Do not hide unnecessary escape characters

CHANGELOG

@@ -7,3 +7,4 @@
  * Change the compilation of `for` loops to throw an exception when a `loop.*` variable is not defined
  * Make `Environment::getGlobals()` private
  * Drop support for PHP < 8.2
+ * Escape characters are no longer ignored

src/Lexer.php

@@ -428,12 +428,7 @@ class Lexer
 
             if (isset(self::SPECIAL_CHARS[$nextChar])) {
                 $result .= self::SPECIAL_CHARS[$nextChar];
-            } elseif ('\\' === $nextChar) {
+            } elseif ($nextChar === '\\' || $nextChar === $quoteType) {
-                $result .= $nextChar;
-            } elseif ("'" === $nextChar || '"' === $nextChar) {
-                if ($nextChar !== $quoteType) {
-                    trigger_deprecation('twig/twig', '3.12', 'Character "%s" at position %d should not be escaped; the "\" character is ignored in Twig v3 but will not be in v4. Please remove the extra "\" character.', $nextChar, $i + 1);
-                }
                 $result .= $nextChar;
             } elseif ('#' === $nextChar && $i + 1 < $length && '{' === $str[$i + 1]) {
                 $result .= '#{';
@@ -451,8 +446,7 @@ class Lexer
                 }
                 $result .= \chr(octdec($octal));
             } else {
-                trigger_deprecation('twig/twig', '3.12', 'Character "%s" at position %d should not be escaped; the "\" character is ignored in Twig v3 but will not be in v4. Please remove the extra "\" character.', $nextChar, $i + 1);
+                $result .= '\\'.$nextChar;
-                $result .= $nextChar;
             }
 
             ++$i;

tests/Fixtures/escape_characters.test

@@ -0,0 +1,14 @@
+--TEST--
+Exception with bad line number
+--TEMPLATE--
+{{ 'Foo\Bar' }}
+{{ 'Foo\\Bar' }}
+{{ 'Foo\\\Bar' }}
+{{ 'Foo\\\\Bar' }}
+--DATA--
+return []
+--EXPECT--
+Foo\Bar
+Foo\Bar
+Foo\\Bar
+Foo\\Bar

tests/Fixtures/functions/enum_cases/invalid_enum_escaping.test

@@ -1,10 +0,0 @@
---TEST--
-"enum_cases" function with missing \ escaping
---CONDITION--
-\PHP_VERSION_ID >= 80100
---TEMPLATE--
-{% for c in enum_cases('Twig\Tests\DummyBackedEnum') %}
-    {{~ c.name }}
-{% endfor %}
---EXCEPTION--
-Twig\Error\SyntaxError: The first argument of the "enum_cases" function must be the name of an enum, "TwigTestsDummyBackedEnum" given in "index.twig" at line 2.

tests/Fixtures/functions/enum_cases/valid.test

@@ -6,10 +6,13 @@
 {% for c in enum_cases('Twig\\Tests\\DummyBackedEnum') %}
     {{~ c.name }}: {{ c.value }}
 {% endfor %}
-{% for c in enum_cases('Twig\\Tests\\DummyUnitEnum') %}
+{% for c in enum_cases('Twig\Tests\DummyBackedEnum') %}
+    {{~ c.name }}: {{ c.value }}
+{% endfor %}
+{% for c in enum_cases('Twig\Tests\DummyUnitEnum') %}
     {{~ c.name }}
 {% endfor %}
-{% set from_variable='Twig\\Tests\\DummyUnitEnum' %}
+{% set from_variable='Twig\Tests\DummyUnitEnum' %}
 {% for c in enum_cases(from_variable) %}
     {{~ c.name }}
 {% endfor %}
@@ -18,6 +21,8 @@ return []
 --EXPECT--
 FOO: foo
 BAR: bar
+FOO: foo
+BAR: bar
 BAR
 BAZ
 BAR

tests/LexerTest.php

@@ -12,7 +12,6 @@ namespace Twig\Tests;
  */
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Bridge\PhpUnit\ExpectDeprecationTrait;
 use Twig\Environment;
 use Twig\Error\SyntaxError;
 use Twig\Lexer;
@@ -22,8 +21,6 @@ use Twig\Token;
 
 class LexerTest extends TestCase
 {
-    use ExpectDeprecationTrait;
-
     public function testNameLabelForTag()
     {
         $template = '{% § %}';
@@ -195,6 +192,18 @@ class LexerTest extends TestCase
 
     public function getStringWithEscapedDelimiter()
     {
+        yield '{{ \'App\Test\' }} => App\Test' => [
+            '{{ \'App\\Test\' }}',
+            'App\Test',
+        ];
+        yield '{{ "foo \\\' bar" }} => foo \' bar' => [
+            '{{ "foo \\\' bar" }}',
+            "foo \' bar",
+        ];
+        yield '{{ \'foo \" bar\' }} => foo \" bar' => [
+            '{{ \'foo \\" bar\' }}',
+            'foo \" bar',
+        ];
         yield '{{ \'\x6\' }} => \x6' => [
             '{{ \'\x6\' }}',
             "\x6",
@@ -229,43 +238,6 @@ class LexerTest extends TestCase
         ];
     }
 
-    /**
-     * @group legacy
-     * @dataProvider getStringWithEscapedDelimiterProducingDeprecation
-     */
-    public function testStringWithEscapedDelimiterProducingDeprecation(string $template, string $expected, string $expectedDeprecation)
-    {
-        $this->expectDeprecation($expectedDeprecation);
-
-        $lexer = new Lexer(new Environment(new ArrayLoader()));
-        $stream = $lexer->tokenize(new Source($template, 'index'));
-        $stream->expect(Token::VAR_START_TYPE);
-        $stream->expect(Token::STRING_TYPE, $expected);
-
-        // add a dummy assertion here to satisfy PHPUnit, the only thing we want to test is that the code above
-        // can be executed without throwing any exceptions
-        $this->addToAssertionCount(1);
-    }
-
-    public function getStringWithEscapedDelimiterProducingDeprecation()
-    {
-        yield '{{ \'App\Test\' }} => AppTest' => [
-            '{{ \'App\\Test\' }}',
-            'AppTest',
-            'Since twig/twig 3.12: Character "T" at position 5 should not be escaped; the "\" character is ignored in Twig v3 but will not be in v4. Please remove the extra "\" character.',
-        ];
-        yield '{{ "foo \\\' bar" }} => foo \' bar' => [
-            '{{ "foo \\\' bar" }}',
-            'foo \' bar',
-            'Since twig/twig 3.12: Character "\'" at position 6 should not be escaped; the "\" character is ignored in Twig v3 but will not be in v4. Please remove the extra "\" character.',
-        ];
-        yield '{{ \'foo \" bar\' }} => foo " bar' => [
-            '{{ \'foo \\" bar\' }}',
-            'foo " bar',
-            'Since twig/twig 3.12: Character """ at position 6 should not be escaped; the "\" character is ignored in Twig v3 but will not be in v4. Please remove the extra "\" character.',
-        ];
-    }
-
     public function testStringWithInterpolation()
     {
         $template = 'foo {{ "bar #{ baz + 1 }" }}';