Support Type Arrays for OpenAPI 3.1 (#917)

* recursive types

* example

* tests for nullable as type array

Author: BrandonGoren

src/transform/schema.ts

@@ -113,10 +113,15 @@ export function transformSchemaObj(node: any, options: TransformSchemaObjOptions
   } else {
     // transform core type
     switch (nodeType(node)) {
+      case "type-array":
+        // This is an array of types as of the 3.1 specification - we should recursively evaluate them
+        output += tsUnionOf((node.type as any[]).map((type) => transformSchemaObj({ ...node, type }, options)));
+        break;
       case "ref": {
         output += node.$ref; // these were transformed at load time when remote schemas were resolved; return as-is
         break;
       }
+      case "null":
       case "string":
       case "number":
       case "boolean":

src/utils.ts

@@ -130,7 +130,10 @@ type SchemaObjectType =
   | "object"
   | "oneOf"
   | "ref"
+  | "null"
   | "string"
+  // Special type so the parent function knows to recursively evaluate each entry
+  | "type-array"
   | "unknown";
 export function nodeType(obj: any): SchemaObjectType {
   if (!obj || typeof obj !== "object") {
@@ -156,11 +159,20 @@ export function nodeType(obj: any): SchemaObjectType {
     return "object";
   }
 
+  // Type array from the 3.1 specification
+  if (Array.isArray(obj.type)) {
+    return "type-array";
+  }
+
   // boolean
   if (obj.type === "boolean") {
     return "boolean";
   }
 
+  // null
+  if (obj.type === "null") {
+    return "null";
+  }
   // string
   if (
     obj.type === "string" ||

test/core/schema.test.js

@@ -256,6 +256,27 @@ describe("SchemaObject", () => {
     });
   });
 
+  describe("(3.1) type arrays", () => {
+    it("nullable type array", () => {
+      expect(transform({ type: ["string", "null"] }, { ...defaults })).to.equal("(string) | (null)");
+    });
+
+    it("nullable type array within an object", () => {
+      const objectWithNullableTypeArray = {
+        type: "object",
+        properties: {
+          object: {
+            properties: { nullableNumber: { type: ["number", "null"] }, string: { type: "string" } },
+            type: "object",
+          },
+        },
+      };
+      expect(transform(objectWithNullableTypeArray, { ...defaults })).to.equal(
+        `{\n"object"?: {\n"nullableNumber"?: (number) | (null);\n"string"?: string;\n\n};\n\n}`
+      );
+    });
+  });
+
   describe("advanced", () => {
     it("additionalProperties", () => {
       // boolean