Raise more descriptive error messages for failed map operations

According to EEP-43 for maps, a 'badmap' exception should be
generated when an attempt is made to update non-map term such as:

   <<>>#{a=>42}

That was not implemented in the OTP 17.

José Valim suggested that we should take the opportunity to
improve the errors coming from map operations:

  http://erlang.org/pipermail/erlang-questions/2015-February/083588.html

This commit implement better errors from map operations similar
to his suggestion.

When a map update operation (Map#{...}) or a BIF that expects a map
is given a non-map term, the exception will be:

  {badmap,Term}

This kind of exception is similar to the {badfun,Term} exception
from operations that expect a fun.

When a map operation requires a key that is not present in a map,
the following exception will be raised:

  {badkey,Key}

José Valim suggested that the exception should be
{badkey,Key,Map}. We decided not to do that because the map
could potentially be huge and cause problems if the error
propagated through links to other processes.

For BIFs, it could be argued that the exceptions could be simply
'badmap' and 'badkey', because the bad map and bad key can be found in
the argument list for the BIF in the stack backtrace. However, for the
map update operation (Map#{...}), the bad map or bad key will not be
included in the stack backtrace, so that information must be included
in the exception reason itself. For consistency, the BIFs should raise
the same exceptions as update operation.

If more than one key is missing, it is undefined which of
keys that will be reported in the {badkey,Key} exception.

1 files changed, 49 insertions, 26 deletions

diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index 98023bbb47..3aebbfdaa3 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -122,7 +122,8 @@ BIF_RETTYPE map_size_1(BIF_ALIST_1) {
 	BIF_RET(res);
     }
 
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_1;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:to_list/1 */
@@ -150,7 +151,8 @@ BIF_RETTYPE maps_to_list_1(BIF_ALIST_1) {
 	return hashmap_to_list(BIF_P, BIF_ARG_1);
     }
 
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_1;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:find/2
@@ -217,34 +219,29 @@ BIF_RETTYPE maps_find_2(BIF_ALIST_2) {
 	}
 	BIF_RET(am_error);
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_2;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:get/2
  * return value if key *matches* a key in the map
- * exception bad_key if none matches
+ * exception badkey if none matches
  */
 
 BIF_RETTYPE maps_get_2(BIF_ALIST_2) {
     if (is_map(BIF_ARG_2)) {
-	Eterm *hp;
-        Eterm error;
         const Eterm *value;
-	char *s_error;
 
         value = erts_maps_get(BIF_ARG_1, BIF_ARG_2);
         if (value) {
             BIF_RET(*value);
 	}
 
-	s_error = "bad_key";
-	error = am_atom_put(s_error, sys_strlen(s_error));
-
-	hp = HAlloc(BIF_P, 3);
-	BIF_P->fvalue = TUPLE2(hp, error, BIF_ARG_1);
-	BIF_ERROR(BIF_P, EXC_ERROR_2);
+	BIF_P->fvalue = BIF_ARG_1;
+	BIF_ERROR(BIF_P, BADKEY);
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_2;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:from_list/1
@@ -911,7 +908,8 @@ BIF_RETTYPE maps_is_key_2(BIF_ALIST_2) {
     if (is_map(BIF_ARG_2)) {
 	BIF_RET(erts_maps_get(BIF_ARG_1, BIF_ARG_2) ? am_true : am_false);
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_2;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:keys/1 */
@@ -939,7 +937,8 @@ BIF_RETTYPE maps_keys_1(BIF_ALIST_1) {
     } else if (is_hashmap(BIF_ARG_1)) {
 	BIF_RET(hashmap_keys(BIF_P, BIF_ARG_1));
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_1;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 /* maps:merge/2 */
 
@@ -951,6 +950,7 @@ BIF_RETTYPE maps_merge_2(BIF_ALIST_2) {
 	    /* Will always become a tree */
 	    BIF_RET(map_merge_mixed(BIF_P, BIF_ARG_1, BIF_ARG_2, 0));
 	}
+	BIF_P->fvalue = BIF_ARG_2;
     } else if (is_hashmap(BIF_ARG_1)) {
 	if (is_hashmap(BIF_ARG_2)) {
 	    BIF_RET(hashmap_merge(BIF_P, BIF_ARG_1, BIF_ARG_2));
@@ -958,8 +958,11 @@ BIF_RETTYPE maps_merge_2(BIF_ALIST_2) {
 	    /* Will always become a tree */
 	    BIF_RET(map_merge_mixed(BIF_P, BIF_ARG_2, BIF_ARG_1, 1));
 	}
+	BIF_P->fvalue = BIF_ARG_2;
+    } else {
+	BIF_P->fvalue = BIF_ARG_1;
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 static Eterm flatmap_merge(Process *p, Eterm nodeA, Eterm nodeB) {
@@ -1398,7 +1401,8 @@ BIF_RETTYPE maps_put_3(BIF_ALIST_3) {
     if (is_map(BIF_ARG_3)) {
 	BIF_RET(erts_maps_put(BIF_P, BIF_ARG_1, BIF_ARG_2, BIF_ARG_3));
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_3;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /* maps:remove/3 */
@@ -1492,7 +1496,8 @@ BIF_RETTYPE maps_remove_2(BIF_ALIST_2) {
 	    BIF_RET(res);
 	}
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_2;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 int erts_maps_update(Process *p, Eterm key, Eterm value, Eterm map, Eterm *res) {
@@ -1688,13 +1693,17 @@ Eterm erts_maps_put(Process *p, Eterm key, Eterm value, Eterm map) {
 /* maps:update/3 */
 
 BIF_RETTYPE maps_update_3(BIF_ALIST_3) {
-    if (is_map(BIF_ARG_3)) {
+    if (is_not_map(BIF_ARG_3)) {
+	BIF_P->fvalue = BIF_ARG_3;
+	BIF_ERROR(BIF_P, BADMAP);
+    } else {
 	Eterm res;
 	if (erts_maps_update(BIF_P, BIF_ARG_1, BIF_ARG_2, BIF_ARG_3, &res)) {
 	    BIF_RET(res);
 	}
+	BIF_P->fvalue = BIF_ARG_1;
+	BIF_ERROR(BIF_P, BADKEY);
     }
-    BIF_ERROR(BIF_P, BADARG);
 }
 
 
@@ -1723,7 +1732,8 @@ BIF_RETTYPE maps_values_1(BIF_ALIST_1) {
     } else if (is_hashmap(BIF_ARG_1)) {
 	BIF_RET(hashmap_values(BIF_P, BIF_ARG_1));
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_1;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 static Eterm hashmap_to_list(Process *p, Eterm node) {
@@ -2546,8 +2556,12 @@ Uint hashmap_over_estimated_heap_size(Uint k)
 BIF_RETTYPE erts_debug_map_info_1(BIF_ALIST_1) {
     if (is_hashmap(BIF_ARG_1)) {
 	BIF_RET(hashmap_info(BIF_P,BIF_ARG_1));
+    } else if (is_flatmap(BIF_ARG_1)) {
+	BIF_ERROR(BIF_P, BADARG);
+    } else {
+	BIF_P->fvalue = BIF_ARG_1;
+	BIF_ERROR(BIF_P, BADMAP);
     }
-    BIF_ERROR(BIF_P, BADARG);
 }
 
 /*
@@ -2560,8 +2574,12 @@ BIF_RETTYPE erts_internal_map_to_tuple_keys_1(BIF_ALIST_1) {
     if (is_flatmap(BIF_ARG_1)) {
 	flatmap_t *mp = (flatmap_t*)flatmap_val(BIF_ARG_1);
 	BIF_RET(mp->keys);
+    } else if (is_hashmap(BIF_ARG_1)) {
+	BIF_ERROR(BIF_P, BADARG);
+    } else {
+	BIF_P->fvalue = BIF_ARG_1;
+	BIF_ERROR(BIF_P, BADMAP);
     }
-    BIF_ERROR(BIF_P, BADARG);
 }
 
 /*
@@ -2589,7 +2607,8 @@ BIF_RETTYPE erts_internal_map_type_1(BIF_ALIST_1) {
                 erl_exit(1, "bad header");
         }
     }
-    BIF_ERROR(BIF_P, BADARG);
+    BIF_P->fvalue = BIF_ARG_1;
+    BIF_ERROR(BIF_P, BADMAP);
 }
 
 /*
@@ -2629,8 +2648,12 @@ BIF_RETTYPE erts_internal_map_hashmap_children_1(BIF_ALIST_1) {
         hp = HAlloc(BIF_P, 2*sz);
         while(sz--) { res = CONS(hp, *ptr++, res); hp += 2; }
         BIF_RET(res);
+    } else if (is_flatmap(BIF_ARG_1)) {
+	BIF_ERROR(BIF_P, BADARG);
+    } else {
+	BIF_P->fvalue = BIF_ARG_1;
+	BIF_ERROR(BIF_P, BADMAP);
     }
-    BIF_ERROR(BIF_P, BADARG);
 }