add when method to Stringable class (#33455)

Co-authored-by: ManojKiran <[email protected]>

Author: ManojKiranA

src/Illuminate/Support/Stringable.php

@@ -600,6 +600,25 @@ public function ucfirst()
         return new static(Str::ucfirst($this->value));
     }
 
+    /**
+     * Apply the callback's string changes if the given "value" is true.
+     *
+     * @param  mixed  $value
+     * @param  callable  $callback
+     * @param  callable|null  $default
+     * @return mixed|$this
+     */
+    public function when($value, $callback, $default = null)
+    {
+        if ($value) {
+            return $callback($this, $value) ?: $this;
+        } elseif ($default) {
+            return $default($this, $value) ?: $this;
+        }
+
+        return $this;
+    }
+
     /**
      * Execute the given callback if the string is empty.
      *

tests/Support/SupportStringableTest.php

@@ -92,6 +92,32 @@ public function testWhenEmpty()
         }));
     }
 
+    public function testWhenFalse()
+    {
+        $this->assertSame('when', (string) $this->stringable('when')->when(false,function($stringable,$value){
+            return $stringable->append($value)->append('false');
+        }));
+        
+        $this->assertSame('when false fallbacks to default', (string) $this->stringable('when false ')->when(false,function($stringable,$value){
+            return $stringable->append($value);
+        },function($stringable){
+            return $stringable->append('fallbacks to default');
+        }));
+    }
+
+    public function testWhenTrue()
+    {
+        $this->assertSame('when true', (string) $this->stringable('when ')->when(true,function($stringable){
+            return $stringable->append('true');
+        }));
+        
+        $this->assertSame('gets a value from if', (string) $this->stringable('gets a value ')->when('from if',function($stringable,$value){
+            return $stringable->append($value);
+        },function($stringable){
+            return $stringable->append('fallbacks to default');
+        }));
+    }
+
     public function testTrimmedOnlyWhereNecessary()
     {
         $this->assertSame(' Taylor Otwell ', (string) $this->stringable(' Taylor Otwell ')->words(3));