feat: new Terminal type (Papooch#26)

* feat: new Terminal type

* test: fix types test

README.md

@@ -431,6 +431,20 @@ declare module 'nestjs-cls' {
 }
 ```
 
+It can happen, that the object you want to store in the context is too complex, or contains cyclic references. In that case, typescript might complain that _type instantiation is too deep, possibly infinite_. That is due to the fact that it tries to generate all possible paths inside the store. If that's the case, you can use the `Terminal` type to stop generating the paths for a certain subtree:
+
+```ts
+interface ClsStore {
+    tenantId: string;
+    user: Terminal<{
+        id: number;
+        authorized: boolean;
+    }>;
+}
+```
+
+This will only generate the paths `tenantId | user` and won't allow directly accessing nested keys (like `cls.get('user.id')`, but you'll still get fully typing for things like `const { id } = cls.get('user')`). See issue #22 for more details.
+
 # API
 
 ## Service interface

src/lib/cls.service.spec.ts

@@ -1,4 +1,5 @@
 import { Test, TestingModule } from '@nestjs/testing';
+import { Terminal } from '../types/recursive-key-of.type';
 import { ClsServiceManager } from './cls-service-manager';
 import { CLS_DEFAULT_NAMESPACE, CLS_ID } from './cls.constants';
 import { ClsStore } from './cls.interfaces';
@@ -137,6 +138,10 @@ describe('ClsService', () => {
                     f: Array<string>;
                 };
                 g: Map<string, number>;
+                h: Terminal<{
+                    i: string;
+                    j: number;
+                }>;
             };
         }
 
@@ -153,6 +158,7 @@ describe('ClsService', () => {
                 typedService.set('b.d.e', false);
                 typedService.set('b.d.f', ['x']);
                 typedService.set('b.g', new Map());
+                typedService.set('b.h', { i: 'i', j: 1 });
 
                 const { a, b } = typedService.get();
                 a;
@@ -164,6 +170,9 @@ describe('ClsService', () => {
                 typedService.get('b.d.e');
                 typedService.get('b.d.f')[0];
                 typedService.get('b.g').get('x');
+                const { i, j } = typedService.get('b.h');
+                i;
+                j;
             });
         });
     });

src/types/recursive-key-of.type.ts

@@ -1,4 +1,4 @@
-type Terminal =
+type TerminalType =
     | string
     | number
     | bigint
@@ -10,8 +10,15 @@ type Terminal =
     | Set<any>
     | Date
     | RegExp
+    | BrandedTerminal
     | ((...args: any) => any);
 
+const TERMINAL_BRAND = Symbol();
+class BrandedTerminal {
+    private [TERMINAL_BRAND]?: void;
+}
+export type Terminal<T> = T & BrandedTerminal;
+
 /**
  * Deep nested keys of an interface with dot syntax
  *
@@ -21,7 +28,7 @@ type Terminal =
 export type RecursiveKeyOf<
     T,
     Prefix extends string = never,
-> = T extends Terminal
+> = T extends TerminalType
     ? never
     : {
           [K in keyof T & string]: [Prefix] extends [never]