feat: New tbl_nrow() to support lazy data frames

NAMESPACE

@@ -76,6 +76,7 @@ S3method(tbl_format_footer,tbl)
 S3method(tbl_format_header,pillar_tbl_format_setup)
 S3method(tbl_format_header,tbl)
 S3method(tbl_format_setup,tbl)
+S3method(tbl_nrow,tbl)
 S3method(tbl_sum,default)
 S3method(tbl_sum,tbl)
 S3method(type_sum,Surv)
@@ -155,6 +156,7 @@ export(tbl_format_body)
 export(tbl_format_footer)
 export(tbl_format_header)
 export(tbl_format_setup)
+export(tbl_nrow)
 export(tbl_sum)
 export(type_sum)
 import(lifecycle)

R/tbl-format-setup.R

@@ -76,7 +76,7 @@ tbl_format_setup <- function(
 
   width <- get_width_print(width)
 
-  n <- get_n_print(n, nrow(x))
+  n <- get_n_print(n, tbl_nrow(x))
 
   max_extra_cols <- get_max_extra_cols(max_extra_cols)
   max_footer_lines <- get_max_footer_lines(max_footer_lines)
@@ -112,7 +112,7 @@ tbl_format_setup.tbl <- function(x, width, ...,
   "!!!!DEBUG tbl_format_setup.tbl()"
 
   # Number of rows
-  rows <- nrow(x)
+  rows <- tbl_nrow(x)
 
   lazy <- is.na(rows)
   if (lazy) {
@@ -183,6 +183,25 @@ tbl_format_setup.tbl <- function(x, width, ...,
   )
 }
 
+#' Number of rows in a tbl object
+#'
+#' This generic will be called by [tbl_format_setup()] to determine the number
+#' of rows in a tbl object.
+#'
+#' @param x A tbl object.
+#' @inheritParams rlang::args_dots_empty
+#' @export
+tbl_nrow <- function(x, ...) {
+  check_dots_empty0(...)
+  UseMethod("tbl_nrow")
+}
+
+#' @export
+tbl_nrow.tbl <- function(x, ...) {
+  nrow(x)
+}
+
+
 #' Construct a setup object for formatting
 #'
 #' @description

_pkgdown.yml

@@ -21,6 +21,7 @@ reference:
       - ctl_new_pillar
       - ctl_new_pillar_list
       - tbl_sum
+      - tbl_nrow
       - glimpse
       - format_glimpse
   - title: Formatting pillars