Closes #3785: rbindlist() now returns correct idcols for lists with d…

…ifferent length vectors
Rdatatable · Aug 21, 2019 · 1b3c24c · 1b3c24c
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Showing 3 changed files with 12 additions and 2 deletions.
diff --git a/NEWS.md b/NEWS.md
@@ -228,6 +228,8 @@
 
 27. `integer64` sum-by-group is now properly optimized, [#1647](https://github.com/Rdatatable/data.table/issues/1647), [#3464](https://github.com/Rdatatable/data.table/issues/3464). Thanks to @mlandry22-h2o for the report.
 
+28. `rbindlist` now returns correct idcols for lists with different length vectors, [#3785](https://github.com/Rdatatable/data.table/issues/3785), [#3786](https://github.com/Rdatatable/data.table/pull/3786). Thanks to @shrektan for the report and fix.
+
 #### NOTES
 
 1. `rbindlist`'s `use.names="check"` now emits its message for automatic column names (`"V[0-9]+"`) too, [#3484](https://github.com/Rdatatable/data.table/pull/3484). See news item 5 of v1.12.2 below.

diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
@@ -15671,6 +15671,14 @@ if (test_bit64) {
   test(2077.06, int64_int32_match(d[, sum(i32, na.rm=TRUE), g], d[, sum(i64, na.rm=TRUE), g]))
 }
 
+# correct rbindlist() idcol for list elements with different length #3785
+x = 1:1000
+X = rbindlist(lapply(x, function(.) list(., 1:2, 2:3)), idcol = 'TAG')
+test(2078.01, X$TAG, rep(x, each = 2))
+
+x = setNames(x, paste0("nm_", x))
+X = rbindlist(lapply(x, function(.) list(., 1:2, 2:3)), idcol = 'TAG')
+test(2078.01, X$TAG, rep(names(x), each = 2))
 
 ###################################
 #  Add new tests above this line  #

diff --git a/src/rbindlist.c b/src/rbindlist.c
@@ -251,7 +251,7 @@ SEXP rbindlist(SEXP l, SEXP usenamesArg, SEXP fillArg, SEXP idcolArg)
       for (int i=0,ansloc=0; i<LENGTH(l); ++i) {
         SEXP li = VECTOR_ELT(l, i);
         if (!length(li)) continue;
-        const int thisnrow = length(VECTOR_ELT(li, 0));
+        const int thisnrow = eachMax[i];
         SEXP thisname = STRING_ELT(listNames, i);
         for (int k=0; k<thisnrow; ++k) SET_STRING_ELT(idval, ansloc++, thisname);
       }
@@ -261,7 +261,7 @@ SEXP rbindlist(SEXP l, SEXP usenamesArg, SEXP fillArg, SEXP idcolArg)
       for (int i=0,ansloc=0; i<LENGTH(l); ++i) {
         SEXP li = VECTOR_ELT(l, i);
         if (!length(li)) continue;
-        const int thisnrow = length(VECTOR_ELT(li, 0));
+        const int thisnrow = eachMax[i];
         for (int k=0; k<thisnrow; ++k) idvald[ansloc++] = i+1;
       }
     }