feat: add omitAdditionalProperties option

README.md

@@ -463,6 +463,24 @@ type Object = FromSchema<typeof openObjectSchema>;
 // => { [x: string]: unknown }
 ```
 
+- `FromSchema` comes with an `omitAdditionalProperties` option which will cause objects to be always typed as closed (without index signature type):
+
+```typescript
+const openObjectSchema = {
+  type: "object",
+  additionalProperties: true,
+  properties: {
+    foo: { type: "string" },
+  },
+} as const;
+
+type Object = FromSchema<
+  typeof tupleSchema,
+  { omitAdditionalProperties: true }
+>;
+// => { foo?: string }
+```
+
 ## Combining schemas
 
 ### AnyOf

package.json

@@ -53,6 +53,7 @@
     "eslint-plugin-prefer-arrow": "^1.2.3",
     "eslint-plugin-prettier": "^5.0.1",
     "eslint-plugin-unused-imports": "^2.0.0",
+    "expect-type": "^1.2.2",
     "jest": "^27.5.1",
     "prettier": "^3.1.0",
     "rollup": "^2.67.3",
@@ -86,4 +87,4 @@
     "url": "https://github.com/ThomasAribart/json-schema-to-ts/issues"
   },
   "homepage": "https://github.com/ThomasAribart/json-schema-to-ts#readme"
-}
+}

src/definitions/fromSchemaOptions.ts

@@ -15,6 +15,7 @@ export type FromSchemaOptions = {
   keepDefaultedPropertiesOptional?: boolean;
   references?: JSONSchemaReference[] | false;
   deserialize?: DeserializationPattern[] | false;
+  omitAdditionalProperties?: boolean;
 };
 
 /**
@@ -26,6 +27,7 @@ export type FromExtendedSchemaOptions<EXTENSION extends JSONSchemaExtension> = {
   keepDefaultedPropertiesOptional?: boolean;
   references?: ExtendedJSONSchemaReference<EXTENSION>[] | false;
   deserialize?: DeserializationPattern[] | false;
+  omitAdditionalProperties?: boolean;
 };
 
 /**
@@ -37,4 +39,5 @@ export type FromSchemaDefaultOptions = {
   keepDefaultedPropertiesOptional: false;
   references: false;
   deserialize: false;
+  omitAdditionalProperties: false;
 };

src/parse-options.ts

@@ -43,4 +43,7 @@ export type ParseOptions<
   deserialize: OPTIONS["deserialize"] extends DeserializationPattern[] | false
     ? OPTIONS["deserialize"]
     : FromSchemaDefaultOptions["deserialize"];
+  omitAdditionalProperties: OPTIONS["omitAdditionalProperties"] extends boolean
+    ? OPTIONS["omitAdditionalProperties"]
+    : FromSchemaDefaultOptions["omitAdditionalProperties"];
 };

src/parse-options.type.test.ts

@@ -33,6 +33,7 @@ type ExpectedOptions = {
   deserialize: FromSchemaDefaultOptions["deserialize"];
   rootSchema: RootSchema;
   references: IndexReferencesById<AllReferences>;
+  omitAdditionalProperties: FromSchemaDefaultOptions["omitAdditionalProperties"];
 };
 
 const assertOptions: A.Equals<ReceivedOptions, ExpectedOptions> = 1;

src/parse-schema/index.ts

@@ -47,6 +47,10 @@ export type ParseSchemaOptions = {
    * To override inferred types if some pattern is matched
    */
   deserialize: DeserializationPattern[] | false;
+  /**
+   * Ignore additionalProperties value and always infer closed objects
+   */
+  omitAdditionalProperties: boolean;
 };
 
 /**

src/parse-schema/object.ts

@@ -41,13 +41,13 @@ export type ParseObjectSchema<
       },
       GetRequired<OBJECT_SCHEMA, OPTIONS>,
       GetOpenProps<OBJECT_SCHEMA, OPTIONS>,
-      GetClosedOnResolve<OBJECT_SCHEMA>
+      GetClosedOnResolve<OBJECT_SCHEMA, OPTIONS>
     >
   : M.$Object<
       {},
       GetRequired<OBJECT_SCHEMA, OPTIONS>,
       GetOpenProps<OBJECT_SCHEMA, OPTIONS>,
-      GetClosedOnResolve<OBJECT_SCHEMA>
+      GetClosedOnResolve<OBJECT_SCHEMA, OPTIONS>
     >;
 
 /**
@@ -108,8 +108,12 @@ type GetOpenProps<
  * @param OPTIONS Parsing options
  * @returns String
  */
-type GetClosedOnResolve<OBJECT_SCHEMA extends ObjectSchema> =
-  OBJECT_SCHEMA extends Readonly<{ unevaluatedProperties: false }>
+type GetClosedOnResolve<
+  OBJECT_SCHEMA extends ObjectSchema,
+  OPTIONS extends ParseSchemaOptions,
+> = OPTIONS["omitAdditionalProperties"] extends true
+  ? true
+  : OBJECT_SCHEMA extends Readonly<{ unevaluatedProperties: false }>
     ? true
     : false;
 

src/parse-schema/object.unit.test.ts

@@ -1,3 +1,5 @@
+import { expectTypeOf } from "expect-type";
+
 import type { FromSchema } from "~/index";
 
 import { ajv } from "./ajv.util.test";
@@ -45,6 +47,17 @@ describe("Object schemas", () => {
       setInstance = { a: 42 };
       expect(ajv.validate(setSchema, setInstance)).toBe(false);
     });
+
+    describe("with omitAdditionalProperties option", () => {
+      it("rejects additional properties", () => {
+        type Set2 = FromSchema<
+          typeof setSchema,
+          { omitAdditionalProperties: true }
+        >;
+
+        expectTypeOf<Set2>().toEqualTypeOf<{}>();
+      });
+    });
   });
 
   describe("Pattern properties", () => {
@@ -95,6 +108,17 @@ describe("Object schemas", () => {
       objInstance = { B: true, S: "str", I: 42, N: null };
       expect(ajv.validate(boolStrOrNumObjSchema, objInstance)).toBe(false);
     });
+
+    describe("with omitAdditionalProperties option", () => {
+      it("rejects object with boolean value", () => {
+        type Set = FromSchema<
+          typeof boolStrOrNumObjSchema,
+          { omitAdditionalProperties: true }
+        >;
+
+        expectTypeOf<Set>().toEqualTypeOf<{}>();
+      });
+    });
   });
 
   describe("Unevaluated properties", () => {
@@ -286,7 +310,7 @@ describe("Object schemas", () => {
       expect(ajv.validate(addressSchema, addressInstance)).toBe(true);
     });
 
-    it("accepts object with missing required properties", () => {
+    it("rejects object with missing required properties", () => {
       // @ts-expect-error
       addressInstance = {
         number: 13,
@@ -295,6 +319,25 @@ describe("Object schemas", () => {
       };
       expect(ajv.validate(addressSchema, addressInstance)).toBe(false);
     });
+
+    describe("with omitAdditionalProperties option", () => {
+      it("rejects object with additional properties", () => {
+        type Address2 = FromSchema<
+          typeof addressSchema,
+          { omitAdditionalProperties: true }
+        >;
+
+        const addressInstance2: Address2 = {
+          number: 13,
+          streetName: "Champs Elysées",
+          streetType: "Avenue",
+          direction: "NW",
+          // @ts-expect-error
+          additionalProperty: ["any", "value"],
+        };
+        expect(ajv.validate(addressSchema, addressInstance2)).toBe(true);
+      });
+    });
   });
 
   describe("Required + Typed additional properties", () => {
@@ -345,6 +388,24 @@ describe("Object schemas", () => {
       };
       expect(ajv.validate(addressSchema, addressInstance)).toBe(false);
     });
+
+    describe("with omitAdditionalProperties option", () => {
+      it("rejects object with valid additional properties", () => {
+        type Address2 = FromSchema<
+          typeof addressSchema,
+          { omitAdditionalProperties: true }
+        >;
+
+        const addressInstance2: Address2 = {
+          number: 13,
+          streetName: "Champs Elysées",
+          streetType: "Avenue",
+          // @ts-expect-error
+          additionalProperty: "additionalProperty",
+        };
+        expect(ajv.validate(addressSchema, addressInstance2)).toBe(true);
+      });
+    });
   });
 
   describe("Required missing in properties", () => {

src/tests/readme/object.type.test.ts

@@ -168,3 +168,29 @@ type AssertObjectWithDefaultedProperty2 = A.Equals<
 >;
 const assertObjectWithDefaultedProperty2: AssertObjectWithDefaultedProperty2 = 1;
 assertObjectWithDefaultedProperty2;
+
+// With omitAdditionalProperties option
+
+const openObjectSchema2 = {
+  type: "object",
+  additionalProperties: true,
+  properties: {
+    foo: { type: "string" },
+  },
+} as const;
+
+type ReceivedOpenObjectWithOmitAdditionalPropertiesOption = FromSchema<
+  typeof openObjectSchema2,
+  { omitAdditionalProperties: true }
+>;
+type ExpectedOpenObjectWithOmitAdditionalPropertiesOption = {
+  foo?: string;
+};
+
+type AssertOpenObjectWithOmitAdditionalPropertiesOption = A.Equals<
+  ReceivedOpenObjectWithOmitAdditionalPropertiesOption,
+  ExpectedOpenObjectWithOmitAdditionalPropertiesOption
+>;
+
+const assertOpenObjectWithOmitAdditionalPropertiesOption: AssertOpenObjectWithOmitAdditionalPropertiesOption = 1;
+assertOpenObjectWithOmitAdditionalPropertiesOption;

yarn.lock

@@ -3340,6 +3340,11 @@ exit@^0.1.2:
   resolved "https://registry.yarnpkg.com/exit/-/exit-0.1.2.tgz#0632638f8d877cc82107d30a0fff1a17cba1cd0c"
   integrity sha1-BjJjj42HfMghB9MKD/8aF8uhzQw=
 
+expect-type@^1.2.2:
+  version "1.2.2"
+  resolved "https://registry.yarnpkg.com/expect-type/-/expect-type-1.2.2.tgz#c030a329fb61184126c8447585bc75a7ec6fbff3"
+  integrity sha512-JhFGDVJ7tmDJItKhYgJCGLOWjuK9vPxiXoUFLwLDc99NlmklilbiQJwoctZtt13+xMw91MCk/REan6MWHqDjyA==
+
 expect@^27.5.1:
   version "27.5.1"
   resolved "https://registry.yarnpkg.com/expect/-/expect-27.5.1.tgz#83ce59f1e5bdf5f9d2b94b61d2050db48f3fef74"