#22: Impl. Abstract classes MUST NOT be marked as public

Magento/Sniffs/Classes/AbstractApiSniff.php

@@ -0,0 +1,68 @@
+<?php
+/**
+ * Copyright © Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Sniffs\Classes;
+
+use PHP_CodeSniffer\Sniffs\Sniff;
+use PHP_CodeSniffer\Files\File;
+
+/**
+ * Detects api annotation for an abstract class.
+ */
+class AbstractApiSniff implements Sniff
+{
+
+    /**
+     * String representation of warning.
+     *
+     * @var string
+     */
+    protected $warningMessage = 'Abstract classes MUST NOT be marked as public @api.';
+
+    /**
+     * Warning violation code.
+     *
+     * @var string
+     */
+    protected $warningCode = 'AbstractApi';
+
+    /**
+     * @inheritDoc
+     */
+    public function register()
+    {
+        return [T_CLASS];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function process(File $phpcsFile, $stackPtr)
+    {
+        $tokens = $phpcsFile->getTokens();
+        $prev = $phpcsFile->findPrevious(T_WHITESPACE, $stackPtr - 1, null, true);
+        if ($prev !== false && $tokens[$prev]['code'] !== T_ABSTRACT) {
+            return;
+        }
+
+        $commentStartPtr = $phpcsFile->findPrevious(T_DOC_COMMENT_OPEN_TAG, $stackPtr - 1, 0);
+        $commentCloserPtr = $tokens[$commentStartPtr]['comment_closer'];
+
+        for ($i = $commentStartPtr; $i <= $commentCloserPtr; $i++) {
+            $token = $tokens[$i];
+
+            if ($token['code'] !== T_DOC_COMMENT_TAG) {
+                continue;
+            }
+
+            if (strpos($token['content'], '@api') === false) {
+                continue;
+            }
+
+            $phpcsFile->addWarning($this->warningMessage, $i, $this->warningCode);
+        }
+    }
+}

Magento/Tests/Classes/AbstractApiUnitTest.inc

@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * Interface FooInterface
+ * @api
+ */
+interface FooInterface
+{
+    public function execute();
+}
+
+/**
+ * // Rule find: api annotation for this class
+ * @api
+ */
+abstract class Foo implements FooInterface
+{
+
+}
+
+/**
+ * // Rule find: api annotation for this class
+ * @api
+ */
+abstract
+class FooBar implements FooInterface
+{
+
+}
+
+
+/**
+ * Class Bar
+ */
+class Bar extends Foo
+{
+    public function execute()
+    {
+        // TODO: Implement execute() method.
+    }
+}

Magento/Tests/Classes/AbstractApiUnitTest.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Tests\Classes;
+
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+
+/**
+ * Class ObjectInstantiationUnitTest
+ */
+class AbstractApiUnitTest extends AbstractSniffUnitTest
+{
+    /**
+     * @inheritdoc
+     */
+    public function getErrorList()
+    {
+        return [];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getWarningList()
+    {
+        return [
+            14 => 1,
+            23 => 1
+        ];
+    }
+}

Magento/ruleset.xml

@@ -105,6 +105,10 @@
     </rule>
 
     <!-- Severity 8 warnings: Magento specific code issues and design violations. -->
+    <rule ref="Magento.Classes.AbstractApi">
+        <severity>8</severity>
+        <type>warning</type>
+    </rule>
     <rule ref="Magento.Classes.ObjectInstantiation">
         <severity>8</severity>
         <type>warning</type>