From b36f621362560eb29c4ac3006f56e91025c563ed Mon Sep 17 00:00:00 2001
From: mattdowle <mattjdowle@gmail.com>
Date: Mon, 18 Nov 2019 14:01:12 -0800
Subject: [PATCH 1/2] backport setAttrib feature in R 3.2.0

---
 R/data.table.R | 18 +++++++++---------
 src/wrappers.c | 11 +++++++++--
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/R/data.table.R b/R/data.table.R
index 08ef6872b1..f8de1462c0 100644
--- a/R/data.table.R
+++ b/R/data.table.R
@@ -855,9 +855,11 @@ replace_dot_alias = function(e) {
 
       jvnames = NULL
       drop_dot = function(x) {
-        tt = x %chin% c(".N",".I",".GRP",".BY")
-        if (any(tt)) x[tt] = substring(x[tt], 2L)
-        x
+        if (length(x)!=1L) stop("Internal error: drop_dot passed ",length(x)," items")  # nocov
+        if (identical(substring(x<-as.character(x),1L,1L), ".") && x %chin% c(".N",".I",".GRP",".BY"))
+          substring(x, 2L)
+        else
+          x
       }
       # handle auto-naming of last item of j (e.g. within {} or if/else, #2478)
       #   e.g. DT[, .(a=sum(v), v, .N), by=] should create columns named a, v, N
@@ -870,18 +872,16 @@ replace_dot_alias = function(e) {
             nm = names(q[-1L])   # check list(a=sum(v),v)
             if (is.null(nm)) nm = rep.int("", qlen-1L)
             # attempt to auto-name unnamed columns
-            idx = which(!nzchar(nm))
-            for (jj in idx) {
+            for (jj in which(nm=="")) {
               thisq = q[[jj + 1L]]
               if (missing(thisq)) stop("Item ", jj, " of the .() or list() passed to j is missing") #3507
-              if (is.name(thisq)) nm[jj] = as.character(thisq)
+              if (is.name(thisq)) nm[jj] = drop_dot(thisq)
               # TO DO: if call to a[1] for example, then call it 'a' too
             }
-            nm[idx] = drop_dot(nm[idx])
             if (!is.null(jvnames) && any(idx <- nm != jvnames))
               warning("Different branches of j expression produced different auto-named columns: ", brackify(sprintf('%s!=%s', nm[idx], jvnames[idx])), '; using the most "last" names', call. = FALSE)
             jvnames <<- nm # TODO: handle if() list(a, b) else list(b, a) better
-            setattr(q, "names", NULL)  # drops the names from the list so it's faster to eval the j for each group. We'll put them back afterwards on the result.
+            setattr(q, "names", NULL)  # drops the names from the list so it's faster to eval the j for each group; reinstated at the end on the result.
           }
           return(q) # else empty list is needed for test 468: adding an empty list column
         }
@@ -899,7 +899,7 @@ replace_dot_alias = function(e) {
       }
       if (is.name(jsub)) {
         # j is a single unquoted column name
-        if (jsub!=".SD") jvnames = drop_dot(as.character(jsub))
+        if (jsub!=".SD") jvnames = drop_dot(jsub)
         # jsub is list()ed after it's eval'd inside dogroups.
       } else jsub = do_j_names(jsub) # else maybe a call to transform or something which returns a list.
       av = all.vars(jsub,TRUE)  # TRUE fixes bug #1294 which didn't see b in j=fns[[b]](c)
diff --git a/src/wrappers.c b/src/wrappers.c
index af9ac39ccf..9101987d9a 100644
--- a/src/wrappers.c
+++ b/src/wrappers.c
@@ -22,11 +22,18 @@ SEXP setattrib(SEXP x, SEXP name, SEXP value)
     UNPROTECT(1);
     return(x);
   }
-  setAttrib(x, name,
-    MAYBE_REFERENCED(value) ? duplicate(value) : value);
+  if (isNull(value) && isPairList(x) && strcmp(CHAR(STRING_ELT(name,0)),"names")==0) {
+    // backport fix in R 3.2.0 to support R 3.1.0; #4048 #3802
+    // apply this backport always (i.e. in R >=3.2.0 too) to avoid a switch on version number or feature test (to avoid more code, tests and nocov)
+    for (SEXP t=x; t!=R_NilValue; t=CDR(t)) {
+      SET_TAG(t, R_NilValue);
+    }
+  } else {
+    setAttrib(x, name, MAYBE_REFERENCED(value) ? duplicate(value) : value);
     // duplicate is temp fix to restore R behaviour prior to R-devel change on 10 Jan 2014 (r64724).
     // TO DO: revisit. Enough to reproduce is: DT=data.table(a=1:3); DT[2]; DT[,b:=2]
     // ... Error: selfrefnames is ok but tl names [1] != tl [100]
+  }
   return(R_NilValue);
 }
 

From 87c856c4a834832ac9fc1e3115726aa7d0e6f417 Mon Sep 17 00:00:00 2001
From: mattdowle <mattjdowle@gmail.com>
Date: Mon, 18 Nov 2019 14:05:46 -0800
Subject: [PATCH 2/2] add test that user explicit naming .(.N=.N) does not drop
 dot

---
 inst/tests/tests.Rraw | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index 0c6494d594..64f9199719 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -16377,6 +16377,8 @@ test(2121.2, DT[ , {{{b = b; .(a, b = b + 1)}}}], DT[ , .(a, b=b+1)])
 test(2121.3, DT[ , if (.N > 1L) .(b), by=a], DT[1:2])
 test(2121.4, DT[ , if (.N > 1L) .(b) else .(c=b), by=a], DT[ , .(a, c=b)],
      warning="Different branches of j expression produced different auto-named columns")
+test(2121.5, DT[, .(.N=.N), by=a], data.table(a=c(1,2), .N=2:1)) # user supplied names preside over autoname dropping leading dot
+
 
 ###################################
 #  Add new tests above this line  #