[fix/response-transformer] concatenating value to response header

Part of the fix for issue #393. New property `concat` added to support adding new value to existing response header. If header  does not exist, a new one will be added

kong/plugins/response-transformer/body_filter.lua

@@ -2,6 +2,9 @@ local utils = require "kong.tools.utils"
 local stringy = require "stringy"
 local cjson = require "cjson"
 
+local table_concat = table.concat
+local pcall = pcall
+
 local _M = {}
 
 local APPLICATION_JSON = "application/json"
@@ -27,7 +30,7 @@ local function read_response_body()
     ngx.arg[1] = nil 
   end
   if eof then 
-    local response_body = table.concat(buffered) 
+    local response_body = table_concat(buffered) 
     return response_body
   end
   return nil

kong/plugins/response-transformer/header_filter.lua

@@ -1,6 +1,9 @@
 local utils = require "kong.tools.utils"
 local stringy = require "stringy"
 
+local table_insert = table.insert
+local type = type
+
 local _M = {}
 
 local APPLICATION_JSON = "application/json"
@@ -24,6 +27,19 @@ local function iterate_and_exec(val, cb)
   end
 end
 
+local function concat_value(current_value, value)
+  local current_value_type = type(current_value)
+
+  if current_value_type  == "string" then
+    return { current_value, value }
+  elseif current_value_type  == "table" then
+    table_insert(current_value, value)
+    return current_value  
+  else
+    return { value } 
+  end
+end
+
 function _M.execute(conf)
   local is_json_body = stringy.startswith(get_content_type(), APPLICATION_JSON)
 
@@ -58,7 +74,16 @@ function _M.execute(conf)
     end
 
   end
-
+
+  if conf.concat then
+
+    -- concat header
+    if conf.concat.headers then
+      iterate_and_exec(conf.concat.headers, function(name, value)
+        ngx.header[name] = concat_value(ngx.header[name], value)
+      end)
+    end
+  end
 end
 
 return _M

kong/plugins/response-transformer/schema.lua

@@ -13,6 +13,12 @@ return {
           headers = { type = "array" }
         }
       }
+    },
+    concat = { type = "table", schema = {
+        fields = {
+          headers = { type = "array" }
+        }
+      }
     }
   }
 }

spec/plugins/response-transformer/filter_spec.lua

@@ -13,7 +13,8 @@ describe("Response Transformer Plugin #proxy", function()
     spec_helper.insert_fixtures {
       api = {
         {name = "tests-response-transformer", request_host = "response.com", upstream_url = "http://httpbin.org"},
-        {name = "tests-response-transformer2", request_host = "response2.com", upstream_url = "http://httpbin.org"}
+        {name = "tests-response-transformer2", request_host = "response2.com", upstream_url = "http://httpbin.org"},
+        {name = "tests-response-transformer3", request_host = "response3.com", upstream_url = "http://httpbin.org"}
       },
       plugin = {
         {
@@ -38,7 +39,19 @@ describe("Response Transformer Plugin #proxy", function()
             }
           },
           __api = 2
-        }
+        },
+        {
+          name = "response-transformer",
+          config = {
+            add = {
+              headers = {"h1:a1"}
+            },
+            concat = {
+              headers = {"h1:a2", "h1:a3", "h2:b1"}
+            }
+          },
+          __api = 3
+        },
       }
     }
 
@@ -96,5 +109,19 @@ describe("Response Transformer Plugin #proxy", function()
     end)
 
   end)
-
+
+  describe("Test concatenating parameters", function()
+
+    it("should create new header if not its missing", function()
+      local _, status, headers = http_client.get(STUB_GET_URL, {}, {host = "response3.com"})
+      assert.are.equal(200, status)
+      assert.are.equal("b1", headers["h2"])
+    end)
+
+    it("should concat value if header exists", function()
+      local _, status, headers = http_client.get(STUB_GET_URL, {}, {host = "response3.com"})
+      assert.are.equal(200, status)
+      assert.are.equal("a1, a2, a3", headers["h1"])
+    end)
+  end)
 end)