refactor: utilize PHP 7.4 null coalescing assignment

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

src/DiffHelper.php

@@ -23,7 +23,7 @@ public static function getProjectDirectory(): string
     {
         static $path;
 
-        return $path = $path ?? realpath(__DIR__ . '/..');
+        return $path ??= realpath(__DIR__ . '/..');
     }
 
     /**

src/Differ.php

@@ -262,7 +262,7 @@ public static function getInstance(): self
     {
         static $singleton;
 
-        return $singleton = $singleton ?? new static([], []);
+        return $singleton ??= new static([], []);
     }
 
     /**

src/Factory/LineRendererFactory.php

@@ -31,11 +31,7 @@ private function __construct()
      */
     public static function getInstance(string $type, ...$ctorArgs): AbstractLineRenderer
     {
-        if (!isset(self::$singletons[$type])) {
-            self::$singletons[$type] = self::make($type, ...$ctorArgs);
-        }
-
-        return self::$singletons[$type];
+        return self::$singletons[$type] ??= self::make($type, ...$ctorArgs);
     }
 
     /**

src/Factory/RendererFactory.php

@@ -31,11 +31,7 @@ private function __construct()
      */
     public static function getInstance(string $renderer, ...$ctorArgs): AbstractRenderer
     {
-        if (!isset(self::$singletons[$renderer])) {
-            self::$singletons[$renderer] = self::make($renderer, ...$ctorArgs);
-        }
-
-        return self::$singletons[$renderer];
+        return self::$singletons[$renderer] ??= self::make($renderer, ...$ctorArgs);
     }
 
     /**

src/Renderer/Html/AbstractHtml.php

@@ -147,8 +147,8 @@ protected function renderChangedExtent(AbstractLineRenderer $lineRenderer, strin
     {
         static $mbOld, $mbNew;
 
-        $mbOld = $mbOld ?? new MbString();
-        $mbNew = $mbNew ?? new MbString();
+        $mbOld ??= new MbString();
+        $mbNew ??= new MbString();
 
         $mbOld->set($old);
         $mbNew->set($new);

src/Renderer/Html/Combined.php

@@ -390,9 +390,9 @@ protected function markReplaceBlockDiff(array $oldBlock, array $newBlock): array
     {
         static $mbOld, $mbNew, $lineRenderer;
 
-        $mbOld = $mbOld ?? new MbString();
-        $mbNew = $mbNew ?? new MbString();
-        $lineRenderer = $lineRenderer ?? LineRendererFactory::make(
+        $mbOld ??= new MbString();
+        $mbNew ??= new MbString();
+        $lineRenderer ??= LineRendererFactory::make(
             $this->options['detailLevel'],
             [], /** @todo is it possible to get the differOptions here? */
             $this->options,

src/Utility/Arr.php

@@ -21,7 +21,7 @@ public static function getPartialByIndex(array $array, int $start = 0, ?int $end
         $count = \count($array);
 
         // make $end set
-        $end = $end ?? $count;
+        $end ??= $count;
 
         // make $start non-negative
         if ($start < 0) {

tests/DiffHelperTest.php

@@ -110,7 +110,7 @@ protected function findRendererOutputTestFiles(string $rendererName): array
             $idx = (int) $matches['idx'];
             $name = $matches['name'];
 
-            $ret[$idx] = $ret[$idx] ?? [];
+            $ret[$idx] ??= [];
             $ret[$idx][$name] = $file;
         }