Merge pull request #182 from RomanTsegelskyi/empty_fix

fix #180 for empty objects

R/pandoc.R

@@ -820,6 +820,17 @@ pandoc.table.return <- function(t, caption, digits = panderOptions('digits'), de
     ## store missing values
     wm <- which(is.na(t), arr.ind = TRUE)
 
+    ## checking for empty data frames
+    if (length(dim(t)) > 1 && dim(t)[1] == 0) {
+        if (!is.null(colnames(t))) {
+            t <- as.data.frame(t)
+            t[1, ] <- NA
+        } else {
+            warning("Object is empty and without header. No output will be produced")
+            return(invisible())
+        }
+    }
+
     ## round numbers & cut digits & apply decimal mark & optionally remove trailing zeros
     if (length(dim(t)) < 2 | !is.null(dim(t)) && length(dim(t)) == 2 && is.data.frame(t))
         t.n <- as.numeric(which(sapply(t, is.numeric)))
@@ -894,9 +905,6 @@ pandoc.table.return <- function(t, caption, digits = panderOptions('digits'), de
         }
     }
 
-    ## checking for empty data frames
-    if (length(dim(t)) > 1 && dim(t)[1] == 0)
-        t[1, ] <- NA
 
     ## get (col/row)names if any
     t.colnames <- tryCatch(colnames(t), error = function(e) NULL)

inst/tests/test-S3.R

@@ -375,6 +375,29 @@ test_that('table.expand behaves correctly',{
   expect_equal(pandoc.table.return(data.frame(a = 'ßß')), "\n---\n a \n---\nßß \n---\n\n")
 })
 
+context("Empty objects")
+
+test_that('Behavior for empty objects is correct', {
+    mt <- mtcars[mtcars$mpg < 0, 1:4]
+    res <- pander_return(mt)
+    expect_equal(res[3], " mpg   cyl   disp   hp ")
+    expect_equal(res[5], " NA    NA     NA    NA ")
+    expect_equal(length(res), 7)
+    colnames(mt) <- NULL
+    res <- pander_return(mt)
+    expect_equal(length(res), 0)
+    expect_warning(pander_return(mt))
+    mt <- matrix(0, nrow = 0, ncol = 5)
+    res <- pander_return(mt)
+    expect_equal(length(res), 0)
+    expect_warning(pander_return(mt))
+    colnames(mt) <- 1:5
+    res <- pander_return(mt)
+    expect_equal(res[3], " 1   2   3   4   5 ")
+    expect_equal(res[5], "NA  NA  NA  NA  NA ")
+    expect_equal(length(res), 7)
+})
+
 context("S3 methods")
 
 test_that('pander.tabular behaves correctly', {