Migrate cbuilder module and adapt it

The original `cbuilder` module (tarantool/test/config-luatest/cbuilder.lua)
has been moved to the current project with minor changes and will be
available as follows:

    local t = require('luatest')
    t.cbuilder:new(...)

The helper requires Tarantool 3.0.0 and newer. Otherwise `Builder:new()`
will cause an error.

Closes #366

Author: Oleg Chaplashkin

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Add more logs (gh-326).
 - Add `justrun` helper as a tarantool runner and output catcher (gh-365).
 - Changed error message for too long Unix domain socket paths (gh-341).
+- Add `cbuilder` helper as a declarative configuration builder (gh-366).
 
 ## 1.0.1
 

config.ld

@@ -8,6 +8,7 @@ file = {
     'luatest/server.lua',
     'luatest/replica_set.lua',
     'luatest/justrun.lua',
+    'luatest/cbuilder.lua'
 }
 topics = {
     'CHANGELOG.md',

luatest/cbuilder.lua

@@ -0,0 +1,235 @@
+--- Configuration builder.
+--
+-- It allows to construct a declarative configuration for a test case using
+-- less boilerplace code/options, especially when a replicaset is to be
+-- tested, not a single instance. All the methods support chaining (return
+-- the builder object back).
+--
+-- @usage
+--
+-- local config = Builder:new()
+--     :add_instance('instance-001', {
+--         database = {
+--             mode = 'rw',
+--         },
+--     })
+--     :add_instance('instance-002', {})
+--     :add_instance('instance-003', {})
+--     :config()
+--
+-- By default, all instances are added to replicaset-001 in group-001,
+-- but it's possible to select a different replicaset and/or group:
+--
+-- local config = Builder:new()
+--     :use_group('group-001')
+--     :use_replicaset('replicaset-001')
+--     :add_instance(<...>)
+--     :add_instance(<...>)
+--     :add_instance(<...>)
+--
+--     :use_group('group-002')
+--     :use_replicaset('replicaset-002')
+--     :add_instance(<...>)
+--     :add_instance(<...>)
+--     :add_instance(<...>)
+--
+--     :config()
+--
+-- The default credentials and iproto options are added to
+-- setup replication and to allow a test to connect to the
+-- instances.
+--
+-- There is a few other methods:
+--
+-- * :set_replicaset_option('foo.bar', value)
+-- * :set_instance_option('instance-001', 'foo.bar', value)
+--
+-- @classmod luatest.cbuilder
+
+local checks = require('checks')
+local fun = require('fun')
+
+local Builder = require('luatest.class').new()
+
+-- Do a post-reqiure of the `internal.config.cluster_config`,
+-- since it is available from version 3.0.0+. Otherwise we
+-- will get an error when initializing the module in `luatest.init`.
+local cluster_config = {}
+
+local base_config = {
+    credentials = {
+        users = {
+            replicator = {
+                password = 'secret',
+                roles = {'replication'},
+            },
+            client = {
+                password = 'secret',
+                roles = {'super'},
+            },
+        },
+    },
+    iproto = {
+        listen = {{
+            uri = 'unix/:./{{ instance_name }}.iproto'
+        }},
+        advertise = {
+            peer = {
+                login = 'replicator',
+            }
+        },
+    },
+    replication = {
+        -- The default value is 1 second. It is good for a real
+        -- usage, but often suboptimal for testing purposes.
+        --
+        -- If an instance can't connect to another instance (say,
+        -- because it is not started yet), it retries the attempt
+        -- after so called 'replication interval', which is equal
+        -- to replication timeout.
+        --
+        -- One second waiting means one more second for a test
+        -- case and, if there are many test cases with a
+        -- replicaset construction, it affects the test timing a
+        -- lot.
+        --
+        -- replication.timeout = 0.1 second reduces the timing
+        -- by half for my test.
+        timeout = 0.1,
+    },
+}
+
+function Builder:inherit(object)
+    setmetatable(object, self)
+    self.__index = self
+    return object
+end
+
+--- Build a config builder object.
+--
+-- @tab[opt] config Table with declarative configuration.
+function Builder:new(config)
+    checks('table', '?table')
+    cluster_config = require('internal.config.cluster_config')
+
+    config = table.deepcopy(config or base_config)
+    self._config = config
+    self._group = 'group-001'
+    self._replicaset = 'replicaset-001'
+    return self
+end
+
+--- Select a group for following calls.
+--
+-- @string group_name Group of replicas.
+function Builder:use_group(group_name)
+    checks('table', 'string')
+    self._group = group_name
+    return self
+end
+
+--- Select a replicaset for following calls.
+--
+-- @string replicaset_name Replica set name.
+function Builder:use_replicaset(replicaset_name)
+    checks('table', 'string')
+    self._replicaset = replicaset_name
+    return self
+end
+
+--- Set option to the cluster config.
+--
+-- @string path Option path.
+-- @param value Option value (int, string, table).
+function Builder:set_global_option(path, value)
+    checks('table', 'string', '?')
+    cluster_config:set(self._config, path, value)
+    return self
+end
+
+--- Set an option for the selected group.
+--
+-- @string path Option path.
+-- @param value Option value (int, string, table).
+function Builder:set_group_option(path, value)
+    checks('table', 'string', '?')
+    path = fun.chain({
+        'groups', self._group,
+    }, path:split('.')):totable()
+
+    cluster_config:set(self._config, path, value)
+    return self
+end
+
+--- Set an option for the selected replicaset.
+--
+-- @string path Option path.
+-- @param value Option value (int, string, table).
+function Builder:set_replicaset_option(path, value)
+    checks('table', 'string', '?')
+    path = fun.chain({
+        'groups', self._group,
+        'replicasets', self._replicaset,
+    }, path:split('.')):totable()
+
+    -- <schema object>:set() validation is too tight. Workaround
+    -- it. Maybe we should reconsider this :set() behavior in a
+    -- future.
+    if value == nil then
+        local cur = self._config
+        for i = 1, #path - 1 do
+            -- Create missed fields.
+            local component = path[i]
+            if cur[component] == nil then
+                cur[component] = {}
+            end
+
+            cur = cur[component]
+        end
+        cur[path[#path]] = value
+        return self
+    end
+
+    cluster_config:set(self._config, path, value)
+    return self
+end
+
+-- Set an option of a particular instance in the selected replicaset.
+--
+-- @string instance_name Instance where the option will be saved.
+-- @string path Option path.
+-- @param value Option value (int, string, table).
+function Builder:set_instance_option(instance_name, path, value)
+    checks('table', 'string', 'string', '?')
+    path = fun.chain({
+        'groups', self._group,
+        'replicasets', self._replicaset,
+        'instances', instance_name,
+    }, path:split('.')):totable()
+
+    cluster_config:set(self._config, path, value)
+    return self
+end
+
+--- Add an instance with the given options to the selected replicaset.
+--
+-- @string instance_name Instance where the config will be saved.
+-- @tab iconfig Declarative config for the instance.
+function Builder:add_instance(instance_name, iconfig)
+    checks('table', 'string', '?')
+    local path = {
+        'groups', self._group,
+        'replicasets', self._replicaset,
+        'instances', instance_name,
+    }
+    cluster_config:set(self._config, path, iconfig)
+    return self
+end
+
+--- Return the resulting configuration.
+--
+function Builder:config()
+    return self._config
+end
+
+return Builder

luatest/init.lua

@@ -43,6 +43,11 @@ luatest.log = require('luatest.log')
 -- @see luatest.justrun
 luatest.justrun = require('luatest.justrun')
 
+--- Declarative configuration builder helper.
+--
+-- @see luatest.cbuilder
+luatest.cbuilder = require('luatest.cbuilder')
+
 --- Add before suite hook.
 --
 -- @function before_suite