Generic/UnnecessaryHeredoc: bug fix - false positives for heredoc with escape sequence

If the original heredoc contained an escape sequence, but no variable interpolation or expressions, it would be flagged as unnecessary and fixed to nowdoc, even though escape sequences are not supported in nowdocs.

Fixed now.

Includes tests.

Author: jrfnl

src/Standards/Generic/Sniffs/Strings/UnnecessaryHeredocSniff.php

@@ -15,6 +15,35 @@
 class UnnecessaryHeredocSniff implements Sniff
 {
 
+    /**
+     * Escape chars which are supported in heredocs, but not in nowdocs.
+     *
+     * @var array<string>
+     */
+    private $escapeChars = [
+        // Octal sequences.
+        '\0',
+        '\1',
+        '\2',
+        '\3',
+        '\4',
+        '\5',
+        '\6',
+        '\7',
+
+        // Various whitespace and the escape char.
+        '\n',
+        '\r',
+        '\t',
+        '\v',
+        '\e',
+        '\f',
+
+        // Hex and unicode sequences.
+        '\x',
+        '\u',
+    ];
+
 
     /**
      * Returns an array of tokens this test wants to listen for.
@@ -81,6 +110,13 @@ public function process(File $phpcsFile, $stackPtr)
 
         $phpcsFile->recordMetric($stackPtr, 'Heredoc contains interpolation or expression', 'no');
 
+        // Check for escape sequences which aren't supported in nowdocs.
+        foreach ($this->escapeChars as $testChar) {
+            if (strpos($body, $testChar) !== false) {
+                return;
+            }
+        }
+
         $warning = 'Detected heredoc without interpolation or expressions. Use nowdoc syntax instead';
 
         $fix = $phpcsFile->addFixableWarning($warning, $stackPtr, 'Found');

src/Standards/Generic/Tests/Strings/UnnecessaryHeredocUnitTest.1.inc

@@ -106,3 +106,17 @@ some text
 some \$text
 some text \\ including a backslash
 END;
+
+$heredoc = <<<EOD
+<?php
+echo 'The below line contains escape characters and should be recognized as needing heredoc';
+echo "aa\xC3\xC3	\xC3\xB8aa";
+EOD;
+
+echo <<<EOT
+This should print a capital 'A': \x41
+EOT;
+
+echo <<<EOT
+Here we should have a tab and 2 'A's: \t \101 \u{41}
+EOT;

src/Standards/Generic/Tests/Strings/UnnecessaryHeredocUnitTest.1.inc.fixed

@@ -106,3 +106,17 @@ some text
 some $text
 some text \ including a backslash
 END;
+
+$heredoc = <<<EOD
+<?php
+echo 'The below line contains escape characters and should be recognized as needing heredoc';
+echo "aa\xC3\xC3	\xC3\xB8aa";
+EOD;
+
+echo <<<EOT
+This should print a capital 'A': \x41
+EOT;
+
+echo <<<EOT
+Here we should have a tab and 2 'A's: \t \101 \u{41}
+EOT;

src/Standards/Generic/Tests/Strings/UnnecessaryHeredocUnitTest.2.inc

@@ -106,3 +106,17 @@ $heredoc = <<< "END"
     some \$text
     some text \\ including a backslash
     END;
+
+$heredoc = <<<EOD
+    <?php
+    echo 'The below line contains escape characters and should be recognized as needing heredoc';
+    echo "aa\xC3\xC3	\xC3\xB8aa";
+    EOD;
+
+echo <<<EOT
+    This should print a capital 'A': \x41
+    EOT;
+
+echo <<<EOT
+    Here we should have a tab and 2 'A's: \t \101 \u{41}
+    EOT;

src/Standards/Generic/Tests/Strings/UnnecessaryHeredocUnitTest.2.inc.fixed

@@ -106,3 +106,17 @@ $heredoc = <<< 'END'
     some $text
     some text \ including a backslash
     END;
+
+$heredoc = <<<EOD
+    <?php
+    echo 'The below line contains escape characters and should be recognized as needing heredoc';
+    echo "aa\xC3\xC3	\xC3\xB8aa";
+    EOD;
+
+echo <<<EOT
+    This should print a capital 'A': \x41
+    EOT;
+
+echo <<<EOT
+    Here we should have a tab and 2 'A's: \t \101 \u{41}
+    EOT;