[8.x] Add unless method on stringable

src/Illuminate/Support/Stringable.php

@@ -708,6 +708,25 @@ public function ucfirst()
         return new static(Str::ucfirst($this->value));
     }
 
+    /**
+     * Apply the callback's string changes if the given "value" is false.
+     *
+     * @param  mixed  $value
+     * @param  callable  $callback
+     * @param  callable|null  $default
+     * @return mixed|$this
+     */
+    public function unless($value, $callback, $default = null)
+    {
+        if (! $value) {
+            return $this->when(true, $callback);
+        } elseif ($default) {
+            return $this->when(false, $callback, $default);
+        }
+
+        return $this;
+    }
+
     /**
      * Apply the callback's string changes if the given "value" is true.
      *

tests/Support/SupportStringableTest.php

@@ -92,6 +92,19 @@ public function testCanBeLimitedByWords()
         $this->assertSame('Taylor Otwell', (string) $this->stringable('Taylor Otwell')->words(3));
     }
 
+    public function testUnless()
+    {
+        $this->assertSame('unless false', (string) $this->stringable('unless')->unless(false, function ($stringable, $value) {
+            return $stringable->append(' false');
+        }));
+
+        $this->assertSame('unless true fallbacks to default', (string) $this->stringable('unless')->unless(true, function ($stringable, $value) {
+            return $stringable->append($value);
+        }, function ($stringable) {
+            return $stringable->append(' true fallbacks to default');
+        }));
+    }
+
     public function testWhenEmpty()
     {
         tap($this->stringable(), function ($stringable) {