Elixir Berln Meetup #83 - Domo 1.3 Automatic models validation in the microservice setting

https://github.com/IvanRublev
https://twitter.com/@levvibraun

More information:
* Package: https://hex.pm/packages/domo
* JSON parsing example: https://github.com/IvanRublev/contentful-elixir-parse-example-nestru-domo
* Ecto integration example: https://github.com/IvanRublev/Domo/tree/master/example_avialia
* Questions and help: https://elixirforum.com/tag/domo

Transcript

1. DOMO 1.3 - AUTOMATIC MODELS VALIDATION IN THE MICROSERVICE SETTING ELIXIR BERLIN MEETUP 83# NOV 2021 Ivan Rublev github.com/IvanRublev twitter.com/@levvibraun
2. DOMO 1.3 ▸ Network input ▸ Database and file input ▸ The Application itself due 
 to errors in logic
 SOURCES OF INVALID STATES OF APPLICATIONS AT RUNTIME PURCHASING APP defmodule Order do defstruct … end DELIVERY APP defmodule Address do defstruct … end ??? ???
3. DOMO 1.3 INVALID STATE %PurchaseOrder{ id: 1000, approved_limit: 200, items: [ %LineItem{amount: 150} ] } ▸ Elixir structs can hold anything you might want and not want. %PurchaseOrder{ id: "@$$>?!||=", approved_limit: 2.00, items: [ %LineItem{amount: :"150"} ] }
4. DOMO 1.3 DOMO ENSURES THAT STRUCT’S DATA MATCHES IT’S @TYPE SPEC AND PRECONDITIONS ▸ Adds the constructor and ensuring functions to the struct ▸ Validates struct’s field values against its @type spec ▸ Check values with precondition functions attached to types by `precond/1` new_ok(fields) :: {:ok, order} | {:error, msg}
 new!(fields) :: order
 ensure_type_ok(order) :: {:ok, order} | {:error, msg}
 ensure_type!(order) :: order
 defmodule PurchaseOrder do use Domo defstruct [id: 1000, approved_limit: 200, items: []] @type id ::: non_neg_integer() precond id: &(1000 <<= &1 and &1 <<= 5000) @type t ::: %___MODULE___{ id: id(), approved_limit: pos_integer(), items: [LineItem.t()] } # new!/1, new_ok/1, ensure_type!/1, ensure_type_ok/1 end
5. DOMO 1.3 LIBRARY USAGE iex> {:ok, po} = PurchaseOrder.new_ok(id: 1000, approved_limit: 200) {:ok, %PurchaseOrder{id: 1000, approved_limit: 200, items: []}} iex> PurchaseOrder.new_ok(id: 500, approved_limit: 0) {:error, [ id: "Invalid value 500 for field :id of %PurchaseOrder{}. Expected the value matching the non_neg_integer() type. And a true value from the precondition function \"&(1000 <<= &1 and &1 <<= 5000)\" defined for PurchaseOrder.id() type.", approved_limit: "Invalid value 0 for field :approved_limit of %PurchaseOrder{}. Expected the value matching the pos_integer() type." ]} @type id ::: non_neg_integer() precond id: &(1000 <<= &1 and &1 <<= 5000) @type t ::: %___MODULE___{ id: id(), approved_limit: pos_integer(), items: [LineItem.t()] }
6. DOMO 1.3 DOMO GENERATES TYPE ENSURER MODULES defmodule PurchaseOrder do use Domo @type t ::: %___MODULE___{.....} # new!/1, new_ok/1, # ensure_type!/1, ensure_type_ok/1 end defmodule PurchaseOrder.TypeEnsurer do ..... end Generated type ensurers code are in the following project’s subdirectory: “_build/ENV/domo_generated_code“
7. JSON PARSE DEMO
8. DOMO 1.3 DOMO RECOMPILES TYPE ENSURERS ON DEPENDENCY CHANGE defmodule PurchaseOrder.TypeEnsurer do ..... end defmodule PurchaseOrder do use Domo @type t ::: %___MODULE___{.....} end defmodule PurchaseOrder.TypeEnsurer do ..... end defmodule LineItem do use Domo @type t ::: %___MODULE___{.....} end defmodule SharedKernel do @type amount ::: integer() end defmodule SharedKernel do @type amount ::: non_neg_integer() end defmodule PurchaseOrder.TypeEnsurer do ..... end defmodule PurchaseOrder.TypeEnsurer do ..... end
9. DOMO 1.3 defmodule Model.Shipment do use Domo @type t ::: %___MODULE___{.....} end DOMO VALIDATES MODELS ACROSS MICROSERVICES VIA SHARED TYPES Boardings microservice Cargos microservice defmodule Model.Shipment do use Domo @type t ::: %___MODULE___{.....} end defmodule SharedKernel do import Domo @type flight_number ::: String.t() precond flight_number: &validate_flight_number/1 ..... end defmodule Model.Passenger do use Domo @type t ::: %___MODULE___{.....} end defmodule Model.Passenger do use Domo @type t ::: %___MODULE___{.....} end
10. MICROSERVICES SETUP DEMO
11. DOMO 1.3 ▸ Domo library ▸ Validates Application models conform to type specs and attached precondition functions across Microservices ▸ Adds new!/1, new_ok/1, ensure_type!/1, ensure_type_ok/2, typed_fields/1, required_fields/1 functions to struct ▸ Supports custom error messages from precondition functions ▸ Validates struct default values at Compile Time! ▸ Integrates with Ecto for changeset validation ▸ Supports Phoenix hot reload ▸ More info ▸ Package https://hex.pm/packages/domo ▸ JSON parsing example https://github.com/IvanRublev/contentful-elixir-parse-example-nestru-domo ▸ Ecto integration example https://github.com/IvanRublev/Domo/tree/master/example_avialia ▸ Questions and help https://elixirforum.com/tag/domo THANKS!