Fantastic Bugs and How to Avoid Them

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Fantastic Bugs and How to Avoid Them PHPUGMRN | JUN 24, 2021 @afilina

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No content

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Anna Filina ‣ Coding since 1997. ‣ PHP since 2003. ‣ Legacy archaeologist. ‣ Test automation. ‣ Talks and workshops. ‣ YouTube videos.

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What is this about? ‣Real-world "silly" bugs. ‣How they came to be. ‣How you can avoid making mistakes. ‣Also, I need to rant about bad code.

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$paths = $this->getPaths(); $urls = array_map(function ($path) { return self::URL_ROOT . $path; }, $paths); array_map(): Expected parameter 2 to be an array, string given

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private function getPaths() { return '[ {"list_products":"/products"}, {"view_cart":"/cart"}, ]'; }

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private function getPaths(): array { return [ $this->path1, $this->path2, ]; }

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$paths = $this->getPaths(); $urls = array_map(function ($path) { return self::URL_ROOT . $path; }, $paths); Array to string conversion

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private $path1 = ['list_products' => '/products']; private $path2 = ['view_cart' => '/cart'];

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private $path1 = '/products'; private $path2 = '/cart';

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$urls = array_map(function (string $path) { return self::URL_ROOT . $path; }, $paths);

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/** * @return array */ private function getPaths(): array

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composer require --dev vimeo/psalm vendor/bin/psalm --init Detected level 7 as a suitable initial default vendor/bin/psalm src

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/** * @return array */ private function getPaths(): array { return [ $this->path1, $this->path2, ]; } ERROR: MixedReturnTypeCoercion - src/TypeMismatch.php:65:16 - The type 'array{0: mixed, 1: mixed}' is more general than the declared return type 'array' ...

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/** * @var string */ private string $path;

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/** * @return array */ private function getPaths(): array { return [ $this->path1, $this->path2, ]; }

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if ($path === '') { throw new InvalidArgumentException('Is blank'); }

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$urls = array_map(function (string $path) { return self::URL_ROOT . $path; }, $paths);

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$urls = array_map(function (Path $path) { return self::URL_ROOT . $path; }, $paths);

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composer require beberlei/assert

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final class Path { private string $path; public function __construct(string $path) { Assert::that($path) ->notBlank(); $this->path = $path; } public function __toString(): string { return $this->path; } }

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/** * @return array */ private function getPaths(): array { return [ new Path('/products'), new Path('/cart'), ]; }

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array_map(function (Path $path) { return self::URL_ROOT . $path; }, $paths);

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public function setPrice(int $price) { $this->price = $price; } $this->setPrice(1.15);

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Strict types. Strict types. Strict types.

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private string $stringPath; private Path $voPath;

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NPEs galore.

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class Product { public $name; } //... $this->findByName($this->product->name); TypeError : Argument 1 passed to MyClass::findByName() must be of the type string, null given

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class Product { public string $name; }

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class ProductEntity { public $name; public $price; } final class Product { private string $name; private int $price; //... }

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return new Product( $product->name, $product->price );

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if ($product->getLastPrice() !== null) { return number_format($product->getLastPrice()); } TypeError : number_format() expects parameter 1 to be float, null given

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public function getLastPrice() { return array_pop($this->prices); }

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$lastPrice = $product->getLastPrice(); if ($lastPrice !== null) { return number_format($lastPrice); }

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@$array[$foo->a()]; public function a() { trigger_error('my error', E_USER_ERROR); } $array[$foo->a()] ?? 'something else';

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interface ApiAware { public function setApi(Api $api); } if ($class instanceof ApiAware) { $class->setApi($api); }

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final class MyClass implements ApiAware { private $api; public function setApi(Api $api): void { $this->api = $api; } public function sendApiRequest() { $product = new Product(); $this->api->sendRequest($product); } }

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Error : Call to a member function sendRequest() on null

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final class MyClass { private Api $api; public function __construct(Api $api) { $this->api = $api; } public function sendApiRequest() { $product = new Product(); $this->api->sendRequest($product); } }

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Dependency injection is your friend.

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if (!empty($array)) { return $array[0]; } Trying to access array offset on value of type bool

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empty(""); empty(0); empty(0.0); empty("0"); empty(null); empty(false); empty(array());

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!== "" !== 0 !== 0.0 !== null === true !== []

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0.99 + 0.01 === 1

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IEEE 754 floating point arithmetic.

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$amountInCents + 1

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/** @var PaymentGatewayInterface */ $gateway = $this->getSelectedGateway(); $gateway->preauthorizePayment();

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@afilina