fix #1595 by automatically adding {} before [

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: knitr
 Type: Package
 Title: A General-Purpose Package for Dynamic Report Generation in R
-Version: 1.32.5
+Version: 1.32.6
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Abhraneel", "Sarma", role = "ctb"),

NEWS.md

@@ -2,7 +2,7 @@
 
 ## BUG FIXES
 
-- Reverted the fix for #1595 since it caused problems in kableExtra (thanks, @bttomio, haozhu233/kableExtra#607).
+- Reverted the fix for #1595 since it caused problems in **kableExtra** (thanks, @bttomio, haozhu233/kableExtra#607), and applied a different fix to the original problem (i.e., add `{}` before `[`).
 
 ## MINOR CHANGES
 

R/table.R

@@ -307,7 +307,7 @@ kable_latex = function(
   } else rep('', nrow(x))
   linesep = ifelse(linesep == "", linesep, paste0('\n', linesep))
 
-  if (escape) x = escape_latex(x)
+  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'
@@ -318,7 +318,7 @@ kable_latex = function(
     if (longtable && cap != '') c(cap, '\\\\'),
     sprintf('\n%s', toprule), '\n',
     if (!is.null(cn <- colnames(x))) {
-      if (escape) cn = escape_latex(cn)
+      cn = escape_latex_table(cn, escape, booktabs)
       paste0(paste(cn, collapse = ' & '), sprintf('\\\\\n%s\n', midrule))
     },
     one_string(apply(x, 1, paste, collapse = ' & '), sprintf('\\\\%s', linesep), sep = ''),
@@ -328,6 +328,15 @@ kable_latex = function(
   ), collapse = '')
 }
 
+# when using booktabs, add {} before [ so that the content in [] won't be
+# treated as parameters of booktabs commands like \midrule:
+# https://github.com/yihui/knitr/issues/1595
+escape_latex_table = function(x, escape = TRUE, brackets = TRUE) {
+  if (escape) x = escape_latex(x)
+  if (brackets) x = gsub('^(\\s*)(\\[)', '\\1{}\\2', x)
+  x
+}
+
 kable_latex_caption = function(x, caption) {
   paste(c(
     '\\begin{table}\n', sprintf('\\caption{%s}\n', caption), x, '\n\\end{table}'

tests/testit/test-table.R

@@ -70,6 +70,19 @@ x & col_name\\\\
   )
 })
 
+assert('kable() adds {} before [] when booktabs = TRUE', {
+  (kable2(data.frame(x = c('[0, 1]', '(1, 2]'), y = c(35, 62)), 'latex', booktabs = TRUE) %==% '
+\\begin{tabular}{lr}
+\\toprule
+x & y\\\\
+\\midrule
+{}[0, 1] & 35\\\\
+(1, 2] & 62\\\\
+\\bottomrule
+\\end{tabular}'
+   )
+})
+
 assert('kable(format = "latex", linesep = ...) works', {
   (kable2(data.frame(x = 1:4), 'latex', linesep  = c('', '', '\\midrule')) %==% '
 \\begin{tabular}{r}