Fix: OpenAPI Schema Handling For Nullable Collection Types

src/OpenApi/src/Extensions/JsonNodeSchemaExtensions.cs

@@ -115,24 +115,20 @@ internal static void ApplyValidationAttributes(this JsonNode schema, IEnumerable
             }
             else if (attribute is MaxLengthAttribute maxLengthAttribute)
             {
-                var targetKey = schema[OpenApiSchemaKeywords.TypeKeyword]?.GetValue<string>() == "array" ? OpenApiSchemaKeywords.MaxItemsKeyword : OpenApiSchemaKeywords.MaxLengthKeyword;
-                schema[targetKey] = maxLengthAttribute.Length;
+                var isArray = MapJsonNodeToSchemaType(schema[OpenApiSchemaKeywords.TypeKeyword]) is { } schemaTypes && schemaTypes.HasFlag(JsonSchemaType.Array);
+                var key = isArray ? OpenApiSchemaKeywords.MaxItemsKeyword : OpenApiSchemaKeywords.MaxLengthKeyword;
+                schema[key] = maxLengthAttribute.Length;
             }
             else if (attribute is MinLengthAttribute minLengthAttribute)
             {
-                if (MapJsonNodeToSchemaType(schema[OpenApiSchemaKeywords.TypeKeyword]) is { } schemaTypes &&
-                    schemaTypes.HasFlag(JsonSchemaType.Array))
-                {
-                    schema[OpenApiSchemaKeywords.MinItemsKeyword] = minLengthAttribute.Length;
-                }
-                else
-                {
-                    schema[OpenApiSchemaKeywords.MinLengthKeyword] = minLengthAttribute.Length;
-                }
+                var isArray = MapJsonNodeToSchemaType(schema[OpenApiSchemaKeywords.TypeKeyword]) is { } schemaTypes && schemaTypes.HasFlag(JsonSchemaType.Array);
+                var key = isArray ? OpenApiSchemaKeywords.MinItemsKeyword : OpenApiSchemaKeywords.MinLengthKeyword;
+                schema[key] = minLengthAttribute.Length;
             }
             else if (attribute is LengthAttribute lengthAttribute)
             {
-                var targetKeySuffix = schema[OpenApiSchemaKeywords.TypeKeyword]?.GetValue<string>() == "array" ? "Items" : "Length";
+                var isArray = MapJsonNodeToSchemaType(schema[OpenApiSchemaKeywords.TypeKeyword]) is { } schemaTypes && schemaTypes.HasFlag(JsonSchemaType.Array);
+                var targetKeySuffix = isArray ? "Items" : "Length";
                 schema[$"min{targetKeySuffix}"] = lengthAttribute.MinimumLength;
                 schema[$"max{targetKeySuffix}"] = lengthAttribute.MaximumLength;
             }

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiSchemaService/OpenApiSchemaService.RequestBodySchemas.cs

@@ -106,15 +106,35 @@ await VerifyOpenApiDocument(builder, document =>
                     Assert.Equal("name", property.Key);
                     Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, property.Value.Type);
                     Assert.Equal(5, property.Value.MinLength);
+                    Assert.Equal(10, property.Value.MaxLength);
                     Assert.Null(property.Value.Default);
                 },
                 property =>
+                {
+                    Assert.Equal("description", property.Key);
+                    Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(5, property.Value.MinLength);
+                    Assert.Equal(10, property.Value.MaxLength);
+                },
+                property =>
                 {
                     Assert.Equal("isPrivate", property.Key);
                     Assert.Equal(JsonSchemaType.Boolean, property.Value.Type);
                     Assert.True(property.Value.Default.GetValue<bool>());
+                },
+                property =>
+                {
+                    Assert.Equal("items", property.Key);
+                    Assert.Equal(JsonSchemaType.Array | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(10, property.Value.MaxItems);
+                },
+                property =>
+                {
+                    Assert.Equal("tags", property.Key);
+                    Assert.Equal(JsonSchemaType.Array | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(5, property.Value.MinItems);
+                    Assert.Equal(10, property.Value.MaxItems);
                 });
-
         });
     }
 

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiSchemaService/OpenApiSchemaService.ResponseSchemas.cs

@@ -130,12 +130,34 @@ await VerifyOpenApiDocument(builder, document =>
                     Assert.Equal("name", property.Key);
                     Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, property.Value.Type);
                     Assert.Equal(5, property.Value.MinLength);
+                    Assert.Equal(10, property.Value.MaxLength);
+                    Assert.Null(property.Value.Default);
+                },
+                property =>
+                {
+                    Assert.Equal("description", property.Key);
+                    Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(5, property.Value.MinLength);
+                    Assert.Equal(10, property.Value.MaxLength);
                 },
                 property =>
                 {
                     Assert.Equal("isPrivate", property.Key);
                     Assert.Equal(JsonSchemaType.Boolean, property.Value.Type);
                     Assert.True(property.Value.Default.GetValue<bool>());
+                },
+                property =>
+                {
+                    Assert.Equal("items", property.Key);
+                    Assert.Equal(JsonSchemaType.Array | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(10, property.Value.MaxItems);
+                },
+                property =>
+                {
+                    Assert.Equal("tags", property.Key);
+                    Assert.Equal(JsonSchemaType.Array | JsonSchemaType.Null, property.Value.Type);
+                    Assert.Equal(5, property.Value.MinItems);
+                    Assert.Equal(10, property.Value.MaxItems);
                 });
 
         });

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Shared/SharedTypes.cs

@@ -183,13 +183,29 @@ internal class ProjectBoard
     public int Id { get; set; }
 
     [MinLength(5)]
+    [MaxLength(10)]
     [DefaultValue(null)]
     [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "Used in tests.")]
     public string? Name { get; set; }
 
+    [Length(5, 10)]
+    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "Used in tests.")]
+    public string? Description { get; set; }
+
     [DefaultValue(true)]
     public required bool IsPrivate { get; set; }
+
+    [MaxLength(10)]
+    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "Used in tests.")]
+    public IList<ProjectBoardItem>? Items { get; set; }
+
+    [Length(5, 10)]
+    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "Used in tests.")]
+    public IEnumerable<string>? Tags { get; set; }
 }
+
+internal sealed record ProjectBoardItem(string Name);
+
 #nullable restore
 
 internal class Account