add check for driver overriding

Added check for an attempt to register a driver with an already
registered name.

Author: LeonidVas

queue/init.lua

@@ -15,6 +15,9 @@ local function register_driver(driver_name, tube_ctr)
         error('tube control methods must contain functions "create_space"'
               .. ' and "new"')
     end
+    if queue.driver[driver_name] then
+        error(('overriding registered driver "%s"'):format(driver_name))
+    end
     queue.driver[driver_name] = tube_ctr
 end
 

t/001-tube-init.t

@@ -12,11 +12,17 @@ local engine = os.getenv('ENGINE') or 'memtx'
 local mock_tube = { create_space = function() end, new = function() end }
 
 test:test('test queue mock addition', function(test)
-    test:plan(2)
+    test:plan(3)
 
     local queue = require('queue')
     queue.register_driver('mock', mock_tube)
     test:is(queue.driver.mock, mock_tube)
+
+    local res, err = pcall(queue.register_driver, 'mock', mock_tube)
+    local check = not res and
+        string.match(err, 'overriding registered driver') ~= nil
+    test:ok(check, 'check a driver override failure')
+
     tnt.cfg{}
 
     test:is(queue.driver.mock, mock_tube)

t/140-register-driver-after-cfg.t

@@ -3,7 +3,7 @@ local tap = require('tap')
 local tnt = require('t.tnt')
 
 local test = tap.test('test driver register')
-test:plan(2)
+test:plan(3)
 
 local mock_tube = {
     create_space = function() end,
@@ -35,6 +35,11 @@ local function check_driver_register()
     end
 
     test:ok(check_standart_drivers, 'standard drivers are defined')
+
+    local res, err = pcall(queue.register_driver, 'mock', mock_tube)
+    local check = not res and
+        string.match(err, 'overriding registered driver') ~= nil
+    test:ok(check, 'check a driver override failure')
 end
 
 check_driver_register()