Tweak {decode_format, false} semantics

Represent the decoded message by its atom-valued name in
diameter_packet.msg, which makes trace much more readable. A
diameter_avp.value is untouched (ie. undefined): the AVP name is already
in the name field.

4 files changed, 36 insertions, 22 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index b7be184058..c31929c3f0 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -810,8 +810,8 @@ dictionary file in question.
 If <c>list</c> or <c>map</c> then a <c>[Name | Avps]</c> pair where
 <c>Avps</c> is either a list of AVP name/values pairs or a map keyed on
 AVP names respectively.
-If <c>false</c> then the representation is omitted and <c>msg</c> and
-<c>value</c> fields are set to <c>false</c>.
+If <c>false</c> then the representation is as the atom-value message
+name, or <c>undefined</c> for a Grouped AVP.
 See also &codec_message;.</p>
 
 <p>
diff --git a/lib/diameter/src/base/diameter_gen.erl b/lib/diameter/src/base/diameter_gen.erl
index 763f70d877..e8f637dd53 100644
--- a/lib/diameter/src/base/diameter_gen.erl
+++ b/lib/diameter/src/base/diameter_gen.erl
@@ -230,7 +230,7 @@ enc(AvpName, Value, Opts, Mod) ->
 %% ---------------------------------------------------------------------------
 
 -spec decode_avps(parent_name(), binary(), map())
-   -> {parent_record() | false, [avp()], Failed}
+   -> {parent_record() | parent_name(), [avp()], Failed}
  when Failed :: [{5000..5999, #diameter_avp{}}].
 
 decode_avps(Name, Bin, #{module := Mod, decode_format := Fmt} = Opts) ->
@@ -301,7 +301,7 @@ decode(Bin, Code, Vid, DataLen, Pad, M, P, Name, Mod, Fmt, Strict, Opts0,
                                 type = type(NameT),
                                 index = Idx},
 
-            Dec = decode(Data, Name, NameT, Mod, Opts, Avp),         %% decode
+            Dec = decode1(Data, Name, NameT, Mod, Fmt, Opts, Avp),
             Acc = decode(T, Name, Mod, Fmt, Strict, Opts, Idx+1, AM),%% recurse
             acc(Acc, Dec, I, Name, Field, Arity, Strict, Mod, Opts);
         _ ->
@@ -449,10 +449,10 @@ field({AvpName, _}) ->
 field(_) ->
     'AVP'.
 
-%% decode/6
+%% decode1/7
 
 %% AVP not in dictionary.
-decode(_Data, _Name, 'AVP', _Mod, _Opts, Avp) ->
+decode1(_Data, _Name, 'AVP', _Mod, _Fmt, _Opts, Avp) ->
     Avp;
 
 %% 6733, 4.4:
@@ -502,7 +502,7 @@ decode(_Data, _Name, 'AVP', _Mod, _Opts, Avp) ->
 %% defined the RFC's "unrecognized", which is slightly stronger than
 %% "not defined".)
 
-decode(Data, Name, {AvpName, Type}, Mod, Opts, Avp) ->
+decode1(Data, Name, {AvpName, Type}, Mod, Fmt, Opts, Avp) ->
     #{dictionary := AppMod, failed_avp := Failed}
         = Opts,
 
@@ -516,26 +516,39 @@ decode(Data, Name, {AvpName, Type}, Mod, Opts, Avp) ->
     %% list of component AVPs.
 
     try avp_decode(Data, AvpName, Opts, DecMod, Mod) of
-        {Rec, As} when Type == 'Grouped' ->
-            A = Avp#diameter_avp{value = Rec},
-            [A | As];
-        V when Type /= 'Grouped' ->
-            Avp#diameter_avp{value = V}
+        V ->
+            set(Type, Fmt, Avp, V)
     catch
         throw: {?MODULE, T} ->
-            decode_error(Failed, T, Avp);
+            decode_error(Failed, Fmt, T, Avp);
         error: Reason ->
             decode_error(Failed, Reason, Name, Mod, Opts, Avp)
     end.
 
-%% decode_error/3
+%% set/4
+
+set('Grouped', false, Avp, V) ->
+    {_Rec, As} = V,
+    [Avp | As];
+
+set('Grouped', _, Avp, V) ->
+    {Rec, As} = V,
+    [Avp#diameter_avp{value = Rec} | As];
+
+set(_, _, Avp, V) ->
+    Avp#diameter_avp{value = V}.
+
+%% decode_error/4
 %%
 %% Error when decoding a grouped AVP.
 
-decode_error(true, {Rec, _, _}, Avp) ->
+decode_error(true, false, _, Avp) ->
+    Avp;
+
+decode_error(true, _, {Rec, _, _}, Avp) ->
     Avp#diameter_avp{value = Rec};
 
-decode_error(false, {_, ComponentAvps, [{RC,A} | _]}, Avp) ->
+decode_error(false, _, {_, ComponentAvps, [{RC,A} | _]}, Avp) ->
     {RC, [Avp | ComponentAvps], Avp#diameter_avp{data = [A]}}.
 
 %% decode_error/6
@@ -817,8 +830,8 @@ empty(Name, #{module := Mod} = Opts) ->
 
 %% newrec/4
 
-newrec(false = No, _, _, _) ->
-    No;
+newrec(false, _, Name, _) ->
+    Name;
 
 newrec(record, Mod, Name, T)
   when T /= decode ->
diff --git a/lib/diameter/src/base/diameter_traffic.erl b/lib/diameter/src/base/diameter_traffic.erl
index 5ee598f513..3cc1c7cce5 100644
--- a/lib/diameter/src/base/diameter_traffic.erl
+++ b/lib/diameter/src/base/diameter_traffic.erl
@@ -1992,10 +1992,10 @@ avp_decode(Dict, 'Experimental-Result' = N, #diameter_avp{data = Bin}
     {V,_} = Dict:avp(decode, Bin, N, decode_opts(Dict)),
     Avp#diameter_avp{name = N, value = V};
 
-avp_decode(Dict, Name, #diameter_avp{value = X,
+avp_decode(Dict, Name, #diameter_avp{value = undefined,
                                      data = Bin}
                        = Avp)
-  when is_binary(Bin), X == undefined orelse X == false ->
+  when is_binary(Bin) ->
     V = Dict:avp(decode, Bin, Name, decode_opts(Dict)),
     Avp#diameter_avp{name = Name, value = V};
 
diff --git a/lib/diameter/test/diameter_traffic_SUITE.erl b/lib/diameter/test/diameter_traffic_SUITE.erl
index 2bc00bf4a1..403d417636 100644
--- a/lib/diameter/test/diameter_traffic_SUITE.erl
+++ b/lib/diameter/test/diameter_traffic_SUITE.erl
@@ -1161,7 +1161,7 @@ to_map(#diameter_packet{header = H, msg = Rec},
 
 %% No record decode: do it ourselves.
 to_map(#diameter_packet{header = H,
-                        msg = false,
+                        msg = Name,
                         bin = Bin},
       #group{server_decoding = false,
              strings = B}) ->
@@ -1169,8 +1169,9 @@ to_map(#diameter_packet{header = H,
              string_decode => B,
              strict_mbit => true,
              rfc => 6733},
-    #diameter_packet{msg = [_MsgName | _Map] = Msg}
+    #diameter_packet{msg = [MsgName | _Map] = Msg}
         = diameter_codec:decode(dict(H), Opts, Bin),
+    {MsgName, _} = {Name, Msg},  %% assert
     Msg.
 
 dict(#diameter_header{application_id = Id,