microsoft · baywet · Sep 7, 2022 · Sep 7, 2022
diff --git a/src/Microsoft.OpenApi/Microsoft.OpenApi.csproj b/src/Microsoft.OpenApi/Microsoft.OpenApi.csproj
@@ -11,7 +11,7 @@
        <Company>Microsoft</Company>
        <Title>Microsoft.OpenApi</Title>
        <PackageId>Microsoft.OpenApi</PackageId>
-        <Version>1.4.0</Version>
+        <Version>1.4.1</Version>
        <Description>.NET models with JSON and YAML writers for OpenAPI specification</Description>
        <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
        <PackageTags>OpenAPI .NET</PackageTags>

diff --git a/src/Microsoft.OpenApi/Models/OpenApiSchema.cs b/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 

 using System.Collections.Generic;
@@ -566,6 +566,13 @@ internal void WriteAsItemsProperties(IOpenApiWriter writer)
            writer.WriteProperty(OpenApiConstants.Type, Type);

            // format
+            if (string.IsNullOrEmpty(Format))
+            {
+                Format = AllOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format ??
+                    AnyOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format ??
+                    OneOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format;
+            }
+
            writer.WriteProperty(OpenApiConstants.Format, Format);

            // items
@@ -630,9 +637,12 @@ internal void WriteAsSchemaProperties(
            }

            // format
-            Format ??= AllOf?.FirstOrDefault(static x => x.Format != null)?.Format ??
-                    AnyOf?.FirstOrDefault(static x => x.Format != null)?.Format ??
-                    OneOf?.FirstOrDefault(static x => x.Format != null)?.Format;
+            if (string.IsNullOrEmpty(Format))
+            {
+                Format = AllOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format ??
+                    AnyOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format ??
+                    OneOf?.FirstOrDefault(static x => !string.IsNullOrEmpty(x.Format))?.Format;
+            }

            writer.WriteProperty(OpenApiConstants.Format, Format);


diff --git a/test/Microsoft.OpenApi.Tests/Models/OpenApiParameterTests.cs b/test/Microsoft.OpenApi.Tests/Models/OpenApiParameterTests.cs
@@ -50,7 +50,12 @@ public class OpenApiParameterTests
            Schema = new OpenApiSchema
            {
                Title = "title2",
-                Description = "description2"
+                Description = "description2",
+                OneOf = new List<OpenApiSchema>
+                {
+                    new OpenApiSchema { Type = "number", Format = "double" },
+                    new OpenApiSchema { Type = "string" }                        
+                }
            },
            Examples = new Dictionary<string, OpenApiExample>
            {
@@ -234,6 +239,15 @@ public void SerializeAdvancedParameterAsV3JsonWorks()
  ""explode"": true,
  ""schema"": {
    ""title"": ""title2"",
+    ""oneOf"": [
+      {
+        ""type"": ""number"",
+        ""format"": ""double""
+      },
+      {
+        ""type"": ""string""
+      }
+    ],
    ""description"": ""description2""
  },
  ""examples"": {
@@ -253,6 +267,27 @@ public void SerializeAdvancedParameterAsV3JsonWorks()
            actual.Should().Be(expected);
        }

+        [Fact]
+        public void SerializeAdvancedParameterAsV2JsonWorks()
+        {
+            // Arrange
+            var expected = @"{
+  ""in"": ""path"",
+  ""name"": ""name1"",
+  ""description"": ""description1"",
+  ""required"": true,
+  ""format"": ""double""
+}";
+
+            // Act
+            var actual = AdvancedPathParameterWithSchema.SerializeAsJson(OpenApiSpecVersion.OpenApi2_0);
+
+            // Assert
+            actual = actual.MakeLineBreaksEnvironmentNeutral();
+            expected = expected.MakeLineBreaksEnvironmentNeutral();
+            actual.Should().Be(expected);
+        }
+
        [Theory]
        [InlineData(true)]
        [InlineData(false)]