Adds missing Content-Type header to CSV-export (#3787)

Credit to @cleverer

modules/backend/models/ExportModel.php

@@ -62,12 +62,7 @@ abstract class ExportModel extends Model
             throw new ApplicationException(Lang::get('backend::lang.import_export.file_not_found_error'));
         }
 
-        $headers = Response::download($csvPath, $outputName)->headers->all();
-        $result = Response::make(File::get($csvPath), 200, $headers);
-
-        @unlink($csvPath);
-
-        return $result;
+        return Response::download($csvPath, $outputName)->deleteFileAfterSend(true);
     }
 
     /**

tests/unit/backend/models/ExportModelTest.php

@@ -8,7 +8,18 @@ class ExampleExportModel extends ExportModel
 {
     public function exportData($columns, $sessionKey = null)
     {
-        return [];
+        return [
+            [
+                'foo' => 'bar',
+                'bar' => 'foo',
+                'foobar' => 'Hello World!',
+            ],
+            [
+                'foo' => 'bar2',
+                'bar' => 'foo2',
+                'foobar' => 'Hello World2!',
+            ],
+        ];
     }
 }
 
@@ -48,4 +59,36 @@ class ExportModelTest extends TestCase
         $this->assertEquals('art direction-roman empire-sci\-fi', $result);
     }
 
+    public function testDownload()
+    {
+        $model = new ExampleExportModel;
+
+        $csvName = $model->export(['foo' => 'title', 'bar' => 'title2'], []);
+
+        $response = $model->download($csvName);
+
+        $request = new Illuminate\Http\Request();
+
+        $response->prepare($request);
+
+        $this->assertTrue($response->headers->has('Content-Type'), "Response is missing the Content-Type header!");
+        $this->assertTrue($response->headers->contains('Content-Type', 'text/plain'), "Content-Type is not \"text/plain\"!");
+
+        ob_start();
+        $response->send();
+        $output = ob_get_clean();
+
+        $utf8BOM = chr(239).chr(187).chr(191);
+
+        $this->assertEquals($utf8BOM."title,title2\nbar,foo\nbar2,foo2\n", $output, "CSV is not right!");
+
+        $filePath = temp_path($csvName);
+
+        $fileGotDeleted = !is_file($filePath);
+
+        $this->assertTrue($fileGotDeleted, "Export-CSV doesn't get deleted.");
+        if (!$fileGotDeleted) {
+            unlink($filePath);
+        }
+    }
 }