Fix broken ts builds with leaked scheduler types

.changeset/fresh-deers-kiss.md

@@ -0,0 +1,5 @@
+---
+'formik': patch
+---
+
+Fixed botched typescript builds including scheduler types

packages/formik/package.json

@@ -20,7 +20,9 @@
   "umd:main": "dist/formik.umd.production.js",
   "module": "dist/formik.esm.js",
   "typings": "dist/index.d.ts",
-  "files": ["dist"],
+  "files": [
+    "dist"
+  ],
   "peerDependencies": {
     "react": ">=16.8.0"
   },
@@ -48,6 +50,7 @@
     "@types/lodash": "^4.14.119",
     "@types/react": "^16.9.55",
     "@types/react-dom": "^16.9.9",
+    "@types/scheduler": "^0.16.1",
     "@types/warning": "^3.0.0",
     "@types/yup": "^0.24.9",
     "just-debounce-it": "^1.1.0",

packages/formik/src/Formik.tsx

@@ -352,8 +352,10 @@ export function useFormik<Values extends FormikValues = FormikValues>({
   // is actually high-priority since we absolutely need to guarantee the
   // form is valid before executing props.onSubmit.
   const validateFormWithLowPriority = useEventCallback(
-    (values: Values = state.values) => {
-      return runWithLowPriority(() => {
+    (
+      values: Values = state.values
+    ): Promise<FormikErrors<Values>> | Promise<void> => {
+      return (runWithLowPriority(() => {
         return runAllValidations(values)
           .then(combinedErrors => {
             if (!!isMounted.current) {
@@ -373,7 +375,12 @@ export function useFormik<Values extends FormikValues = FormikValues>({
               );
             }
           });
-      });
+        // The scheduler package is a transitive dependency installed with React
+        // If we leave this type as is, scheduler types leak and be exported in the build
+        // which would require folks to install @types/scheduler if they had
+        // skipLibCheck: false. Or we'd have to add @types/scheduler as a dep.
+        // Both are unecessary.
+      }) as unknown) as Promise<FormikErrors<Values>> | Promise<void>;
     }
   );