README

FileGenerator for OpenAPI Tools that emits EventSauce ObjectHydrator mappers for generated schema classes. Each path (and optionally each webhook) gets a dedicated hydrator; a central Internal\Hydrators facade implements ObjectMapper and routes by class name.

Installation

composer require openapi-tools/generator-hydrator

Where it fits

This package runs during step 4 of the OpenAPI Tools pipeline — after generator-schema has emitted the schema classes this generator reflects on:

flowchart LR
  spec[OpenAPI spec] --> gatherer[Gatherer]
  gatherer --> rep[Representation]
  rep --> ns["namespace()"]
  ns --> schema[Schema generator]
  schema --> hydrator[Hydrator generator]
  hydrator --> perPath["Internal/Hydrator/*"]
  hydrator --> facade[Internal/Hydrators]

Register Hydrator after Schema. The generator run loop include_onces each written file so later generators can depend on freshly emitted types; this generator uses ReflectionMethod on schema constructors when deciding which classes to pass to ObjectMapperCodeGenerator.

Components

Class	Purpose
`Hydrator`	Entry-point `FileGenerator`; emits per-scope hydrators and the central `Internal\Hydrators` facade

AST construction delegates to generator-utils (ExpressionBuilder, MatchBuilder, StatementBuilder). Hydration and serialization logic is produced by EventSauce's ObjectMapperCodeGenerator.

Usage

Hydrator takes a shared nikic/php-parser BuilderFactory and a flag controlling webhook hydrators. Attach it to a package's generators list after Schema:

use OpenAPITools\Generator\Hydrator\Hydrator;
use OpenAPITools\Generator\Schema\Schema;
use PhpParser\BuilderFactory;

$builderFactory = new BuilderFactory();

// inside Package(..., generators: [
//     new Schema($builderFactory),
//     new Hydrator($builderFactory, includeWebHookHydrators: true),
//     ...
// ])

Set includeWebHookHydrators to false when the package has no webhooks or when another generator (such as generator-psr-15-webhook-middleware) owns webhook hydration.

A full configuration example lives in openapi-tools/generator.

Direct invocation

Useful in tests and custom tooling:

use OpenAPITools\Generator\Hydrator\Hydrator;
use OpenAPITools\Generator\Schema\Schema;
use PhpParser\BuilderFactory;

$builderFactory = new BuilderFactory();

// Schema classes must exist before Hydrator runs — eval or include them first.
foreach (new Schema($builderFactory)->generate($package, $namespacedRepresentation) as $file) {
    // load $file into the runtime ...
}

foreach (new Hydrator($builderFactory, true)->generate($package, $namespacedRepresentation) as $file) {
    // $file->pathPrefix  — e.g. "src"
    // $file->fqcn        — e.g. "Internal\Hydrators" or "Internal\Hydrator\Operation\Root"
    // $file->contents    — PhpParser Node or pre-rendered string (ObjectMapperCodeGenerator output)
}

Generation order

Hydrator::generate() walks hydrators from the namespaced representation:

Path hydrators — one per entry in $representation->client->paths.
Webhook hydrators — one per entry in $representation->webHooks when includeWebHookHydrators is true.

For each scope it yields a dedicated ObjectMapper class, then yields the shared Internal\Hydrators facade last.

Within each per-scope hydrator, only schema classes whose __construct has at least one parameter are passed to ObjectMapperCodeGenerator. Schemas without constructor parameters are omitted from the generated mapper.

Output layout

Given namespace ApiClients\Client\Example and a single root path operation:

Relative path	Kind
`Internal/Hydrator/Operation/Root.php`	Per-path `ObjectMapper` for schemas used on that path
`Internal/Hydrators.php`	Central facade implementing `ObjectMapper`

Webhook scopes use Internal/Hydrator/WebHook/{Name}.php instead of Operation/….

Generated code

Per-scope hydrators

Each hydrator is a class generated by EventSauce's ObjectMapperCodeGenerator. It implements ObjectMapper with optimized hydrateObject, hydrateObjects, serializeObject, and serializeObjects methods — no reflection at runtime. Custom value types (such as Ramsey\Uuid\UuidInterface) get dedicated serialize helpers.

namespace ApiClients\Client\Example\Internal\Hydrator\Operation;

use EventSauce\ObjectHydrator\ObjectMapper;

class Root implements ObjectMapper
{
    public function hydrateObject(string $className, array $payload): object
    {
        return match ($className) {
            \ApiClients\Client\Example\Schema\Basic::class => $this->hydrateApiClients⚡️Client⚡️Example⚡️Schema⚡️Basic($payload),
            default => throw new \RuntimeException("Cannot hydrate unknown class: {$className}"),
        };
    }

    // hydrateObjects, serializeObject, serializeObjects, and per-class helpers ...
}

Central facade

Internal\Hydrators implements ObjectMapper and delegates to the per-scope hydrators. Schemas shared across paths appear once in the routing match, even when multiple hydrators reference them.

Lazy getters initialize each per-scope mapper on first use:

namespace ApiClients\Client\Example\Internal;

final class Hydrators implements \EventSauce\ObjectHydrator\ObjectMapper
{
    private ?\ApiClients\Client\Example\Internal\Hydrator\Operation\Root $operation🌀Root = null;

    public function hydrateObject(string $className, array $payload): object
    {
        return match ($className) {
            \ApiClients\Client\Example\Schema\Basic::class
                => $this->getObjectMapperOperation🌀Root()->hydrateObject($className, $payload),
            default => throw new \RuntimeException("Cannot hydrate unknown class: {$className}"),
        };
    }

    public function getObjectMapperOperation🌀Root(): \ApiClients\Client\Example\Internal\Hydrator\Operation\Root
    {
        if (! $this->operation🌀Root instanceof \ApiClients\Client\Example\Internal\Hydrator\Operation\Root) {
            $this->operation🌀Root = new \ApiClients\Client\Example\Internal\Hydrator\Operation\Root();
        }

        return $this->operation🌀Root;
    }

    // hydrateObjects, serializeObject, serializeObjects, and getters for other scopes ...
}

Method names on the facade mirror the hydrator methodName from the representation (for example Operation🌀Root, WebHook🪝Ping).

Schema deduplication

When the same schema class is collected by more than one path or webhook hydrator, the central Internal\Hydrators match includes it only once. Per-scope hydrators still list every schema they need; deduplication applies only to the facade's class-name routing.

Supported patterns

Behaviour is locked down through shared fixtures in openapi-tools/test-data. Each YAML file has a matching assertion class under tests/DataTests/.

Fixture	What it exercises
`Basic`	Minimal object, `$ref`, UUID format, response headers
`ExampleData`	Scalars, formats, patterns, arrays, nullable unions
`Aliases`	Structurally identical inline objects → alias classes hydrated by one mapper
`NestedSchema`	Inline nested objects without `$ref`
`NestedReferenceSchema`	Nested objects via component `$ref`
`TripleNestedSchema`	Deep nesting with `$ref` on nested `schema` keyword
`DoubleUseOfTypes`	OpenAPI 3.1 `type` array combined with `anyOf` on one property
`BasicWebHooks`	Separate hydrators per webhook event
`DiscriminatedWebHooks`	Webhook payload with discriminated request-body variants
`MultiVariantWebHooks`	One webhook mapping to multiple schema variants

Run the suite:

make unit-testing

For the full fixture roadmap and situation coverage matrix, see test-data/src/DataSets/PLAN.md.

Related packages

Package	Relationship
`contract`	`FileGenerator` and `Package` interfaces
`representation`	Input model (`Namespaced\Hydrator`, path and webhook hydrator metadata)
`gatherer`	Builds the representation and assigns schemas to path/webhook hydrators
`generator-schema`	Must run before this package
`generator-utils`	AST builders used for the facade class
`generator`	CLI and run loop that orchestrates all generators
`eventsauce/object-hydrator`	Runtime `ObjectMapper` interface and code generator

Contributing

Please see CONTRIBUTING for details.

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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