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https://github.com/nxt-insurance/nxt_schema

A schema that suits them all
https://github.com/nxt-insurance/nxt_schema

dry-rb dry-types dry-validations params schema validations

Last synced: 6 months ago
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A schema that suits them all

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README 

        
# NxtSchema



## Installation



Add this line to your application's Gemfile:



```ruby

gem 'nxt_schema'

```



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install nxt_schema



## What is it for?



NxtSchema is a type coercion and validation framework that allows you to coerce and validate arbitrary nested 

structures of data. The original idea is taken from https://dry-rb.org/gems/dry-schema and 

https://dry-rb.org/gems/dry-validation from the amazing dry.rb eco system. In contrast to dry-schema, 

NxtSchema aims to be a simpler solution that hopefully is easier to understand and debug. 

It also ships with some handy features that dry-schema does not implement. 



### Usage



```ruby

PERSON = NxtSchema.schema(:person) do

  node(:first_name, :String)

  node(:last_name, :String)

  node(:email, :String, optional: true).validate(:includes, '@')

end



input = {

  first_name: 'Ändy',

  last_name: 'Robecke',

  email: '[email protected]'

}



result = PERSON.apply(input: input)



result.valid? # => true

result.output # => input

```  



### Nodes



A schema consists of a number of nodes. Every node has a name and an associated type for casting it's input when the 

schema is applied. Schemas can consist of 4 different kinds of nodes: 



```ruby

NxtSchema::Node::Schema # => Hash of values 

NxtSchema::Node::Collection # => Array of values

NxtSchema::Node::AnyOf # => Any of the defined schemas

NxtSchema::Node::Leaf # => Node without sub nodes

```



The kind of node dictates how the schema is applied to the input. On the root level the following methods are available

to create schemas:



```ruby

  NxtSchema.schema { ... } # => Creates a schema node 

  NxtSchema.collection { ... } # => Creates an array of nodes

  NxtSchema.any_of { ... } # => Creates a collection of allowed schemas

```



#### Node predicate aliases



Of course these nodes can be combined and nested in arbitrary manner. When defining nodes within a schema, nodes are 

always required per default. You can create nodes with the node method or several useful helper methods. 



```ruby

NxtSchema.schema(:person) do

  required(:first_name, :String) # => same as node(:first_name, :String)

  optional(:last_name, :String) # => same as node(:first_name, :String, optional: true)

  omnipresent(:email, :String) # => same as node(:first_name, :String, omnipresent: true)

end

```



**NOTE: The methods above only apply to the keys of your schema and do not make any assumptions about values!**



In other word this means that making a node optional only makes your node optional. When your input contains the key but

the value is nil, you will still get an error in case there is no default or maybe expression that applies. Omnipresent

node also only inject the node into the schema but do not inject a default value. In order to inject a key with value 

into a schema you also have to combine the node predicates with default value method described below. For clarification

check out the examples below:



```ruby

# Optional node without default value



schema = NxtSchema.schema(:person) do

  optional(:email, :String)

end



result = schema.apply(input: { email: nil })

result.errors # => {"person.email"=>["nil violates constraints (type?(String, nil) failed)"]}

result.output # => {:email=>nil}



result = schema.apply(input: {})

result.errors # => {}

result.output # => {}

```



```ruby

# Optional node with default value



schema = NxtSchema.schema(:person) do

  optional(:email, :String).default('[email protected]')

end



result = schema.apply(input: { email: nil })

result.errors # => {}

result.output # => {:email=>"[email protected]"}



result = schema.apply(input: {})

result.errors # => {}

result.output # => {}

```



```ruby

# Omnipresent node without default value



schema = NxtSchema.schema(:person) do

  omnipresent(:email, :String)

end



result = schema.apply(input: {})

result.errors # => {}

result.output # => {:email=>NxtSchema::Undefined}

```



```ruby

# Omnipresent node with default value and maybe expression to allow default value to break type contract.



schema = NxtSchema.schema(:person) do

  omnipresent(:email, :String).default(nil).maybe(:nil?)

end



result = schema.apply(input: {})

result.errors # => {}

result.output # => {:email=>nil}



result = schema.apply(input: { email: '[email protected]' })

result.errors # => {}

result.output # => {:email=>"[email protected]"}

```



##### Conditionally optional nodes



You can also pass a proc as the optional option. This is a shortcut for adding a validation to the parent node 

that will result in a validation error in case the optional condition does not apply and the parent node does not 

contain a sub node with that name (here contact schema not including an email node). 



```ruby

schema = NxtSchema.schema(:contact) do

  required(:first_name, :String)

  required(:last_name, :String)

  node(:email, :String, optional: ->(node) { node.up[:last_name].input == 'Robecke' })

end



result = schema.apply(input: { first_name: 'Andy', last_name: 'Other' })

result.errors # => {"contact"=>["Required key :email is missing"]}



result = schema.apply(input: { first_name: 'Andy', last_name: 'Robecke' })

result.errors # => {}

```  



#### Combining Schemas



You can also simply reuse a schema by passing it to the node method as the type of a node. When doing so the schema 

will be cloned with the same options and configuration as the schema passed in. 



```ruby

ADDRESS = NxtSchema.schema(:address) do

  required(:street, :String)

  required(:town, :String)

  required(:zip_code, :String)

end 



PERSON = NxtSchema.schema(:person) do

  required(:first_name, :String)

  required(:last_name, :String)

  optional(:address, ADDRESS)

end

```



### Types



The type system is built with dry-types from the amazing https://dry-rb.org eco system. Even though dry-types also

offers features such as default values for types as well as maybe types, these features are built directly into 

NxtSchema. 



In NxtSchema every node has a type and you can either provide a symbol that will be resolved 

through the type system of the schema or you can directly provide an instance of dry type and thus use your 

custom types. This means you can basically build any kind of objects such as structs and models from your data and 

you are not limited to just hashes arrays and primitives.  



#### Default type system



You can tell your schema which default type system it should use. Dry-Types comes with a few built in type systems.

Per default NxtSchema will use nominal types if not specified otherwise. If the type cannot be resolved from the default

type system that was specified NxtSchema will always fallback to nominal types. In theory you can provide

a separate type system per node if that's what you need. 

                               

```ruby

NxtSchema.schema do

  required(:test, :String) # The :String will resolve to NxtSchema::Types::Nominal::String

end



NxtSchema.schema(type_system: NxtSchema::Types::JSON) do

  required(:test, :Date) # The :Date will resolve to NxtSchema::Types::JSON::Date

  # When the type does not exist in the default type system (there is non JSON::String) we fallback to nominal types

  required(:test, :String) 

end

```



#### NxtSchema.params



NxtSchema.params will give you a schema as root node with NxtSchema::Types::Params as default type system.

This is suitable to validate and coerce your query params. 



```ruby

NxtSchema.params do

  required(:effective_at, :DateTime) # would resolve to Types::Params::DateTime 

  required(:test, :String) # The :String will resolve to NxtSchema::Types::Nominal::String

  required(:advanced, NxtSchema::Types::Registry::Bool) # long version of required(:advanced, :Bool)

end

```



#### NxtSchema::Registry



To make use of NxtSchema.params in your controller you can simply include the `NxtSchema::Registry` to easily register 

and apply schemas: 



```ruby

class UsersController < ApplicationController

  include NxtSchema::Registry

  

  # register the schema for the :create action

  schemas.register(

    :create, 

    NxtSchema.params do

      required(:first_name, :String)

      required(:last_name, :String)

    end

  )

  

  def create

    User.create!(**create_params) 

  end

  

  private



  def create_params

    # apply the registered schema  

    schemas.apply!(:create, params.fetch(:user))

  end

end



```



#### Custom types



You can also register custom types. In order to check out all the cool things you can do with dry types you should 

check out dry-types on https://dry-rb.org. But here is how you can add a type to the `NxtSchema::Types` module. 



```ruby

NxtSchema.register_type(

  :MyCustomStrippedString,

  NxtSchema::Types::Strict::String.constructor(->(string) { string&.strip })

)



# once registered you can use the type in your schema



NxtSchema.schema(:company) do

  required(:name, :MyCustomStrippedString)

end

```



### Values



#### Default values



```ruby

# Define default values with the default method

required(:test, :DateTime).default(nil)

required(:test, :DateTime).default(-> { Time.current })

```



#### Maybe values 



With maybe expressions you can halt coercion and allow your values to break the type contract. 

**Note: This means that your output will simply be set to the input without coercing the value!**



```ruby

# Define maybe values (values that do not match the type)

required(:test, :String).maybe(:nil?)



nodes(:tests).maybe(:empty?) do # will allow the collection to be empty and thus not contain strings

  required(:test, :String)

end



```  



### Validations



NxtSchema comes with a simple validation system and ships with a small set of useful validators. Every node in a schema

implements the `:validate` method. Similar to ActiveModel::Validations it allows you to simply add errors to a node

based on some condition. When the node is yielded to your validation proc you have access to the nodes input with

`node.input` and `node.index` when the node is within a collection of nodes as well as `node.name`. Furthermore you have 

access to the context that was passed in when defining the schema or passed to the apply method later.



**NOTE: Validations only run when no maybe expression applies and the node input could be coerced successfully**



```ruby

  # Simple custom validation

  required(:test, :String).validate(-> (node) { node.add_error("#{node.input} is not valid") if node.input == 'not allowed' })

  # Built in validations

  required(:test, :String).validate(:attribute, :size, ->(s) { s < 7 }) 

  required(:test, :String).validate(:equal_to, 'same') 

  required(:test, :String).validate(:excluded_in, %w[not_allowed]) # excluded in the target: %w[not_allowed]

  required(:test, :String).validate(:included_in, %w[allowed]) # included in the target: %w[allowed]

  required(:test, :Array).validate(:excludes, 'excluded') # array value itself must exclude 'excluded' 

  required(:test, :Array).validate(:includes, 'included') # array value itself must include 'included'

  required(:test, :Integer).validate(:greater_than, 1) 

  required(:test, :Integer).validate(:greater_than_or_equal, 1) 

  required(:test, :Integer).validate(:less_than, 1) 

  required(:test, :Integer).validate(:less_than_or_equal, 1) 

  required(:test, :String).validate(:pattern, /\A.*@.*\z/) 

  required(:test, :String).validate(:query, :present?) 

```



#### Custom validators



You can also register your custom validators. Therefore you can simply implement a class that returns a lambda on build.

This lambda will be called with the node the validations runs on and it's input value. Except this, you are free in 

how your validator can be used. Check out the specs for some examples. 



```ruby

class MyCustomExclusionValidator

  def initialize(target)

    @target = target

  end



  attr_reader :target



  def build

    lambda do |node, value|

      if target.exclude?(value)

        true

      else

        node.add_error("#{target} should not contain #{value}")

        false # validators must return false in the bad case (add_error already does this as per default)

      end

    end

  end

end



# Register your validators  

NxtSchema.register_validator(MyCustomExclusionValidator, :my_custom_exclusion_validator)



# and then simply reference it with the key you've registered it

schema = NxtSchema.schema(:company) do

  requires(:name, :String).validate(:my_custom_exclusion_validator, %w[lemonade])

end



schema.apply(name: 'lemonade').valid? # => false

```



#### Validation messages



- Allow to specify a path to translations

- Add translated errors

- Interpolate with actual vs. expected 



#### Combining validators



`node(:test, String).validate(...)` basically adds a validator to the node. Of course you can add multiple validators.

But that means that they will all be executed. If you want your validator to only run in case 

another was false, you can use `:validat_with do ... end` in order to combine validators based on custom logic. 



 ```ruby

NxtSchema.schema do

  required(:test, :Integer).validate_with do

    validator(:greater_than, 5) &&

      validator(:greater_than, 6) ||

      validator(:greater_than, 7)

  end

end

```



Note that this will not run subsequent validators once one was valuated to false and thus might not contain all error 

messages of all validators that would have failed.  



### Schema options

 

#### Optional keys strategies



Schemas in NxtSchema only look at the keys that you have defined in your schema, others are ignored per default.

You can change this behaviour by providing a strategy for the `:additional_keys` option. 



```ruby

# This will simply ignore any other key except test 

NxtSchema.schema(additional_keys: :ignore) do

  required(:test, :String) 

end



# This would give you an error in case you apply anything other than { test: '...' }

NxtSchema.schema(additional_keys: :restrict) do

  required(:test, :String) 

end



# This will merge other keys into your output

schema = NxtSchema.schema(additional_keys: :allow) do

  required(:test, :String) 

end



schema.apply(input: {test: 'getsafe', other: 'Heidelberg'})

schema.valid? # => true

schema.value # => { test: 'getsafe', other: 'Heidelberg' }

```



#### Transform keys



To transform the keys of your output simply specify the transform_output_keys option. This might be useful

when you want your schema to return only symbolized keys for example. 



```ruby

schema = NxtSchema.schema(transform_output_keys: ->(key) { key.to_sym }) do

  required(:test, :String)

end



schema.apply(input: { 'test' => 'getsafe' }) # => {:test=>"getsafe"}

schema.apply(input: { test: 'getsafe' }) # => {:test=>"getsafe"}

``` 



#### Adding meta data to nodes



You want to give nodes an ID or some other meta data? You can use the meta method on nodes for adding additional 

information onto any node.  



```ruby

schema = NxtSchema.schema do

  ERROR_MESSAGES = {

    test: 'This is always broken'

  }



  required(:test, :String).meta(ERROR_MESSAGES).validate ->(node) { node.add_error(node.meta.fetch(node.name)) }

end



schema.apply(input: { test: 'getsafe' }) 

schema.error #  {"root.test"=>["This is always broken"]}

```



#### Contexts



When defining a schema it is possible to pass in a context option. This can be anything that you would like to access

during building your schema. A context could provide custom validators or default values depending of the name of your

nodes for instance.  



##### Build time



```ruby

context = OpenStruct.new(email_validator: ->(node) { node.input && node.input.includes?('@') }) 



NxtSchema.schema(:developers, context: context) do

  required(:first_name, :String)

  required(:last_name, :String)

  required(:email, :String).validate(context.email_validator)

end

```



##### Apply time



You can also pass in a context at apply time. If you do not pass in a specific 

context at apply time you can still access the context passed in at build time. 

Basically passing in a context at apply time will overwrite the context from before. You can access it simply through

the node.  



```ruby

build_context = OpenStruct.new(email_validator: ->(node) { node.input.includes?('@') })

apply_context = OpenStruct.new(default_role: 'BOSS')



schema = NxtSchema.schema(:developers, context: build_context) do

  # context at build time

  required(:email, :String).validate(context.email_validator) # 

  # access the context at apply time through the node 

  required(:role, :String).default { |_, node| node.context.default_role }

end



schema.apply(input: input, context: apply_context)

```



## Development



After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.



To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).



## Contributing



Bug reports and pull requests are welcome on GitHub at https://github.com/getand.



## License



The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).



## TODO:



- Explain node interface

- Add apply! method to readme

- Allow to disable validation when applying 

    --> Are there attributes that should be moved to apply time?

- Should we have a global and a local registry for validators?

    --> Would be cool to register things for the schema only

    --> Would be cool if this was extendable 

- Do we need all off in order to combine multiple schemas?

- Allow custom errors

- Spec inheritance of params