🐛 address extension change in the code and in the docs

UPGRADE.md

@@ -1,3 +1,14 @@
+# Upgrading from v2.4 to v2.5
+
+* To address the question raised in the previous version, now the original extension '.csv' is retained
+  even if the mime type is guessed as 'text/plain'.
+
+# Upgrading from v2.3 to v2.4
+
+* To address a security question, the original extension of the uploaded file is not preserved anymore.
+  Instead, it is replaced by the extension of the matching mime type. This could cause a different
+  behaviour only if you use some non-standard extension, otherwise it should not change anything.
+
 # Upgrading from v2.1 to v2.2
 
 * The signature of `StorageInterface::resolveStream` method was changed. The $fieldName parameter is now nullable. 

src/Naming/Polyfill/FileExtensionTrait.php

@@ -8,6 +8,11 @@
 
 trait FileExtensionTrait
 {
+    // extensions safe to keep
+    private static array $keep = [
+        'txt' => 'csv',
+    ];
+
     /**
      * Guess the extension of the given file.
      */
@@ -18,6 +23,13 @@ private function getExtension(File $file): ?string
         }
 
         if ('' !== ($extension = $file->guessExtension())) {
+            if (isset(self::$keep[$extension])) {
+                $originalExtension = \pathinfo($file->getClientOriginalName(), \PATHINFO_EXTENSION);
+                if (self::$keep[$extension] === $originalExtension) {
+                    return $originalExtension;
+                }
+            }
+
             return $extension;
         }
 

tests/Naming/SmartUniqidNamerTest.php

@@ -24,6 +24,7 @@ public static function fileDataProvider(): array
             'double uppercase extension' => ['lala.JPEG.JPEG', 'jpg', '/lala-jpeg-[[:xdigit:]]{22}\.jpg/'],
             'dot in filename' => ['filename has . spaces (2).jpg', 'jpg', '/filename-has-spaces-2-[[:xdigit:]]{22}\.jpg/'],
             'file with no extension with null mimetype' => ['lala', null, '/lala-[[:xdigit:]]{22}$/'],
+            'csv retains extension even if guessed as txt' => ['lala.csv', 'txt', '/lala-[[:xdigit:]]{22}\.csv/'],
         ];
     }
 
@@ -34,7 +35,6 @@ public function testNameReturnsAnUniqueName(string $originalName, ?string $guess
     {
         $file = $this->getUploadedFileMock();
         $file
-            ->expects(self::once())
             ->method('getClientOriginalName')
             ->willReturn($originalName)
         ;