fix(dashboard): Clean Edit Variant form payload of empty strings (#7512)

* fix(dashboard): Clean Edit Variant form paylod of empty strings

* fix(dashboard,medusa): Allow passing null to update variant to unset fields

* fix product edit form

* cleanup

* cleanup

* pass prop

packages/admin-next/dashboard/src/lib/form-helpers.ts

@@ -0,0 +1,48 @@
+import { castNumber } from "./cast-number"
+
+export function parseOptionalFormValue<T>(
+  value: T,
+  nullify = true
+): T | undefined | null {
+  if (typeof value === "string" && value.trim() === "") {
+    return nullify ? null : undefined
+  }
+
+  if (Array.isArray(value) && value.length === 0) {
+    return nullify ? null : undefined
+  }
+
+  return value
+}
+
+type Nullable<T> = { [K in keyof T]: T[K] | null }
+
+export function parseOptionalFormData<T extends Record<string, unknown>>(
+  data: T,
+  nullify = true
+): Nullable<T> {
+  return Object.entries(data).reduce((acc, [key, value]) => {
+    return {
+      ...acc,
+      [key]: parseOptionalFormValue(value, nullify),
+    }
+  }, {} as Nullable<T>)
+}
+
+export function parseOptionalFormNumber(
+  value?: string | number,
+  nullify = true
+) {
+  if (
+    typeof value === "undefined" ||
+    (typeof value === "string" && value.trim() === "")
+  ) {
+    return nullify ? null : undefined
+  }
+
+  if (typeof value === "string") {
+    return castNumber(value)
+  }
+
+  return value
+}