Squiz/ClosingDeclarationCommentSniff: prevent non-problematic bug

This commit fixes a non-problematic bug on line 96. The code `if
(rtrim($tokens[$next]['content']) === $comment)` was not taking into
account that `$next` can be false. To fix it, a `$next !== false` check
was added to the if condition.

This problem did not cause any issues because when `$next` is `false`, the
code would check the content of the first token
(`$tokens[0]['content']`) and this token can only be the PHP open tag or
inline HTML. The code would only produce false positives if the content
of the first token would be `// end ...` which is unlikely and would be
invalid HTML.

A test was added exercising the code path where `$next` is `false`.

And another tests which actually hits the bug and safeguards against potential regressions for the
non-problematic bug fix.

src/Standards/Squiz/Sniffs/Commenting/ClosingDeclarationCommentSniff.php

@@ -88,7 +88,7 @@ public function process(File $phpcsFile, $stackPtr)
         $data = [$comment];
         if (isset($tokens[($closingBracket + 1)]) === false || $tokens[($closingBracket + 1)]['code'] !== T_COMMENT) {
             $next = $phpcsFile->findNext(T_WHITESPACE, ($closingBracket + 1), null, true);
-            if (rtrim($tokens[$next]['content']) === $comment) {
+            if ($next !== false && rtrim($tokens[$next]['content']) === $comment) {
                 // The comment isn't really missing; it is just in the wrong place.
                 $fix = $phpcsFile->addFixableError('Expected %s directly after closing brace', $closingBracket, 'Misplaced', $data);
                 if ($fix === true) {

src/Standards/Squiz/Tests/Commenting/ClosingDeclarationCommentUnitTest.4.inc

@@ -0,0 +1,8 @@
+<?php
+
+// This should be the only test in this file.
+// Testing that the sniff is triggered when the closing bracket is
+// the last character in the file (no newline after it).
+
+function closingBraceAtEndOfFile() {
+}

src/Standards/Squiz/Tests/Commenting/ClosingDeclarationCommentUnitTest.4.inc.fixed

@@ -0,0 +1,8 @@
+<?php
+
+// This should be the only test in this file.
+// Testing that the sniff is triggered when the closing bracket is
+// the last character in the file (no newline after it).
+
+function closingBraceAtEndOfFile() {
+}//end closingBraceAtEndOfFile()

src/Standards/Squiz/Tests/Commenting/ClosingDeclarationCommentUnitTest.5.inc

@@ -0,0 +1,11 @@
+//end closingBraceAtEndOfFileMissingComment()
+
+<?php
+
+// This should be the only test in this file.
+// Testing that the sniff is triggered and the fixer works when the closing bracket is
+// the last character in the file (no newline after it) and the content of the first token
+// is a "//end closingBraceAtEndOfFileMissingComment()" comment.
+
+function closingBraceAtEndOfFileMissingComment() {
+}

src/Standards/Squiz/Tests/Commenting/ClosingDeclarationCommentUnitTest.5.inc.fixed

@@ -0,0 +1,11 @@
+//end closingBraceAtEndOfFileMissingComment()
+
+<?php
+
+// This should be the only test in this file.
+// Testing that the sniff is triggered and the fixer works when the closing bracket is
+// the last character in the file (no newline after it) and the content of the first token
+// is a "//end closingBraceAtEndOfFileMissingComment()" comment.
+
+function closingBraceAtEndOfFileMissingComment() {
+}//end closingBraceAtEndOfFileMissingComment()

src/Standards/Squiz/Tests/Commenting/ClosingDeclarationCommentUnitTest.php

@@ -52,9 +52,15 @@ public function getErrorList($testFile='')
                 110 => 1,
             ];
 
+        case 'ClosingDeclarationCommentUnitTest.4.inc':
+            return [8 => 1];
+
+        case 'ClosingDeclarationCommentUnitTest.5.inc':
+            return [11 => 1];
+
         default:
             return [];
-        }
+        }//end switch
 
     }//end getErrorList()