Add multipleOf support (#358)

Author: samchungy

README.md

@@ -717,7 +717,8 @@ For example in `z.string().nullable()` will be rendered differently
 - ZodNullable
 - ZodNumber
   - `integer` `type` mapping for `.int()`
-  - `exclusiveMin`/`min`/`exclusiveMax`/`max` mapping for `.min()`, `.max()`, `lt()`, `gt()`
+  - `exclusiveMin`/`min`/`exclusiveMax`/`max` mapping for `.min()`, `.max()`, `lt()`, `gt()`, `.positive()`, `.negative()`, `.nonnegative()`, `.nonpositive()`.
+  - `multipleOf` mapping for `.multipleOf()`
 - ZodObject
   - `additionalProperties` mapping for `.catchall()`, `.strict()`
   - `allOf` mapping for `.extend()` when the base object is registered and does not have `catchall()`, `strict()` and extension does not override a field.

src/create/schema/parsers/number.test.ts

@@ -104,4 +104,19 @@ describe('createNumberSchema', () => {
 
     expect(result).toStrictEqual(expected);
   });
+
+  it('supports multipleOf', () => {
+    const expected: Schema = {
+      type: 'schema',
+      schema: {
+        type: 'number',
+        multipleOf: 2,
+      },
+    };
+    const schema = z.number().multipleOf(2);
+
+    const result = createNumberSchema(schema, createOutputState());
+
+    expect(result).toStrictEqual(expected);
+  });
 });

src/create/schema/parsers/number.ts

@@ -13,17 +13,26 @@ export const createNumberSchema = (
 
   const minimum = mapMinimum(zodNumberChecks, state.components.openapi);
   const maximum = mapMaximum(zodNumberChecks, state.components.openapi);
+  const multipleOf = mapMultipleOf(zodNumberChecks);
 
   return {
     type: 'schema',
     schema: {
       type: mapNumberType(zodNumberChecks),
+      ...(multipleOf && multipleOf),
       ...(minimum && (minimum as oas31.SchemaObject)), // Union types are not easy to tame
       ...(maximum && (maximum as oas31.SchemaObject)),
     },
   };
 };
 
+export const mapMultipleOf = (
+  zodNumberCheck: ZodNumberCheckMap,
+): Pick<oas31.SchemaObject | oas30.SchemaObject, 'multipleOf'> | undefined =>
+  zodNumberCheck.multipleOf
+    ? { multipleOf: zodNumberCheck.multipleOf.value }
+    : undefined;
+
 export const mapMaximum = (
   zodNumberCheck: ZodNumberCheckMap,
   openapi: ZodOpenApiVersion,