modify an existing custom formula, but it shows the formula not the result

Steps to Reproduce

1. load a blank file
2. enter =SUM(2,2) at A1
3. modify it to =SUM(1,3)

Current Result

A1 shows the formula itself in cell not the value

Expected Result

show 4

Debug Information

• for ZSS-1164, keikai writes user input text into cell DOM to show user input immediately without waiting the server response, especially under slow network. But when updating a cell with server data, cell widget doesn't change the cell DOM text when the result text doesn't change (after fixing KEIKAI-470). Hence, if I edit a formula but it still produces the same result, cell widget doesn't change its text in DOM, so it keeps showing the entered formula.

Workaround

keikai-528.js

• For a cell with a formula, don't write formula text into DOM, since formula is not a result. That case is useful when user input a text or a number.