Shiki Compatibility

DocTest handles Shiki line highlights, diff markers, and hide markers used in any Shiki-powered documentation tool — VitePress, Astro, Nuxt Content, Slidev, or direct Shiki usage.

What Shiki Adds

Shiki-powered documentation tools support special markers in code blocks:

Line Highlights

Curly braces in the fence info string highlight specific lines:

```php{1,4-6}
$a = 1;
$b = 2;
$c = 3;
$d = 4;
$e = 5;
$f = 6;
```

Diff Markers

Comments mark lines as added or removed:

```php
$old = 'before'; 
$new = 'after';  
```

Hide Markers

Hide lines from rendered output while keeping them for execution:

```php
··· 2 hidden lines▲ 2 hidden lines
<?phprequire_once 'vendor/autoload.php'; 
$user = User::find(1);
echo $user->name;
```

Or hide a block of lines:

```php
··· 4 hidden lines▲ 4 hidden lines
<?phpdeclare(strict_types=1);require_once 'vendor/autoload.php';use App\Models\User;
$user = User::find(1);
echo $user->name;
```

Other Visual Markers

Shiki also supports highlight, focus, warning, error, and word:xxx markers for visual styling in rendered docs.

Want to know how DocTest processes each marker?

See the Marker Reference for the complete technical breakdown of what ShikiFilter does with every marker type.

Practical Examples

Diff Testing

Write VitePress documentation with diff markers and DocTest will execute the "after" version:

```php
$greeting = 'Hello';           
$greeting = 'Hello, World!';   
echo $greeting;
```
<!-- doctest: Hello, World! -->

This renders as a nice diff in VitePress while DocTest correctly tests the updated code.

Hidden Boilerplate

Hide setup code that readers don't need to see:

```php
··· 2 hidden lines▲ 2 hidden lines
<?phprequire_once 'vendor/autoload.php'; 
echo 'Hello from DocTest!';
```
<!-- doctest: Hello from DocTest! -->

Readers see only the meaningful code. DocTest executes the full snippet including the hidden lines.

Hidden Block Setup

Hide a larger setup block:

```php
··· 4 hidden lines▲ 4 hidden lines
<?phpdeclare(strict_types=1);require_once 'vendor/autoload.php';use App\Support\Collection;
$items = Collection::make([1, 2, 3]);
echo $items->sum();
```
<!-- doctest: 6 -->

Rendering Hidden Lines

To render hide markers visually in the browser (collapsed placeholders, expand/collapse toggle), use the companion npm package:

shiki-hide-lines documentation →

No Configuration Needed

Shiki filtering is always active in DocTest. It runs automatically during the parsing phase before any execution occurs. No configuration is needed — all // [!code xxx] markers are handled transparently.