improve: move try_read_attr function into table.lua (apache#2257)

apisix/core/table.lua

@@ -59,6 +59,22 @@ function _M.set(tab, ...)
 end
 
 
+function _M.try_read_attr(tab, ...)
+    local count = select('#', ...)
+
+    for i = 1, count do
+        local attr = select(i, ...)
+        if type(tab) ~= "table" then
+            return nil
+        end
+
+        tab = tab[attr]
+    end
+
+    return tab
+end
+
+
 -- only work under lua51 or luajit
 function _M.setmt__gc(t, mt)
     local prox = newproxy(true)

apisix/plugins/skywalking.lua

@@ -22,6 +22,7 @@ local math = math
 local select = select
 local type = type
 local require = require
+local try_read_attr = core.table.try_read_attr
 
 local plugin_name = "skywalking"
 local metadata_schema = {
@@ -103,20 +104,6 @@ function _M.log(conf, ctx)
 end
 
 
-local function try_read_attr(t, ...)
-    local count = select('#', ...)
-    for i = 1, count do
-        local attr = select(i, ...)
-        if type(t) ~= "table" then
-            return nil
-        end
-        t = t[attr]
-    end
-
-    return t
-end
-
-
 function _M.init()
     if process.type() ~= "worker" and process.type() ~= "single" then
         return

t/core/table.t

@@ -77,3 +77,31 @@ GET /t
 ok
 --- no_error_log
 [error]
+
+
+
+=== TEST 3: try_read_attr
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local try_read_attr = core.table.try_read_attr
+
+            local t = {level1 = {level2 = "value"}}
+
+            local v = try_read_attr(t, "level1", "level2")
+
+            ngx.say(v)
+
+            loval v2 = try_read_attr(t, "level1", "level3")
+
+            ngx.say(v2)
+        }
+    }
+--- request
+GET /t
+--- response_body
+"value"
+""
+--- no_error_log
+[error]