsonSchemaFactory` when creating the `JsonSchema`
    ```java
    class Demo{ 
-    void demo() {
+     void demo() {
         SchemaValidatorsConfig config = new SchemaValidatorsConfig();
         config.setOpenAPI3StyleDiscriminators(true); // defaults to false
-        JsonSchema schema = validatorFactory.getSchema(schemaURI, schemaJacksonJsonNode, config);
-    }
+        JsonSchemaFactory factory = JsonSchemaFactory.getInstance(VersionFlag.V202012);
+        JsonSchema schema = factory.getSchema(schemaURI, schemaJacksonJsonNode, config);
+     }
    }
    ```
 3. Ensure that the type field that you want to use as discriminator `propertyName` is required in your schema
@@ -43,9 +47,6 @@ those parts that are indisputable are considered at this moment.
 
 * `propertyName` redefinition is prohibited on additive discriminators
 * `mapping` key redefinition is also prohibited on additive discriminators
-* `oneOf` ignores discriminators as today it is not clear from the spec whether `oneOf` + `discriminator` should be equal to
-  `anyOf` + `discriminator` or not. Especially if `oneOf` should respect the discriminator and skip the other schemas, it's
-  functionally not JSON Schema `oneOf` anymore as multiple matches would not make the validation fail anymore.
 * the specification indicates that inline properties should be ignored.
   So, this example would respect `foo`
     ```yaml
@@ -71,11 +72,11 @@ those parts that are indisputable are considered at this moment.
 
 ## Schema Examples
 
-more examples in https://github.com/networknt/json-schema-validator/blob/master/src/test/resources/openapi3/discriminator.json
+More examples in https://github.com/networknt/json-schema-validator/blob/master/src/test/resources/openapi3/discriminator.json
 
 ### Base type and extended type (the `anyOf` forward references are required)
 
-#### the simplest example:
+#### Example:
 
 ```json
 {

src/main/java/com/networknt/schema/AnyOfValidator.java

@@ -32,7 +32,6 @@ public class AnyOfValidator extends BaseJsonValidator {
     private static final String DISCRIMINATOR_REMARK = "and the discriminator-selected candidate schema didn't pass validation";
 
     private final List<JsonSchema> schemas = new ArrayList<>();
-    private final DiscriminatorContext discriminatorContext;
 
     private Boolean canShortCircuit = null;
 
@@ -43,12 +42,6 @@ public AnyOfValidator(SchemaLocation schemaLocation, JsonNodePath evaluationPath
             this.schemas.add(validationContext.newSchema(schemaLocation.append(i), evaluationPath.append(i),
                     schemaNode.get(i), parentSchema));
         }
-
-        if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
-            this.discriminatorContext = new DiscriminatorContext();
-        } else {
-            this.discriminatorContext = null;
-        }
     }
 
     @Override
@@ -59,7 +52,7 @@ public Set<ValidationMessage> validate(ExecutionContext executionContext, JsonNo
         ValidatorState state = executionContext.getValidatorState();
 
         if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
-            executionContext.enterDiscriminatorContext(this.discriminatorContext, instanceLocation);
+            executionContext.enterDiscriminatorContext(new DiscriminatorContext(), instanceLocation);
         }
 
         boolean initialHasMatchedNode = state.hasMatchedNode();
@@ -113,7 +106,7 @@ && canShortCircuit() && canShortCircuit(executionContext)) {
                         // return empty errors.
                         return errors;
                     } else if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
-                        if (this.discriminatorContext.isDiscriminatorMatchFound()) {
+                        if (executionContext.getCurrentDiscriminatorContext().isDiscriminatorMatchFound()) {
                             if (!errors.isEmpty()) {
                                 // The following is to match the previous logic adding to all errors
                                 // which is generally discarded as it returns errors but the allErrors
@@ -143,7 +136,8 @@ && canShortCircuit() && canShortCircuit(executionContext)) {
                 executionContext.setFailFast(failFast);
             }
 
-            if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators() && this.discriminatorContext.isActive()) {
+            if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()
+                    && executionContext.getCurrentDiscriminatorContext().isActive()) {
                 return Collections.singleton(message().instanceNode(node).instanceLocation(instanceLocation)
                         .locale(executionContext.getExecutionConfig().getLocale())
                         .arguments(

src/main/java/com/networknt/schema/DiscriminatorValidator.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.networknt.schema;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+/**
+ * {@link JsonValidator} that resolves discriminator.
+ */
+public class DiscriminatorValidator extends BaseJsonValidator {
+    private final String propertyName;
+    private final Map<String, String> mapping;
+
+    public DiscriminatorValidator(SchemaLocation schemaLocation, JsonNodePath evaluationPath, JsonNode schemaNode,
+            JsonSchema parentSchema, ValidationContext validationContext) {
+        super(schemaLocation, evaluationPath, schemaNode, parentSchema, ValidatorTypeCode.DISCRIMINATOR,
+                validationContext);
+        ObjectNode discriminator = schemaNode.isObject() ? (ObjectNode) schemaNode : null;
+        if (discriminator != null) {
+            JsonNode propertyName = discriminator.get("propertyName");
+            this.propertyName = propertyName != null ? propertyName.asText() : "";
+            JsonNode mappingNode = discriminator.get("mapping");
+            ObjectNode mapping = mappingNode != null && mappingNode.isObject() ? (ObjectNode) mappingNode : null;
+            if (mapping != null) {
+                this.mapping = new HashMap<>();
+                for (Iterator<Entry<String, JsonNode>> iter = mapping.fields(); iter.hasNext();) {
+                    Entry<String, JsonNode> entry = iter.next();
+                    this.mapping.put(entry.getKey(), entry.getValue().asText());
+                }
+            } else {
+                this.mapping = Collections.emptyMap();
+            }
+        } else {
+            this.propertyName = "";
+            this.mapping = Collections.emptyMap();
+        }
+    }
+
+    @Override
+    public Set<ValidationMessage> validate(ExecutionContext executionContext, JsonNode node, JsonNode rootNode,
+            JsonNodePath instanceLocation) {
+        return Collections.emptySet();
+    }
+
+    /**
+     * Gets the property name of the discriminator.
+     * 
+     * @return the property name
+     */
+    public String getPropertyName() {
+        return propertyName;
+    }
+
+    /**
+     * Gets the mapping to map the property name value to the schema name.
+     * 
+     * @return the discriminator mappings
+     */
+    public Map<String, String> getMapping() {
+        return mapping;
+    }
+}

src/main/java/com/networknt/schema/JsonMetaSchema.java

@@ -358,6 +358,14 @@ public JsonValidator newValidator(ValidationContext validationContext, SchemaLoc
         try {
             Keyword kw = this.keywords.get(keyword);
             if (kw == null) {
+                if ("message".equals(keyword) && validationContext.getConfig().isCustomMessageSupported()) {
+                    return null;
+                }
+                if (ValidatorTypeCode.DISCRIMINATOR.getValue().equals(keyword)
+                        && validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
+                    return ValidatorTypeCode.DISCRIMINATOR.newValidator(schemaLocation, evaluationPath, schemaNode,
+                            parentSchema, validationContext);
+                }
                 if (UNKNOWN_KEYWORDS.put(keyword, keyword) == null) {
                     logger.warn("Unknown keyword {} - you should define your own Meta Schema. If the keyword is irrelevant for validation, just use a NonValidationKeyword", keyword);
                 }

src/main/java/com/networknt/schema/OneOfValidator.java

@@ -62,6 +62,15 @@ public Set<ValidationMessage> validate(ExecutionContext executionContext, JsonNo
         // Save flag as nested schema evaluation shouldn't trigger fail fast
         boolean failFast = executionContext.isFailFast();
         try {
+            DiscriminatorValidator discriminator = null;
+            if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
+                DiscriminatorContext discriminatorContext = new DiscriminatorContext();
+                executionContext.enterDiscriminatorContext(discriminatorContext, instanceLocation);
+
+                // check if discriminator present
+                discriminator = (DiscriminatorValidator) this.getParentSchema().getValidators().stream()
+                        .filter(v -> "discriminator".equals(v.getKeyword())).findFirst().orElse(null);
+            }
             executionContext.setFailFast(false);
             for (JsonSchema schema : this.schemas) {
                 Set<ValidationMessage> schemaErrors = Collections.emptySet();
@@ -95,23 +104,62 @@ public Set<ValidationMessage> validate(ExecutionContext executionContext, JsonNo
                     // note that the short circuit means that only 2 valid schemas are reported even if could be more
                     break;
                 }
-
-                if (!schemaErrors.isEmpty() && reportChildErrors(executionContext)) {
+
+                if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
+                    // The discriminator will cause all messages other than the one with the
+                    // matching discriminator to be discarded. Note that the discriminator cannot
+                    // affect the actual validation result.
+                    if (discriminator != null && !discriminator.getPropertyName().isEmpty()) {
+                        String discriminatorPropertyValue = node.get(discriminator.getPropertyName()).asText();
+                        discriminatorPropertyValue = discriminator.getMapping().getOrDefault(discriminatorPropertyValue,
+                                discriminatorPropertyValue);
+                        JsonNode refNode = schema.getSchemaNode().get("$ref");
+                        if (refNode != null) {
+                            String ref = refNode.asText();
+                            if (ref.equals(discriminatorPropertyValue) || ref.endsWith("/" + discriminatorPropertyValue)) {
+                                executionContext.getCurrentDiscriminatorContext().markMatch();
+                            }
+                        }
+                    }
+                    boolean discriminatorMatchFound = executionContext.getCurrentDiscriminatorContext().isDiscriminatorMatchFound();
+                    if (discriminatorMatchFound && childErrors == null) {
+                        // Note that the match is set if found and not reset so checking if childErrors
+                        // found is null triggers on the correct schema
+                        childErrors = new SetView<>();
+                        childErrors.union(schemaErrors);
+                    }
+                } else if (!schemaErrors.isEmpty() && reportChildErrors(executionContext)) {
+                    // This is the normal handling when discriminators aren't enabled
                     if (childErrors == null) {
                         childErrors = new SetView<>();
                     }
                     childErrors.union(schemaErrors);
                 }
                 index++;
             }
+
+            if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()
+                    && (discriminator != null || executionContext.getCurrentDiscriminatorContext().isActive())
+                    && !executionContext.getCurrentDiscriminatorContext().isDiscriminatorMatchFound()) {
+                errors = Collections.singleton(message().instanceNode(node).instanceLocation(instanceLocation)
+                        .locale(executionContext.getExecutionConfig().getLocale())
+                        .arguments(
+                                "based on the provided discriminator. No alternative could be chosen based on the discriminator property")
+                        .build());
+            }
         } finally {
             // Restore flag
             executionContext.setFailFast(failFast);
+
+            if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()) {
+                executionContext.leaveDiscriminatorContextImmediately(instanceLocation);
+            }
         }
 
         // ensure there is always an "OneOf" error reported if number of valid schemas
         // is not equal to 1.
-        if (numberOfValidSchema != 1) {
+        // errors will only not be null in the discriminator case where no match is found
+        if (numberOfValidSchema != 1 && errors == null) {
             ValidationMessage message = message().instanceNode(node).instanceLocation(instanceLocation)
                     .messageKey(numberOfValidSchema > 1 ? "oneOf.indexes" : "oneOf")
                     .locale(executionContext.getExecutionConfig().getLocale())

src/main/java/com/networknt/schema/ValidatorTypeCode.java

@@ -32,6 +32,7 @@ JsonValidator newInstance(SchemaLocation schemaLocation, JsonNodePath evaluation
 }
 
 enum VersionCode {
+    None(new SpecVersion.VersionFlag[] { }),
     AllVersions(new SpecVersion.VersionFlag[] { SpecVersion.VersionFlag.V4, SpecVersion.VersionFlag.V6, SpecVersion.VersionFlag.V7, SpecVersion.VersionFlag.V201909, SpecVersion.VersionFlag.V202012 }),
     MinV6(new SpecVersion.VersionFlag[] { SpecVersion.VersionFlag.V6, SpecVersion.VersionFlag.V7, SpecVersion.VersionFlag.V201909, SpecVersion.VersionFlag.V202012 }),
     MinV7(new SpecVersion.VersionFlag[] { SpecVersion.VersionFlag.V7, SpecVersion.VersionFlag.V201909, SpecVersion.VersionFlag.V202012 }),
@@ -51,8 +52,8 @@ enum VersionCode {
     }
 
     EnumSet<VersionFlag> getVersions() {
-		return this.versions;
-	}
+        return this.versions;
+    }
 }
 
 public enum ValidatorTypeCode implements Keyword, ErrorMessageType {
@@ -66,6 +67,7 @@ public enum ValidatorTypeCode implements Keyword, ErrorMessageType {
     DEPENDENCIES("dependencies", "1007", DependenciesValidator::new, VersionCode.AllVersions),
     DEPENDENT_REQUIRED("dependentRequired", "1045", DependentRequired::new, VersionCode.MinV201909),
     DEPENDENT_SCHEMAS("dependentSchemas", "1046", DependentSchemas::new, VersionCode.MinV201909),
+    DISCRIMINATOR("discriminator", "2001", DiscriminatorValidator::new, VersionCode.None),
     DYNAMIC_REF("$dynamicRef", "1051", DynamicRefValidator::new, VersionCode.MinV202012),
     ENUM("enum", "1008", EnumValidator::new, VersionCode.AllVersions),
     EXCLUSIVE_MAXIMUM("exclusiveMaximum", "1038", ExclusiveMaximumValidator::new, VersionCode.MinV6),