Fix merge cells style problem when using table substitution

[kennycreeper]

Reproduce The Error

1. Use table substitution, put the placeholder in a merge cells (B9:C9)
2. Generate the output
3. You can see the range C10:C23 border lines doesn't applied

Template

Output

Resolution

In source code Workbook.prototype.substituteTable function

First declare a mergeCell variable represent the current cell equals to the start cell of some mergeCells
const mergeCell = self.sheet.root.findall("mergeCells/mergeCell").find(c => self.splitRange(c.attrib.ref).start === cell.attrib.r)

Second, if current cell is the start cell, copy the original merge cells, then for loop to append the last of cells in mergeRange

if(mergeCell) {
  var mergeRange    = self.splitRange(mergeCell.attrib.ref),
  mergeStart    = self.splitRef(mergeRange.start),
  mergeEnd      = self.splitRef(mergeRange.end);
  for (let colNum = self.charToNum(mergeStart.col) + 1; colNum <= self.charToNum(mergeEnd.col); colNum++) {
      const lastRow = self.sheet.root.find('sheetData').getItem(mergeStart.row - 1)
      const upperCell = lastRow.getItem(colNum - 1)
  
      const cell = self.cloneElement(upperCell);
      cell.attrib.r = self.joinRef({
        row: newRow.attrib.r,
        col: self.numToChar(colNum)
      });
      newRow.append(cell);
  }
}

[kant2002]

Thanks for contribution. Can you add test case which validates your scenario, once it is done, I would gladly accept this PR

[kant2002]

can you use let instead of var and make each variable as separate variable on individual line.

[kennycreeper]

Ok! I'll work on it

[kant2002]

Do you have a chance to work on the suggestions?

[muyoungko]

Hello,
Thanks for very useful library.
I really need this feature.
Can I know why not merged yet?

[kant2002]

@muyoungko can I assume that you take care of this scenario in #188 ?

[muyoungko]

Yes~

[kant2002]

Thanks for filing this PR. Unfortunately due to long time other contributor come along and provide this fix with tests