Provide a better error message for non-existent summary or grand summary rows

[olivroy]

Summary

For discussion. I need to think about this a bit more. Maybe could use summary it can find.

A case like the following could be considered too.

My PR seems to address a very narrow problem compared to what's proposed in #1608.

# Create a table from `mtcars` that has all the different components data <- mtcars %>% gt(rownames_to_stub = TRUE) %>% cols_move_to_start(columns = c("gear", "carb")) %>% tab_stubhead(label = "cars") %>% cols_hide(columns = "mpg") %>% cols_hide(columns = "vs") %>% tab_row_group( label = "Mercs", rows = contains("Merc"), ) %>% tab_row_group( label = "Mazdas", rows = contains("Mazda"), ) %>% tab_options(row_group.default_label = "Others") %>% tab_spanner( label = "gear_carb_cyl", id = "gcc", columns = c(gear, carb, cyl) ) %>% row_group_order(groups = c("Mazdas", "Mercs")) %>% cols_merge_range( col_begin = "disp", col_end = "drat" ) %>% tab_header( title = "Title", subtitle = "Subtitle" ) %>% tab_source_note(source_note = "this is a source note") %>% summary_rows( groups = c("Mazdas", "Mercs"), columns = c(hp, wt, qsec), fns = list( ~mean(., na.rm = TRUE), ~sum(., na.rm = TRUE) ) ) %>% grand_summary_rows( columns = c(hp, wt), fns = list( ~mean(., na.rm = TRUE), ~sum(., na.rm = TRUE) ) ) # My PR doesn't solve the fact that you can't send all summaries here due to not having summary rows everywhere. data %>% tab_footnote("footnote in summary", cells_summary()) #> Error in `tab_footnote()`: #> ! Can't add footnote "footnote in summary". #> Caused by error: #> ! `everything()` must be used within a *selecting* function. # need the following: data %>% tab_footnote("footnote in summary", cells_summary(c(1, 3)))

Related GitHub Issues and PRs

• Ref: Support use of non-existent cells_*() within tab_style(locations = ...) #1608

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.