fix(request-transformer) header transf called before body (#4)

Header transform must be executed before body transform, as the content-type
must be correctly set before changing body.

This change fixes issue #1

kong/plugins/request-transformer/access.lua

@@ -260,8 +260,11 @@ local function transform_json_body(conf, body, content_length)
   local removed, renamed, replaced, added, appended = false, false, false, false, false
   local content_length = (body and #body) or 0
   local parameters = parse_json(body)
-  if parameters == nil and content_length > 0 then
-    return false, nil
+  if parameters == nil then
+    if content_length > 0 then
+      return false, nil
+    end
+    parameters = {}
   end
 
   if content_length > 0 and #conf.remove.body > 0 then
@@ -484,8 +487,8 @@ function _M.execute(conf)
   clear_environment()
   transform_uri(conf)
   transform_method(conf)
-  transform_body(conf)
   transform_headers(conf)
+  transform_body(conf)
   transform_querystrings(conf)
 end
 

spec/02-access_spec.lua

@@ -86,6 +86,9 @@ describe("Plugin: request-transformer(access) [#" .. strategy .. "]", function()
       paths = { "/requests/user1/(?<user1>\\w+)/user2/(?<user2>\\S+)" },
       strip_path = false
     })
+    local route20 = bp.routes:insert({
+      hosts = { "test20.com" }
+    })
 
     bp.plugins:insert {
       route = { id = route1.id },
@@ -307,6 +310,20 @@ describe("Plugin: request-transformer(access) [#" .. strategy .. "]", function()
       }
     }
 
+    bp.plugins:insert {
+      route = { id = route20.id },
+      name = "request-transformer",
+      config = {
+        http_method = "POST",
+        add = {
+          headers = {
+            "Content-Type:application/json"
+          },
+          body = { "body:somecontent" }
+        },
+      }
+    }
+
     assert(helpers.start_kong({
       database = strategy,
       plugins = "bundled, request-transformer",
@@ -359,6 +376,22 @@ describe("Plugin: request-transformer(access) [#" .. strategy .. "]", function()
       assert.equal("world", json.uri_args.hello)
       assert.equal("marco", json.uri_args.name)
     end)
+    it("changes the HTTP method from GET to POST and adds JSON body", function()
+      local r = assert(client:send {
+        method = "GET",
+        path = "/request",
+        headers = {
+          host = "test20.com",
+        }
+      })
+      assert.response(r).has.status(200)
+      local json = assert.response(r).has.jsonbody()
+      assert.request(r).has.jsonbody()
+      assert.equal("POST", json.vars.request_method)
+      assert.is_nil(json.post_data.error)
+      local header_content_type = assert.request(r).has.header("Content-Type")
+      assert.equals("application/json", header_content_type)
+    end)
   end)
   describe("remove", function()
     it("specified header", function()