Support for tabularx and xltabular

DESCRIPTION

@@ -8,6 +8,7 @@ Authors@R: c(
     person("Adam", "Vogt", role = "ctb"),
     person("Alastair", "Andrew", role = "ctb"),
     person("Alex", "Zvoleff", role = "ctb"),
+    person("Amar", "Al-Zubaidi", role = "ctb"),
     person("Andre", "Simon", role = "ctb", comment = "the CSS files under inst/themes/ were derived from the Highlight package http://www.andre-simon.de"),
     person("Aron", "Atkins", role = "ctb"),
     person("Aaron", "Wolen", role = "ctb"),

NEWS.md

@@ -4,6 +4,8 @@
 
 - Per suggestion of @jakubkaczor (#2116) and discussion with @pedropark99 (#2140), the chunk option `fig.sep` can also be used to add LaTeX code before the first sub-figure now. Previously this option can only be used for adding LaTeX code *after* each sub-figure.
 
+- `knitr::kable()` supports `tabularx` and `xltabular` environments now for LaTeX tables, e.g., `knitr::kable(head(iris), format = 'latex', tabular = 'tabularx')` (thanks, @amarakon, #2138).
+
 ## MINOR CHANGES
 
 - When the inline R code cannot be correctly parsed, the error message will show the original code in addition to the parsing error, which can make it easier to identify the code error in the source document (thanks, @AlbertLei, #2141).

R/table.R

@@ -274,7 +274,9 @@ knit_print.knitr_kable = function(x, ...) {
 }
 
 kable_latex = function(
-  x, booktabs = FALSE, longtable = FALSE, valign = 't', position = '', centering = TRUE,
+  x, booktabs = FALSE, longtable = FALSE, tabular = if (longtable) 'longtable' else 'tabular',
+  valign = if (tabular %in% c('tabularx', 'xltabular')) '{\\linewidth}' else '[t]',
+  position = '', centering = TRUE,
   vline = getOption('knitr.table.vline', if (booktabs) '' else '|'),
   toprule = getOption('knitr.table.toprule', if (booktabs) '\\toprule' else '\\hline'),
   bottomrule = getOption('knitr.table.bottomrule', if (booktabs) '\\bottomrule' else '\\hline'),
@@ -291,7 +293,7 @@ kable_latex = function(
   # vertical align only if 'caption' is not NULL (may be NA) or 'valign' has
   # been explicitly specified
   valign = if ((!is.null(caption) || !missing(valign)) && valign != '') {
-    sprintf('[%s]', valign)
+    if (grepl('^[[{]', valign)) valign else sprintf('[%s]', valign)
   } else ''
   if (identical(caption, NA)) caption = NULL
   if (position != '') position = paste0('[', position, ']')
@@ -310,12 +312,11 @@ kable_latex = function(
   x = escape_latex_table(x, escape, booktabs)
   if (!is.character(toprule)) toprule = NULL
   if (!is.character(bottomrule)) bottomrule = NULL
-  tabular = if (longtable) 'longtable' else 'tabular'
 
   paste(c(
-    if (!longtable) c(env1, cap, centering),
+    if (cap_env <- !tabular %in% c('longtable', 'xltabular')) c(env1, cap, centering),
     sprintf('\n\\begin{%s}%s', tabular, valign), align,
-    if (longtable && cap != '') c(cap, '\\\\'),
+    if (!cap_env && cap != '') c(cap, '\\\\'),
     sprintf('\n%s', toprule), '\n',
     if (!is.null(cn <- colnames(x))) {
       cn = escape_latex_table(cn, escape, booktabs)
@@ -324,7 +325,7 @@ kable_latex = function(
     one_string(apply(x, 1, paste, collapse = ' & '), sprintf('\\\\%s', linesep), sep = ''),
     sprintf('\n%s', bottomrule),
     sprintf('\n\\end{%s}', tabular),
-    if (!longtable) env2
+    if (cap_env) env2
   ), collapse = '')
 }