[Mime] Leverage PHP 8's detection of CSV files.

src/Symfony/Component/Mime/MimeTypes.php

@@ -166,6 +166,7 @@ final class MimeTypes implements MimeTypesInterface
         'application/cdmi-queue' => ['cdmiq'],
         'application/cdr' => ['cdr'],
         'application/coreldraw' => ['cdr'],
+        'application/csv' => ['csv'],
         'application/cu-seeme' => ['cu'],
         'application/davmount+xml' => ['davmount'],
         'application/dbase' => ['dbf'],
@@ -1817,7 +1818,7 @@ final class MimeTypes implements MimeTypesInterface
         'csp' => ['application/vnd.commonspace'],
         'css' => ['text/css'],
         'cst' => ['application/x-director'],
-        'csv' => ['text/csv', 'text/x-comma-separated-values', 'text/x-csv'],
+        'csv' => ['text/csv', 'text/x-comma-separated-values', 'text/x-csv', 'application/csv'],
         'csvs' => ['text/csv-schema'],
         'cu' => ['application/cu-seeme'],
         'cue' => ['application/x-cue'],

src/Symfony/Component/Mime/Tests/Fixtures/mimetypes/abc.csv

@@ -0,0 +1,3 @@
+a,b,c
+d,e,f
+g,h,i

src/Symfony/Component/Mime/Tests/MimeTypesTest.php

@@ -73,4 +73,18 @@ class MimeTypesTest extends AbstractMimeTypeGuesserTest
         $this->assertContains('text/baz', $mt->getMimeTypes('foo'));
         $this->assertSame(['foo', 'moof'], $mt->getExtensions('text/baz'));
     }
+
+    /**
+     * PHP 8 detects .csv files as "application/csv" while PHP 7 returns "text/plain".
+     *
+     * @requires PHP 8
+     */
+    public function testCsvExtension()
+    {
+        $mt = new MimeTypes();
+
+        $mime = $mt->guessMimeType(__DIR__.'/Fixtures/mimetypes/abc.csv');
+        $this->assertSame('application/csv', $mime);
+        $this->assertSame(['csv'], $mt->getExtensions($mime));
+    }
 }