Write NA as string

[renkun-ken]

What problem did you solve?

Closes #776

Since JSON does not support NA, NaN, Inf values, they can only be written as strings in the following way:

jsonlite::write_json(x, file, na = "string", null = "null", auto_unbox = TRUE)

One remaining issue is that these values will not work properly when filtering is used in the data viewer, i.e. if one filters a column by "Greater than 0", Inf is not regarded as Inf > 0 but ignored.

(If you have)Screenshot

How can I check this pull request?

The following code should open a data viewer where Inf and NA values are correctly displayed in the data grid.

dt <- data.frame(
  id = 1:6,
  x = c(1, 2, NA, 3, Inf, -Inf),
  y = c("A", "B", NA, NA, NA, "D")
)

View(dt)

[ElianHugh]

LGTM! In the future we could probably look at comparators for sorting the values properly

[renkun-ken]

It looks like JavaScript has support for NaN and infinite values but JSON has no way to represent them. We are only using jsonlite to write the structure to be inserted as part of the HTML, not really reading it as json anyway. In the future, we might have a better way to simply produce the correct JavaScript object directly.