Fix compiled float literals depending on the serialize_precision ini setting

CHANGELOG

@@ -1,5 +1,6 @@
 # 3.31.0 (2026-XX-XX)
 
+ * Fix compiled float literals depending on the `serialize_precision` ini setting
  * Fix the `loop` variable being undefined when used in the sequence of a nested `for` tag
  * Reject a deprecated `Template` instance created by another environment in `Environment::resolveTemplate()`
  * Fix a compilation error inside an `autoescape` tag leaking its escaping strategy into the next compiled template

src/Compiler.php

@@ -166,8 +166,15 @@ class Compiler
                 setlocale(\LC_NUMERIC, 'C');
             }
 
+            // var_export() follows serialize_precision, -1 gives the shortest representation that reads back as the same float
+            $precision = \is_float($value) ? ini_set('serialize_precision', '-1') : false;
+
             $this->raw(var_export($value, true));
 
+            if (false !== $precision) {
+                ini_set('serialize_precision', $precision);
+            }
+
             if (false !== $locale) {
                 setlocale(\LC_NUMERIC, $locale);
             }

tests/CompilerTest.php

@@ -64,4 +64,17 @@ class CompilerTest extends TestCase
 
         setlocale(\LC_NUMERIC, $locale);
     }
+
+    public function testReprFloatDoesNotDependOnSerializePrecision(): void
+    {
+        $compiler = new Compiler(new Environment(new ArrayLoader()));
+        $precision = ini_set('serialize_precision', '17');
+
+        try {
+            $this->assertSame('0.1', $compiler->repr(0.1)->getSource());
+            $this->assertSame('17', \ini_get('serialize_precision'));
+        } finally {
+            ini_set('serialize_precision', $precision);
+        }
+    }
 }