[PATCH v1 1/1] box: allow box.session{.exists, .fd} without args

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

Allow to call box.session.exists() and box.session.fd() without
any arguments. In such case, current session is used.
The box.session.peer() already support such feature, so we need
it to be consistent.

Closes #4021

http://github.com/tarantool/tarantool/tree/kshch/gh-4021-optional-session-id
https://github.com/tarantool/tarantool/issues/4021
---
 src/box/lua/session.c         | 19 +++++++++++++------
 test/box-tap/session.test.lua |  5 +++--
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/box/lua/session.c b/src/box/lua/session.c
index a4ddb201c..c0ac4917b 100644
--- a/src/box/lua/session.c
+++ b/src/box/lua/session.c
@@ -214,11 +214,15 @@ lbox_session_su(struct lua_State *L)
 static int
 lbox_session_exists(struct lua_State *L)
 {
-	if (lua_gettop(L) != 1)
+	if (lua_gettop(L) > 1)
 		luaL_error(L, "session.exists(sid): bad arguments");
 
-	uint64_t sid = luaL_checkint64(L, -1);
-	lua_pushboolean(L, session_find(sid) != NULL);
+	struct session *session;
+	if (lua_gettop(L) == 1)
+		session = session_find(luaL_checkint64(L, -1));
+	else
+		session = current_session();
+	lua_pushboolean(L, session != NULL);
 	return 1;
 }
 
@@ -228,11 +232,14 @@ lbox_session_exists(struct lua_State *L)
 static int
 lbox_session_fd(struct lua_State *L)
 {
-	if (lua_gettop(L) != 1)
+	if (lua_gettop(L) > 1)
 		luaL_error(L, "session.fd(sid): bad arguments");
 
-	uint64_t sid = luaL_checkint64(L, -1);
-	struct session *session = session_find(sid);
+	struct session *session;
+	if (lua_gettop(L) == 1)
+		session = session_find(luaL_checkint64(L, -1));
+	else
+		session = current_session();
 	if (session == NULL)
 		luaL_error(L, "session.fd(): session does not exist");
 	lua_pushinteger(L, session_fd(session));
diff --git a/test/box-tap/session.test.lua b/test/box-tap/session.test.lua
index 857bc643b..b6b08d209 100755
--- a/test/box-tap/session.test.lua
+++ b/test/box-tap/session.test.lua
@@ -15,7 +15,7 @@ session = box.session
 space = box.schema.space.create('tweedledum')
 index = space:create_index('primary', { type = 'hash' })
 
-test:plan(55)
+test:plan(56)
 
 ---
 --- Check that Tarantool creates ADMIN session for #! script
@@ -23,7 +23,7 @@ test:plan(55)
 test:ok(session.exists(session.id()), "session is created")
 test:isnil(session.peer(session.id()), "session.peer")
 local ok, err = pcall(session.exists)
-test:is(err, "session.exists(sid): bad arguments", "exists bad args #1")
+test:ok(ok, "session.exists()")
 ok, err = pcall(session.exists, 1, 2, 3)
 test:is(err, "session.exists(sid): bad arguments", "exists bad args #2")
 test:ok(not session.exists(1234567890), "session doesn't exist")
@@ -166,6 +166,7 @@ test:is(
 )
 local uri = inspector:eval('session', 'box.cfg.listen')[1]
 conn = net.box.connect(uri)
+test:ok(conn:eval("return box.session.fd()"), "get session fd")
 test:ok(conn:eval("return box.session.exists(box.session.id())"), "remote session exist check")
 test:isnt(conn:eval("return box.session.peer(box.session.id())"), nil, "remote session peer check")
 test:ok(conn:eval("return box.session.peer() == box.session.peer(box.session.id())"), "remote session peer check")
-- 
2.21.0