Workaround plan unit tests

Unit tests for plan module fails to run without cofigured vshard.router
after introduction of improved sharding key extraction in 408d1cf.
This patch sets up dummy 'crud.common.sharding_key' modules for plan
unit tests.

Follows up #213

test/helper.lua

@@ -332,4 +332,19 @@ function helpers.update_cache(cluster, space_name)
     ]], {space_name})
 end
 
+function helpers.set_sharding_key_module_dummy()
+    package.loaded['crud.common.sharding_key'] = {
+        fetch_on_router = function(_) return nil; end
+    }
+
+    -- Reload 'crud.select.plan' so it recursively
+    -- reload 'crud.common.sharding_key'.
+    package.loaded['crud.select.plan'] = nil
+end
+
+function helpers.unset_sharding_key_module_dummy()
+    package.loaded['crud.common.sharding_key'] = nil
+    package.loaded['crud.select.plan'] = nil
+end
+
 return helpers

test/unit/select_dropped_indexes_test.lua

@@ -66,10 +66,20 @@ g.before_all = function()
 
     -- We need this check to make sure that test actually covers a problem.
     t.assert_not_equals(#box.space.customers.index, table.maxn(box.space.customers.index))
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_all = function()
     box.space.customers:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end
 
 g.test_before_dropped_index_field = function()

test/unit/select_executor_test.lua

@@ -58,6 +58,13 @@ g.before_all = function()
     })
 
     crud.init_storage()
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_each(function()
@@ -66,6 +73,9 @@ end)
 
 g.after_all(function()
     box.space.customers:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end)
 
 g.test_one_condition_no_index = function()

test/unit/select_filters_test.lua

@@ -81,11 +81,21 @@ g.before_all = function()
             if_not_exists = true,
         })
     end
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_all(function()
     box.space.customers:drop()
     box.space.cars:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end)
 
 g.test_empty_conditions = function()

test/unit/select_filters_uuid_test.lua

@@ -38,10 +38,20 @@ g.before_all = function()
             if_not_exists = true,
         })
     end
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_all(function()
     box.space.customers:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end)
 
 g.test_parse = function()

test/unit/select_plan_bad_indexes_test.lua

@@ -65,10 +65,20 @@ g.before_all = function()
         unique = false,
         if_not_exists = true,
     })
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_all = function()
     box.space.customers:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end
 
 g.test_select_all_bad_primary = function()

test/unit/select_plan_test.lua

@@ -64,10 +64,20 @@ g.before_all = function()
         parts = { {field = 'bucket_id'} },
         if_not_exists = true,
     })
+
+    -- Workaround for plan failing to build without cofigured vshard.router.
+    -- crud.common.call function 'any' fails to use vshard.router.routeall()
+    -- which leads to fail of crud.common.sharding_key function 'fetch_on_router'
+    -- in critical section of 'reentrant_fetch' in the same module.
+    helpers.set_sharding_key_module_dummy()
+    select_plan = require('crud.select.plan')
 end
 
 g.after_all(function()
     box.space.customers:drop()
+
+    -- Unset workaround from g.before_all.
+    helpers.unset_sharding_key_module_dummy()
 end)
 
 g.test_indexed_field = function()