Support alternative mail syntax

src/MailableResolver.php

@@ -16,6 +16,8 @@ class MailableResolver
 
     private ?string $content = null;
 
+    private bool $hasBuild = false;
+
     public function __construct(public string|Closure|Mailable $mailable)
     {
     }
@@ -92,6 +94,12 @@ public function content(): string
 
     private function build(Mailable $instance): Mailable
     {
+        if ($this->hasBuild) {
+            return $instance;
+        }
+
+        $this->hasBuild = true;
+
         $locale = MailbookFacade::getLocale();
 
         if ($locale) {

tests/AlternativeMailTest.php

@@ -0,0 +1,22 @@
+<?php
+
+use Xammie\Mailbook\Facades\Mailbook;
+use Xammie\Mailbook\Tests\Mails\AlternativeMail;
+use Xammie\Mailbook\Tests\Mails\ClassicMail;
+
+it('can get mail subject and content', function ($mailable) {
+    $item = Mailbook::add($mailable);
+
+    expect($item->subject())->toBe('Invoice Paid')
+        ->and($item->content())->toBe('Test mail content')
+        ->and($item->from())->toBe(['Example <hello@example.com>'])
+        ->and($item->replyTo())->toBe([])
+        ->and($item->to())->toBe([])
+        ->and($item->cc())->toBe(['Example Name <foo@example.com>'])
+        ->and($item->bcc())->toBe([]);
+})
+    ->with([
+        new ClassicMail(),
+        new AlternativeMail(),
+    ])
+    ->skip(! class_exists('Illuminate\Mail\Mailables\Envelope'), 'Alternative mailables are not available in this version of Laravel');

tests/Mails/AlternativeMail.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Xammie\Mailbook\Tests\Mails;
+
+use Illuminate\Mail\Mailable;
+use Illuminate\Mail\Mailables\Address;
+use Illuminate\Mail\Mailables\Content;
+use Illuminate\Mail\Mailables\Envelope;
+
+final class AlternativeMail extends Mailable
+{
+    public function envelope(): Envelope
+    {
+        return new Envelope(
+            cc: [new Address('foo@example.com', 'Example Name')],
+            subject: 'Invoice Paid',
+        );
+    }
+
+    public function content(): Content
+    {
+        return new Content(
+            htmlString: 'Test mail content',
+        );
+    }
+}

tests/Mails/ClassicMail.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Xammie\Mailbook\Tests\Mails;
+
+use Illuminate\Mail\Mailable;
+
+final class ClassicMail extends Mailable
+{
+    public function build(): self
+    {
+        return $this
+            ->subject('Invoice Paid')
+            ->cc('foo@example.com', 'Example Name')
+            ->html('Test mail content');
+    }
+}