hotfix(db) allow plugins on empty services (#4312)

Before this change, assigning a plugin to an empty service (with no routes) would result in an “no compatible routes found in service” error. That is considered a breaking change (for things like automatic setups) and has been altered now: when a plugin is assigned to a service, and the service has no routes, then there will be no error. The error will still be raised when the service has at least one route, but none of its routes are compatible.

kong/db/dao/plugins.lua

@@ -35,16 +35,21 @@ local function has_a_common_protocol_with_route(plugin, route)
 end
 
 
-local function has_a_compatible_route_in_service(self, plugin, service_pk)
+local function has_common_protocol_with_service(self, plugin, service_pk)
+  local had_at_least_one_route = false
   for route, err, err_t in self.db.routes:each_for_service(service_pk) do
     if not route then
       return nil, err, err_t
     end
 
+    had_at_least_one_route = true
+
     if has_a_common_protocol_with_route(plugin, route) then
       return true
     end
   end
+
+  return not had_at_least_one_route
 end
 
 
@@ -64,7 +69,7 @@ local function check_protocols_match(self, plugin)
   end
 
   if type(plugin.service) == "table" then
-    if not has_a_compatible_route_in_service(self, plugin, plugin.service) then
+    if not has_common_protocol_with_service(self, plugin, plugin.service) then
       local err_t = self.errors:schema_violation({
         protocols = "must match the protocols of at least one route " ..
                     "pointing to this Plugin's service",

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

@@ -25,7 +25,8 @@ for _, strategy in helpers.each_strategy() do
 
     before_each(function()
       service = bp.services:insert()
-      route = bp.routes:insert({ protocols = { "tcp" },
+      route = bp.routes:insert({ service = { id = service.id },
+                                 protocols = { "tcp" },
                                  sources = { { ip = "127.0.0.1" } },
                                })
     end)
@@ -76,7 +77,7 @@ for _, strategy in helpers.each_strategy() do
                       [["},consumer=null}']], err_t.message)
         end)
 
-        it("returns an error when inserting mismatched plugins", function()
+        it("does not validate when associated to an incompatible route, or a service with only incompatible routes", function()
           local plugin, _, err_t = db.plugins:insert({ name = "key-auth",
                                                        protocols = { "http" },
                                                        route = { id = route.id },
@@ -85,13 +86,23 @@ for _, strategy in helpers.each_strategy() do
           assert.equals(err_t.fields.protocols, "must match the associated route's protocols")
 
           local plugin, _, err_t = db.plugins:insert({ name = "key-auth",
-                                                       protocols = { "tcp" },
+                                                       protocols = { "http" },
                                                        service = { id = service.id },
                                                      })
           assert.is_nil(plugin)
           assert.equals(err_t.fields.protocols,
                         "must match the protocols of at least one route pointing to this Plugin's service")
         end)
+
+        it("validates when associated to a service with no routes", function()
+          local service_with_no_routes = bp.services:insert()
+          local plugin, _, err_t = db.plugins:insert({ name = "key-auth",
+                                                       protocols = { "http" },
+                                                       service = { id = service_with_no_routes.id },
+                                                     })
+          assert.truthy(plugin)
+          assert.is_nil(err_t)
+        end)
       end)
 
       describe(":update()", function()