Talk of Aleksandra Stolyar, Ruby developer at DataArt, at Ruby Meditation #29 Kyiv 14.12.2019 Next conference - http://www.rubymeditation.com/ Description: I will talk about dry-rb ecosystem and it’s major components - dry-validation and dry-schema which are very helpful for validations. This year dry-rb introduced a major update to its’ gems and I faced some problems when decided to marry these updates with a project. This talk will cover some of differences and specifics of dry-validation and dry-schema updates. Announcements and conference materials https://www.fb.me/RubyMeditation News https://twitter.com/RubyMeditation Photos https://www.instagram.com/RubyMeditation The stream of Ruby conferences (not just ours) https://t.me/RubyMeditation

1. Oleksandra Stolyar (Tomilina)
dry-validation vs dry-schema 1.*.*

2. Harry Potter and…
the Very Important Gem
Update
to the Major Version

3. “a set of gems that bring solutions
to common problems”
dry-struct
dry-logic
dry-container
dry-validation
dry-transaction
dry-schema
…
dry-rb

4. Backstory…
ME
dry-validation

5. Yeah, that feeling…

6. 2017,
February
• Plans for dry-validation + dry-schema (a new gem!) by Piotr Solnica
2019,
January
• dry-schema introduced
2019,
May
• dry-schema v1.0.0 released
2019,
June
• dry-validation v1.0.0 released
gems update timeline

7. exceptionally about my experience
how I structured knowledge about these gems
features that were crucial for me
workarounds
successes and failures
conclusions, decisions and their consequences
What this talk will be about?

8. bugs that were fixed since dry-validation 0.13
all great features that dry-validation or dry-schema can provide
What I won’t cover?

9. The Challenge

10. Operations gem ‘trailblazer-operation’
Params schema and Validation Macro in operations gem ‘dry-validation’
Error normalization Macro for errors in operations gem ‘error_normalizer’
I had:

11. Trailblazer Operation v2.0 Contract documentation mentions the ability of validation using:
Dry::Schema (dry-validation < v0.13.3 Schema)
Reform
Trailblazer Macro Contract has dry-validation v0.11.1 dependency
Reform status:
Since September 2019 Emanuele Magliozzi started pushing commits for old and new API compatibility
which use dry-validation < v0.13.3 and dry-validation > v1.0.0 respectively.
In November 2019 he pushed into Trailblazer Reform v2.3.0 with new api which uses
Dry::Validation::Contract
Yet docs are still not updated and 🤔
Trailblazer usage

12. For same purposes you can use:
dry-transaction (active v0.13.0, release of v1.0.0 is planned but further development will be
stopped)
dry-monads
gem ‘interactor’
Other approaches

13. That is the question… 🤔

14. Reusing schemas
Rules
Custom Predicates
Custom Error Messages
Schema/Contract Configuration
Features to migrate:

15. dry-validation <
0.13
dry-validation > 1.0
(business
validations)
dry-schema > 1.0
(shape & type
validations)
Main changes

16. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema

17. Reusing Schemas

18. {
"sender": {
"first_name": "Draco",
"last_name": "Malfoy"
},
"receiver": {
"first_name": "Lord",
"last_name": "Voldemort"
},
"receiver_address": "Castle",
"text": "I'm scared",
"asap": true
}
it needs to be validated:

19. Reusing Schemas dry-validation 0.13
optional(:sender).schema(PersonalInfo::FormValidation)
required(:receiver).schema(PersonalInfo::FormValidation)
required(:receiver_address).filled(:str?)
required(:text).filled(:str?)
optional(:asap).filled(:bool?)
module PersonalInfo
FormValidation = Dry::Validation.Schema
required(:first_name).filled(:str?)
required(:last_name).filled(:str?)
end
end

20. Reusing Schemas dry-validation 1.3.1
params do
optional(:sender).hash(PersonalInfo::FormValidation)
required(:receiver).hash(PersonalInfo::FormValidation)
required(:receiver_address).filled(:string)
required(:text).filled(:string)
optional(:asap).filled(:bool)
end
module PersonalInfo
FormValidation = Dry::Schema.Params do
required(:first_name).filled(:string)
required(:last_name).filled(:string)
end
end

21. Reusing Schemas dry-schema 1.3.4
optional(:sender).hash(PersonalInfo::FormValidation)
required(:receiver).hash(PersonalInfo::FormValidation)
required(:receiver_address).filled(:string)
required(:text).filled(:string)
optional(:asap).filled(:bool)
module PersonalInfo
FormValidation = Dry::Schema.Params do
required(:first_name) { filled? > str? }
required(:last_name).filled(:string)
end
end

22. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema
Achieved with
defining Schema

23. Rules

24. {
"hogwarts_student": {
"name": "Sasha",
"age": 18,
"parents_owl_id": "hedwig_was_the_best@owail.com",
"has_owl": true,
"has_cat_or_toad": true
}
}
it needs to be validated:

25. required(:hogwarts_student).schema do
required(:name).filled(:str?)
required(:age).filled(:int?, gt?: 11, lteq?: 18)
required(:parents_owl_id).filled(:str?)
optional(:has_owl).filled(:bool?)
optional(:has_cat_or_toad).filled(:bool?)
rule(inadmissible_animal_quantity:
[:has_owl, :has_cat_or_toad]) do |owl, not_owl|
owl.true? ^ not_owl.true?
end
end
Rules dry-validation 0.13

26. params do
required(:hogwarts_student).schema do
required(:name).filled(:string)
required(:age).filled(:integer)
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
end
rule('hogwarts_student.age').validate(gteq?: 11)
rule('hogwarts_student.age').validate(lteq?: 18)
rule(hogwarts_student: [:has_owl, :has_cat_or_toad]) do
unless values[:hogwarts_student][:has_owl] ^ values[:hogwarts_student][:has_cat_or_toad]
key(:owl_errors).failure(:inadmissible_animal_quantity)
end
end
Rules dry-validation 1.3.1

27. required(:hogwarts_student).schema do
required(:name).filled(:string)
required(:age).filled(:integer, gt?: 11, lteq?: 18)
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
step :check_inadmissible_animal_quantity
fail AddError('inadmissible_animal_quantity', path: 'has_owl'),
fail_fast: true
def check_inadmissible_animal_quantity(opts, output:, **)
hogwarts_student = output[:hogwarts_student]
hogwarts_student[:has_owl] ^ hogwarts_student[:has_cat_or_toad]
end
Rules dry-schema 1.3.4

28. {
"hogwarts_house": {
"name": "Slotherin",
"head": "Snape",
"ghost": "Bloody Baron",
"immutable_info": {
"founder_name": "Salazar Slytherin",
"element": "Water",
"flag": "flag_img",
"animal": "Serpent",
"traits": [
"Resourcefulness",
...
"Lineage"
]
},
"common_room": {
"name": "Slytherin Dungeon",
"location": "hell"
}
}
}
it needs to be validated:

29. required(:hogwarts_house).schema do
# ...
required(:head).filled(:str?,
size?: 1..255,
format?: SOME_MAGIC_REGEX)
# ...
required(:common_room).schema do
required(:name).filled(:str?)
required(:location).filled(:str?, included_in?: %w[tower underground])
end
end
Rules dry-validation 0.13

30. params do
required(:hogwarts_house).schema do
# ...
required(:head).filled(:string)
# ...
required(:common_room).schema do
required(:name).filled(:string)
required(:location).filled(:string)
end
end
end
rule('hogwarts_house.head') do
key.failure(:invalid_format) unless SOME_MAGIC_REGEX.match?(value)
key.failure(:invalid_size, range: 1..255) unless (1..255).cover?(value.length)
end
rule('hogwarts_house.common_room.location') do
Rules dry-validation 1.3.1

31. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema

32. Custom predicates

33. it needs to be validated:
{
"hogwarts_student": {
"name": "Sasha",
"age": 18,
"parents_owl_id": "hedwig_was_the_best@owail.com",
"has_owl": true,
"has_cat_or_toad": true
}
}

34. required(:hogwarts_student).schema do
# ...
required(:parents_owl_id).filled(:str?, :owl_id?)
optional(:has_owl).filled(:bool?)
optional(:has_cat_or_toad).filled(:bool?)
end
class CommonSchema < Dry::Validation::Schema::Params
configure do
# ...
end
def owl_id?(value)
OwlLib.valid?(value)
end
end
Dry::Validation.Schema(CommonSchema, {}, &block)
Custom Predicates dry-validation 0.13

35. params do
required(:hogwarts_student).schema do
# ...
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
end
## 1
rule(hogwarts_student: :parents_owl_id) do
key.failure(:invalid_owl_id) unless OwlLib.valid?(value)
end
Custom Predicates dry-validation 1.3.0

36. params do
required(:hogwarts_student).schema do
# ...
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
end
## 2
rule('hogwarts_student.parents_owl_id') do
unless owl_validator.valid?(value)
key.failure('invalid_owl_id')
end
end
Custom Predicates dry-validation 1.3.0

37. ## 2
class CommonContract < Dry::Validation::Contract
option :owl_validator
end
class OwlValidator
def self.valid?(value)
OwlLib.valid?(value)
end
end
MyContract.new(owl_validator: OwlValidator)
Custom Predicates dry-validation 1.3.0

38. params do
required(:hogwarts_student).schema do
# ...
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
end
## 3
rule(hogwarts_student: :parents_owl_id).validate(:owl_id_format)
Custom Predicates dry-validation 1.3.0

39. class CommonContract < Dry::Validation::Contract
register_macro(:owl_id_format) do
unless OwlLib.valid?(value)
key.failure('not a valid owl id format')
end
end
end
MyContract.new
Custom Predicates dry-validation 1.3.0

40. Custom Predicates dry-schema 1.3.4

41. required(:hogwarts_student).schema do
# ...
required(:parents_owl_id).filled(:string)
required(:has_owl).filled(:bool)
required(:has_cat_or_toad).filled(:bool)
end
step Validate()
fail NormalizeErrors(), fail_fast: true
step ValidateOwl(:hogwarts_student, :parents_owl_id)
fail AddError('invalid_parents_owl_id', path: 'parents_owl_id'), fail_fast: true
def ValidateOwl(*args)
step = lambda do |_input, options|
value = options[:output].dig(*args)
OwlLib.valid?(value)
end
end
Custom Predicates dry-schema 1.3.4

42. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema
Rules
Achieved with
Macro

43. Custom Error Messages

44. Custom Error Messages dry-validation 0.13
class CommonSchema < Dry::Validation::Schema::Params
configure do
I18n.config.backend.load_translations('somewhere/custom_error_messages.yml')
config.messages = :i18n
end
end
en:
errors:
bool?: "must be bla bla bla"
owl_number?: "must be in owl number international format"
rules:
inadmissible_animal_quantity: "either owl or something else"

45. Custom Error Messages dry-validation 1.3.1
class CommonContract < Dry::Validation::Contract
config.messages.load_paths << 'somewhere/custom_error_messages.yml'
end
en:
dry_validation:
errors:
bool?: "must be bla bla bla"
rules:
hogwarts_house:
common_room:
location:
invalid: "must be somewhere in: %{list}"
head:
invalid_format: "must not contain magic"
invalid_size: "length must be within %{range}"
hogwarts_student:
parents_owl_number:
invalid_owl_number: "must be in owl number international format"
owl_errors:
inadmissible_animal_quantity: "either owl or something else"

46. Custom Error Messages dry-schema 1.3.4
en:
dry_schema:
errors:
bool?: "must be bla bla bla"
CommonConfig = Dry::Schema.Params do
config.messages.load_paths << 'somewhere/custom_error_messages.yml'
end

47. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema

48. Configuration parameters

49. class CommonSchema < Dry::Validation::Schema::Params
configure do
# custom errors files and I18n configs
end
# predicates
# custom validation blocks
end
Dry::Validation.Schema(CommonSchema, {}, &block)
Configuration parameters dry-validation 0.13

50. Configuration parameters dry-validation 1.3.1
class CommonContract < Dry::Validation::Contract
# custom errors files and I18n configs
# external dependencies
# predicates as macros
end
MyContract.new(
# list of validators
)

51. Configuration parameters dry-schema 1.3.4
CommonConfig = Dry::Schema.Params do
# custom errors files and I18n configs
# custom types
end
Dry::Schema.Params(
processor: 'Params',
config: CommonConfig.config,
&block
)

52. Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema
Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema

53. Totals
Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema
Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema
Reusing
schemas
Rules
Custom
predicates
Custom
Error
Messages
Configuration
Parameters
dry-validation
(Contract)
dry-schema

55. This separation will not only make dry-v much simpler internally, but also allow us to have schemas for
processing/validating input at the HTTP boundary, and then having domain validators that can be called
in the application layer. Schemas and validators can be composed, it means that you’ll be able to specify
schemas and reuse them in validators. This way your application’s domain validation will live in the app
layer, and hairy HTTP processing/validation will be in the HTTP layer (ie controllers, roda routes, etc.)
and this will be possible with 0 code duplication (ie you won’t have to define same attributes in two
places).
The main idea behind dry-schema is to be a fast type checker and a coercion mechanism. It does
support lots of predicates OOTB through dry-logic but it’s important to understand that for “domain
validation” it is not a good fit. Good use cases for dry-schema with additional predicates (as in, other than
type checks) may include things like processing and validating application configuration or HTTP params
pre-processing (before it is passed down to domain layer where further processing may take place).
Proving the idea by Piotr Solnica

56. How can we draw a line between dry-validation
and dry-schema?
Use dry-validation or use both.
dry-schema for high-level http params
validation
dry-validation for specific and complex
validations, business logic
Ex.:
dry-schema in Controllers
dry-validation in Operations or whatever you
use to process data
Figuring it out

57. About dry-rb gems
https://www.rubyguides.com/2019/01/what-is-dry-rb/
Piotr Solnica about dry-schema 1.0 release
https://solnic.codes/2019/01/31/introducing-dry-schema/
Piotr Solnica about dry-validation 1.0 release
https://dry-rb.org/news/2019/06/10/dry-validation-1-0-0-released/
Tim Riley “A tour of dry-schema and dry-validation 1.0”
https://speakerdeck.com/timriley/a-tour-of-dry-schema-and-dry-validation-1-dot-0
Igor Morozov upgrading dry-gems
https://www.morozov.is/2019/05/31/upgrading-dry-gems.html
Helpful links:

58. Questions?

59. Thanks for listening 🎉🐱