False positive: WordPress.WP.AlternativeFunctions.file_system_operations_fopen for php://output CSV streaming

Summary

The WordPress.WP.AlternativeFunctions.file_system_operations_fopen and WordPress.WP.AlternativeFunctions.file_system_operations_fclose checks report an error when using php://output for streaming a CSV download.

In this case, the warning appears to be a false positive because php://output is an output stream rather than a filesystem path, and there is no equivalent WordPress API (WP_Filesystem) for writing streamed CSV responses.

Minimal Reproduction

header( 'Content-Type: text/csv; charset=utf-8' );
header( 'Content-Disposition: attachment; filename=test.csv' );

$output = fopen( 'php://output', 'w' );

foreach ( $rows as $row ) {
	fputcsv( $output, $row );
}

fclose( $output );
exit;

Current Result

Plugin Check reports:

• WordPress.WP.AlternativeFunctions.file_system_operations_fopen
• WordPress.WP.AlternativeFunctions.file_system_operations_fclose

Expected Result

The check should not report an error for php://output, since:

• php://output is not a filesystem path.
• WP_Filesystem cannot be used to replace this functionality.
• Streaming CSV responses using fopen( 'php://output', 'w' ) and fputcsv() is a common PHP pattern, and there is currently no WordPress-native alternative.

If this usage is intentionally unsupported, it would be helpful for the documentation to explain the recommended approach.

Disclaimer: Claude was used to help investigate and draft this issue. I verified the behavior and confirmed the reproduction before submitting.

Start from the WordPress.WP.AlternativeFunctions.file_system_operations_fopen and file_system_operations_fclose checks and reproduce the reported behavior with the minimal php://output CSV example. Done means the checks no longer report this stream, or the supported alternative is documented if the usage remains intentionally unsupported.