Avoid ArgumentNullException being thrown generating examples

src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/OpenApiAnyFactory.cs

@@ -10,6 +10,11 @@ public static IOpenApiAny CreateFromJson(string json)
 
     public static IOpenApiAny CreateFromJson(string json, JsonSerializerOptions options)
     {
+        if (json is null)
+        {
+            return null;
+        }
+
         try
         {
             var element = JsonSerializer.Deserialize<JsonElement>(json, options);

test/Swashbuckle.AspNetCore.SwaggerGen.Test/XmlComments/XmlCommentsExampleHelperTests.cs

@@ -8,7 +8,7 @@ public class XmlCommentsExampleHelperTests
     private readonly SchemaRepository schemaRepository = new();
 
     [Fact]
-    public void Create_BuildsOpenApiArrayJson__When_NotStringTypeAndDataIsArray()
+    public void Create_Builds_OpenApiArrayJson_When_Not_String_Type_And_Data_Is_Array()
     {
         var schema = new OpenApiSchema();
 
@@ -31,10 +31,13 @@ public void Create_BuildsOpenApiArrayJson__When_NotStringTypeAndDataIsArray()
         Assert.Equal("three", item3.Value);
     }
 
-    [Fact]
-    public void Create_BuildsOpenApiString_When_TypeString()
+    [Theory]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("foo")]
+    [InlineData("example string with special characters\"<>\r\n\"")]
+    public void Create_Builds_OpenApiString_When_Type_String(string exampleString)
     {
-        string exampleString = "example string with special characters\"<>\r\n\"";
         var schema = new OpenApiSchema { Type = JsonSchemaTypes.String };
         schemaRepository.AddDefinition("test", schema);
 
@@ -48,7 +51,30 @@ public void Create_BuildsOpenApiString_When_TypeString()
     }
 
     [Fact]
-    public void Create_ReturnsNull_When_TypeString_and_ValueNull()
+    public void Create_Returns_Null_When_Type_String_And_Value_Is_Null()
+    {
+        var schema = new OpenApiSchema { Type = JsonSchemaTypes.String };
+        schemaRepository.AddDefinition("test", schema);
+
+        var example = XmlCommentsExampleHelper.Create(
+            schemaRepository, schema, null);
+
+        Assert.NotNull(example);
+
+        var actual = Assert.IsType<OpenApiNull>(example);
+        Assert.Equal(AnyType.Null, actual.AnyType);
+    }
+
+    [Fact]
+    public void Create_Returns_Null_When_Value_And_Schema_Are_Null()
+    {
+        var example = XmlCommentsExampleHelper.Create(schemaRepository, null, null);
+
+        Assert.Null(example);
+    }
+
+    [Fact]
+    public void Create_Returns_Null_When_Type_String_And_Value_Null_String_Literal()
     {
         var schema = new OpenApiSchema { Type = JsonSchemaTypes.String };
         schemaRepository.AddDefinition("test", schema);
@@ -63,7 +89,7 @@ public void Create_ReturnsNull_When_TypeString_and_ValueNull()
     }
 
     [Fact]
-    public void Create_AllowsSchemaToBeNull()
+    public void Create_Allows_Schema_To_Be_Null()
     {
         OpenApiSchema schema = null;
 
@@ -74,4 +100,32 @@ public void Create_AllowsSchemaToBeNull()
         var actual = Assert.IsType<OpenApiArray>(example);
         Assert.Empty(actual);
     }
+
+    [Fact]
+    public void Create_Builds_OpenApiString_When_Type_Integer()
+    {
+        string exampleString = "1";
+        var schema = new OpenApiSchema { Type = JsonSchemaTypes.Integer };
+        schemaRepository.AddDefinition("test", schema);
+
+        var example = XmlCommentsExampleHelper.Create(
+            schemaRepository, schema, exampleString);
+
+        Assert.NotNull(example);
+
+        var actual = Assert.IsType<OpenApiInteger>(example);
+        Assert.Equal(1, actual.Value);
+    }
+
+    [Fact]
+    public void Create_Returns_Null_When_Type_Integer_And_Value_Is_Null()
+    {
+        var schema = new OpenApiSchema { Type = JsonSchemaTypes.Integer };
+        schemaRepository.AddDefinition("test", schema);
+
+        var example = XmlCommentsExampleHelper.Create(
+            schemaRepository, schema, null);
+
+        Assert.Null(example);
+    }
 }