fix: 🐛 Fix the TypeScript signature

✅ Closes: #134

Author: NoriSte

cypress/types/plugin.spec.ts

@@ -77,3 +77,8 @@ cy.waitUntil<boolean>(() => true, {
 })
 cy.waitUntil<boolean>(() => true, { log: false })
 cy.waitUntil<boolean>(() => true, { customMessage: 'custom message' })
+
+cy.wrap('').waitUntil((subject) => subject.length)
+cy.wrap('').waitUntil<boolean>((subject) => !!subject.length)
+cy.wrap<string>('').waitUntil<boolean>((subject) => !!subject.length)
+cy.wrap<string>('').waitUntil((subject) => subject.length)

index.d.ts

@@ -21,8 +21,10 @@ interface WaitUntilOptions<Subject = any> {
 
 declare namespace Cypress {
   interface Chainable<Subject = any> {
-    waitUntil<Subject>(
-      checkFunction: () => Subject | Chainable<Subject> | Promise<Subject>,
+    waitUntil<ReturnType = any>(
+      checkFunction: (
+        subject: Subject | undefined
+      ) => ReturnType | Chainable<ReturnType> | Promise<ReturnType>,
       options?: WaitUntilOptions<Subject>
     ): Chainable<Subject>
   }