Improve validation

src/config/normalize/lib/wild_wild_path/remove.js

@@ -1,12 +1,13 @@
 import { handleMissingValue } from './iterate/expand.js'
-import { reduceParents, setValue } from './set.js'
+import { validateClasses, reduceParents, setValue } from './set.js'
 
 // Same as `set()` but removing a value
 export const remove = function (
   target,
   query,
   { classes = false, mutate = false } = {},
 ) {
+  validateClasses(classes, mutate)
   const setFunc = removeAnyEntry.bind(undefined, { classes, mutate })
   return reduceParents({ target, query, setFunc, classes })
 }

src/config/normalize/lib/wild_wild_path/set.js

@@ -13,10 +13,20 @@ export const set = function (
   value,
   { classes = false, mutate = false } = {},
 ) {
+  validateClasses(classes, mutate)
   const setFunc = setEntry.bind(undefined, { value, classes, mutate })
   return reduceParents({ target, query, setFunc, classes })
 }
 
+// Class instances are not clonable. Therefore, they require `mutate`.
+export const validateClasses = function (classes, mutate) {
+  if (classes && !mutate) {
+    throw new Error(
+      'The "mutate" option must be true when the "classes" option is true.',
+    )
+  }
+}
+
 // Modify a target object multiple times for each matched property.
 export const reduceParents = function ({ target, query, setFunc, classes }) {
   const entries = list(target, query, {