stdlib: Improve the Erlang shell's handling of references

As of Erlang/OTP 20.0, the type of ETS tables, ets:tid(), is a
reference(). A request was put forward that the Erlang shell should be
able to handle references in its input.

This commit introduces an extended parser in module lib. It can parse
pids, ports, references, and external funs under the condition that
they can be created in the running system. The parser is meant to be
used internally in Erlang/OTP. The alternative, to extend erl_scan and
erl_parse, was deemed inferior as it would require the abstract format
be able to represent pids, ports, references, and funs, which would be
confusing as they are not expressions as such, but data types.

1 files changed, 91 insertions, 2 deletions

diff --git a/lib/stdlib/test/shell_SUITE.erl b/lib/stdlib/test/shell_SUITE.erl
index 56002dda25..99411bc8fd 100644
--- a/lib/stdlib/test/shell_SUITE.erl
+++ b/lib/stdlib/test/shell_SUITE.erl
@@ -31,7 +31,7 @@
 	 progex_lc/1, progex_funs/1,
 	 otp_5990/1, otp_6166/1, otp_6554/1,
 	 otp_7184/1, otp_7232/1, otp_8393/1, otp_10302/1, otp_13719/1,
-         otp_14285/1]).
+         otp_14285/1, otp_14296/1]).
 
 -export([ start_restricted_from_shell/1, 
 	  start_restricted_on_command_line/1,restricted_local/1]).
@@ -92,7 +92,7 @@ groups() ->
        progex_funs]},
      {tickets, [],
       [otp_5990, otp_6166, otp_6554, otp_7184,
-       otp_7232, otp_8393, otp_10302, otp_13719, otp_14285]}].
+       otp_7232, otp_8393, otp_10302, otp_13719, otp_14285, otp_14296]}].
 
 init_per_suite(Config) ->
     Config.
@@ -2841,6 +2841,95 @@ otp_14285(Config) ->
     test_server:stop_node(Node),
     ok.
 
+otp_14296(Config) when is_list(Config) ->
+    fun() ->
+            F = fun() -> a end,
+            LocalFun = term_to_string(F),
+            S = LocalFun ++ ".",
+            "1: syntax error before: Fun" = comm_err(S)
+    end(),
+
+    fun() ->
+            F = fun mod:func/1,
+            ExternalFun = term_to_string(F),
+            S = ExternalFun ++ ".",
+            R = ExternalFun ++ ".\n",
+            R = t(S)
+    end(),
+
+    fun() ->
+            UnknownPid = "<100000.0.0>",
+            S = UnknownPid ++ ".",
+            "1: syntax error before: '<'" = comm_err(S)
+    end(),
+
+    fun() ->
+            KnownPid = term_to_string(self()),
+            S = KnownPid ++ ".",
+            R = KnownPid ++ ".\n",
+            R = t(S)
+    end(),
+
+    fun() ->
+            Port = open_port({spawn, "ls"}, [line]),
+            KnownPort = erlang:port_to_list(Port),
+            S = KnownPort ++ ".",
+            R = KnownPort ++ ".\n",
+            R = t(S)
+    end(),
+
+    fun() ->
+            UnknownPort = "#Port<100000.0>",
+            S = UnknownPort ++ ".",
+            "1: syntax error before: Port" = comm_err(S)
+    end(),
+
+    fun() ->
+            UnknownRef = "#Ref<100000.0.0.0>",
+            S = UnknownRef ++ ".",
+            "1: syntax error before: Ref" = comm_err(S)
+    end(),
+
+    fun() ->
+            KnownRef = term_to_string(make_ref()),
+            S = KnownRef ++ ".",
+            R = KnownRef ++ ".\n",
+            R = t(S)
+    end(),
+
+    %% Test lib:extended_parse_term/1
+    TF = fun(S) ->
+                 {ok, Ts, _} = erl_scan:string(S++".", 1, [text]),
+                 case lib:extended_parse_term(Ts) of
+                     {ok, Term} -> Term;
+                     {error, _}=Error -> Error
+                 end
+         end,
+    Fun = fun m:f/1,
+    Fun = TF(term_to_string(Fun)),
+    Fun = TF("fun m:f/1"),
+    Pid = self(),
+    Pid = TF(term_to_string(Pid)),
+    Ref = make_ref(),
+    Ref = TF(term_to_string(Ref)),
+    Term = {[10, a], {"foo", []}, #{x => <<"bar">>}},
+    Term = TF(lists:flatten(io_lib:format("~p", [Term]))),
+    {$a, F1, "foo"} = TF("{$a, 1.0, \"foo\"}"),
+    true = is_float(F1),
+    3 = TF("+3"),
+    $a = TF("+$a"),
+    true = is_float(TF("+1.0")),
+    true  = -3 =:= TF("-3"),
+    true = -$a =:= TF("-$a"),
+    true = is_float(TF("-1.0")),
+    {error, {_, _, ["syntax error"++_|_]}} = TF("{1"),
+    {error, {_,_,"bad term"}} = TF("fun() -> foo end"),
+    {error, {_,_,"bad term"}} = TF("1, 2"),
+    ok.
+
+term_to_string(T) ->
+    lists:flatten(io_lib:format("~w", [T])).
+
 scan(B) ->
     F = fun(Ts) -> 
                 case erl_parse:parse_term(Ts) of