Alternative Validation implementation

src/Microsoft.OpenApi/Properties/SRResource.resx

@@ -129,6 +129,9 @@
   <data name="IndentationLevelInvalid" xml:space="preserve">
     <value>Indentation level cannot be lower than 0.</value>
   </data>
+  <data name="InputItemShouldBeType" xml:space="preserve">
+    <value>The input item should be in type of '{0}'.</value>
+  </data>
   <data name="ObjectScopeNeededForPropertyNameWriting" xml:space="preserve">
     <value>The active scope must be an object scope for property name '{0}' to be written.</value>
   </data>
@@ -177,4 +180,25 @@
   <data name="SourceExpressionHasInvalidFormat" xml:space="preserve">
     <value>The source expression '{0}' has invalid format.</value>
   </data>
+  <data name="UnknownVisitorType" xml:space="preserve">
+    <value>Can not find visitor type registered for type '{0}'.</value>
+  </data>
+  <data name="Validation_ComponentsKeyMustMatchRegularExpr" xml:space="preserve">
+    <value>The key '{0}' in '{1}' of components MUST match the regular expression '{2}'.</value>
+  </data>
+  <data name="Validation_ExtensionNameMustBeginWithXDash" xml:space="preserve">
+    <value>The extension name '{0}' in '{1}' object MUST begin with 'x-'.</value>
+  </data>
+  <data name="Validation_FieldIsRequired" xml:space="preserve">
+    <value>The field '{0}' in '{1}' object is REQUIRED.</value>
+  </data>
+  <data name="Validation_PathItemMustBeginWithSlash" xml:space="preserve">
+    <value>The path item name '{0}' MUST begin with a slash.</value>
+  </data>
+  <data name="Validation_RuleAddTwice" xml:space="preserve">
+    <value>The same rule cannot be in the same rule set twice.</value>
+  </data>
+  <data name="Validation_StringMustBeEmailAddress" xml:space="preserve">
+    <value>The string '{0}' MUST be in the format of an email address.</value>
+  </data>
 </root>

src/Microsoft.OpenApi/Services/OpenApiValidator.cs

@@ -2,8 +2,10 @@
 // Licensed under the MIT license. 
 
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.OpenApi.Exceptions;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Validations;
 
 namespace Microsoft.OpenApi.Services
 {
@@ -12,20 +14,43 @@ namespace Microsoft.OpenApi.Services
     /// </summary>
     public class OpenApiValidator : OpenApiVisitorBase
     {
-        /// <summary>
-        /// Exceptions related to this validation.
-        /// </summary>
-        public List<OpenApiException> Exceptions { get; } = new List<OpenApiException>();
+        readonly ValidationRuleSet _ruleSet;
+        readonly ValidationContext _context;
 
         /// <summary>
-        /// Visit Open API Response element.
+        /// Create a vistor that will validate an OpenAPIDocument
         /// </summary>
-        /// <param name="response">Response element.</param>
-        public override void Visit(OpenApiResponse response)
+        /// <param name="ruleSet"></param>
+        public OpenApiValidator(ValidationRuleSet ruleSet = null)
+        {
+            _ruleSet = ruleSet ?? ValidationRuleSet.DefaultRuleSet;
+            _context = new ValidationContext(_ruleSet);
+        }
+
+        public override void Visit(OpenApiDocument item) => Validate(item);
+        public override void Visit(OpenApiInfo item) => Validate(item);
+        public override void Visit(OpenApiContact item) => Validate(item);
+        public override void Visit(OpenApiComponents item) => Validate(item);
+
+        public override void Visit(OpenApiResponse item) => Validate(item);
+
+        public override void Visit(OpenApiExternalDocs item) => Validate(item);
+
+        public override void Visit(OpenApiLicense item) => Validate(item);
+        public override void Visit(OpenApiOAuthFlow item) => Validate(item);
+        public override void Visit(OpenApiTag item) => Validate(item);
+        public override void Visit(OpenApiServer item) => Validate(item);
+
+
+        public IEnumerable<ValidationError> Errors => _context.Errors;
+
+        private void Validate<T>(T item)
         {
-            if (string.IsNullOrEmpty(response.Description))
+            if (item == null) return;  // Required fields should be checked by higher level objects
+            var rules = _ruleSet.Where(r => r.ElementType == typeof(T));
+            foreach (var rule in rules)
             {
-                Exceptions.Add(new OpenApiException("Response must have a description"));
+                rule.Evaluate(_context, item);
             }
         }
     }

src/Microsoft.OpenApi/Services/OpenApiVisitorBase.cs

@@ -13,143 +13,186 @@ namespace Microsoft.OpenApi.Services
     public abstract class OpenApiVisitorBase
     {
         /// <summary>
-        /// Validates <see cref="OpenApiDocument"/>
+        /// Visits <see cref="OpenApiDocument"/>
         /// </summary>
         public virtual void Visit(OpenApiDocument doc)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiInfo"/>
+        /// Visits <see cref="OpenApiInfo"/>
         /// </summary>
         public virtual void Visit(OpenApiInfo info)
         {
         }
 
         /// <summary>
-        /// Validates list of <see cref="OpenApiServer"/>
+        /// Visits <see cref="OpenApiContact"/>
+        /// </summary>
+        public virtual void Visit(OpenApiContact contact)
+        {
+        }
+
+
+        /// <summary>
+        /// Visits <see cref="OpenApiLicense"/>
+        /// </summary>
+        public virtual void Visit(OpenApiLicense license)
+        {
+        }
+
+        /// <summary>
+        /// Visits list of <see cref="OpenApiServer"/>
         /// </summary>
         public virtual void Visit(IList<OpenApiServer> servers)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiServer"/>
+        /// Visits <see cref="OpenApiServer"/>
         /// </summary>
         public virtual void Visit(OpenApiServer server)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiPaths"/>
+        /// Visits <see cref="OpenApiPaths"/>
         /// </summary>
         public virtual void Visit(OpenApiPaths paths)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiPathItem"/>
+        /// Visits <see cref="OpenApiPathItem"/>
         /// </summary>
         public virtual void Visit(OpenApiPathItem pathItem)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiServerVariable"/>
+        /// Visits <see cref="OpenApiServerVariable"/>
         /// </summary>
         public virtual void Visit(OpenApiServerVariable serverVariable)
         {
         }
 
         /// <summary>
-        /// Validates the operations.
+        /// Visits the operations.
         /// </summary>
         public virtual void Visit(IDictionary<OperationType, OpenApiOperation> operations)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiOperation"/>
+        /// Visits <see cref="OpenApiOperation"/>
         /// </summary>
         public virtual void Visit(OpenApiOperation operation)
         {
         }
 
         /// <summary>
-        /// Validates list of <see cref="OpenApiParameter"/>
+        /// Visits list of <see cref="OpenApiParameter"/>
         /// </summary>
         public virtual void Visit(IList<OpenApiParameter> parameters)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiParameter"/>
+        /// Visits <see cref="OpenApiParameter"/>
         /// </summary>
         public virtual void Visit(OpenApiParameter parameter)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiRequestBody"/>
+        /// Visits <see cref="OpenApiRequestBody"/>
         /// </summary>
         public virtual void Visit(OpenApiRequestBody requestBody)
         {
         }
 
         /// <summary>
-        /// Validates responses.
+        /// Visits responses.
         /// </summary>
         public virtual void Visit(IDictionary<string, OpenApiResponse> responses)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiResponse"/>
+        /// Visits <see cref="OpenApiResponse"/>
         /// </summary>
         public virtual void Visit(OpenApiResponse response)
         {
         }
 
         /// <summary>
-        /// Validates media type content.
+        /// Visits media type content.
         /// </summary>
         public virtual void Visit(IDictionary<string, OpenApiMediaType> content)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiMediaType"/>
+        /// Visits <see cref="OpenApiMediaType"/>
         /// </summary>
         public virtual void Visit(OpenApiMediaType mediaType)
         {
         }
 
         /// <summary>
-        /// Validates the examples.
+        /// Visits the examples.
         /// </summary>
         public virtual void Visit(IDictionary<string, OpenApiExample> examples)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiSchema"/>
+        /// Visits <see cref="OpenApiComponents"/>
+        /// </summary>
+        public virtual void Visit(OpenApiComponents components)
+        {
+        }
+
+
+        /// <summary>
+        /// Visits <see cref="OpenApiComponents"/>
+        /// </summary>
+        public virtual void Visit(OpenApiExternalDocs externalDocs)
+        {
+        }
+
+        /// <summary>
+        /// Visits <see cref="OpenApiSchema"/>
         /// </summary>
         public virtual void Visit(OpenApiSchema schema)
         {
         }
 
         /// <summary>
-        /// Validates the links.
+        /// Visits the links.
         /// </summary>
         public virtual void Visit(IDictionary<string, OpenApiLink> links)
         {
         }
 
         /// <summary>
-        /// Validates <see cref="OpenApiLink"/>
+        /// Visits <see cref="OpenApiLink"/>
         /// </summary>
         public virtual void Visit(OpenApiLink link)
         {
         }
+
+        /// <summary>
+        /// Visits <see cref="OpenApiTag"/>
+        /// </summary>
+        public virtual void Visit(OpenApiTag tag)
+        {
+        }
+        /// <summary>
+        /// Visits <see cref="OpenApiOAuthFlow"/>
+        /// </summary>
+        public virtual void Visit(OpenApiOAuthFlow openApiOAuthFlow)
+        {
+        }
     }
 }