From b16a01191925c9563133dd1b14f5182e2acf5702 Mon Sep 17 00:00:00 2001
From: Ashish Tiwari <ashishjaitiwari15112000@gmail.com>
Date: Tue, 24 Dec 2024 14:11:45 +0530
Subject: [PATCH] fix: deepcopy should copy same table exactly only once

---
 apisix/core/table.lua |  12 +++--
 t/core/table.t        | 112 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+), 4 deletions(-)

diff --git a/apisix/core/table.lua b/apisix/core/table.lua
index 4346863079cf..b69db8e80be0 100644
--- a/apisix/core/table.lua
+++ b/apisix/core/table.lua
@@ -118,16 +118,20 @@ end
 local deepcopy
 do
     local function _deepcopy(orig, copied)
-        -- prevent infinite loop when a field refers its parent
-        copied[orig] = true
         -- If the array-like table contains nil in the middle,
         -- the len might be smaller than the expected.
         -- But it doesn't affect the correctness.
         local len = #orig
         local copy = new_tab(len, nkeys(orig) - len)
+        -- prevent infinite loop when a field refers its parent
+        copied[orig] = copy
         for orig_key, orig_value in pairs(orig) do
-            if type(orig_value) == "table" and not copied[orig_value] then
-                copy[orig_key] = _deepcopy(orig_value, copied)
+            if type(orig_value) == "table" then
+                if copied[orig_value] then
+                    copy[orig_key] = copied[orig_value]
+                else
+                    copy[orig_key] = _deepcopy(orig_value, copied)
+                end
             else
                 copy[orig_key] = orig_value
             end
diff --git a/t/core/table.t b/t/core/table.t
index c3ec5a7c0d1f..c5d93ecb198d 100644
--- a/t/core/table.t
+++ b/t/core/table.t
@@ -215,3 +215,115 @@ GET /t
 GET /t
 --- response_body
 ok
+
+
+
+=== TEST 8: deepcopy copy same table only once
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local tmp = { name = "tmp", priority = 1, enabled = true }
+            local origin = { a = { b = tmp }, c = tmp}
+            local copy = core.table.deepcopy(origin)
+            if not core.table.deep_eq(copy, origin) then
+                ngx.say("copy: ", json.encode(expect), ", origin: ", json.encode(actual))
+                return
+            end
+            if copy.a.b ~= copy.c then
+                ngx.say("copy.a.b should be the same as copy.c")
+                return
+            end
+            ngx.say("ok")
+        }
+    }
+--- request
+GET /t
+--- response_body
+ok
+
+
+
+=== TEST 9: reference same table
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local deepcopy = core.table.deepcopy
+            local tab1 = {name = "tab1"}
+            local tab2 = {
+                a = tab1,
+                b = tab1
+            }
+            local tab_copied = deepcopy(tab2)
+
+            ngx.say("table copied: ", require("toolkit.json").encode(tab_copied))
+
+            ngx.say("tab1 == tab2.a: ", tab1 == tab2.a)
+            ngx.say("tab2.a == tab2.b: ", tab2.a == tab2.b)
+
+            ngx.say("tab_copied.a == tab1: ", tab_copied.a == tab1)
+            ngx.say("tab_copied.a == tab_copied.b: ", tab_copied.a == tab_copied.b)
+        }
+    }
+--- request
+GET /t
+--- response_body
+table copied: {"a":{"name":"tab1"},"b":{"name":"tab1"}}
+tab1 == tab2.a: true
+tab2.a == tab2.b: true
+tab_copied.a == tab1: false
+tab_copied.a == tab_copied.b: true
+
+
+
+=== TEST 10: reference table self(root node)
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local deepcopy = core.table.deepcopy
+            local tab1 = {name = "tab1"}
+            local tab2 = {
+                a = tab1,
+            }
+            tab2.c = tab2
+
+            local tab_copied = deepcopy(tab2)
+
+            ngx.say("tab_copied.a == tab1: ", tab_copied.a == tab_copied.b)
+            ngx.say("tab_copied == tab_copied.c: ", tab_copied == tab_copied.c)
+        }
+    }
+--- request
+GET /t
+--- response_body
+tab_copied.a == tab1: false
+tab_copied == tab_copied.c: true
+
+
+
+=== TEST 11: reference table self(sub node)
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local deepcopy = core.table.deepcopy
+            local tab_org = {
+                a = {
+                    a2 = "a2"
+                },
+            }
+            tab_org.b = tab_org.a
+
+            local tab_copied = deepcopy(tab_org)
+            ngx.say("table copied: ", require("toolkit.json").encode(tab_copied))
+            ngx.say("tab_copied.a == tab_copied.b: ", tab_copied.a == tab_copied.b)
+        }
+    }
+--- request
+GET /t
+--- response_body
+table copied: {"a":{"a2":"a2"},"b":{"a2":"a2"}}
+tab_copied.a == tab_copied.b: true
+