type-processors.md

title	weight
Type processors	3

You can use type processors to change an entity's internal Type before it is transpiled into TypeScript.

Default type processors

• ReplaceDefaultsTypeProcessor replaces some types defined in the configuration
• DtoCollectionTypeProcessor replaces DtoCollections from the spatie/data-transfer-object package with their TypeScript equivalent

Specifically for Laravel, we also include the following type processors in the Laravel package:

• LaravelCollectionTypeProcessor handles Laravel's Collection classes like arrays

Using type processors in your transformers

When you're using the TransformsTypes trait in your transformer and use the reflectionToTypeScript then you can additionally pass type processors:

$this->reflectionToTypeScript(
    $reflection, 
    $missingSymbolsCollection,
    new ReplaceDefaultsTypeProcessor(),
    new DtoCollectionTypeProcessor(),
    // and so on ...
);

Writing type processors

A class property processor is any class that implements the ClassPropertyProcessor interface:

class MyClassPropertyProcessor implements TypeProcessor
{
    public function process(
        Type $type,
        ReflectionProperty|ReflectionParameter|ReflectionMethod $reflection,
        MissingSymbolsCollection $missingSymbolsCollection
    ): ?Type
    {
        // Transform the types of the property
    }
}

Returning a type

You can either return a PHPDocumenter type or a TypeScriptType instance for literal TypeScript types.

Let's take a look at an example. With this type processor, it will convert each property type into a string.

Using a TypeScriptType:

class MyClassPropertyProcessor implements TypeProcessor
{
    public function process(
        Type $type,
        ReflectionProperty|ReflectionParameter|ReflectionMethod $reflection,
        MissingSymbolsCollection $missingSymbolsCollection
    ): ?Type
    {
        return TypeScriptType::create('SomeGenericType<string>');
    }
}

Or using a PHPDocumenter type:

class MyClassPropertyProcessor implements TypeProcessor
{
    public function process(
        Type $type,
        ReflectionProperty|ReflectionParameter|ReflectionMethod $reflection,
        MissingSymbolsCollection $missingSymbolsCollection
    ): ?Type
    {
        return new String_();
    }
}

You can find all the possible PHPDocumenter types here.

Walking over types

Since any type can exist of arrays, compound types, nullable types, and more, you'll sometimes need to walk (or loop) over these types to specify types case by case. This can be done by including the ProcessesTypes trait into your type processor.

This trait will add a walk method that takes an initial type and closure.

Let's say you have a compound type like string|bool|int. The walk method will run a string, bool and int type through the closure. You can then decide a type to be returned for each type given to the closure. Finally, the updated compound type will also be passed to the closure.

You can remove a type by returning null.

Let's take a look at an example where we only keep string types and remove any others:

class MyClassPropertyProcessor implements TypeProcessor
{
    use ProcessesTypes;

    public function process(
        Type $type,
        ReflectionProperty|ReflectionParameter|ReflectionMethod $reflection,
        MissingSymbolsCollection $missingSymbolsCollection
    ): ?Type
    {
        return $this->walk($type, function (Type $type) {
            if ($type instanceof _String || $type instanceof Compound) {
                return $type;
            }

            return null;
        });
    }
}

As you can see, we check in the closure if the type is a string or a compound type. If it is none of these two types, we remove it by returning null.

Why checking if the given type is a compound type? In the end, the compound type will be given to the closure. If we removed it, the whole property could be removed from the TypeScript definition.