the server mode supports sub data.frame in its column now

[shrektan]

Closes #525

Some user wants to implement some heavy customized datatable style, such as in #525, a child table for each row. The current implement cleanDataFrame() doesn't support this and leads to a broken datatable in the server-side processing mode. This PR is going to fix this.

Example Code

• Before this PR : The browser will throw an error says

DataTables warning: table id=DataTables_Table_0 - Error in `[<-.data.frame`(`*tmp*`, , j, value = list(structure(list(A = c("A", : replacement element 1 is a matrix/data frame of 3 rows, need 2

• After this PR : It works.

---

library(data.table)
library(shiny)
library(DT)

dat <- local({
  n <- 6
  DT <- data.table(
    HEADER = '&#9658;',
    A = rep_len(LETTERS, n),
    B = rep_len(1:10, n),
    C = rep_len(c("GRP1", "GRP2"), n)
  )
  DT[, .(D=.(.SD)), by = .(HEADER, C)]
})


callback_js <-
  JS("
var init_tbl = function(id) {
  return '<table id=\"' + id + '\" class=\"display\" width=\"100%\"></table>';
}

var init_datatable = function(id, d) {
  id = '#'+id;
  $(id).DataTable({
    data: d,
    columns: [
    { data: 'A' },
    { data: 'B' }
    ]  
  }).draw();
}
var sub_tbl_id = 0;
table.on('click', 'td.details-control', function() {
  var table = $(this).closest('table');
  var td = $(this);
  var row = $(table).DataTable().row(td.closest('tr'));
if (row.child.isShown()) {
  row.child.hide();
  td.html('&#9658;');
} else {
  sub_tbl_id = sub_tbl_id + 1;
  var id = 'sub_tbl_id_' + sub_tbl_id;
  row.child(init_tbl(id)).show();
  init_datatable(id, row.data()[3]);
  td.html('&#9660;');
}
})
     ")

runApp(list(
  ui = fluidPage(DT::DTOutput("tbl")),
  server = function(input, output) {
    output$tbl <- DT::renderDT({
      datatable(
        dat,
        escape = FALSE,
        options = list(
          columnDefs = list(
            list(orderable = FALSE, className = 'details-control', targets = 1),
            list(visible = FALSE, targets = -1)
          )
        ),
        callback = callback_js
      )
    }, server = TRUE)
  }), port = 33333)

[yihui]

Thanks! This is an elegant fix.