fix#375-Added ValidateSchemaRequiredFields and ValidateSchemaDiscriminator

Author: senthilkumarmohan

src/Microsoft.OpenApi/Properties/SRResource.Designer.cs

@@ -216,6 +216,15 @@
   <data name="Validation_RuleAddTwice" xml:space="preserve">
     <value>The same rule cannot be in the same rule set twice.</value>
   </data>
+  <data name="Validation_SchemaMustContainPropertySpecifiedInTheDiscriminator" xml:space="preserve">
+    <value>Schema {0} must contain property specified in the discriminator {1}.</value>
+  </data>
+  <data name="Validation_SchemaMustContainPropertySpecifiedInTheRequiredField" xml:space="preserve">
+    <value>Schema {0} must contain property specified in the required field {0}.</value>
+  </data>
+  <data name="Validation_SchemaRequiredFieldListMustContainThePropertySpecifiedInTheDiscriminator" xml:space="preserve">
+    <value>Schema {0} must contain property specified in the discriminator {1} in the required field list.</value>
+  </data>
   <data name="Validation_StringMustBeEmailAddress" xml:space="preserve">
     <value>The string '{0}' MUST be in the format of an email address.</value>
   </data>

src/Microsoft.OpenApi/Properties/SRResource.resx

@@ -772,7 +772,7 @@ internal void Walk(OpenApiSchema schema)
 
             if (schema.AnyOf != null)
             {
-                Walk("anyOf", () => Walk(schema.AllOf));
+                Walk("anyOf", () => Walk(schema.AnyOf));
             }
 
             if (schema.Properties != null) {
@@ -883,7 +883,7 @@ internal void Walk(IList<OpenApiSchema> schemas)
                 }
             }
         }
-
+        
         /// <summary>
         /// Visits <see cref="OpenApiOAuthFlows"/> and child objects
         /// </summary>

src/Microsoft.OpenApi/Services/OpenApiWalker.cs

@@ -57,6 +57,62 @@ public static class OpenApiSchemaRules
                     context.Exit();
                 });
 
+        /// <summary>
+        /// Validates Schema Required Fields
+        /// </summary>
+        public static ValidationRule<OpenApiSchema> ValidateSchemaRequiredFields =>
+            new ValidationRule<OpenApiSchema>(
+                (context, schema) =>
+                {
+                    // discriminator
+                    context.Enter("required");
+
+                    if (schema.Reference != null)
+                    {
+                        foreach (var requiredField in schema.Required)
+                        {
+                            if (!schema.Properties.ContainsKey(requiredField))
+                            {
+                                context.CreateError(nameof(ValidateSchemaDiscriminator),
+                                                    string.Format(SRResource.Validation_SchemaMustContainPropertySpecifiedInTheRequiredField,
+                                                                                    requiredField));
+                            }
+                        }
+                    }
+
+                    context.Exit();
+                });
+
+        /// <summary>
+        /// Validates Schema Discriminator
+        /// </summary>
+        public static ValidationRule<OpenApiSchema> ValidateSchemaDiscriminator =>
+            new ValidationRule<OpenApiSchema>(
+                (context, schema) =>
+                {
+                    // discriminator
+                    context.Enter("discriminator");
+
+                    if(schema.Reference != null && schema.Discriminator != null)
+                    {
+                        if (!schema.Properties.ContainsKey(schema.Discriminator.PropertyName))
+                        {
+                            context.CreateError(nameof(ValidateSchemaDiscriminator),
+                                                string.Format(SRResource.Validation_SchemaMustContainPropertySpecifiedInTheDiscriminator,
+                                                                                schema.Reference.Id, schema.Discriminator.PropertyName));
+                        }
+
+                        if (!schema.Required.Contains(schema.Discriminator?.PropertyName))
+                        {
+                            context.CreateError(nameof(ValidateSchemaDiscriminator),
+                                                string.Format(SRResource.Validation_SchemaRequiredFieldListMustContainThePropertySpecifiedInTheDiscriminator,
+                                                                                schema.Reference.Id, schema.Discriminator.PropertyName));
+                        }
+                    }
+
+                    context.Exit();
+                });
+
         /// <summary>
         /// Validates OneOf Discriminator
         /// </summary>
@@ -97,7 +153,7 @@ public static class OpenApiSchemaRules
 
         // add more rule.
 
-        
+
         /// <summary>
         /// Checks if the schemas in the list contain a property with the property name specified by the discriminator.
         /// </summary>