fix(validation): fix path for additional properties validation (#102)

When it fails validating a child, the error path should be for the child key, not the root.

keywords_object.go

@@ -325,14 +325,16 @@ func (ap *AdditionalProperties) ValidateKeyword(ctx context.Context, currentStat
 			if currentState.IsLocallyEvaluatedKey(key) {
 				continue
 			}
-			if ap.schemaType == schemaTypeFalse {
-				currentState.AddError(data, "additional properties are not allowed")
-				return
-			}
+
 			currentState.SetEvaluatedKey(key)
 			subState.ClearState()
 			subState.DescendInstanceFromState(currentState, key)
 
+			if ap.schemaType == schemaTypeFalse {
+				subState.AddError(data, "additional properties are not allowed")
+				return
+			}
+
 			(*Schema)(ap).ValidateKeyword(ctx, subState, obj[key])
 			currentState.UpdateEvaluatedPropsAndItems(subState)
 		}

schema_test.go

@@ -666,6 +666,18 @@ func TestValidateBytes(t *testing.T) {
 				`/1: false type should be string, got boolean`,
 				`/2: type should be string, got null`,
 			}},
+		{`{
+		"type": "object",
+		"properties" : {
+		},
+		"additionalProperties" : false
+	}`,
+			`{
+	"port": 80
+}`,
+			[]string{
+				`/port: {"port":80} additional properties are not allowed`,
+			}},
 	}
 
 	for i, c := range cases {