Also dispatch in dim.data.table()

Author: MichaelChirico

src/assign.c

@@ -239,7 +239,7 @@ SEXP setdt_nrows(SEXP x)
       len_xi = INTEGER(dim_xi)[0];
     } else {
       // Be sure to do length() dispatch, #4800
-      len_xi = INTEGER(length_with_dispatch(xi))[0];
+      len_xi = length_with_dispatch(xi);
     }
     if (!base_length) {
       base_length = len_xi;

src/data.table.h

@@ -258,6 +258,7 @@ SEXP islockedR(SEXP x);
 bool need2utf8(SEXP x);
 SEXP coerceUtf8IfNeeded(SEXP x);
 SEXP coerceAs(SEXP x, SEXP as, SEXP copyArg);
+int length_with_dispatch(SEXP);
 void internal_error(const char *call_name, const char *format, ...);
 
 // types.c
@@ -350,6 +351,5 @@ SEXP test_dt_win_snprintf(void);
 SEXP dt_zlib_version(void);
 SEXP dt_has_zlib(void);
 SEXP startsWithAny(SEXP, SEXP, SEXP);
-SEXP length_with_dispatch(SEXP);
 SEXP convertDate(SEXP, SEXP);
 SEXP fastmean(SEXP);

src/utils.c

@@ -449,8 +449,8 @@ SEXP startsWithAny(const SEXP x, const SEXP y, SEXP start) {
   return ScalarLogical(false);
 }
 
-SEXP length_with_dispatch(SEXP x) {
-  SEXP l = PROTECT(eval(PROTECT(lang2(install("length"), x)), R_GlobalEnv));
+int length_with_dispatch(SEXP x) {
+  int l = INTEGER(PROTECT(eval(PROTECT(lang2(install("length"), x)), R_GlobalEnv)))[0];
   UNPROTECT(2);
   return l;
 }

src/wrappers.c

@@ -113,7 +113,8 @@ SEXP dim(SEXP x)
     INTEGER(ans)[1] = 0;
   }
   else {
-    INTEGER(ans)[0] = length(VECTOR_ELT(x, 0));
+    // Column class might require dispatch to get length() correct
+    INTEGER(ans)[0] = length_with_dispatch(VECTOR_ELT(x, 0));
     INTEGER(ans)[1] = length(x);
   }
   UNPROTECT(1);