Add missing Arr tests and fix issues identified

- Fix bug in `Arr::sortDesc()` where keys are not preserved correctly
- In `Arr::trim()`, remove keys from the array if removing empty values
- In `Arr::toScalars()`, preserve `null` values

Author: lkrms

src/Utility/Arr.php

@@ -197,7 +197,7 @@ public static function sortDesc(
         bool $preserveKeys = false,
         int $flags = \SORT_REGULAR
     ): array {
-        if (!$preserveKeys) {
+        if ($preserveKeys) {
             arsort($array, $flags);
             return $array;
         }
@@ -560,8 +560,8 @@ public static function implode(string $separator, iterable $array): string
     }
 
     /**
-     * Remove whitespace from the beginning and end of each value in an array
-     * of strings and Stringables before optionally removing empty strings
+     * Remove whitespace from the beginning and end of each value in an array of
+     * strings and Stringables before optionally removing empty strings
      *
      * @template TKey of array-key
      * @template TValue of int|float|string|bool|Stringable|null
@@ -570,7 +570,7 @@ public static function implode(string $separator, iterable $array): string
      * @param string|null $characters Optionally specify characters to remove
      * instead of whitespace.
      *
-     * @return array<TKey,string>
+     * @return ($removeEmpty is false ? array<TKey,string> : list<string>)
      */
     public static function trim(
         iterable $array,
@@ -582,7 +582,10 @@ public static function trim(
                 $characters === null
                     ? trim((string) $value)
                     : trim((string) $value, $characters);
-            if ($removeEmpty && $value === '') {
+            if ($removeEmpty) {
+                if ($value !== '') {
+                    $trimmed[] = $value;
+                }
                 continue;
             }
             $trimmed[$key] = $value;
@@ -641,7 +644,7 @@ public static function upper(iterable $array): array
     public static function toScalars(iterable $array): array
     {
         foreach ($array as $key => $value) {
-            if (!is_scalar($value)) {
+            if ($value !== null && !is_scalar($value)) {
                 if (Test::isStringable($value)) {
                     $value = (string) $value;
                 } elseif ($value instanceof Jsonable) {

tests/fixtures/Concern/Immutable/MyImmutableClass.php

@@ -57,7 +57,7 @@ class MyImmutableClass
 
     public function __construct()
     {
-        $this->Obj = new \stdClass();
+        $this->Obj = new stdClass();
         $this->Coll = new ImmutableCollection();
     }
 

tests/unit/Concern/ImmutableTest.php

@@ -4,6 +4,7 @@
 
 use Lkrms\Tests\Concern\Immutable\MyImmutableClass;
 use Lkrms\Tests\TestCase;
+use stdClass;
 
 final class ImmutableTest extends TestCase
 {
@@ -44,7 +45,7 @@ public function testWithPropertyValue(): void
             ->with('A', 1)  // Changes to $f should be no-ops
             ->with('Obj', $obj);
 
-        $g = $f->with('Coll', $f->Coll->set('g', new \stdClass()));
+        $g = $f->with('Coll', $f->Coll->set('g', new stdClass()));
 
         $this->assertNotSame($a, $b);
         $this->assertNotEquals($a, $b);
@@ -85,7 +86,7 @@ public function testWithPropertyValue(): void
         ];
         $A->Obj->A = 'aa';
         $A->Obj->B = 'bb';
-        $A->Coll = $A->Coll->set('g', new \stdClass());
+        $A->Coll = $A->Coll->set('g', new stdClass());
 
         $this->assertEquals($A, $g);
     }