Tokenizer/PHP: bug fix in improved context sensitive keyword support

As reported in 3609, the `empty` keyword, as well as the `isset` and `unset` keywords, was not included in the list of context sensitive keyword. This is a regression compared to PHPCS 3.6.2.

Fixed now, including unit tests.

Note: I've now done a full comparison with the [reserved keyword list as per the PHP manual](https://www.php.net/manual/en/reserved.keywords.php). This should hopefully fix the remaining stranglers.

Fixes 3609

Author: jrfnl

src/Util/Tokens.php

@@ -687,6 +687,7 @@ final class Tokens
         T_ECHO         => T_ECHO,
         T_ELSE         => T_ELSE,
         T_ELSEIF       => T_ELSEIF,
+        T_EMPTY        => T_EMPTY,
         T_ENDDECLARE   => T_ENDDECLARE,
         T_ENDFOR       => T_ENDFOR,
         T_ENDFOREACH   => T_ENDFOREACH,
@@ -712,6 +713,7 @@ final class Tokens
         T_INSTANCEOF   => T_INSTANCEOF,
         T_INSTEADOF    => T_INSTEADOF,
         T_INTERFACE    => T_INTERFACE,
+        T_ISSET        => T_ISSET,
         T_LIST         => T_LIST,
         T_LOGICAL_AND  => T_LOGICAL_AND,
         T_LOGICAL_OR   => T_LOGICAL_OR,
@@ -732,6 +734,7 @@ final class Tokens
         T_THROW        => T_THROW,
         T_TRAIT        => T_TRAIT,
         T_TRY          => T_TRY,
+        T_UNSET        => T_UNSET,
         T_USE          => T_USE,
         T_VAR          => T_VAR,
         T_WHILE        => T_WHILE,

tests/Core/Tokenizer/ContextSensitiveKeywordsTest.inc

@@ -22,6 +22,7 @@ class ContextSensitiveKeywords
     const /* testEcho */ ECHO = 'ECHO';
     const /* testElse */ ELSE = 'ELSE';
     const /* testElseIf */ ELSEIF = 'ELSEIF';
+    const /* testEmpty */ EMPTY = 'EMPTY';
     const /* testEndDeclare */ ENDDECLARE = 'ENDDECLARE';
     const /* testEndFor */ ENDFOR = 'ENDFOR';
     const /* testEndForeach */ ENDFOREACH = 'ENDFOREACH';
@@ -47,6 +48,7 @@ class ContextSensitiveKeywords
     const /* testInstanceOf */ INSTANCEOF = 'INSTANCEOF';
     const /* testInsteadOf */ INSTEADOF = 'INSTEADOF';
     const /* testInterface */ INTERFACE = 'INTERFACE';
+    const /* testIsset */ ISSET = 'ISSET';
     const /* testList */ LIST = 'LIST';
     const /* testMatch */ MATCH = 'MATCH';
     const /* testNamespace */ NAMESPACE = 'NAMESPACE';
@@ -66,6 +68,7 @@ class ContextSensitiveKeywords
     const /* testThrows */ THROW = 'THROW';
     const /* testTrait */ TRAIT = 'TRAIT';
     const /* testTry */ TRY = 'TRY';
+    const /* testUnset */ UNSET = 'UNSET';
     const /* testUse */ USE = 'USE';
     const /* testVar */ VAR = 'VAR';
     const /* testWhile */ WHILE = 'WHILE';
@@ -121,7 +124,7 @@ $object = /* testNewIsKeyword */ new SomeClass();
 $object /* testInstanceOfIsKeyword */ instanceof SomeClass;
 $copy = /* testCloneIsKeyword */ clone $object;
 
-/* testIfIsKeyword */ if (true):
+/* testIfIsKeyword */ if (/* testEmptyIsKeyword */ empty($a)):
 /* testElseIfIsKeyword */ elseif (false):
 /* testElseIsKeyword */ else:
 /* testEndIfIsKeyword */ endif;
@@ -170,6 +173,10 @@ die($foo);
 eval('<?php echo 5;');
 /* testExitIsKeyword */
 exit;
+/* testIssetIsKeyword */
+$a = isset($a);
+/* testUnsetIsKeyword */
+unset($a);
 
 /* testIncludeIsKeyword */
 include 'file.php';

tests/Core/Tokenizer/ContextSensitiveKeywordsTest.php

@@ -65,6 +65,7 @@ public function dataStrings()
             ['/* testEcho */'],
             ['/* testElse */'],
             ['/* testElseIf */'],
+            ['/* testEmpty */'],
             ['/* testEndDeclare */'],
             ['/* testEndFor */'],
             ['/* testEndForeach */'],
@@ -90,6 +91,7 @@ public function dataStrings()
             ['/* testInstanceOf */'],
             ['/* testInsteadOf */'],
             ['/* testInterface */'],
+            ['/* testIsset */'],
             ['/* testList */'],
             ['/* testMatch */'],
             ['/* testNamespace */'],
@@ -109,6 +111,7 @@ public function dataStrings()
             ['/* testThrows */'],
             ['/* testTrait */'],
             ['/* testTry */'],
+            ['/* testUnset */'],
             ['/* testUse */'],
             ['/* testVar */'],
             ['/* testWhile */'],
@@ -278,6 +281,10 @@ public function dataKeywords()
                 '/* testIfIsKeyword */',
                 'T_IF',
             ],
+            [
+                '/* testEmptyIsKeyword */',
+                'T_EMPTY',
+            ],
             [
                 '/* testElseIfIsKeyword */',
                 'T_ELSEIF',
@@ -388,6 +395,14 @@ public function dataKeywords()
                 '/* testExitIsKeyword */',
                 'T_EXIT',
             ],
+            [
+                '/* testIssetIsKeyword */',
+                'T_ISSET',
+            ],
+            [
+                '/* testUnsetIsKeyword */',
+                'T_UNSET',
+            ],
 
             [
                 '/* testIncludeIsKeyword */',