Dry-validation update. Dry-validation vs Dry-schema 1.0 - Aleksandra Stolyar | Ruby Meditation 29

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

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

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

Backstory…
ME
dry-validation

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

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?

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?

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:

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

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

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

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

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

{
"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:

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

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

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

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

{
"hogwarts_student": {
"name": "Sasha",
"age": 18,
"parents_owl_id": "hedwig_was_the_best@owail.com",
"has_owl": true,
"has_cat_or_toad": true
}
}

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

params 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

required(:age).filled(:integer, gt?: 11, lteq?: 18)
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

{
"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"
}
}
}

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

params do
required(:hogwarts_house).schema do
# ...
required(:head).filled(:string)
# ...
required(:common_room).schema do
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

{
"hogwarts_student": {
"name": "Sasha",
"age": 18,
"parents_owl_id": "hedwig_was_the_best@owail.com",
"has_owl": true,
"has_cat_or_toad": true
}
}

# ...
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

params do
# ...
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

params do
# ...
end
end
## 2
rule('hogwarts_student.parents_owl_id') do
unless owl_validator.valid?(value)
key.failure('invalid_owl_id')
end
end

## 2
class CommonContract < Dry::Validation::Contract
option :owl_validator
end
class OwlValidator
def self.valid?(value)
end
end
MyContract.new(owl_validator: OwlValidator)

params do
# ...
end
end
## 3
rule(hogwarts_student: :parents_owl_id).validate(:owl_id_format)

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-schema 1.3.4

# ...
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)
end
end
Custom Predicates dry-schema 1.3.4

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

Custom Error Messages dry-validation 0.13
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"

Custom Error Messages dry-validation 1.3.1
config.messages.load_paths << 'somewhere/custom_error_messages.yml'
end
en:
dry_validation:
errors:
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"

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

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

Configuration parameters dry-validation 1.3.1
# external dependencies
# predicates as macros
end
MyContract.new(
# list of validators
)

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

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

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

Dry-validation update. Dry-validation vs Dry-schema 1.0 - Aleksandra Stolyar | Ruby Meditation 29

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

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

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:

Dry-validation update. Dry-validation vs Dry-schema 1.0 - Aleksandra Stolyar | Ruby Meditation 29

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