Fix duped keys in key coercer and validator

lib/dry/schema/dsl.rb

@@ -437,7 +437,7 @@ def parent_filter_schemas
       #
       # @api private
       def key_validator
-        KeyValidator.new(key_map: key_map + parent_key_map)
+        KeyValidator.new(key_map: key_map)
       end
 
       # Build a key coercer
@@ -446,7 +446,7 @@ def key_validator
       #
       # @api private
       def key_coercer
-        KeyCoercer.symbolized(key_map + parent_key_map)
+        KeyCoercer.symbolized(key_map)
       end
 
       # Build a value coercer

spec/integration/schema/steps_spec.rb

@@ -204,4 +204,24 @@
       }.to raise_error(ArgumentError, /oops/)
     end
   end
+
+  context "with an inherited params" do
+    describe "core step key maps" do
+      it "copies key map from the parent and includes new keys from child" do
+        parent = Dry::Schema.Params do
+          config.validate_keys = true
+
+          required(:name).filled(:string)
+        end
+
+        child = Dry::Schema.Params(parent: parent) do
+          required(:email).filled(:string)
+        end
+
+        %i[key_validator key_coercer].each do |step|
+          expect(child.steps[step].executor.key_map.map(&:name)).to eql(%w[name email])
+        end
+      end
+    end
+  end
 end

spec/integration/schema/unexpected_keys_spec.rb

@@ -150,4 +150,21 @@
       end
     end
   end
+
+  context "with an inherited params" do
+    it "copies key map from the parent and includes new keys from child" do
+      parent = Dry::Schema.Params do
+        config.validate_keys = true
+
+        required(:name).filled(:string)
+      end
+
+      child = Dry::Schema.Params(parent: parent) do
+        required(:email).filled(:string)
+      end
+
+      expect(child.(name: "Jane", email: "[email protected]", unexpected_key: "boo!").errors.to_h)
+        .to eql({unexpected_key: ["is not allowed"]})
+    end
+  end
 end