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generator-schema

FileGenerator for OpenAPI Tools that turns gathered schema metadata into PHP source files: readonly value objects, contract interfaces, throwable error wrappers, and property caster attributes for union-typed fields.

Requirements

• PHP ^8.4
• ext-json

Installation

Where it fits

This package runs during step 4 of the OpenAPI Tools pipeline — after gatherer has built a representation and class names have been resolved with Representation::namespace():

Register Schema before generator-hydrator. Hydrators reflect on the schema classes this generator emits, and the generator run loop include_onces each written file so later generators can depend on freshly emitted types.

Components

Type resolution and PHPDoc formatting delegate to generator-utils (PropertyTypeResolver, UnionTypeUtils, DocBlockBuilder).

Usage

Schema takes a shared nikic/php-parser BuilderFactory and is attached to a package's generators list:

A full configuration example lives in openapi-tools/generator. At minimum you need gathering with schema aliasing enabled when your spec contains structurally identical inline objects:

Direct invocation

Useful in tests and custom tooling:

Generation order

Schema::generate() yields files in a fixed order for every schema in the representation:

1. Contracts — one interface per unique contract, deduplicated by FQCN across all schemas.
2. Errors — one \Error subclass at {namespace}\Schema\Error\{SchemaName}.
3. Schema classes — the readonly value object, any alias classes, and per-property union caster attributes.

Union caster classes are emitted as part of step 3 when a property needs them.

Output layout

Given namespace ApiClients\Client\Example and a component schema named Basic:

The {hash} in alias abstract class names is derived from the schema's serialized JSON so structurally identical schemas share one abstract base.

Generated code

Contract interfaces

Interfaces carry @property PHPDoc from the contract properties gathered for that shape. The interface body is empty; schemas implement it:

Schema classes

Every schema class is readonly, implements its contract(s), and exposes metadata through constants:

Constructor parameters are public promoted properties. Property names in PHP may differ from JSON keys — when they do, EventSauce ObjectHydrator #[MapFrom('json_key')] is attached.

Downstream code (webhook middleware, validators) reads SCHEMA_JSON for JSON Schema validation without shipping a separate schema file.

Nested objects and arrays

For scalar unions such as Jira-style issue field values, duplicate type tokens are collapsed so you get string\|int\|float, not string\|int\|float\|int:

Object unions without discriminator

When a property resolves to multiple object schemas, the generator emits a PropertyCaster that fingerprints incoming arrays by sorted key names (and enum values when present), then hydrates the matching schema class:

Caster classes live under Internal\Attribute\CastUnionToType\ and are referenced as parameter attributes on the schema constructor.

Schema aliases

When registry records structurally identical inline schemas as aliases (useAliasesForDuplication: true), the generator:

1. Moves the shared implementation into an abstract readonly class under Schema\AliasAbstract\.
2. Emits one final readonly alias class per registered name, each extending the abstract base.

The canonical class name from gathering becomes the last alias; the abstract base holds the constructor, constants, and union casters.

Error classes

Each schema gets a final error class extending \Error. Instances carry the HTTP status code and a hydrated copy of the schema:

These are used for error responses registered during gathering (ThrowableSchema in the registry). The representation also tracks an errorClassNameAliased path for deduplicated error shapes; this generator emits the primary Schema\Error\{Name} class.

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/.

Run the suite:

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

Related packages

Contributing

Please see CONTRIBUTING for details.

License

The MIT License (MIT)

Copyright (c) 2026 Cees-Jan Kiewiet

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.