fix(core): stop shallow_prefix from matching sibling paths

Address review feedback: `has_prefix(parent, shallow_prefix)` also matched
siblings such as "self.value.plugins2", and the comment on the deepcopy call
in merge_consumer_route still described the old, wrong rationale.

Signed-off-by: AlinsRan <alinsran@apache.org>

Author: AlinsRan

apisix/core/table.lua

@@ -31,7 +31,9 @@ local pairs        = pairs
 local type         = type
 local ngx_re       = require("ngx.re")
 local isarray      = require("table.isarray")
+local str_byte     = string.byte
 local str_has_prefix = require("apisix.core.string").has_prefix
+local DOT          = str_byte(".")
 
 
 local _M = {
@@ -121,6 +123,18 @@ end
 
 local deepcopy
 do
+    -- the members of `parent` are shallow-copied when `parent` is `prefix`
+    -- itself or one of its descendants. The match has to stop at a path
+    -- separator, otherwise a prefix like "self.value.plugins" would also
+    -- claim a sibling named "self.value.plugins2".
+    local function under_shallow_prefix(parent, prefix)
+        if not str_has_prefix(parent, prefix) then
+            return false
+        end
+
+        return #parent == #prefix or str_byte(parent, #prefix + 1) == DOT
+    end
+
     local function _deepcopy(orig, copied, parent, opts)
         -- If the array-like table contains nil in the middle,
         -- the len might be smaller than the expected.
@@ -132,7 +146,8 @@ do
         for orig_key, orig_value in pairs(orig) do
             local path = parent .. "." .. tostring(orig_key)
             if opts and (array_find(opts.shallows, path) or
-                (opts.shallow_prefix and str_has_prefix(parent, opts.shallow_prefix))) then
+                (opts.shallow_prefix and
+                 under_shallow_prefix(parent, opts.shallow_prefix))) then
                 copy[orig_key] = orig_value
             else
                 if type(orig_value) == "table" then

apisix/plugin.lua

@@ -818,8 +818,12 @@ local function merge_consumer_route(route_conf, consumer_conf, consumer_group_co
         return route_conf
     end
 
-    -- the plugins subtree is fully overwritten below, so there is no need to
-    -- deep-copy it; shallow-copy that subtree to avoid the wasted work
+    -- some plugins cache request-time state on their conf object (resolved DNS
+    -- nodes, probed backend versions, ...). Deep-copying the plugin confs would
+    -- hand every consumer its own copy and drop that state, so keep them shared
+    -- by reference, as they already are on the route without consumer auth. The
+    -- `plugins` container itself is still a fresh table, so the merge below
+    -- overwrites its keys without touching the original route conf.
     local new_route_conf = core.table.deepcopy(route_conf,
         { shallow_prefix = "self.value.plugins" })
 

t/core/table.t

@@ -393,3 +393,31 @@ table copied: {"plugins":{"p1":{"name":"plugin1_new_modified"},"p2":{"name":"plu
 table original: {"plugins":{"p1":{"name":"plugin1"},"p2":{"name":"plugin2_modified"}}}
 --- no_error_log
 [error]
+
+
+
+=== TEST 14: shallow_prefix only matches at a path separator
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local deepcopy = core.table.deepcopy
+            local tab = {
+                plugins = { p1 = {name = "p1"} },
+                -- a sibling whose name starts with the prefix
+                plugins2 = { p2 = {name = "p2"} },
+            }
+
+            local tab_copied = deepcopy(tab, { shallow_prefix = "self.plugins" })
+
+            ngx.say("plugins.p1 shared: ", tab_copied.plugins.p1 == tab.plugins.p1)
+            ngx.say("plugins2.p2 shared: ", tab_copied.plugins2.p2 == tab.plugins2.p2)
+        }
+    }
+--- request
+GET /t
+--- response_body
+plugins.p1 shared: true
+plugins2.p2 shared: false
+--- no_error_log
+[error]