Closes #500. lapply(L, "[", Time ==3L) works as expected.

Subset data.tables using lapply doesn't redirect to `[.data.frame` anymore.

R/cedta.R

@@ -11,7 +11,8 @@ cedta = function(n=2L) {
     ans = nsname == "data.table" ||
         "data.table" %chin% names(getNamespaceImports(te)) ||
         "data.table" %chin% tryCatch(get(".Depends",paste("package",nsname,sep=":"),inherits=FALSE),error=function(e)NULL) ||
-        (nsname == "utils" && exists("debugger.look",parent.frame(n+1L))) ||
+        (nsname == "utils" && exists("debugger.look",parent.frame(n+1L))) || 
+        (nsname == "base"  && all(c("FUN", "X") %in% ls(parent.frame(n)))  ) || # lapply
         nsname %chin% cedta.override ||
         identical(TRUE, tryCatch(get(".datatable.aware",asNamespace(nsname),inherits=FALSE),error=function(e)NULL))
     if (!ans && getOption("datatable.verbose"))

README.md

@@ -260,6 +260,8 @@ We moved from R-Forge to GitHub on 9 June 2014, including history.
 
   43. Segfault on joins of the form X[Y, c(..), by=.EACHI] is now fixed. Closes [#744](https://github.com/Rdatatable/data.table/issues/743). Thanks to @nigmastar (Michele Carriero) for the excellent minimal example. 
 
+  44. Subset on data.table using `lapply` of the form `lapply(L, "[", Time == 3L)` works now without error due to "[.data.frame" redirection. Closes [#500](https://github.com/Rdatatable/data.table/issues/500). Thanks to Garrett See for reporting.
+
 #### NOTES
 
   1.  Reminder: using `rolltolast` still works but since v1.9.2 now issues the following warning:  

inst/tests/tests.Rraw

@@ -4966,6 +4966,10 @@ sample <- c("A", "B")
 test(1360.1, dt[sample, c(.N), by = .EACHI], dt[sample, list(V1=.N), by=.EACHI])
 test(1360.2, copy(dt)[sample, N := c(.N), by = .EACHI], copy(dt)[sample, N := .N, by = .EACHI])
 
+# Fix for #500 - `lapply` call shouldn't redirect to `[.data.frame`.
+L <- list(data.table(BOD), data.table(BOD))
+test(1361, lapply(L, "[", Time==3L), list(L[[1L]][Time == 3L], L[[2L]][Time == 3L]))
+
 ##########################