fix: functions filter and if wrongly filtering on empty strings

Author: josdejong

src/functions.ts

@@ -81,7 +81,7 @@ export const functions: FunctionBuildersMap = {
   filter: <T>(predicate: JSONQuery[]) => {
     const _predicate = compile(predicate)
 
-    return (data: T[]) => data.filter(_predicate)
+    return (data: T[]) => data.filter((item) => truthy(_predicate(item)))
   },
 
   sort: <T>(path: JSONQueryProperty = ['get'], direction?: 'asc' | 'desc') => {
@@ -209,7 +209,7 @@ export const functions: FunctionBuildersMap = {
     const _valueIfTrue = compile(valueIfTrue)
     const _valueIfFalse = compile(valueIfFalse)
 
-    return (data: unknown) => (_condition(data) ? _valueIfTrue(data) : _valueIfFalse(data))
+    return (data: unknown) => (truthy(_condition(data)) ? _valueIfTrue(data) : _valueIfFalse(data))
   },
   in: (path: string, values: JSONQuery) => {
     const getter = compile(path)
@@ -248,3 +248,5 @@ export const functions: FunctionBuildersMap = {
     return Number(`${num}e${-digits}`)
   })
 }
+
+const truthy = (x: unknown) => x !== null && x !== 0 && x !== false

test-suite/compile.test.json

@@ -228,6 +228,13 @@
       "query": ["filter", ["get"]],
       "output": [-1, 1, 2, 3]
     },
+    {
+      "category": "filter",
+      "description": "should filter an array with strings",
+      "input": ["hello", "", "world", " "],
+      "query": ["filter", ["get"]],
+      "output": ["hello", "", "world", " "]
+    },
 
     {
       "category": "sort",
@@ -983,7 +990,7 @@
       "description": "should calculate if (7)",
       "input": null,
       "query": ["if", "", true, false],
-      "output": false
+      "output": true
     },
     {
       "category": "if",