fix(typings): add support for optional values in "where" clauses (#12337)

types/lib/model.d.ts

@@ -339,8 +339,10 @@ export type WhereValue =
   | OrOperator
   | AndOperator
   | WhereGeometryOptions
-  | (string | number | Buffer | WhereAttributeHash)[]; // implicit [Op.or]
-
+  | (string | number | Buffer | WhereAttributeHash)[] // implicit [Op.or]
+    // allow optional values in where object types
+    // Sequelize will still throw when a value in the object has the value undefined
+  | undefined;
 /**
  * A hash of attributes to describe your search.
  */

types/test/where.ts

@@ -25,6 +25,15 @@ where = {
   date: new Date()
 };
 
+// Optional values 
+let whereWithOptionals: { needed: number; optional?: number } = { needed: 2 };
+where = whereWithOptionals;
+
+// Misusing optional values (typings allow this, sequelize will throw an error during runtime)
+// This might be solved by updates to typescript itself (https://github.com/microsoft/TypeScript/issues/13195)
+whereWithOptionals = { needed: 2, optional: undefined };
+where = whereWithOptionals;
+
 // Operators
 
 const and: AndOperator = {