Error Identifier: pureMethod.nonOptionalParameterPassed

← Back to pureMethod.*

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

class Replacer
{

	/**
	 * @param-out int $count
	 * @pure-unless-parameter-passed $count
	 */
	public function replace(string $subject, int &$count): string // ERROR: Method Replacer::replace() is marked @pure-unless-parameter-passed for parameter $count, but $count is not optional, so method Replacer::replace() is never pure.
	{
		$count = 1;

		return $subject;
	}

}

Why is it reported? #

The @pure-unless-parameter-passed tag marks a method as pure unless an argument is passed for the named by-reference parameter. Calls that omit the argument are pure, calls that pass it write into the caller’s variable.

Here $count has no default value, so every call has to pass it. The condition under which the method would be pure can never be met, which makes the tag meaningless — the method is effectively always impure. This mirrors pureFunction.nonOptionalParameterPassed for functions.

How to fix it #

Make the parameter optional by giving it a default value, so callers can omit it and get a pure call:

 	/**
 	 * @param-out int $count
 	 * @pure-unless-parameter-passed $count
 	 */
-	public function replace(string $subject, int &$count): string
+	public function replace(string $subject, int &$count = 0): string
 	{

If the parameter has to stay required, the method is never pure. Remove the tag:

 	/**
 	 * @param-out int $count
-	 * @pure-unless-parameter-passed $count
 	 */
 	public function replace(string $subject, int &$count): string

How to ignore this error #

You can use the identifier pureMethod.nonOptionalParameterPassed to ignore this error using a comment:

// @phpstan-ignore pureMethod.nonOptionalParameterPassed
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: pureMethod.nonOptionalParameterPassed

Rules that report this error #

• PHPStan\Rules\Pure\PureFunctionRule [1]
• PHPStan\Rules\Pure\PureMethodRule [1]
• PHPStan\Rules\Pure\PurePropertyHookRule [1]