Make includeIf infer types from the condition as well

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 #### 🚀 Enhancement
 
-- Add regex validator [#17](https://github.com/opencreek/vlad/pull/17) ([@reckter](https://github.com/reckter))
+- Add regex validator [#17](https://github.com/opencreek/vlad/pull/17)
+  ([@reckter](https://github.com/reckter))
 
 #### Authors: 1
 

polyfill/objectHasOwn.ts

@@ -1,6 +1,5 @@
 declare global {
   interface Object {
-    // deno-lint-ignore ban-types
     hasOwn(subject: object, property: PropertyKey): boolean;
   }
 }

src/validators/includeIf.ts

@@ -33,12 +33,16 @@ export type Condition<V1 extends Validator> =
  * ```
  */
 
-export function includeIf<V1 extends Validator>(
+export function includeIf<
+  // deno-lint-ignore no-explicit-any
+  Subject extends any,
+  V1 extends Validator,
+>(
   condition:
-    | ((value: SubjectType<V1>, context: ContextType<V1>) => boolean)
+    | ((value: Subject, context: ContextType<V1>) => boolean)
     | boolean,
   validator1: V1,
-): V1 {
+): Validator<SubjectType<V1> & Subject, ReturnType<V1>> {
   return function includeIfValidator(subject, context) {
     const conditionResult = resolveCondition(subject, context, condition);
 

src/validators/requiredObject.ts

@@ -23,7 +23,6 @@ export function requiredObject(
   message: string,
 ): Validator<
   // we actually want all non-primitives here
-  // deno-lint-ignore ban-types
   object,
   ObjectTopLevelError<PrimitiveErrors>
 >;

test/validators/includeIf.test.ts

@@ -1,4 +1,10 @@
-import { includeIf, is, minItems } from "../../src/vlad.ts";
+import {
+  includeIf,
+  is,
+  minItems,
+  object,
+  requiredPrimitive,
+} from "../../src/vlad.ts";
 import { assertEquals } from "../testingDeps.ts";
 
 Deno.test("should not change the result of a single is validator", () => {
@@ -13,7 +19,7 @@ Deno.test("should not change the result of a single is validator", () => {
 
 Deno.test("Should correctly include validator on condition", () => {
   const validator = includeIf(
-    (value) => (value?.[0] ?? 0) < 5,
+    (value: Array<number>) => (value?.[0] ?? 0) < 5,
     minItems(4, "Should have at least 5 items"),
   );
   const outputInvalid = validator([1]);
@@ -42,3 +48,19 @@ Deno.test("Should correctly include validator on static condition - false", () =
 
   assertEquals(outputInvalid, undefined);
 });
+
+Deno.test("Should correctly infer types from the boolean condition", () => {
+  const validator = includeIf(
+    (value: { length: number }) => value.length > 5,
+    object({
+      foo: requiredPrimitive("foo is required"),
+    }),
+  );
+  const outputInvalid = validator({ length: 6 });
+  const outputValid = validator({ length: 6, foo: "bla" });
+  const outputValid2 = validator({ length: 2 });
+
+  assertEquals(outputInvalid, { foo: ["foo is required"] });
+  assertEquals(outputValid, undefined);
+  assertEquals(outputValid2, undefined);
+});