fix: union properties can be optional & nullable (#66)

* fix: union properties can be optional & nullable

* fix: handle null value in union types

src/core/generateZodSchema.test.ts

@@ -680,6 +680,45 @@ describe("generateZodSchema", () => {
     `);
   });
 
+  it("should allow nullable on optional properties", () => {
+    const source = `export interface A {
+      a?: number | null;
+    }
+    `;
+
+    expect(generate(source)).toMatchInlineSnapshot(`
+      "export const aSchema = z.object({
+          a: z.number().optional().nullable()
+      });"
+    `);
+  });
+
+  it("should allow nullable on union properties", () => {
+    const source = `export interface A {
+      a: number | string | null;
+    }
+    `;
+
+    expect(generate(source)).toMatchInlineSnapshot(`
+      "export const aSchema = z.object({
+          a: z.union([z.number(), z.string()]).nullable()
+      });"
+    `);
+  });
+
+  it("should allow nullable on optional union properties", () => {
+    const source = `export interface A {
+      a?: number | string | null;
+    }
+    `;
+
+    expect(generate(source)).toMatchInlineSnapshot(`
+      "export const aSchema = z.object({
+          a: z.union([z.number(), z.string()]).optional().nullable()
+      });"
+    `);
+  });
+
   it("should deal with @default with all types", () => {
     const source = `export interface WithDefaults {
      /**

src/core/generateZodSchema.ts

@@ -439,7 +439,7 @@ function buildZodPrimitive({
       return buildZodPrimitive({
         z,
         typeNode: nodes[0],
-        isOptional: false,
+        isOptional,
         isNullable: hasNull,
         jsDocTags,
         sourceFile,
@@ -462,6 +462,14 @@ function buildZodPrimitive({
         skipParseJSDoc,
       })
     );
+
+    // Handling null value outside of the union type
+    if (hasNull) {
+      zodProperties.push({
+        identifier: "nullable",
+      });
+    }
+
     return buildZodSchema(
       z,
       "union",