Work around not having the default empty object value from TS constru…

…ctor anymore

src/common/default-value.ts

@@ -0,0 +1,17 @@
+const get = (type: any) => Reflect.getMetadata(key, type) ?? {};
+
+const set =
+  (value: any): PropertyDecorator =>
+  ({ constructor: type }, propertyKey) =>
+    Reflect.defineMetadata(key, { ...get(type), [propertyKey]: value }, type);
+
+/**
+ * A helper to get/set default values for classes.
+ * Usage of this is discouraged in favor or more common practices.
+ * This is mostly useful with abstractions.
+ * Note that the defaults aren't automatically applied, this just holds
+ * a container for them - They need to be fetched explicitly.
+ */
+export const DefaultValue = { Get: get, Set: set };
+
+const key = 'DefaultValue';

src/common/filter-field.ts

@@ -3,6 +3,7 @@ import { Field } from '@nestjs/graphql';
 import { Transform, Type } from 'class-transformer';
 import { ValidateNested } from 'class-validator';
 import { HasRequiredKeys } from 'type-fest';
+import { DefaultValue } from './default-value';
 import { AbstractClassType } from './types';
 
 /**
@@ -23,10 +24,11 @@ export const FilterField = <T extends object>(
       : [
           Field(() => type, {
             nullable: true,
-            defaultValue: {},
+            defaultValue: {}, // Only for GQL schema & not always applied in TS
           }),
         ]),
     Type(() => type),
     ValidateNested(),
-    Transform(({ value }) => value || {})
+    DefaultValue.Set({}), // Default when omitted
+    Transform(({ value }) => value || {}) // null -> {}
   );

src/common/pagination.input.ts

@@ -3,6 +3,7 @@ import { Args, ArgsOptions, Field, InputType, Int } from '@nestjs/graphql';
 import { Matches, Max, Min } from 'class-validator';
 import { stripIndent } from 'common-tags';
 import { DataObject } from './data-object';
+import { DefaultValue } from './default-value';
 import { Order } from './order.enum';
 import { AbstractClassType } from './types';
 
@@ -106,7 +107,7 @@ export const ListArg = <T extends PaginationInput>(
       name: 'input',
       type: () => input,
       nullable: true,
-      defaultValue: DataObject.defaultValue(input),
+      defaultValue: DataObject.defaultValue(input, DefaultValue.Get(input)),
       ...opts,
     },
     ...pipes