How markdown emails work in Laravel using `league/commonmark` package

From the About section of league/commonmark package:

Highly-extensible PHP Markdown parser which fully supports the CommonMark and GFM specs.

This package helps us parse markdown in PHP. If you are not familiar with markdown, GitHub has super helpful guide about it here.

Mail in Laravel

Laravel provides simple and easy ways to send emails. There are two options in Laravel to send emails:

Mailables
Notifications

I created a poll on Twitter to see how Developers usually send emails in their Laravel apps. Based on the results, seems like Mailable is the go-to choice. We'll also use Mailable to explore further.

(Interesting replies on this tweet, give them a read)

Markdown Mailables

Let's generate a markdown mailable using Artisan.

> php artisan make:mail NewsletterSubscribed --markdown=emails.newsletter.subscribed

We get two files as a result of this command.

App\Mail\NewsletterSubscribed class
resources/views/emails/newsletter/subscribed.blade.php file

Let's take a look at view file:

@component('mail::message')
# Hello

You have subscribed to our newsletter.

@component('mail::button', ['url' => ''])
Button Text
@endcomponent

Thanks,<br>
{{ config('app.name') }}
@endcomponent

We can see that there's a combination of Blade Components and Markdown in this file. These components and others are made available by Laravel, read more about components here. When we send out this mailable, league/commonmark package comes into play and parse this markdown to HTML.

What happens when you Mail::to()→send() ?

Mail::to($request->user())->send(new NewsletterSubscribed());

We are specifying the recipient in to() method and the mailable class in send() method.

Code Dive

Let's dive into send() method. It leads us to Illuminate\Mail\PendingMail class.

<?php

namespace Illuminate\Mail

use Illuminate\Contracts\Mail\Mailable as MailableContract;
use Illuminate\Contracts\Mail\Mailer as MailerContract;

class PendingMail
{
        /**
     * The mailer instance.
     *
     * @var \Illuminate\Contracts\Mail\Mailer
     */
    protected $mailer;

        /**
     * Send a new mailable message instance.
     *
     * @param  \Illuminate\Contracts\Mail\Mailable  $mailable
     * @return mixed
     */
    public function send(MailableContract $mailable)
    {
        return $this->mailer->send($this->fill($mailable));
    }

        /**
     * Populate the mailable with the addresses.
     *
     * @param  \Illuminate\Contracts\Mail\Mailable  $mailable
     * @return \Illuminate\Mail\Mailable
     */
    protected function fill(MailableContract $mailable)
    {
        return tap($mailable->to($this->to)
            ->cc($this->cc)
            ->bcc($this->bcc), function (MailableContract $mailable) {
            if ($this->locale) {
                $mailable->locale($this->locale);
            }
        });
    }
}

Mailable class is being filled with addresses and then its calling send method on the given Mailer instance. As we can see, $mailer is an instance of class which implements the Mailer contract. Where do we find its concrete class implementation?

Finding the Mailer

When request comes in and Laravel registers the ServiceProviders, part of these providers is Illumiate\Mail\MailServiceProvider. Let's take a look at its register method.

    use Illuminate\Mail\MailManager;

        /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        $this->registerIlluminateMailer();
        $this->registerMarkdownRenderer();
    }

    /**
     * Register the Illuminate mailer instance.
     *
     * @return void
     */
    protected function registerIlluminateMailer()
    {
        $this->app->singleton('mail.manager', function ($app) {
            return new MailManager($app);
        });

        $this->app->bind('mailer', function ($app) {
            return $app->make('mail.manager')->mailer();
        });
    }

    /**
     * Register the Markdown renderer instance.
     *
     * @return void
     */
    protected function registerMarkdownRenderer()
    {
        $this->app->singleton(Markdown::class, function ($app) {
            $config = $app->make('config');

            return new Markdown($app->make('view'), [
                'theme' => $config->get('mail.markdown.theme', 'default'),
                'paths' => $config->get('mail.markdown.paths', []),
            ]);
        });
    }

It is binding a singleton of MailManager class and then bind Mailer by calling mailer() method on mail.manager singleton above.

We can already see a Markdown class being registered. We will eventually reach to this class.
Read more about singleton() and bind() binding methods in the documentation

Let's dig into mailer() method of MailManager class.

<?php

namespace Illuminate\Mail;

class MailManager
{
        /* Get a mailer instance by name.
     *
     * @param  string|null  $name
     * @return \Illuminate\Mail\Mailer
     */
    public function mailer($name = null)
    {
        $name = $name ?: $this->getDefaultDriver();

        return $this->mailers[$name] = $this->get($name);
    }

        /**
     * Get the default mail driver name.
     *
     * @return string
     */
    public function getDefaultDriver()
    {
        return $this->app['config']['mail.driver'] ??
            $this->app['config']['mail.default'];
    }

        /**
     * Attempt to get the mailer from the local cache.
     *
     * @param  string  $name
     * @return \Illuminate\Mail\Mailer
     */
    protected function get($name)
    {
        return $this->mailers[$name] ?? $this->resolve($name);
    }

    /**
     * Resolve the given mailer.
     *
     * @param  string  $name
     * @return \Illuminate\Mail\Mailer
     *
     * @throws \InvalidArgumentException
     */
    protected function resolve($name)
    {
        //ripped off version of resolve method

        $config = $this->getConfig($name);
            $mailer = new Mailer(
            $name,
            $this->app['view'],
            $this->createSwiftMailer($config),
            $this->app['events']
        );

        return $mailer;

    }
}

Above code can be roughly translated to:

Get the default mail driver / default mailer (which is smtp) then call get() method on it. get() method checks if given mailer has already been resolved ( local cache ), otherwise resolve the concrete class for the given mailer.

We found the Mailer concrete class. Yay!

It's located at Illuminate\Mail\Mailer. It was kind of obvious, but finding it through code-dive was fun. Alright, moving on...

The Mailer

We are interested in send() method on the Mailer class. Let's take a look:

<?php

namespace Illuminate\Mail;

use Illuminate\Contracts\Mail\Mailable as MailableContract;
use Illuminate\Contracts\Mail\Mailer as MailerContract;

class Mailer implements MailerContract
{

    /**
     * The name that is configured for the mailer.
     *
     * @var string
     */
    protected $name;

    /**
     * Send a new message using a view.
     *
     * @param  \Illuminate\Contracts\Mail\Mailable|string|array  $view
     * @param  array  $data
     * @param  \Closure|string|null  $callback
     * @return void
     */
    public function send($view, array $data = [], $callback = null)
    {
        if ($view instanceof MailableContract) {
            return $this->sendMailable($view);
        }

            //.. code ripped off
        }

    /**
     * Send the given mailable.
     *
     * @param  \Illuminate\Contracts\Mail\Mailable  $mailable
     * @return mixed
     */
    protected function sendMailable(MailableContract $mailable)
    {
        return $mailable instanceof ShouldQueue
            ? $mailable->mailer($this->name)->queue($this->queue)
            : $mailable->mailer($this->name)->send($this);
    }
}

In the send() method it checks if $view is an instance of Mailable , in our case this is true. We are indeed working with Mailable and we passed a mailable from PendingMail class.

Then it sets Mailer on Mailable class itself and then calls send method on the Mailable.

The Mailable

If we were to find concrete class that implements Mailable class, this post will become huge.

Therefore, we are just going to assume that Illuminate\Mail\Mailable class is what we need as our NewsletterSubscribed class extends it and it also implements Illuminate\Contracts\Mail\Mailable interface.

<?php

namespace Illuminate\Mail;

use Illuminate\Container\Container;
use Illuminate\Contracts\Mail\Mailable as MailableContract;

class Mailable implements MailableContract, Renderable
{
    /**
     * Set the name of the mailer that should send the message.
     *
     * @param  string  $mailer
     * @return $this
     */
    public function mailer($mailer)
    {
        $this->mailer = $mailer;

        return $this;
    }

    /**
     * Send the message using the given mailer.
     *
     * @param  \Illuminate\Contracts\Mail\Factory|\Illuminate\Contracts\Mail\Mailer  $mailer
     * @return void
     */
    public function send($mailer)
    {
        return $this->withLocale($this->locale, function () use ($mailer) {
            Container::getInstance()->call([$this, 'build']);

            $mailer = $mailer instanceof MailFactory
                ? $mailer->mailer($this->mailer)
                : $mailer;

            return $mailer->send(
                **$this->buildView(),
                $this->buildViewData()**,
                function ($message) {
                    $this->buildFrom($message)
                        ->buildRecipients($message)
                        ->buildSubject($message)
                        ->runCallbacks($message)
                        ->buildAttachments($message);
            });
        });
    }
}

In context of our topic, buildView() method is of our interest. Below is its implementation and related methods.

/**
     * Build the view for the message.
     *
     * @return array|string
     *
     * @throws \ReflectionException
     */
    protected function buildView()
    {
        //code ripped off

        if (isset($this->markdown)) {
            return $this->buildMarkdownView();
        }
    }

    /**
     * Build the Markdown view for the message.
     *
     * @return array
     *
     * @throws \ReflectionException
     */
    protected function buildMarkdownView()
    {
        $markdown = Container::getInstance()->make(Markdown::class);

        if (isset($this->theme)) {
            $markdown->theme($this->theme);
        }

        $data = $this->buildViewData();

        return [
            'html' => $markdown->render($this->markdown, $data),
            'text' => $this->buildMarkdownText($markdown, $data),
        ];
    }

buildMarkdownView() method is where it is initialising Markdown class from container and rendering the markdown view of our NewlsetterSubscribed mail.

The Markdown

In the Markdown class, there are two important methods. render and parse.

<?php

namespace Illuminate\Mail;

use Illuminate\Contracts\View\Factory as ViewFactory;
use Illuminate\Support\HtmlString;
use Illuminate\Support\Str;
use League\CommonMark\CommonMarkConverter;
use League\CommonMark\Environment;
use League\CommonMark\Extension\Table\TableExtension;
use TijsVerkoyen\CssToInlineStyles\CssToInlineStyles;

class Markdown
{
    /**
     * The view factory implementation.
     *
     * @var \Illuminate\Contracts\View\Factory
     */
    protected $view;

    protected $theme = 'default';

    public function __construct(ViewFactory $view, array $options = [])
    {
        $this->view = $view;
        $this->theme = $options['theme'] ?? 'default';
        $this->loadComponentsFrom($options['paths'] ?? []);
    }

    /**
     * Render the Markdown template into HTML.
     *
     * @param  string  $view
     * @param  array  $data
     * @param  \TijsVerkoyen\CssToInlineStyles\CssToInlineStyles|null  $inliner
     * @return \Illuminate\Support\HtmlString
     */
    public function render($view, array $data = [], $inliner = null)
    {
        $this->view->flushFinderCache();

        $contents = $this->view->replaceNamespace(
            'mail',
            $this->htmlComponentPaths()
        )->make($view, $data)->render();

        if ($this->view->exists($this->theme)) {
            $theme = $this->theme;
        } else {
            $theme = Str::contains($this->theme, '::')
                ? $this->theme
                : 'mail::themes.' . $this->theme;
        }

        return new HtmlString(($inliner ?: new CssToInlineStyles)->convert(
            $contents,
            $this->view->make($theme, $data)->render()
        ));
    }

    /**
     * Parse the given Markdown text into HTML.
     *
     * @param  string  $text
     * @return \Illuminate\Support\HtmlString
     */
    public static function parse($text)
    {
        $environment = Environment::createCommonMarkEnvironment();

        $environment->addExtension(new TableExtension);

        $converter = new CommonMarkConverter([
            'allow_unsafe_links' => false,
        ], $environment);

        return new HtmlString($converter->convertToHtml($text));
    }
}

And we can finally see inside the parse() method that it utilizes classes from league/commonmark package like CommonMarkConverter and TableExtension etc.

But we never called parse() method from anywhere? And we can see nothing inside the render() method related to markdown either?

Well, parse() method is called from within the email views. Our subscribed.blade.php view uses @component('mail::message') which in-turn uses @component('mail::layout') , and if we take a look at layout component at Mail\resources\views\html\layout.blade.php , we see an HTML template with table layout and some styling.

There we see the following code in which parse() method is being called.

<td class="content-cell">
{{ Illuminate\Mail\Markdown::parse($slot) }}

{{ $subcopy ?? '' }}
</td>

When the subscribed view is rendered, parse gets called and our markdown content is parsed using league/commonmark package.

Interesting facts about Markdown in Laravel

Laravel started supporting Markdown syntax in emails ****in **version 5.4**
The first package used to parse markdown was erusev/parsedown
In Laravel v6.0, they switched from erusev/parsedown to league/commonmark for safety features.
Taylor Otwell removed erusev/parsedown from composer.json and added league/commonmark on 30 Dec, 2019.
Commit on GitHub can be found on this link

I hope you enjoyed this post. Next, we will see how Laravel uses league/flysystem package. You can follow me on Twitter or join my newsletter to keep yourself updated.

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