throw a meaningful exception when parsing dotenv files with BOM

Author: xabbuh

Dotenv.php

@@ -568,7 +568,13 @@ private function doLoad(bool $overrideExistingVars, array $paths): void
                 throw new PathException($path);
             }
 
-            $this->populate($this->parse(file_get_contents($path), $path), $overrideExistingVars);
+            $data = file_get_contents($path);
+
+            if ("\xEF\xBB\xBF" === substr($data, 0, 3)) {
+                throw new FormatException('Loading files starting with a byte-order-mark (BOM) is not supported.', new FormatExceptionContext($data, $path, 1, 0));
+            }
+
+            $this->populate($this->parse($data, $path), $overrideExistingVars);
         }
     }
 }

Tests/DotenvTest.php

@@ -604,4 +604,14 @@ public function testBootEnv()
         $resetContext();
         rmdir($tmpdir);
     }
+
+    public function testExceptionWithBom()
+    {
+        $dotenv = new Dotenv();
+
+        $this->expectException(FormatException::class);
+        $this->expectExceptionMessage('Loading files starting with a byte-order-mark (BOM) is not supported.');
+
+        $dotenv->load(__DIR__.'/fixtures/file_with_bom');
+    }
 }

Tests/fixtures/file_with_bom

@@ -0,0 +1 @@
+FOO=BAR