From ac2c97467b3e633735c6948e7638a0abc5c4b821 Mon Sep 17 00:00:00 2001
From: Aryaman Dhingra <aryamandhingra@bitgo.com>
Date: Thu, 13 Jun 2024 11:13:03 -0400
Subject: [PATCH] feat: add support for unions that are nullable and optional

DX-480
---
 packages/openapi-generator/src/openapi.ts     | 10 ++-
 .../openapi-generator/test/openapi.test.ts    | 90 +++++++++++++++++++
 2 files changed, 98 insertions(+), 2 deletions(-)

diff --git a/packages/openapi-generator/src/openapi.ts b/packages/openapi-generator/src/openapi.ts
index e061ae4e..7eeb6a02 100644
--- a/packages/openapi-generator/src/openapi.ts
+++ b/packages/openapi-generator/src/openapi.ts
@@ -86,11 +86,17 @@ function schemaToOpenAPI(
         // If there are two schemas and one of the schemas is undefined, that means the union is a case of `optional` type
         const undefinedSchema = schema.schemas.find((s) => s.type === 'undefined');
         const nonUndefinedSchema = schema.schemas.find((s) => s.type !== 'undefined');
+        // If nullSchema exists, that means that the union is also nullable
+        const nullSchema = schema.schemas.find((s) => s.type === 'null');
         // and we can just return the other schema (while attaching the comment to that schema)
         const isOptional =
-          schema.schemas.length == 2 && undefinedSchema && nonUndefinedSchema;
+          schema.schemas.length >= 2 && undefinedSchema && nonUndefinedSchema;
         if (isOptional) {
-          return schemaToOpenAPI({ ...nonUndefinedSchema, comment: schema.comment });
+          return schemaToOpenAPI({
+            ...nonUndefinedSchema,
+            comment: schema.comment,
+            ...(nullSchema ? { nullable: true } : {}),
+          });
         }
 
         for (const s of schema.schemas) {
diff --git a/packages/openapi-generator/test/openapi.test.ts b/packages/openapi-generator/test/openapi.test.ts
index 2ad41f4c..3cadde00 100644
--- a/packages/openapi-generator/test/openapi.test.ts
+++ b/packages/openapi-generator/test/openapi.test.ts
@@ -2736,3 +2736,93 @@ testCase('route with optional array query parameter and documentation', ROUTE_WI
     schemas: {}
   }
 });
+
+
+const ROUTE_WITH_ARRAY_UNION_NULL_UNDEFINED_QUERY_PARAM = `
+import * as t from 'io-ts';
+import * as h from '@api-ts/io-ts-http';
+
+/**
+ * A simple route with type descriptions for references
+ *
+ * @operationId api.v1.test
+ * @tag Test Routes
+ */
+export const route = h.httpRoute({
+  path: '/foo',
+  method: 'GET',
+  request: h.httpRequest({
+    query: {
+      /** 
+       * This is a foo description. 
+       * @example abc
+       * @pattern ^[a-z]+$
+       */
+      ipRestrict: t.union([t.array(t.string), t.null, t.undefined]),
+    },
+  }),
+  response: {
+    200: {
+      test: t.string
+    }
+  },
+});
+`;
+
+testCase('route with array union of null and undefined', ROUTE_WITH_ARRAY_UNION_NULL_UNDEFINED_QUERY_PARAM, {
+  openapi: '3.0.3',
+  info: {
+    title: 'Test',
+    version: '1.0.0'
+  },
+  paths: {
+    '/foo': {
+      get: {
+        summary: 'A simple route with type descriptions for references',
+        operationId: 'api.v1.test',
+        tags: [
+          'Test Routes'
+        ],
+        parameters: [
+          {
+            description: 'This is a foo description.',
+            in: 'query',
+            name: 'ipRestrict',
+            schema: {
+              items: {
+                description: 'This is a foo description.',
+                example: 'abc',
+                type: 'string',
+                pattern: '^[a-z]+$'
+              },
+              type: 'array'
+            }
+          }
+        ],
+        responses: {
+          '200': {
+            description: 'OK',
+            content: {
+              'application/json': {
+                schema: {
+                  type: 'object',
+                  properties: {
+                    test: {
+                      type: 'string'
+                    }
+                  },
+                  required: [
+                    'test'
+                  ]
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  components: {
+    schemas: {}
+  }
+});