Avoid a duplicate id error in tab_spanner_delim().

[olivroy]

Summary

Avoid spanner ids collision by initializing the existing spanner ids first and then try to resolve the new spanner id

I get the result I expected with the following code

  df <- data.frame(
    pop_rural_young_num = c(1000, 2000),
    pop_rural_young_pct = c(0.33, 0.66),
    pop_rural_old_num = c(1000, 2000),
    pop_rural_old_pct = c(0.33, 0.66),
    pop_urban_young_num = c(1000, 2000),
    pop_urban_young_pct = c(0.33, 0.66),
    pop_urban_old_num = c(1000, 2000),
    pop_urban_old_pct = c(0.33, 0.66)
  )

 gt::gt(df) %>%
    tab_spanner_delim(
      delim = "_",
      contains("rural"),
      limit = 2
    ) %>%
    tab_spanner_delim(
      delim = "_",
      contains("urban"),
      limit = 2
    )

Previously, I would get this:

Error in `tab_spanner()`:
! The spanner `id` provided ("spanner-young_num") is
  not unique.
• The `id` must be unique across existing spanner and column
  IDs.
• Provide a unique ID value for this spanner.

Note that my code worked if I had only one of the tab_spanner_delim() calls.

Checklist

• I understand and agree to the Code of Conduct.
• I have listed any major changes in the NEWS.
• I have added testthat unit tests to tests/testthat for any new functionality.

[olivroy]

@rich-iannone I think I found a better way to fix the issue by initializing existing spanner ids!

[rich-iannone]

LGTM!