refactor(db) replace deprecated cjson.empty_array_mt with cjson.array_mt

1. `dao:rows_to_entities` will now properly set `array_mt` on returned
   entities

2. schema's `make_array` will now set `array_mt` even on non-empty
   arrays

3. schema's `make_set` will now set `array_mt`, it still sets `Set_mt`
   for non-empty arrays which the `cjson.encode` does not support, but
   it works as long as the value is not turned to e.g. hash afterwards.

kong/db/dao/init.lua

@@ -1018,7 +1018,7 @@ end
 function DAO:rows_to_entities(rows, options)
   local count = #rows
   if count == 0 then
-    return setmetatable(rows, cjson.empty_array_mt)
+    return setmetatable(rows, cjson.array_mt)
   end
 
   local entities = new_tab(count, 0)
@@ -1032,7 +1032,7 @@ function DAO:rows_to_entities(rows, options)
     entities[i] = entity
   end
 
-  return entities
+  return setmetatable(entities, cjson.array_mt)
 end
 
 

kong/db/dao/snis.lua

@@ -85,7 +85,7 @@ end
 
 -- Returns the name list for a given certificate
 function _SNIs:list_for_certificate(cert_pk, options)
-  local name_list = setmetatable({}, cjson.empty_array_mt)
+  local name_list = setmetatable({}, cjson.array_mt)
 
   for sni, err, err_t in self:each_for_certificate(cert_pk, 1000, options) do
     if err then

kong/db/schema/init.lua

@@ -1308,22 +1308,22 @@ local Set_mt = {
 
 
 --- Sets (or replaces) metatable of an array:
--- 1. array is a proper sequence, but empty, `cjson.empty_array_mt`
+-- 1. array is a proper sequence, `cjson.array_mt`
 --    will be used as a metatable of the returned array.
 -- 2. otherwise no modifications are made to input parameter.
 -- @param array The table containing an array for which to apply the metatable.
 -- @return input table (with metatable, see above)
 local function make_array(array)
-  if is_sequence(array) and #array == 0 then
-    return setmetatable(array, cjson.empty_array_mt)
+  if is_sequence(array) then
+    return setmetatable(array, cjson.array_mt)
   end
 
   return array
 end
 
 
 --- Sets (or replaces) metatable of a set and removes duplicates:
--- 1. set is a proper sequence, but empty, `cjson.empty_array_mt`
+-- 1. set is a proper sequence, but empty, `cjson.array_mt`
 --    will be used as a metatable of the returned set.
 -- 2. set a proper sequence, and has values, `Set_mt`
 --    will be used as a metatable of the returned set.
@@ -1338,7 +1338,7 @@ local function make_set(set)
   local count = #set
 
   if count == 0 then
-    return setmetatable(set, cjson.empty_array_mt)
+    return setmetatable(set, cjson.array_mt)
   end
 
   local o = {}

spec/01-unit/01-db/01-schema/01-schema_spec.lua

@@ -2347,7 +2347,21 @@ describe("schema", function()
       assert.equals(5.5, tbl.fingers)
     end)
 
-    it("adds cjson.empty_array_mt on empty array and set fields", function()
+    it("adds cjson.array_mt on non-empty array fields", function()
+      local Test = Schema.new({
+        fields = {
+          { arr = { type = "array", elements = { type = "string" } } },
+        },
+      })
+
+      local tbl = Test:process_auto_fields({
+        arr = { "hello" },
+      }, "insert")
+
+      assert.same(cjson.array_mt, getmetatable(tbl.arr))
+    end)
+
+    it("adds cjson.array_mt on empty array and set fields", function()
       local Test = Schema.new({
         fields = {
           { arr = { type = "array", elements = { type = "string" } } },
@@ -2360,11 +2374,11 @@ describe("schema", function()
         set = {}
       }, "insert")
 
-      assert.same(cjson.empty_array_mt, getmetatable(tbl.arr))
-      assert.same(cjson.empty_array_mt, getmetatable(tbl.set))
+      assert.same(cjson.array_mt, getmetatable(tbl.arr))
+      assert.same(cjson.array_mt, getmetatable(tbl.set))
     end)
 
-    it("adds cjson.empty_array_mt on empty array and set fields", function()
+    it("adds cjson.array_mt on empty array and set fields", function()
       local Test = Schema.new({
         fields = {
           { arr = { type = "array", elements = { type = "string" } } },
@@ -2378,8 +2392,8 @@ describe("schema", function()
           set = {}
         }, operation)
 
-        assert.same(cjson.empty_array_mt, getmetatable(tbl.arr))
-        assert.same(cjson.empty_array_mt, getmetatable(tbl.set))
+        assert.same(cjson.array_mt, getmetatable(tbl.arr))
+        assert.same(cjson.array_mt, getmetatable(tbl.set))
       end
     end)
 
@@ -2404,29 +2418,42 @@ describe("schema", function()
       end
     end)
 
-    it("does not add a helper metatable to arrays or maps", function()
+    it("does not add a helper metatable to maps", function()
       local Test = Schema.new({
         fields = {
-          { arr = { type = "array", elements = { type = "string" } } },
           { map = { type = "map", keys = { type = "string" }, values = { type = "boolean" } } },
         },
       })
 
       for _, operation in pairs{ "insert", "update", "select", "delete" } do
         local tbl = Test:process_auto_fields({
-          arr = { "http", "https" },
           map = { http = true },
         }, operation)
 
-        assert.is_nil(getmetatable(tbl.arr))
         assert.is_nil(getmetatable(tbl.map))
-        assert.is_equal("http", tbl.arr[1])
-        assert.is_nil(tbl.arr.http)
         assert.is_true(tbl.map.http)
         assert.is_nil(tbl.map.https)
       end
     end)
 
+    it("does add array_mt metatable to arrays", function()
+      local Test = Schema.new({
+        fields = {
+          { arr = { type = "array", elements = { type = "string" } } },
+        },
+      })
+
+      for _, operation in pairs{ "insert", "update", "select", "delete" } do
+        local tbl = Test:process_auto_fields({
+          arr = { "http", "https" },
+        }, operation)
+
+        assert.is_equal(cjson.array_mt, getmetatable(tbl.arr))
+        assert.is_equal("http", tbl.arr[1])
+        assert.is_nil(tbl.arr.http)
+      end
+    end)
+
     it("sets 'read_before_write' to true when updating field type record", function()
       local Test = Schema.new({
         name = "test",

spec/02-integration/03-db/02-db_core_entities_spec.lua

@@ -3,6 +3,7 @@ local utils   = require "kong.tools.utils"
 local helpers = require "spec.helpers"
 local cjson   = require "cjson"
 
+
 local fmt      = string.format
 local unindent = helpers.unindent
 
@@ -21,6 +22,8 @@ for _, strategy in helpers.each_strategy() do
         "basicauth_credentials",
         "upstreams",
         "targets",
+        "certificates",
+        "snis",
       })
     end)
 
@@ -72,9 +75,11 @@ for _, strategy in helpers.each_strategy() do
         it("returns a table encoding to a JSON Array when empty", function()
 
           local rows, err, err_t, offset = db.routes:page()
+
           assert.is_nil(err_t)
           assert.is_nil(err)
           assert.is_table(rows)
+          assert.equal(cjson.array_mt, getmetatable(rows))
           assert.equal(0, #rows)
           assert.is_nil(offset)
           assert.equals("[]", cjson.encode(rows))
@@ -99,6 +104,7 @@ for _, strategy in helpers.each_strategy() do
             assert.is_nil(err_t)
             assert.is_nil(err)
             assert.is_table(rows)
+            assert.equal(cjson.array_mt, getmetatable(rows))
             assert.equal(10, #rows)
             assert.is_nil(offset)
           end)
@@ -254,6 +260,7 @@ for _, strategy in helpers.each_strategy() do
             assert.is_nil(err_t)
             assert.is_nil(err)
             assert.is_table(rows)
+            assert.equal(cjson.array_mt, getmetatable(rows))
             assert.equal(100, #rows)
 
             -- invokes schema post-processing
@@ -1951,5 +1958,27 @@ for _, strategy in helpers.each_strategy() do
         end)
       end)
     end)
+
+
+    describe("SNIs", function()
+      local certificate
+      lazy_setup(function()
+        certificate = db.certificates.schema:extract_pk_values(bp.certificates:insert())
+      end)
+      describe(":list_for_certificate()", function()
+        it("returns array with cjson.array_mt metatable", function()
+          local snis = assert(db.snis:list_for_certificate(certificate))
+          local json = cjson.encode(snis)
+          assert.equal("[]", json)
+          assert.equal(cjson.array_mt, getmetatable(snis))
+
+          db.snis:update_list(certificate, {"example.org"})
+          snis = assert(db.snis:list_for_certificate(certificate))
+          json = cjson.encode(snis)
+          assert.equal('["example.org"]', json)
+          assert.equal(cjson.array_mt, getmetatable(snis))
+        end)
+      end)
+    end)
   end) -- kong.db [strategy]
 end