Make shard optional

Fixes tarantool#218.

Author: Totktonada

graphql/accessor_shard_cache.lua

@@ -1,6 +1,6 @@
 local json = require('json')
-local shard = require('shard')
 local utils = require('graphql.utils')
+local shard = utils.optional_require('shard')
 local request_batch = require('graphql.request_batch')
 local accessor_shard_index_info = require('graphql.accessor_shard_index_info')
 

test/extra/no_shard/shard.lua

@@ -0,0 +1 @@
+error('shard should not be mandatory dependency')

test/extra/shard_optional.lua

@@ -0,0 +1,35 @@
+#!/usr/bin/env tarantool
+
+-- https://github.com/tarantool/graphql/issues/218
+
+local fio = require('fio')
+local tap = require('tap')
+
+-- require in-repo version of graphql/ sources despite current working directory
+local cur_dir = fio.abspath(debug.getinfo(1).source:match("@?(.*/)")
+    :gsub('/./', '/'):gsub('/+$', ''))
+package.path =
+    cur_dir .. '/../../?/init.lua' .. ';' ..
+    cur_dir .. '/../../?.lua' .. ';' ..
+    package.path
+
+-- require no_shard/shard.lua instead of the real shard module
+package.path =
+    cur_dir .. '/no_shard/?/init.lua' .. ';' ..
+    cur_dir .. '/no_shard/?.lua' .. ';' ..
+    package.path
+
+local graphql = require('graphql')
+local testdata = require('test.testdata.common_testdata')
+
+local test = tap.test('optional shard')
+test:plan(1)
+
+box.cfg{wal_mode='none'}
+
+local cfg = testdata.get_test_metadata()
+cfg.accessor = 'space'
+local ok = pcall(graphql.new, cfg)
+test:ok(ok, 'shard is optional')
+
+os.exit(test:check() == true and 0 or 1)

test/test_utils.lua

@@ -10,10 +10,10 @@ local log = require('log')
 local yaml = require('yaml')
 local avro_schema = require('avro_schema')
 local digest = require('digest')
-local shard = require('shard')
+local utils = require('graphql.utils')
+local shard = utils.optional_require('shard')
 local graphql = require('graphql')
 local multirunner = require('test.common.multirunner')
-local utils = require('graphql.utils')
 local test_run = utils.optional_require('test_run')
 test_run = test_run and test_run.new()