JIT evaluation of 'view', 'exclude', 'use', etc so that order doesn't…

… matter

Signed-off-by: Jordan Hollinger <[email protected]>

lib/blueprinter/v2.rb

@@ -3,6 +3,7 @@
 require 'blueprinter/v2/dsl'
 require 'blueprinter/v2/options'
 require 'blueprinter/v2/reflection'
+require 'blueprinter/v2/view_builder'
 
 module Blueprinter
   # Base class for V2 Blueprints
@@ -11,26 +12,37 @@ class V2
     extend Reflection
 
     class << self
-      attr_accessor :views, :fields, :partials, :extensions, :options
-      # The fully-qualified name, e.g. "MyBlueprint", or "MyBlueprint.foo.bar"
+      # Options set on this Blueprint
+      attr_accessor :options
+      # Extensions set on this Blueprint
+      attr_accessor :extensions
+      # @api private The fully-qualified name, e.g. "MyBlueprint", or "MyBlueprint.foo.bar"
       attr_accessor :blueprint_name
+      # @api private
+      attr_accessor :views, :fields, :excludes, :partials, :used_partials, :eval_mutex
     end
 
-    self.views = {}
+    self.views = ViewBuilder.new(self)
     self.fields = {}
+    self.excludes = []
     self.partials = {}
+    self.used_partials = []
     self.extensions = []
     self.options = Options.new(DEFAULT_OPTIONS)
     self.blueprint_name = name
+    self.eval_mutex = Mutex.new
 
     # Initialize subclass
     def self.inherited(subclass)
-      subclass.views = { default: subclass }
+      subclass.views = ViewBuilder.new(subclass)
       subclass.fields = fields.transform_values(&:dup)
+      subclass.excludes = []
       subclass.partials = partials.dup
+      subclass.used_partials = []
       subclass.extensions = extensions.dup
       subclass.options = options.dup
       subclass.blueprint_name = subclass.name || blueprint_name
+      subclass.eval_mutex = Mutex.new
     end
 
     # A descriptive name for the Blueprint view, e.g. "WidgetBlueprint.extended"
@@ -44,6 +56,7 @@ def self.to_s
     end
 
     # Append the sub-view name to blueprint_name
+    # @api private
     def self.append_name(name)
       self.blueprint_name = "#{blueprint_name}.#{name}"
     end
@@ -64,6 +77,31 @@ def self.[](view)
       end
     end
 
+    # Apply partials and field exclusions
+    # @api private
+    def self.eval!(lock = true)
+      return if @evaled
+
+      if lock
+        eval_mutex.synchronize { run_eval! unless @evaled }
+      else
+        run_eval!
+      end
+    end
+
+    # @api private
+    def self.run_eval!
+      used_partials.each do |name|
+        if !(p = partials[name])
+          raise Errors::UnknownPartial, "Partial '#{name}' could not be found in Blueprint '#{self}'"
+        end
+        class_eval(&p)
+      end
+
+      excludes.each { |f| fields.delete f }
+      @evaled = true
+    end
+
     # Render the object
     def self.render(obj, options = {})
       new.render(obj, options)

lib/blueprinter/v2/dsl.rb

@@ -12,15 +12,11 @@ module DSL
       #
       # @param name [Symbol] Name of the view
       # @yield Define the view in the block
-      # @return [Class] An annonymous subclass of Blueprinter::V2
       #
       def view(name, &definition)
         raise Errors::InvalidBlueprint, "View name may not contain '.'" if name.to_s =~ /\./
 
-        view = Class.new(self)
-        view.append_name(name)
-        view.class_eval(&definition) if definition
-        views[name.to_sym] = view
+        views[name.to_sym] = definition
       end
 
       #
@@ -39,12 +35,7 @@ def partial(name, &definition)
       # @param name [Array<Symbol>] One or more partial names
       #
       def use(*names)
-        names.each do |name|
-          if !(p = partials[name])
-            raise Errors::UnknownPartial, "Partial '#{name}' could not be found in Blueprint '#{self}'. NOTE: partials must be defined before your views!"
-          end
-          class_eval(&p)
-        end
+        names.each { |name| used_partials << name.to_sym }
       end
 
       #
@@ -97,16 +88,7 @@ def association(name, blueprint, from: name, view: nil, **options, &definition)
       # @param name [Array<Symbol>] One or more fields or associations to exclude
       #
       def exclude(*names)
-        unknown = []
-        names.each do |name|
-          name_sym = name.to_sym
-          if fields.key? name_sym
-            fields.delete name_sym
-          else
-            unknown << name.to_s
-          end
-        end
-        raise Errors::InvalidBlueprint, "Unknown excluded fields in '#{self}': #{unknown.join(', ')}" if unknown.any?
+        self.excludes += names.map(&:to_sym)
       end
     end
   end

lib/blueprinter/v2/reflection.rb

@@ -7,33 +7,27 @@ module Blueprinter
   class V2
     # API for reflecting on Blueprints
     module Reflection
-      def self.extended(klass)
-        klass.class_eval do
-          private_class_method :flatten_children
-        end
-      end
-
       #
       # Returns a Hash of views keyed by name.
       #
       # @return [Hash<Symbol, Blueprinter::V2::Reflection::View>]
       #
       def reflections
+        eval! unless @evaled
         @reflections ||= flatten_children(self, :default)
       end
 
       # Builds a flat Hash of nested views
+      # @api private
       def flatten_children(parent, child_name, path = [])
         ref_key = path.empty? ? child_name : path.join('.').to_sym
         child_view = parent.views.fetch(child_name)
         child_ref = View.new(child_view, ref_key)
 
-        child_view.views.
-          except(:default).
-          reduce({ ref_key => child_ref }) do |acc, (name, _)|
-            children = flatten_children(child_view, name, path + [name])
-            acc.merge(children)
-          end
+        child_view.views.reduce({ ref_key => child_ref }) do |acc, (name, _)|
+          children = name == :default ? {} : flatten_children(child_view, name, path + [name])
+          acc.merge(children)
+        end
       end
 
       #
@@ -47,6 +41,10 @@ class View
         # @return [Hash<Symbol, Blueprinter::V2::Association>] Associations defined on the view
         attr_reader :associations
 
+
+        # @param blueprint [Class] A subclass of Blueprinter::V2
+        # @param name [Symbol] Name of the view
+        # @api private
         def initialize(blueprint, name)
           @name = name
           @fields = blueprint.fields.select { |_, f| f.is_a? Field }

lib/blueprinter/v2/view_builder.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module Blueprinter
+  class V2
+    #
+    # A Hash-like class that defers evaluation of "view" blocks until they're accessed.
+    # This allows things like a parent's fields and partials to be defined AFTER views
+    # and have inheritance still work as expected.
+    #
+    class ViewBuilder
+      include Enumerable
+
+      # @param parent [Class] A subclass of Blueprinter::V2
+      def initialize(parent)
+        @parent = parent
+        @views = { default: parent }
+        @pending = {}
+        @mut = Mutex.new
+      end
+
+      #
+      # Add a view definition.
+      #
+      # @param name [Symbol]
+      # @param definition [Proc]
+      #
+      def []=(name, definition)
+        @pending[name.to_sym] = definition
+      end
+
+      #
+      # Return, and build if necessary, the view.
+      #
+      # @param name [Symbol] Name of the view
+      # @return [Class] An anonymous subclass of @parent
+      #
+      def [](name)
+        name = name.to_sym
+        if !@views.key?(name) and @pending.key?(name)
+          @mut.synchronize do
+            next if @views.key?(name)
+
+            view = Class.new(@parent, &@pending[name])
+            view.append_name(name)
+            view.eval!(false)
+            @views[name] = view
+          end
+        end
+        @views[name]
+      end
+
+      # Works like Hash#fetch
+      def fetch(name)
+        self[name] || raise(KeyError, "View '#{name}' not found")
+      end
+
+      def each(&block)
+        enum = Enumerator.new do |y|
+          y.yield(:default, self[:default])
+          @pending.each_key { |name| y.yield(name, self[name]) }
+        end
+        block ? enum.each(&block) : enum
+      end
+    end
+  end
+end

spec/v2/declarative_api_spec.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+describe "Blueprinter::V2 Declarative API" do
+  it "should inherit fields defined after the view" do
+    blueprint = Class.new(Blueprinter::V2) do
+      view :desc do
+        field :description
+      end
+
+      field :id
+      field :name
+    end
+
+    refs = blueprint.reflections
+    expect(refs[:desc].fields.keys.sort).to eq %i(id name description).sort
+  end
+
+  it "should include partials defined after the view" do
+    blueprint = Class.new(Blueprinter::V2) do
+      field :name
+
+      view :foo do
+        use :desc
+      end
+
+      partial :desc do
+        field :description
+      end
+    end
+
+    refs = blueprint.reflections
+    expect(refs[:foo].fields.keys.sort).to eq %i(name description).sort
+  end
+
+  it "should include partials defined after the use statement" do
+    blueprint = Class.new(Blueprinter::V2) do
+      field :name
+      use :desc
+
+      partial :desc do
+        field :description
+      end
+    end
+
+    refs = blueprint.reflections
+    expect(refs[:default].fields.keys.sort).to eq %i(name description).sort
+  end
+
+  it "should exclude fields added after the exclude statement" do
+    blueprint = Class.new(Blueprinter::V2) do
+      field :id
+      field :name
+
+      view :foo do
+        exclude :name, :description2, :description3
+        use :desc
+        field :description3
+      end
+
+      partial :desc do
+        field :description
+        field :description2
+      end
+    end
+
+    refs = blueprint.reflections
+    expect(refs[:foo].fields.keys.sort).to eq %i(id description).sort
+  end
+end