Added ContextNode, refactored with_context, cast_errors and structure…

… cleaning (#3)

* Fix merge message keys
* Extracted ContextNode
* Refactored with_context to new ContextNode
* Refactored cast_errors to ContextNode

---------

Co-authored-by: Pavel Egorov <[email protected]>

README.md

@@ -1221,7 +1221,10 @@ schema =
 
 schema.(user_id: 'wrong')  # => #<Datacaster::ErrorResult({:user_id=>["must be integer"]})>
 ```
-any instance of `Datacaster` can be passed to `.cast_errors`
+
+`.cast_errors` will extract errors from the `ErrorResult` and provide them as hash value for the provided caster. If that caster returns `ErrorResult`, runtime exception is raised. If that caster returns `ValidResult`, it is packed back into `ErrorResult` and returned.
+
+Any instance of `Datacaster` can be passed to `.cast_errors`.
 
 
 ## Registering custom 'predefined' types

datacaster.gemspec

@@ -27,4 +27,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec', '~> 3.0'
 
   spec.add_runtime_dependency 'dry-monads', '>= 1.3', '< 1.4'
+  spec.add_runtime_dependency 'zeitwerk', '>= 2', '< 3'
 end

lib/datacaster.rb

@@ -1,41 +1,23 @@
+require 'zeitwerk'
+loader = Zeitwerk::Loader.for_gem
+loader.inflector.inflect('definition_dsl' => 'DefinitionDSL')
+loader.setup
+
 require_relative 'datacaster/result'
-require_relative 'datacaster/version'
-
-require_relative 'datacaster/absent'
-require_relative 'datacaster/base'
-require_relative 'datacaster/predefined'
-require_relative 'datacaster/definition_context'
-require_relative 'datacaster/terminator'
-require_relative 'datacaster/config'
-
-require_relative 'datacaster/array_schema'
-require_relative 'datacaster/caster'
-require_relative 'datacaster/checker'
-require_relative 'datacaster/comparator'
-require_relative 'datacaster/hash_mapper'
-require_relative 'datacaster/hash_schema'
-require_relative 'datacaster/message_keys_merger'
-require_relative 'datacaster/transformer'
-require_relative 'datacaster/trier'
-
-require_relative 'datacaster/and_node'
-require_relative 'datacaster/and_with_error_aggregation_node'
-require_relative 'datacaster/or_node'
-require_relative 'datacaster/then_node'
 
 module Datacaster
   extend self
 
   def schema(&block)
-    build_schema(Terminator::Raising.instance, &block)
+    ContextNodes::StructureCleaner.new(build_schema(&block), :fail)
   end
 
   def choosy_schema(&block)
-    build_schema(Terminator::Sweeping.instance, &block)
+    ContextNodes::StructureCleaner.new(build_schema(&block), :remove)
   end
 
   def partial_schema(&block)
-    build_schema(nil, &block)
+    ContextNodes::StructureCleaner.new(build_schema(&block), :pass)
   end
 
   def absent
@@ -44,19 +26,15 @@ def absent
 
   private
 
-  def build_schema(terminator, &block)
+  def build_schema(&block)
     raise "Expected block" unless block
 
-    definition_context = DefinitionContext.new
-
-    datacaster = definition_context.instance_exec(&block)
+    datacaster = DefinitionDSL.eval(&block)
 
     unless datacaster.is_a?(Base)
       raise "Datacaster instance should be returned from a block (e.g. result of 'hash_schema(...)' call)"
     end
 
-    datacaster = (datacaster & terminator) if terminator
-    datacaster.set_definition_context(definition_context)
     datacaster
   end
 end

lib/datacaster/and_node.rb

@@ -5,13 +5,11 @@ def initialize(left, right)
       @right = right
     end
 
-    def cast(object)
-      object = super(object)
-
-      left_result = @left.(object)
+    def cast(object, runtime:)
+      left_result = @left.with_runtime(runtime).(object)
       return left_result unless left_result.valid?
 
-      @right.(left_result)
+      @right.with_runtime(runtime).(left_result.value)
     end
 
     def inspect

lib/datacaster/and_with_error_aggregation_node.rb

@@ -7,14 +7,13 @@ def initialize(left, right)
 
     # Works like AndNode, but doesn't stop at first error — in order to aggregate all Failures
     # Makes sense only for Hash Schemas
-    def cast(object)
-      object = super(object)
-      left_result = @left.(object)
+    def cast(object, runtime:)
+      left_result = @left.with_runtime(runtime).(object)
 
       if left_result.valid?
-        @right.(left_result)
+        @right.with_runtime(runtime).(left_result.value)
       else
-        right_result = @right.(object)
+        right_result = @right.with_runtime(runtime).(object)
         if right_result.valid?
           left_result
         else

lib/datacaster/array_schema.rb

@@ -1,28 +1,24 @@
 module Datacaster
   class ArraySchema < Base
     def initialize(element_caster)
-      # support of shortcut nested validation definitions, e.g. array_schema({a: [integer], b: {c: integer}})
-      @element_caster = shortcut_definition(element_caster)
+      @element_caster = element_caster
     end
 
-    def cast(object)
-      object = super(object)
-      checked_schema = object.meta[:checked_schema] || []
-
-      array = object.value
-
+    def cast(array, runtime:)
       return Datacaster.ErrorResult(["must be array"]) if !array.respond_to?(:map) || !array.respond_to?(:zip)
       return Datacaster.ErrorResult(["must not be empty"]) if array.empty?
 
+      runtime.will_check!
+
       result =
-        array.zip(checked_schema).map do |x, schema|
-          x = Datacaster.ValidResult(x, meta: {checked_schema: schema})
-          @element_caster.(x)
+        array.map.with_index do |x, i|
+          runtime.checked_key!(i) do
+            @element_caster.with_runtime(runtime).(x)
+          end
         end
 
       if result.all?(&:valid?)
-        checked_schema = result.map { |x| x.meta[:checked_schema] }
-        Datacaster.ValidResult(result.map(&:value), meta: {checked_schema: checked_schema})
+        Datacaster.ValidResult(result.map!(&:value))
       else
         Datacaster.ErrorResult(result.each.with_index.reject { |x, _| x.valid? }.map { |x, i| [i, x.errors] }.to_h)
       end

lib/datacaster/base.rb

@@ -1,5 +1,3 @@
-require "ostruct"
-
 module Datacaster
   class Base
     def self.merge_errors(left, right)
@@ -43,66 +41,41 @@ def *(other)
       AndWithErrorAggregationNode.new(self, other)
     end
 
-    def then(other)
-      ThenNode.new(self, other)
+    def cast_errors(error_caster)
+      ContextNodes::ErrorsCaster.new(self, error_caster)
     end
 
-    def set_definition_context(definition_context)
-      @definition_context = definition_context
+    def then(other)
+      ThenNode.new(self, other)
     end
 
-    def with_context(additional_context)
-      @definition_context.context = OpenStruct.new(additional_context)
-      self
+    def with_context(context)
+      unless context.is_a?(Hash)
+        raise "with_context expected Hash as argument, got #{context.inspect} instead"
+      end
+      ContextNodes::UserContext.new(self, context)
     end
 
     def call(object)
-      object = cast(object)
-
-      return object if object.valid? || @cast_errors.nil?
-
-      error_cast = @cast_errors.(object.errors)
-
-      raise "#cast_errors must return Datacaster.ValidResult, currently it is #{error_cast.inspect}" unless error_cast.valid?
+      call_with_runtime(object, Runtime.new)
+    end
 
-      Datacaster.ErrorResult(
-        @cast_errors.(object.errors).value,
-        meta: object.meta
-      )
+    def call_with_runtime(object, runtime)
+      result = cast(object, runtime: runtime)
+      unless result.is_a?(Result)
+        raise RuntimeError.new("Caster should've returned Datacaster::Result, but returned #{result.inspect} instead")
+      end
+      result
     end
 
-    def cast_errors(object)
-      @cast_errors = shortcut_definition(object)
-      self
+    def with_runtime(runtime)
+      ->(object) do
+        call_with_runtime(object, runtime)
+      end
     end
 
     def inspect
       "#<Datacaster::Base>"
     end
-
-    private
-
-    def cast(object)
-      Datacaster.ValidResult(object)
-    end
-
-    # Translates hashes like {a: <IntegerChecker>} to <HashSchema {a: <IntegerChecker>}>
-    #   and arrays like [<IntegerChecker>] to <ArraySchema <IntegerChecker>>
-    def shortcut_definition(definition)
-      case definition
-      when Datacaster::Base
-        definition
-      when Array
-        if definition.length != 1
-          raise ArgumentError.new("Datacaster: shortcut array definitions must have exactly 1 element in the array, e.g. [integer]")
-        end
-        ArraySchema.new(definition.first)
-      when Hash
-        HashSchema.new(definition)
-      else
-        return definition if definition.respond_to?(:call)
-        raise ArgumentError.new("Datacaster: Unknown definition #{definition.inspect}, which doesn't respond to #call")
-      end
-    end
   end
 end

lib/datacaster/caster.rb

@@ -7,11 +7,8 @@ def initialize(name, &block)
       @cast = block
     end
 
-    def cast(object)
-      intermediary_result = super(object)
-      object = intermediary_result.value
-
-      result = @cast.(object)
+    def cast(object, runtime:)
+      result = Runtime.(runtime, @cast, object)
 
       raise TypeError.new("Either Datacaster::Result or Dry::Monads::Result " \
         "should be returned from cast block") unless [Datacaster::Result, Dry::Monads::Result].any? { |k| result.is_a?(k) }

lib/datacaster/checker.rb

@@ -8,11 +8,8 @@ def initialize(name, error, &block)
       @check = block
     end
 
-    def cast(object)
-      intermediary_result = super(object)
-      object = intermediary_result.value
-
-      if @check.(object)
+    def cast(object, runtime:)
+      if Runtime.(runtime, @check, object)
         Datacaster.ValidResult(object)
       else
         Datacaster.ErrorResult([@error])

lib/datacaster/comparator.rb

@@ -6,10 +6,7 @@ def initialize(value, name, error = nil)
       @error = error || "must be equal to #{value.inspect}"
     end
 
-    def cast(object)
-      intermediary_result = super(object)
-      object = intermediary_result.value
-
+    def cast(object, runtime:)
       if @value == object
         Datacaster.ValidResult(object)
       else

lib/datacaster/context_node.rb

@@ -0,0 +1,43 @@
+module Datacaster
+  class ContextNode < Base
+    def initialize(base)
+      @base = base
+    end
+
+    def cast(object, runtime:)
+      @runtime = create_runtime(runtime)
+      result = @base.with_runtime(@runtime).call(object)
+      transform_result(result)
+    end
+
+    def inspect
+      "#<Datacaster::ContextNode base: #{@base.inspect}>"
+    end
+
+    private
+
+    def create_runtime(parent)
+      parent
+    end
+
+    def runtime
+      @runtime
+    end
+
+    def transform_result(result)
+      if result.valid?
+        Datacaster.ValidResult(transform_success(result.value))
+      else
+        Datacaster.ErrorResult(transform_errors(result.errors))
+      end
+    end
+
+    def transform_success(value)
+      value
+    end
+
+    def transform_errors(errors)
+      errors
+    end
+  end
+end

lib/datacaster/context_nodes/errors_caster.rb

@@ -0,0 +1,21 @@
+module Datacaster
+  module ContextNodes
+    class ErrorsCaster < Datacaster::ContextNode
+      def initialize(base, error_caster)
+        super(base)
+        @caster = error_caster
+      end
+
+      private
+
+      def transform_errors(errors)
+        result = @caster.with_runtime(@runtime).(errors)
+        if result.valid?
+          result.value
+        else
+          raise RuntimeError.new("Error caster tried to cast these errors: #{errors.inspect}, but didn't return ValidResult: #{result.inspect}")
+        end
+      end
+    end
+  end
+end