PHPStan narrowing complex array/list types with assert

Introduction

Check complex array/list types in runtime (via assert) and narrow variables for PHPStan.

This library is "in proof of concept" state. It could be changed or canceled anytime. Source code and tests are written in "it is working just fine" way. Parsing types is very naive and is not well tested.

The goal of this library is to get rid of @var annotations. You can check complex array/list types with assert PHP function in the same way as for the simple types (assert(is_int($var));).

Array/object shapes are not supported. Arrays must be defined with <...>, [] syntax is not supported.

There is one global function is_type(mixed $var, string $type) or static method Forrest79\NarrowTypes::isType(mixed $var, string $type). That really check data in $var against the type description and there is corresponding PHPStan extension so PHPStan will understand, that $var is in described type.

Example:

$arr = [3.14, 5, 10];
assert(is_type($arr, 'list<float|int>'));

In common the assert function is disabled on production, so check is performed only on devel/test environments and there is no need to distribute this library on the production environment.

Installation

To use this extension, require it in Composer:

composer require --dev forrest79/phpstan-narrow-types

You probably want this extension only for dev.

Using

All simple types with correspondent is_... function are supported NULL, int, float, string, bool, callable and object. Arrays array and lists list can be defined with specified types with classic <...> syntax (known from PHPStan).

You can also use | operator like int|string.

All strings that are not matched as an internal simple types are resolved as object name. Object name can be defined with whole namespace (when starting with \) or is completed from actual class namespace/use in a classic way (thanks to nikic/php-parser).

Simple example:

assert(is_type($var, 'int'));
assert(is_type($var, 'int|string'));

For simple types is recommended to use internal PHP functions is_....

The main goal is to replace something like this:

/** @var array<string|int, list<Db\Row>> $arr
$arr = json_decode($data);

With:

$arr = json_decode($data);
assert(is_type($arr, 'array<string|int, list<Db\Row>>'));

With the benefit variable $arr is checked for defined type.

To use this library as PHPStan extension include extension.neon in your project's PHPStan config:

includes:
    - vendor/forrest79/phpstan-narrow-types/extension.neon