Allow empty strings on select prompt (#99)

* Allow empty string keys on `select` prompts

* Remove truthy check on `required`

src/Prompt.php

@@ -307,9 +307,9 @@ private function validate(mixed $value): void
     {
         $this->validated = true;
 
-        if (($this->required ?? false) && ($value === '' || $value === [] || $value === false || $value === null)) {
+        if ($this->required !== false && $this->isInvalidWhenRequired($value)) {
             $this->state = 'error';
-            $this->error = is_string($this->required) ? $this->required : 'Required.';
+            $this->error = is_string($this->required) && strlen($this->required) > 0 ? $this->required : 'Required.';
 
             return;
         }
@@ -330,6 +330,14 @@ private function validate(mixed $value): void
         }
     }
 
+    /**
+     * Determine whether the given value is invalid when the prompt is required.
+     */
+    protected function isInvalidWhenRequired(mixed $value): bool
+    {
+        return $value === '' || $value === [] || $value === false || $value === null;
+    }
+
     /**
      * Check whether the environment can support the prompt.
      */

src/SelectPrompt.php

@@ -96,4 +96,12 @@ public function visible(): array
     {
         return array_slice($this->options, $this->firstVisible, $this->scroll, preserve_keys: true);
     }
+
+    /**
+     * Determine whether the given value is invalid when the prompt is required.
+     */
+    protected function isInvalidWhenRequired(mixed $value): bool
+    {
+        return $value === null;
+    }
 }

tests/Feature/SelectPromptTest.php

@@ -257,6 +257,20 @@
     expect($result)->toBe('Blue');
 });
 
+it('allows empty strings', function () {
+    Prompt::fake([Key::ENTER]);
+
+    $result = select(
+        label: 'What is your favorite color?',
+        options: [
+            '' => 'Empty',
+            'not-empty' => 'Not empty',
+        ],
+    );
+
+    expect($result)->toBe('');
+});
+
 it('fails when there is no default in non-interactive mode', function () {
     Prompt::interactive(false);