if encoding.encode(&s).0 == buffer {

            let reencoded = encoding.encode(&s).0;
            // Special handling for UTF-8 BOM: encoding_rs doesn't preserve BOM during encode,
            // but the file is still valid UTF-8 text. Check if the only difference is a UTF-8 BOM.
            if reencoded == buffer {
                return Some(e);
            } else if encoding == encoding_rs::UTF_8
                && buffer.starts_with(b"\xef\xbb\xbf")
                && &buffer[3..] == &*reencoded {
                // The file has a UTF-8 BOM prefix, which is removed during decode/encode.
                // This is still valid UTF-8 text.