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.

5 files changed, 87 insertions, 34 deletions

diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index ae3f30d82f..8fdcbb4058 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -104,7 +104,7 @@ atom await_sched_wall_time_modifications
 atom awaiting_load
 atom awaiting_unload
 atom backtrace backtrace_depth
-atom badarg badarith badarity badfile badmatch badsig badfun
+atom badarg badarith badarity badfile badfun badkey badmap badmatch badsig
 atom bag
 atom band
 atom big
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 7e242640ed..6a5128e7f8 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -2493,7 +2493,13 @@ do {								\
 	 StoreResult(res, Arg(2));
 	 Next(5+Arg(4));
      } else {
-	 goto badarg;
+	 /*
+	  * This can only happen if the code was compiled
+	  * with the compiler in OTP 17.
+	  */
+	 c_p->freason = BADMAP;
+	 c_p->fvalue = map;
+	 goto lb_Cl_error;
      }
  }
 
@@ -2511,7 +2517,7 @@ do {								\
 	 StoreResult(res, Arg(2));
 	 Next(5+Arg(4));
      } else {
-	 goto badarg;
+	 goto lb_Cl_error;
      }
  }
 
@@ -5261,7 +5267,9 @@ Eterm error_atom[NUMBER_EXIT_CODES] = {
   am_notalive,		/* 14 */
   am_system_limit,	/* 15 */
   am_try_clause,	/* 16 */
-  am_notsup		/* 17 */
+  am_notsup,		/* 17 */
+  am_badmap,		/* 18 */
+  am_badkey,		/* 19 */
 };
 
 /*
@@ -5517,6 +5525,8 @@ expand_error_value(Process* c_p, Uint freason, Eterm Value) {
     case (GET_EXC_INDEX(EXC_TRY_CLAUSE)):
     case (GET_EXC_INDEX(EXC_BADFUN)):
     case (GET_EXC_INDEX(EXC_BADARITY)):
+    case (GET_EXC_INDEX(EXC_BADMAP)):
+    case (GET_EXC_INDEX(EXC_BADKEY)):
         /* Some common exceptions: value -> {atom, value} */
         ASSERT(is_value(Value));
 	hp = HAlloc(c_p, 3);
@@ -6814,8 +6824,11 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
 	/* apparently the compiler does not emit is_map instructions,
 	 * bad compiler */
 
-	if (is_not_hashmap(map))
+	if (is_not_hashmap(map)) {
+	    p->freason = BADMAP;
+	    p->fvalue = map;
 	    return THE_NON_VALUE;
+	}
 
 	res = map;
 	E = p->stop;
@@ -6825,8 +6838,11 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
 	    hx = hashmap_make_hash(new_key);
 
 	    res = erts_hashmap_insert(p, hx, new_key, val, res,  1);
-	    if (is_non_value(res))
+	    if (is_non_value(res)) {
+		p->fvalue = new_key;
+		p->freason = BADKEY;
 		return res;
+	    }
 
 	    if (p->mbuf) {
 		Uint live = Arg(3);
@@ -6849,6 +6865,9 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
      */
 
     if (num_old == 0) {
+	E = p->stop;
+	p->freason = BADKEY;
+	GET_TERM(new_p[0], p->fvalue);
 	return THE_NON_VALUE;
     }
 
@@ -6918,6 +6937,8 @@ update_map_exact(Process* p, Eterm* reg, Eterm map, BeamInstr* I)
      * update list did not previously exist.
      */
     ASSERT(hp == p->htop + need);
+    p->freason = BADKEY;
+    p->fvalue = new_key;
     return THE_NON_VALUE;
 }
 #undef GET_TERM
diff --git a/erts/emulator/beam/erl_bif_guard.c b/erts/emulator/beam/erl_bif_guard.c
index e7d84ebda1..069327ee9d 100644
--- a/erts/emulator/beam/erl_bif_guard.c
+++ b/erts/emulator/beam/erl_bif_guard.c
@@ -467,7 +467,8 @@ Eterm erts_gc_map_size_1(Process* p, Eterm* reg, Uint live)
     } else if (is_hashmap(arg)) {
 	size = hashmap_size(arg);
     } else {
-	BIF_ERROR(p, BADARG);
+	p->fvalue = arg;
+	BIF_ERROR(p, BADMAP);
     }
     if (IS_USMALL(0, size)) {
 	return make_small(size);
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);
 }
 
 
diff --git a/erts/emulator/beam/error.h b/erts/emulator/beam/error.h
index ddc2c1396d..e63967adb6 100644
--- a/erts/emulator/beam/error.h
+++ b/erts/emulator/beam/error.h
@@ -140,7 +140,13 @@
 #define EXC_NOTSUP		((17 << 8) | EXC_ERROR)
 					/* Not supported */
 
-#define NUMBER_EXIT_CODES 18	/* The number of exit code indices */
+#define EXC_BADMAP		((18 << 8) | EXC_ERROR)
+					/* Bad map */
+
+#define EXC_BADKEY		((19 << 8) | EXC_ERROR)
+					/* Bad key in map */
+
+#define NUMBER_EXIT_CODES 20	/* The number of exit code indices */
 
 /*
  * Internal pseudo-error codes.
@@ -152,6 +158,8 @@
  */
 #define BADARG EXC_BADARG
 #define BADARITH EXC_BADARITH
+#define BADKEY EXC_BADKEY
+#define BADMAP EXC_BADMAP
 #define BADMATCH EXC_BADMATCH
 #define SYSTEM_LIMIT EXC_SYSTEM_LIMIT