fix: handle deserializing and writing empty security requirements #1426

src/Microsoft.OpenApi/Models/OpenApiOperation.cs

@@ -213,8 +213,8 @@ private void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion version
             writer.WriteProperty(OpenApiConstants.Deprecated, Deprecated, false);
 
             // security
-            writer.WriteOptionalCollection(OpenApiConstants.Security, Security, callback);
-
+            writer.WriteOptionalOrEmptyCollection(OpenApiConstants.Security, Security, callback);
+            
             // servers
             writer.WriteOptionalCollection(OpenApiConstants.Servers, Servers, callback);
 

src/Microsoft.OpenApi/Reader/V2/OpenApiOperationDeserializer.cs

@@ -10,7 +10,7 @@
 using Microsoft.OpenApi.Models.References;
 using Microsoft.OpenApi.Models.Interfaces;
 using System;
-using Microsoft.OpenApi.Interfaces;
+using System.Text.Json.Nodes;
 
 namespace Microsoft.OpenApi.Reader.V2
 {
@@ -96,7 +96,10 @@ internal static partial class OpenApiV2Deserializer
                 },
                 {
                     "security",
-                    (o, n, t) => o.Security = n.CreateList(LoadSecurityRequirement, t)
+                    (o, n, t) => { if (n.JsonNode is JsonArray)
+                    {
+                        o.Security = new List<OpenApiSecurityRequirement>(n.CreateList(LoadSecurityRequirement, t)); 
+                    } }
                 },
             };
 

src/Microsoft.OpenApi/Reader/V3/OpenApiOperationDeserializer.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json.Nodes;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Models.References;
@@ -83,7 +84,13 @@ internal static partial class OpenApiV3Deserializer
                 },
                 {
                     "security",
-                    (o, n, t) => o.Security = n.CreateList(LoadSecurityRequirement, t)
+                    (o, n, t) =>
+                    { 
+                        if (n.JsonNode is JsonArray)
+                        {
+                            o.Security = n.CreateList(LoadSecurityRequirement, t);
+                        } 
+                    }
                 },
                 {
                     "servers",

src/Microsoft.OpenApi/Reader/V31/OpenApiOperationDeserializer.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json.Nodes;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Models.References;
@@ -96,8 +97,11 @@ internal static partial class OpenApiV31Deserializer
                 },
                 {
                     "security", (o, n, t) =>
-                    {
-                        o.Security = n.CreateList(LoadSecurityRequirement, t);
+                    { 
+                        if (n.JsonNode is JsonArray)
+                        {
+                            o.Security = new List<OpenApiSecurityRequirement>(n.CreateList(LoadSecurityRequirement, t)); 
+                        } 
                     }
                 },
                 {

src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs

@@ -217,6 +217,26 @@ public static void WriteOptionalCollection<T>(
                 writer.WriteCollectionInternal(name, elements, action);
             }
         }
+
+        /// <summary>
+        /// Write the optional or empty Open API object/element collection.
+        /// </summary>
+        /// <typeparam name="T">The Open API element type. <see cref="IOpenApiElement"/></typeparam>
+        /// <param name="writer">The Open API writer.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="elements">The collection values.</param>
+        /// <param name="action">The collection element writer action.</param>
+        public static void WriteOptionalOrEmptyCollection<T>(
+            this IOpenApiWriter writer,
+            string name,
+            IEnumerable<T>? elements,
+            Action<IOpenApiWriter, T> action)
+        {
+            if (elements != null)
+            {
+                writer.WriteCollectionInternal(name, elements, action);
+            }
+        }
 
         /// <summary>
         /// Write the required Open API object/element collection.

test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj

@@ -56,5 +56,13 @@
     </None>
 
     <None Update="PublicApi\PublicApi.approved.txt" CopyToOutputDirectory="Always" />
+
+    <None Update="Models\Samples\docWithoutOperationSecurity.yaml">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+
+    <None Update="Models\Samples\docWithEmptyOperationSecurity.yaml">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 </Project>

test/Microsoft.OpenApi.Tests/Models/OpenApiDocumentTests.cs

@@ -9,12 +9,10 @@
 using System.Threading.Tasks;
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
-using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Models.Interfaces;
 using Microsoft.OpenApi.Models.References;
 using Microsoft.OpenApi.Writers;
-using Microsoft.VisualBasic;
 using VerifyXunit;
 using Xunit;
 
@@ -2179,7 +2177,7 @@ public void SerializeAsThrowsIfVersionIsNotSupported()
         }
 
         [Fact]
-        public async Task SerializeDocWithSecuritySchemeWithInlineRefererencesWorks()
+        public async Task SerializeDocWithSecuritySchemeWithInlineReferencesWorks()
         {
             var expected = @"openapi: 3.0.4
 info:
@@ -2220,5 +2218,70 @@ public async Task SerializeDocWithSecuritySchemeWithInlineRefererencesWorks()
             var actual = stringWriter.ToString();
             Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), actual.MakeLineBreaksEnvironmentNeutral());
         }
+
+        [Fact]
+        public async Task SerializeDocWithoutOperationSecurityWorks()
+        {
+            var expected = """
+                           openapi: 3.0.4
+                           info:
+                             title: Repair Service
+                             version: 1.0.0
+                           servers:
+                             - url: https://pluginrentu.azurewebsites.net/api
+                           paths:
+                             /repairs:
+                               get:
+                                 summary: List all repairs
+                                 description: Returns a list of repairs with their details and images
+                                 operationId: listRepairs
+                                 responses:
+                                   '200':
+                                     description: A list of repairs
+                                     content:
+                                       application/json:
+                                         schema:
+                                           type: object
+                           """;
+
+            var doc = (await OpenApiDocument.LoadAsync("Models/Samples/docWithoutOperationSecurity.yaml", SettingsFixture.ReaderSettings)).Document;
+            var stringWriter = new StringWriter();
+            doc!.SerializeAsV3(new OpenApiYamlWriter(stringWriter, new OpenApiWriterSettings { InlineLocalReferences = true }));
+            var actual = stringWriter.ToString();
+            Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), actual.MakeLineBreaksEnvironmentNeutral());
+        }
+
+        [Fact]
+        public async Task SerializeDocWithEmptyOperationSecurityWorks()
+        {
+            var expected = """
+                           openapi: 3.0.4
+                           info:
+                             title: Repair Service
+                             version: 1.0.0
+                           servers:
+                             - url: https://pluginrentu.azurewebsites.net/api
+                           paths:
+                             /repairs:
+                               get:
+                                 summary: List all repairs
+                                 description: Returns a list of repairs with their details and images
+                                 operationId: listRepairs
+                                 responses:
+                                   '200':
+                                     description: A list of repairs
+                                     content:
+                                       application/json:
+                                         schema:
+                                           type: object
+                                 security: [ ]
+                           """;
+
+            var doc = (await OpenApiDocument.LoadAsync("Models/Samples/docWithEmptyOperationSecurity.yaml", SettingsFixture.ReaderSettings)).Document;
+            var stringWriter = new StringWriter();
+            doc!.SerializeAsV3(new OpenApiYamlWriter(stringWriter, new OpenApiWriterSettings { InlineLocalReferences = true }));
+            var actual = stringWriter.ToString();
+            Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), actual.MakeLineBreaksEnvironmentNeutral());
+        }
     }
 }

test/Microsoft.OpenApi.Tests/Models/Samples/docWithEmptyOperationSecurity.yaml

@@ -0,0 +1,20 @@
+openapi: 3.0.0
+info:
+  title: Repair Service
+  version: 1.0.0
+servers:
+  - url: https://pluginrentu.azurewebsites.net/api
+paths:
+  /repairs:
+    get:
+      operationId: listRepairs
+      summary: List all repairs
+      description: Returns a list of repairs with their details and images
+      responses:
+        '200':
+          description: A list of repairs
+          content:
+            application/json:
+              schema:
+                type: object
+      security: []

test/Microsoft.OpenApi.Tests/Models/Samples/docWithoutOperationSecurity.yaml

@@ -0,0 +1,19 @@
+openapi: 3.0.0
+info:
+  title: Repair Service
+  version: 1.0.0
+servers:
+  - url: https://pluginrentu.azurewebsites.net/api
+paths:
+  /repairs:
+    get:
+      operationId: listRepairs
+      summary: List all repairs
+      description: Returns a list of repairs with their details and images
+      responses:
+        '200':
+          description: A list of repairs
+          content:
+            application/json:
+              schema:
+                type: object

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -1975,6 +1975,7 @@ namespace Microsoft.OpenApi.Writers
         public static void WriteOptionalMap<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, System.Collections.Generic.Dictionary<string, T>? elements, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, string, T> action)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
         public static void WriteOptionalObject<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, T? value, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action) { }
+        public static void WriteOptionalOrEmptyCollection<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, System.Collections.Generic.IEnumerable<T>? elements, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action) { }
         public static void WriteProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, string? value) { }
         public static void WriteProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, bool value, bool defaultValue = false) { }
         public static void WriteProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, bool? value, bool defaultValue = false) { }