skip vignettes when engine unavailable (#6145)

* skip vignettes when engine unavailable

* set to run again tomorrow

* turn off quiet=TRUE to see if that gives any hint of what's going wrong

.github/workflows/R-CMD-check-occasional.yaml

@@ -1,6 +1,6 @@
 on:
   schedule:
-   - cron: '17 13 19 * *' # 18th of month at 13:17 UTC
+   - cron: '17 13 21 * *' # 18th of month at 13:17 UTC
 
 # A more complete suite of checks to run monthly; each PR/merge need not pass all these, but they should pass before CRAN release
 name: R-CMD-check-occasional
@@ -135,12 +135,15 @@ jobs:
             Sys.unsetenv("TEST_DATA_TABLE_WITH_OTHER_PACKAGES")
           }
 
-          args <- c("--no-manual", "--as-cran")
+          do_vignettes <- requireNamespace("knitr", quietly=TRUE)
+
+          vignette_args <- if (!do_vignettes) "--no-build-vignettes"
+          args <- c("--no-manual", "--as-cran", vignette_args)
           if (requireNamespace("rcmdcheck", quietly=TRUE)) {
             rcmdcheck::rcmdcheck(args = args, error_on = "warning", check_dir = "check")
           } else {
             Rbin = if (.Platform$OS.type == "windows") "R.exe" else "R"
-            system2(Rbin, c("CMD", "build", "."))
+            system2(Rbin, c("CMD", "build", ".", vignette_args))
             dt_tar <- list.files(pattern = "^data[.]table_.*[.]tar[.]gz$")
             if (!length(dt_tar)) stop("Built tar.gz not found among: ", toString(list.files()))
             res = system2(Rbin, c("CMD", "check", dt_tar[1L], args), stdout=TRUE)

inst/tests/other.Rraw

@@ -23,7 +23,7 @@ INT = data.table:::INT
 if (anyDuplicated(pkgs)) stop("Packages defined to be loaded for integration tests in 'inst/tests/other.Rraw' contains duplicates.")
 
 f = function(pkg) suppressWarnings(suppressMessages(isTRUE(
-  library(pkg, character.only=TRUE, logical.return=TRUE, quietly=TRUE, warn.conflicts=FALSE, pos="package:base")  # attach at the end for #5101
+  library(pkg, character.only=TRUE, logical.return=TRUE, warn.conflicts=FALSE, pos="package:base")  # attach at the end for #5101
 )))
 loaded = sapply(pkgs, f)
 if (!all(loaded)) {