Tutorial: Module compat

This tutorial covers the following compat module API and its usage:

The options list is serialized in the interactive console with additional details for user convenience:

• All non-obsolete options in order new > old > default.
• Serialization returns array-like table with tables {<option> = <value>}.
• The result of compat serialization can still be indexed as a normal key-value table.

 
tarantool> compat = require('compat')---...tarantool> compat---- - json_escape_forward_slash: new- - option_2: old- - option_default_old: default (old)- - option_default_new: default (new)...

• current – the state of the option.
• default – the default state of the option.
• brief – text options description with a link to more detailed description.

 
tarantool> compat.option_default_new---- current: olddefault: newbrief: <...>...

You can do it directly, or by passing a table with option-value. Possible values to assign are 'new' , 'old', and 'default'.

 
tarantool> compat.json_escape_forward_slash = 'old'---...tarantool> compat{json_escape_forward_slash = 'new', option_2 = 'default'}---...

By setting 'default' value to an option:

 
tarantool> compat.option_2 = 'default'---...tarantool> compat.option_2---- current: default- default: new- brief: <...>...

 
tarantool> compat({         >     obsolete_set_explicitly = 'new',         >     option_set_old = 'old',         >     option_set_new = 'new'         > })---...tarantool> compat---- - option_set_old: old- - option_set_new: new- - option_default_old: default (old)- - option_default_new: default (new)...# Obsolete options are not returned in serialization, but have the following values:# - obsolete_option_default: default (new)# - obsolete_set_explicitly: new# nil does output obsolete unset options as 'default'tarantool> compat.dump()---- require('compat')({            option_set_old          = 'old',            option_set_new          = 'new',            option_default_old      = 'default',            option_default_new      = 'default',            obsolete_option_default = 'default', -- obsolete since X.Y            obsolete_set_explicitly = 'new',     -- obsolete since X.Y    })...# 'current' is the same as nil with default set to current valuestarantool> compat.dump('current')---- require('compat')({            option_set_old          = 'old',            option_set_new          = 'new',            option_default_old      = 'old',            option_default_new      = 'new',            obsolete_option_default = 'new',     -- obsolete since X.Y            obsolete_set_explicitly = 'new',     -- obsolete since X.Y    })...# 'new' outputs obsolete as 'new'.tarantool> compat.dump('new')---- require('compat')({            option_set_old          = 'new',            option_set_new          = 'new',            option_default_old      = 'new',            option_default_new      = 'new',            obsolete_option_default = 'new',     -- obsolete since X.Y            obsolete_set_explicitly = 'new',     -- obsolete since X.Y    })...# 'old' outputs obsolete options as 'new'.tarantool> compat.dump('old')---- require('compat')({            option_set_old          = 'old',            option_set_new          = 'old',            option_default_old      = 'old',            option_default_new      = 'old',            obsolete_option_default = 'new',     -- obsolete since X.Y            obsolete_set_explicitly = 'new',     -- obsolete since X.Y    })...# 'default' does output obsolete options as default.tarantool> dump('default')---- require('compat')({            option_set_old          = 'default',            option_set_new          = 'default',            option_default_old      = 'default',            option_default_new      = 'default',            obsolete_option_default = 'default', -- obsoleted since X.Y            obsolete_set_explicitly = 'default', -- obsoleted since X.Y    })...

• use compat.dump() to get a specific configuration
• copy and paste it into console (or use loadstring())

 
tarantool> compat.dump('new')---- require('compat')({      option_2 = 'new',      json_escape_forward_slash = 'new',  })...tarantool> require('compat')({      option_2 = 'new',      json_escape_forward_slash = 'new',  })---...tarantool> compat---- - json_escape_forward_slash: new- - option_2: new...

User must provide a table with:

• name (string)
• default ('new' / 'old')
• brief (explanation of the option, can be multiline string)
• obsolete ('X.Y' / nil) –- tarantool version that marked option as obsolete. When nil, option is treated as non-obsolete)
• action function (argument - boolean is_new, changes the behavior accordingly)
• run_action_now (true / false / nil) if add_options should run action afterwards, false by default

Option hot reload:

You can change an existing option in runtime using add_option(), it will update all the fields but keep currently selected behavior if any. The new action will be called afterwards.

 
tarantool> compat.add_option{                 name = 'option_4',                 default = 'new',                 brief = "<...>",                 obsolete = nil,          -- you can explicitly mark the option as non-obsolete                 action = function(is_new)                      print(("option_4 action was called with is_new = %s!"):format(is_new))                 end,                 run_action_now = true           }option_4 postaction was called with is_new = true!---...tarantool> compat.add_option{             -- hot reload of option_4                 name = 'option_4',                 default = 'old',         -- different default                 brief = "<...>",                 action = function(is_new)                      print(("new option_4 action was called with is_new = %s!"):format(is_new))                 end           }---...         -- action is not called by default