chore: add more comments for bind display perference

CHANGES-5.0.md

@@ -10,9 +10,6 @@
 * Fix GET /listeners API crash When some nodes still in initial configuration. [#9002](https://github.com/emqx/emqx/pull/9002)
 * Fix empty variable interpolation in authentication and authorization. Placeholders for undefined variables are rendered now as empty strings and do not cause errors anymore. [#8963](https://github.com/emqx/emqx/pull/8963)
 * Fix the latency statistics error of the slow subscription module when `stats_type` is `internal` or `response`. [#8986](https://github.com/emqx/emqx/pull/8986)
-* Change the format of the listener when displaying bind field.
-  i.e: from `:1883` to `1883`, this fix will affect the output of the HTTP API
-  and CLI. [#9047](https://github.com/emqx/emqx/pull/9047)
 
 # 5.0.8
 

apps/emqx/src/emqx_listeners.erl

@@ -521,12 +521,16 @@ merge_default(Options) ->
     integer() | {tuple(), integer()} | string() | binary()
 ) -> io_lib:chars().
 format_bind(Port) when is_integer(Port) ->
-    io_lib:format("~w", [Port]);
-%% Print only the port number when bound on all interfaces
-format_bind({{0, 0, 0, 0}, Port}) ->
-    format_bind(Port);
-format_bind({{0, 0, 0, 0, 0, 0, 0, 0}, Port}) ->
-    format_bind(Port);
+    %% **Note**:
+    %% 'For TCP, UDP and IP networks, if the host is empty or a literal
+    %% unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for
+    %% TCP and UDP, "", "0.0.0.0" or "::" for IP, the local system is
+    %% assumed.'
+    %%
+    %% Quoted from: https://pkg.go.dev/net
+    %% Decided to use this format to display the bind for all interfaces and
+    %% IPv4/IPv6 support
+    io_lib:format(":~w", [Port]);
 format_bind({Addr, Port}) when is_list(Addr) ->
     io_lib:format("~ts:~w", [Addr, Port]);
 format_bind({Addr, Port}) when is_tuple(Addr), tuple_size(Addr) == 4 ->

apps/emqx/test/emqx_listeners_SUITE.erl

@@ -148,6 +148,33 @@ t_wss_conn(_) ->
     {ok, Socket} = ssl:connect({127, 0, 0, 1}, 9998, [{verify, verify_none}], 1000),
     ok = ssl:close(Socket).
 
+t_format_bind(_) ->
+    ?assertEqual(
+        ":1883",
+        lists:flatten(emqx_listeners:format_bind(1883))
+    ),
+    ?assertEqual(
+        "0.0.0.0:1883",
+        lists:flatten(emqx_listeners:format_bind({{0, 0, 0, 0}, 1883}))
+    ),
+    ?assertEqual(
+        "[::]:1883",
+        lists:flatten(emqx_listeners:format_bind({{0, 0, 0, 0, 0, 0, 0, 0}, 1883}))
+    ),
+    ?assertEqual(
+        "127.0.0.1:1883",
+        lists:flatten(emqx_listeners:format_bind({{127, 0, 0, 1}, 1883}))
+    ),
+    ?assertEqual(
+        ":1883",
+        lists:flatten(emqx_listeners:format_bind("1883"))
+    ),
+    %% due to the emqx_schema:to_ip_port/1, automaticlly add the IPv4 address
+    ?assertEqual(
+        "0.0.0.0:1883",
+        lists:flatten(emqx_listeners:format_bind(":1883"))
+    ).
+
 render_config_file() ->
     Path = local_path(["etc", "emqx.conf"]),
     {ok, Temp} = file:read_file(Path),