Exporting to JSON Schema
************************

<div class=perex>

Your schema is already a precise description of what the configuration may contain, and that description is useful outside PHP as well. Exported to JSON Schema, it lets editors:

- offer completion of keys and values right in the configuration file
- underline mistakes before the application even runs
- show the descriptions of the options as hints

</div>


Export .{data-version:1.4.0}
============================

`JsonSchema::export()` turns your schema into a "JSON Schema":https://json-schema.org document, the format editors read to offer completion and underline mistakes directly in the JSON or YAML file:

```php
use Nette\Schema\Expect;
use Nette\Schema\JsonSchema;

$schema = Expect::structure([
	'host' => Expect::string('localhost')->description('Database server hostname'),
	'port' => Expect::int(3306)->min(1)->max(65535),
	'user' => Expect::string()->required(),
]);

echo json_encode(JsonSchema::export($schema), JSON_PRETTY_PRINT);
```

```json
{
	"type": "object",
	"properties": {
		"host": {"type": "string", "description": "Database server hostname"},
		"port": {"type": "integer", "minimum": 1, "maximum": 65535},
		"user": {"type": "string"}
	},
	"required": ["user"],
	"additionalProperties": false
}
```

Save the result into a file and point your editor to it; how exactly depends on the editor and the format of the configuration file.


What the Export Contains
========================

The export describes the **shape** of the data: types, ranges, patterns, required items, enum values and the texts you added with [description() |types#Description: description()].

Default values, `castTo()` and `transform()` are deliberately left out, because they describe what happens to the data after validation, and JSON Schema has no way to say that.

A type that exists only in PHP, such as a class (`Expect::type(Address::class)`), a callable or a resource, cannot be exported at all. Instead of producing a document that would quietly describe something else, the export throws `Nette\NotSupportedException`. The same goes for a [custom element |custom-elements], whose rules the export cannot know.


Differences from Validation
===========================

Two differences remain between the export and the validation. JSON Schema counts the length of a string in characters, while `Expect::string()` counts bytes, so use `Expect::unicode()` for text that is not plain ASCII. And a `pattern()` is exported as it is, but a JSON Schema validator reads it as an ECMAScript regular expression, so constructions specific to PCRE may be understood differently there.

{{maintitle: Nette Schema: Export to JSON Schema for Editor Completion}}
{{description: Export a Nette Schema to JSON Schema, so editors offer completion and underline mistakes in configuration files. What the export contains and where it differs.}}