Validation fixes based on PR review

Author: darrelmiller

src/Microsoft.OpenApi/Interfaces/IOpenApiExtension.cs

@@ -1,9 +1,7 @@
-using Microsoft.OpenApi.Writers;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. 
+
+using Microsoft.OpenApi.Writers;
 
 namespace Microsoft.OpenApi.Interfaces
 {

src/Microsoft.OpenApi/Services/OpenApiVisitorBase.cs

@@ -10,7 +10,7 @@
 namespace Microsoft.OpenApi.Services
 {
     /// <summary>
-    /// Open API visitor base providing base validation logic for each <see cref="IOpenApiElement"/>
+    /// Open API visitor base provides common logic for concrete vistors
     /// </summary>
     public abstract class OpenApiVisitorBase
     {
@@ -285,5 +285,11 @@ public virtual void Visit(IOpenApiExtension openApiExtension)
         {
         }
 
+        /// <summary>
+        /// Visits list of <see cref="OpenApiExample"/>
+        /// </summary>
+        public virtual void Visit(IList<OpenApiExample> example)
+        {
+        }
     }
 }

src/Microsoft.OpenApi/Services/OpenApiWalker.cs

@@ -51,9 +51,15 @@ internal void Walk(IList<OpenApiTag> tags)
             _visitor.Enter(OpenApiConstants.Tags);
             _visitor.Visit(tags);
 
-            foreach (var tag in tags)
+            // Visit tags
+            if (tags != null)
             {
-                Walk(tag);
+                for (int i = 0; i < tags.Count; i++)
+                {
+                    _visitor.Enter(i.ToString());
+                    Walk(tags[i]);
+                    _visitor.Exit();
+                }
             }
             _visitor.Exit();
 
@@ -91,7 +97,7 @@ internal void Walk(OpenApiPaths paths)
             _visitor.Visit(paths);
             foreach (var pathItem in paths)
             {
-                _visitor.Enter(pathItem.Key.Replace("/","~1"));
+                _visitor.Enter(pathItem.Key.Replace("/","~1"));  // JSON Pointer uses ~1 as an escape character for /
                 Walk(pathItem.Value);
                 _visitor.Exit();
             }
@@ -110,9 +116,11 @@ internal void Walk(IList<OpenApiServer> servers)
             // Visit Servers
             if (servers != null)
             {
-                foreach (var server in servers)
+                for (int i = 0; i < servers.Count; i++)
                 {
-                    Walk(server);
+                    _visitor.Enter(i.ToString());
+                    Walk(servers[i]);
+                    _visitor.Exit();
                 }
             }
             _visitor.Exit();
@@ -195,11 +203,9 @@ internal void Walk(OpenApiTag tag)
         /// <param name="server"></param>
         internal void Walk(OpenApiServer server)
         {
-            _visitor.Enter(OpenApiConstants.Server);
             _visitor.Visit(server);
             Walk(server.Variables);
             _visitor.Visit(server as IOpenApiExtensible);
-            _visitor.Exit();
         }
 
         /// <summary>
@@ -272,16 +278,19 @@ internal void Walk(OpenApiOperation operation)
         /// <param name="parameters"></param>
         internal void Walk(IList<OpenApiParameter> parameters)
         {
+            _visitor.Enter(OpenApiConstants.Parameters);
+            _visitor.Visit(parameters);
+
             if (parameters != null)
             {
-                _visitor.Enter(OpenApiConstants.Parameters);
-                _visitor.Visit(parameters);
-                foreach (var parameter in parameters)
+                for (int i = 0; i < parameters.Count; i++)
                 {
-                    Walk(parameter);
+                    _visitor.Enter(i.ToString());
+                    Walk(parameters[i]);
+                    _visitor.Exit();
                 }
-                _visitor.Exit();
             }
+            _visitor.Exit();
         }
 
         /// <summary>
@@ -466,10 +475,20 @@ internal void Walk(OpenApiExample example)
         /// <param name="examples"></param>
         internal void Walk(IList<OpenApiExample> examples)
         {
-            foreach (var item in examples)
+            _visitor.Enter(OpenApiConstants.Examples);
+            _visitor.Visit(examples);
+
+            // Visit Examples
+            if (examples != null)
             {
-                _visitor.Visit(item);
+                for (int i = 0; i < examples.Count; i++)
+                {
+                    _visitor.Enter(i.ToString());
+                    Walk(examples[i]);
+                    _visitor.Exit();
+                }
             }
+            _visitor.Exit();
         }
 
         /// <summary>

src/Microsoft.OpenApi/Services/VisitorContext.cs

@@ -14,7 +14,6 @@ namespace Microsoft.OpenApi.Validations
     /// </summary>
     public interface IValidationContext 
     {
-
         /// <summary>
         /// Register an error with the validation context.
         /// </summary>

src/Microsoft.OpenApi/Validations/ValidationContext.cs renamed to src/Microsoft.OpenApi/Validations/IValidationContext.cs

@@ -150,7 +150,12 @@ public void AddError(ValidationError error)
         /// <param name="item">The object to be validated</param>
         public override void Visit(IOpenApiExtension item) => Validate(item, item.GetType());
 
-        
+        /// <summary>
+        /// Execute validation rules against a list of <see cref="OpenApiExample"/>
+        /// </summary>
+        /// <param name="items">The object to be validated</param>
+        public override void Visit(IList<OpenApiExample> items) => Validate(items, items.GetType());
+
         private void Validate<T>(T item)
         {
             var type = typeof(T);

src/Microsoft.OpenApi/Validations/OpenApiValidator.cs

@@ -52,5 +52,38 @@ public void ResponseMustHaveADescription()
                             String.Format(SRResource.Validation_FieldIsRequired, "description", "response"))
         });
         }
+
+        [Fact]
+        public void ServersShouldBeReferencedByIndex()
+        {
+            var openApiDocument = new OpenApiDocument();
+            openApiDocument.Info = new OpenApiInfo()
+            {
+                Title = "foo",
+                Version = "1.2.2"
+            };
+            openApiDocument.Servers = new List<OpenApiServer> {
+                new OpenApiServer
+                {
+                    Url = "http://example.org"
+                },
+                new OpenApiServer
+                {
+
+                }
+            };
+            
+            var validator = new OpenApiValidator();
+            var walker = new OpenApiWalker(validator);
+            walker.Walk(openApiDocument);
+
+            validator.Errors.ShouldBeEquivalentTo(
+                    new List<ValidationError>
+                    {
+                        new ValidationError(ErrorReason.Required, "#/servers/1/url",
+                            String.Format(SRResource.Validation_FieldIsRequired, "url", "server"))
+        });
+        }
+
     }
 }