#24: [New Rule] Static methods SHOULD NOT be used

Author: Lars Roettig

Magento/Sniffs/Functions/StaticFunctionSniff.php

@@ -0,0 +1,61 @@
+<?php
+/**
+ * Copyright © Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Sniffs\Functions;
+
+use PHP_CodeSniffer\Sniffs\Sniff;
+use PHP_CodeSniffer\Files\File;
+
+/**
+ * Detects static function definitions.
+ */
+class StaticFunctionSniff implements Sniff
+{
+    /**
+     * String representation of warning.
+     *
+     * @var string
+     */
+    // phpcs:ignore Magento.Files.LineLength.MaxExceeded
+    protected $warningMessage = 'The use of `static` methods is discouraged';
+
+    /**
+     * Warning violation code.
+     *
+     * @var string
+     */
+    protected $warningCode = 'StaticFunction';
+
+    /**
+     * @inheritDoc
+     */
+    public function register()
+    {
+        return [T_STATIC];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function process(File $phpcsFile, $stackPtr)
+    {
+        $posOfFunction = $phpcsFile->findNext(T_FUNCTION, $stackPtr) + 1;
+        $tokens = array_slice($phpcsFile->getTokens(), $stackPtr, $posOfFunction - $stackPtr);
+
+        $allowedTypes = ['T_STATIC' => '', 'T_WHITESPACE' => '', 'T_FUNCTION' => ''];
+
+        foreach ($tokens as $token) {
+            $type = $token['type'];
+            if (!array_key_exists($type, $allowedTypes)) {
+                break;
+            }
+
+            if ($type === 'T_FUNCTION') {
+                $phpcsFile->addWarning($this->warningMessage, $posOfFunction, $this->warningCode);
+            }
+        }
+    }
+}

Magento/Tests/Functions/StaticFunctionUnitTest.inc

@@ -0,0 +1,26 @@
+<?php
+
+namespace Foo\Bar;
+
+interface  FooInterface
+{
+    public static
+    function aStaticMethod();
+
+    public function normalMethod();
+}
+
+class Foo implements FooInterface
+{
+    private static $property;
+
+    public static function aStaticMethod()
+    {
+        return self::$property;
+    }
+
+    public function normalMethod()
+    {
+        return $this;
+    }
+}

Magento/Tests/Functions/StaticFunctionUnitTest.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Tests\Functions;
+
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+
+/**
+ * Class StaticFunctionSniffTest
+ */
+class StaticFunctionUnitTest extends AbstractSniffUnitTest
+{
+    /**
+     * @inheritdoc
+     */
+    protected function getErrorList()
+    {
+        return [];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    protected function getWarningList()
+    {
+        return [
+            8 => 1,
+            17 => 1
+        ];
+    }
+}

Magento/ruleset.xml

@@ -72,6 +72,9 @@
     <rule ref="Magento.Exceptions.Namespace">
         <severity>8</severity>
     </rule>
+    <rule ref="Magento.Functions.StaticFunction">
+        <severity>6</severity>
+    </rule>
     <rule ref="Magento.Files.LineLength">
         <properties>
             <property name="lineLimit" value="120"/>