Fix error schema failing to parse when field is missing from JSON response (#108)

* Make error schema work when fields are missing

* Add a test

* fix assertions

Author: niekert

src/schemas/error-response.test.ts

@@ -0,0 +1,49 @@
+import { OpenRouterErrorResponseSchema } from "./error-response";
+
+describe("OpenRouterErrorResponseSchema", () => {
+  it("should be valid without a type, code, and param", () => {
+    const errorWithoutTypeCodeAndParam = {
+      error: {
+        message: "Example error message",
+        metadata: { provider_name: "Morph" },
+      },
+      user_id: "example_1",
+    };
+
+    const result = OpenRouterErrorResponseSchema.parse(
+      errorWithoutTypeCodeAndParam
+    );
+
+    expect(result).toEqual({
+      error: {
+        message: "Example error message",
+        code: null,
+        type: null,
+        param: null,
+      },
+    });
+  });
+
+  it("should be invalid with a type", () => {
+    const errorWithType = {
+      error: {
+        message: "Example error message with type",
+        type: "invalid_request_error",
+        code: 400,
+        param: "canBeAnything",
+        metadata: { provider_name: "Morph" },
+      },
+    };
+
+    const result = OpenRouterErrorResponseSchema.parse(errorWithType);
+
+    expect(result).toEqual({
+      error: {
+        code: 400,
+        message: "Example error message with type",
+        type: "invalid_request_error",
+        param: "canBeAnything",
+      },
+    });
+  });
+});

src/schemas/error-response.ts

@@ -3,10 +3,10 @@ import { z } from "zod/v4";
 
 export const OpenRouterErrorResponseSchema = z.object({
   error: z.object({
-    code: z.union([z.string(), z.number()]).nullable(),
+    code: z.union([z.string(), z.number()]).nullable().optional().default(null),
     message: z.string(),
-    type: z.string().nullable(),
-    param: z.any().nullable(),
+    type: z.string().nullable().optional().default(null),
+    param: z.any().nullable().optional().default(null),
   }),
 });