fix rstudio/bookdown#663: if a log file contains warnings, don't dele…

…te it

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: tinytex
 Type: Package
 Title: Helper Functions to Install and Maintain 'TeX Live', and Compile 'LaTeX' Documents
-Version: 0.9.3
+Version: 0.9.4
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666")),
   person(family = "RStudio, Inc.", role = "cph"),
@@ -20,4 +20,4 @@ URL: https://github.com/yihui/tinytex
 BugReports: https://github.com/yihui/tinytex/issues
 Encoding: UTF-8
 LazyData: true
-RoxygenNote: 6.1.0
+RoxygenNote: 6.1.1

R/latex.R

@@ -159,7 +159,7 @@ latexmk_emu = function(
   on.exit({
     files2 = exist_files(aux_files)
     files3 = setdiff(files2, files1)
-    if (keep_log) files3 = setdiff(files3, logfile)
+    if (keep_log || latex_warning(logfile)) files3 = setdiff(files3, logfile)
     if (clean) unlink(files3)
   }, add = TRUE)
 
@@ -302,6 +302,15 @@ show_latex_error = function(file, logfile = gsub('[.]tex$', '.log', basename(fil
   }
 }
 
+# whether a LaTeX log file contains warnings
+latex_warning = function(file) {
+  if (!file.exists(file)) return(FALSE)
+  x = readLines(file, warn = FALSE)
+  if (length(i <- grep(r <- '^LaTeX Warning:', x)) == 0) return(FALSE)
+  warning(paste(c('LaTeX Warning(s):', gsub(r, ' ', x[i])), collapse = '\n'), call. = FALSE)
+  TRUE
+}
+
 # check the version of latexmk
 check_latexmk_version = function() {
   out = system2('latexmk', '-v', stdout = TRUE)