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graphql-php-validation-toolkit

GraphQL is great when it comes to validating types and checking syntax, but isn't much help when it comes to providing additional validation on user input. The authors of GraphQL have generally opined that the correct response to bad user input is not to throw an exception, but rather to return any validation feedback along with the result.

As Lee Byron explains here:

...allow for data for a user-facing report in the payload of your mutation. It's often the case that mutation payloads include a "didSucceed" field and a "userError" field. If your UI requires rich information about potential errors, then you should include this information in your payload as well.

That's where this small library comes in.

graphql-php-validation-toolkit extends the built-in definitions provided by the wonderful graphql-php library with a new ValidatedFieldDefinition class. Simply instantiate one of these in place of the usual field config, add validate callback properties to your args definitions, and the type of your field will be replaced by a new, dynamically-generated ResultType with queryable error fields for each of your args. It's a recursive process, so your args can have InputObjectType types with subfields and validate callbacks of their own. Your originally-defined type gets moved to the result field of the generated type.

Installation

Via composer:

Documentation

• Basic Usage
• The Validate Callback
• Custom Error Codes
• Managing Created Types
• Examples

Basic Usage

In a nutshell, replace your usual vanilla field definition with an instance of ValidatedFieldDefinition, and add validate callbacks to one or more of the args configs. Let's say you want to make a mutation called updateBook:

In the sample above, the book type property of your field definition will be replaced by a new dynamically-generated type called UpdateBookResultType.

The type generation process is recursive, traveling down through any nested InputObjectType or ListOf types and checking their fields for more validate callbacks. Every field definition--including the very top one--that has a validate callback will be represented by a custom, generated type with the following queryable fields:

The top-level <field-name>ResultType will have a few additional fields:

You can then simply query for these fields along with result:

The Validate Callback

Any field definition can have a validate callback. The first argument passed to the validate callback will be the value to validate. If the value is valid, return 0, otherwise 1.

The required property

You can mark any field as required, and if the value is not provided, then an automatic validation will happen for you (thus removing the need for you to weaken your validation callback with null types). You can set it to true, or you can provide an error array similar to the one returned by your validate callback. You can also set it to a callable that returns the same bool or error array.

If you want to return an error message, return an array with the message in the second bucket:

Generated ListOf error types also have a path field that you can query so you can know the exact address in the multidimensional array of each item that failed validation:

Custom Error Codes

If you would like to use custom error codes, add an errorCodes property at the same level as your validate callback and feed it the path to a PHP native enum:

Keep in mind that the library will generate unique names for the error code types, and they can become quite long depending on how deeply they are nested in the field structure:

If this becomes a problem for you, be sure to provide a type setter (see example) that returns the type that was set, and then the generated name will simply be the name of the enum class that was passed in, plus "ErrorCode":

Managing Created Types

This library will create new types as needed. If you are using some kind of type manager to store and retrieve types, you can integrate it by providing a typeSetter callback. Make sure it returns the type that was set:

Examples

The best way to understand how all this works is to experiment with it. There are a series of increasingly complex one-page samples in the /examples folder. Each is accompanied by its own README.md, with instructions for running the code. Run each sample, and be sure to inspect the dynamically-generated types in ChromeiQL.

1. basic-scalar-validation
2. custom-error-types
3. input-object-validation
4. list-of-validation

Contribute

Contributions are welcome. Please refer to CONTRIBUTING.md for guidelines.