nullable property is not nullable in generated code

[rwb196884]

Here is a property in my swagger.json

          "Retained9": {
            "maximum": 100,
            "minimum": 0,
            "type": "integer",
            "description": "Retained9\r\nThis property is....\r\n",
            "format": "int32",
            "default": "100",
            "nullable": true
          },

Using openapi-typescript version 6.7.6 this generates

      /**
       * Format: int32
       * @description Retained9
       * This property is...
       *
       * @default 100
       */      Retained9?: number | null;

But using openapi-typescript version 7.4.4 this generates

            /**
             * Format: int32
             * @description Retained9
             *     This property is used...
             *
             * @default 100
             */
            Retained9: number;

It is good that the useless and annoying ? has gone, but in the specification the property is nullable and therefore it is an error to have removed the | null.

[drwpow]

Could you run your schema through Redocly’s validator, and confirm there are no schema issues?

We do have tests in place for nullable: true so if you are experiencing an issue with a valid schema, we’ll need more information or a reproduction to tell what’s going on here.

[rwb196884]

Here's an example.
WebApplicationOpenApi.zip

C# property is

        [Column("Retained9", Order = 30)]
        [Editable(true)]
        [Display(Name = "Retained9", Description = "Retained9")]
        [DefaultValue((short)100)]
        [Range(0, 100)]
        public short? Retained9 { get; set; }

swaggergen produces

          "retained9": {
            "maximum": 100,
            "minimum": 0,
            "type": "integer",
            "format": "int32",
            "default": 100,
            "nullable": true
          }

and then openqpi-typescript produces

            /**
             * Format: int32
             * @default 100
             */
            retained9: number;

It seems to be the [DefaultValue that causes the nullability to be ignored.

[rwb196884]

It is a breaking change that nullable properties with default values have their nullability changed.

[rwb196884]

The option --default-non-nullable false adds the ? which allows undefined but not the | null to allow null.

[jawnothin]

The issue is that this package targets openapi 3.1, which swashbuckle doesn't support. It ignores how openapi 3.0 generates it. I commented on another similar issue a while ago about this, but it went stale.

I've discovered the cause of this, at least for my use case. My openapi spec is based off 3.0.1, and it uses the "nullable", which this package seems to ignore as it's marked as deprecated because it's not a concept in the 3.1 spec (presumably, I didn't dig into it more)

This is the patch, which I didn't open a PR as there's probably other considerations.

diff --git a/packages/openapi-typescript/src/transform/schema-object.ts b/packages/openapi-typescript/src/transform/schema-object.ts
index 0885324..e4fceaf 100644
--- a/packages/openapi-typescript/src/transform/schema-object.ts
+++ b/packages/openapi-typescript/src/transform/schema-object.ts
@@ -458,6 +458,7 @@ function transformSchemaObjectCore(schemaObject: SchemaObject, options: Transfor
             options.ctx.defaultNonNullable &&
             !options.path?.includes("parameters") &&
             !options.path?.includes("requestBody")) // parameters can’t be required, even with defaults
+            || !("nullable" in v) || ("nullable" in v && v.nullable === false)
             ? undefined
             : QUESTION_TOKEN;
         let type =