fix: some filters throw on nil input, see #481

src/util/collection.ts

@@ -1,4 +1,4 @@
-import { isString, isObject, isArray } from './underscore'
+import { isNil, isString, isObject, isArray } from './underscore'
 
 export function toEnumerable (val: any) {
   if (isArray(val)) return val
@@ -8,6 +8,7 @@ export function toEnumerable (val: any) {
 }
 
 export function toArray (val: any) {
+  if (isNil(val)) return []
   if (isArray(val)) return val
   return [ val ]
 }

src/util/underscore.ts

@@ -3,6 +3,8 @@ import { Drop } from '../drop/drop'
 const toStr = Object.prototype.toString
 const toLowerCase = String.prototype.toLowerCase
 
+export const hasOwnProperty = Object.hasOwnProperty
+
 export function isString (value: any): value is string {
   return typeof value === 'string'
 }
@@ -72,7 +74,7 @@ export function forOwn <T> (
 ) {
   obj = obj || {}
   for (const k in obj) {
-    if (Object.hasOwnProperty.call(obj, k)) {
+    if (hasOwnProperty.call(obj, k)) {
       if (iteratee(obj[k], k, obj) === false) break
     }
   }
@@ -150,3 +152,7 @@ export function caseInsensitiveCompare (a: any, b: any) {
   if (a > b) return 1
   return 0
 }
+
+export function argumentsToValue<F extends (...args: any) => any> (fn: F) {
+  return (...args: Parameters<F>) => fn(...args.map(toValue))
+}