changed ITEM_ROOT value to empty string, fixed INDEXOF_REGEX, FUNCTION_REGEX

Author: odobosh-lohika-tix

src/index.ts

@@ -86,7 +86,7 @@ export type QueryOptions<T> = ExpandOptions<T> & {
   aliases: Alias[];
 }
 
-export const ITEM_ROOT = '__item';
+export const ITEM_ROOT = "";
 
 export default function <T>({
   select: $select,
@@ -188,9 +188,9 @@ function buildFilter(filters: Filter = {}, propPrefix = ''): string {
             if (filterKey === ITEM_ROOT) {
               propName = propPrefix;
             } else if (INDEXOF_REGEX.test(filterKey)) {
-              propName = filterKey.replace(INDEXOF_REGEX, `(${propPrefix}/$1)`);
+              propName = filterKey.replace(INDEXOF_REGEX, (_,$1)=>$1.trim() === ITEM_ROOT ? `(${propPrefix})` : `(${propPrefix}/${$1.trim()})`);
             } else if (FUNCTION_REGEX.test(filterKey)) {
-              propName = filterKey.replace(FUNCTION_REGEX, `(${propPrefix}/$1)`);
+              propName = filterKey.replace(FUNCTION_REGEX, (_,$1)=>$1.trim() === ITEM_ROOT ? `(${propPrefix})` : `(${propPrefix}/${$1.trim()})`);
             } else {
               propName = `${propPrefix}/${filterKey}`;
             }

test/index.test.ts

@@ -703,6 +703,20 @@ describe('filter', () => {
       const actual = buildQuery({ filter });
       expect(actual).toEqual(expected);
     })
+
+    it('should handle collection operator with a function on the item of a simple collection', () => {
+      const filter = {
+        tags: {
+          any: {
+            [`tolower(${ITEM_ROOT})`]: 'tag1'
+          }
+        }
+      }
+      const expected =
+          "?$filter=tags/any(tags:tolower(tags) eq 'tag1')";
+      const actual = buildQuery({ filter });
+      expect(actual).toEqual(expected);
+    });
   });
 
   describe('data types', () => {