Closes #833, as.data.table.list works like base R with matrices.

R/as.data.table.R

@@ -95,6 +95,16 @@ as.data.table.matrix <- function(x, keep.rownames=FALSE, ...) {
 
 as.data.table.list <- function(x, keep.rownames=FALSE, ...) {
     if (!length(x)) return( null.data.table() )
+    # fix for #833, as.data.table.list with matrix/data.frame/data.table as a list element..
+    # TODO: move this entire logic (along with data.table() to C
+    for (i in seq_along(x)) {
+        dims = dim(x[[i]])
+        if (!is.null(dims)) {
+            ans = do.call("data.table", x)
+            setnames(ans, make.unique(names(ans)))
+            return(ans)
+        }
+    }
     n = vapply(x, length, 0L)
     mn = max(n)
     x = copy(x)

README.md

@@ -132,6 +132,8 @@
 
   36. `fread()` handles embedded double quotes in json fields as expected, [#1164](https://github.com/Rdatatable/data.table/issues/1164). Thanks @richardtessier.
 
+  37. `as.data.table.list` handles list elements that are matrices/data.frames/data.tables properly, [#833](https://github.com/Rdatatable/data.table/issues/833). Thanks to @talexand.
+
 #### NOTES
 
   1. Updated error message on invalid joins to reflect the new `on=` syntax, [#1368](https://github.com/Rdatatable/data.table/issues/1368). Thanks @MichaelChirico.

inst/tests/tests.Rraw

@@ -7487,6 +7487,12 @@ test(1610.1, capture.output(print(DT1, print.class=TRUE)),
 #        "2: 2016-01-02 2016-01-02 01:00:00   TRUE 2016-01-02      2", 
 #        "3: 2016-01-03 2016-01-03 01:00:00   TRUE 2016-01-03      3"))
 
+# fix for #833
+l1 = list(a=seq_len(5), matrix(seq_len(25),ncol = 5, nrow = 5))
+l2 = list(seq_len(5), matrix(seq_len(25),ncol = 5, nrow = 5))
+test(1611.1, as.data.table(l1), setnames(setDT(as.data.frame(l1)), c("a", paste("V", 1:5, sep=""))))
+test(1611.2, as.data.table(l2), setnames(setDT(as.data.frame(l2)), c("V1", "V1.1", paste("V", 2:5, sep=""))))
+
 ##########################
 
 # TODO: Tests involving GForce functions needs to be run with optimisation level 1 and 2, so that both functions are tested all the time.