Merge pull request #466 from dry-rb/infer-nested-structs

Infer types from nested structs (fixes #464)

Gemfile

@@ -28,8 +28,8 @@ group :tools do
 end
 
 group :benchmarks do
-  gem "actionpack", "~> 5.0"
-  gem "activemodel", "~> 5.0"
+  gem "actionpack"
+  gem "activemodel"
   gem "benchmark-ips"
   gem "hotch", platform: :mri
   gem "virtus"

lib/dry/schema/extensions/struct.rb

@@ -5,20 +5,42 @@
 module Dry
   module Schema
     module Macros
+      class StructToSchema < ::Dry::Struct::Compiler
+        def call(struct)
+          visit(struct.to_ast)
+        end
+
+        # strip away structs from AST
+        def visit_struct(node)
+          _, ast = node
+          visit(ast)
+        end
+      end
+
+      Hash.option :struct_compiler, default: proc { StructToSchema.new(schema_dsl.config.types) }
+
       Hash.prepend(::Module.new {
         def call(*args)
-          if args.size >= 1 && args[0].is_a?(::Class) && args[0] <= ::Dry::Struct
+          if args.size >= 1 && struct?(args[0])
             if block_given?
               raise ArgumentError, "blocks are not supported when using "\
                                    "a struct class (#{name.inspect} => #{args[0]})"
             end
 
-            super(args[0].schema, *args.drop(1))
-            type(schema_dsl.types[name].constructor(args[0].schema))
+            schema = struct_compiler.(args[0])
+
+            super(schema, *args.drop(1))
+            type(schema_dsl.types[name].constructor(schema))
           else
             super
           end
         end
+
+        private
+
+        def struct?(type)
+          type.is_a?(::Class) && type <= ::Dry::Struct
+        end
       })
     end
 

spec/extensions/struct_spec.rb

@@ -47,6 +47,38 @@
         )
       end
     end
+
+    context "complex struct" do
+      let(:struct) do
+        Class.new(Dry::Struct) do
+          attribute :name, Types::String
+          attribute :addresses, Types::Array do
+            attribute  :city,   Types::String
+            attribute? :street, Types::String
+          end
+        end
+      end
+
+      context "with valid input" do
+        let(:input) do
+          {foo: {name: "Jane", addresses: [{city: "New York"}]}}
+        end
+
+        it "has no errors" do
+          expect(schema.(input).errors.to_h).to eq({})
+        end
+      end
+
+      context "with empty nested array" do
+        let(:input) do
+          {foo: {name: "Jane", addresses: []}}
+        end
+
+        it "has no errors" do
+          expect(schema.(input).errors.to_h).to eq({})
+        end
+      end
+    end
   end
 
   context "value macro" do