feat: Identity serialiser

src/core.ts

@@ -29,6 +29,11 @@ export function defaultSerialiser(...args: any[]): string {
   return JSON.stringify(args);
 }
 
+/** @internal */
+export function identitySerialiser<T>(value: T): T {
+  return value;
+}
+
 interface Memoised<T, A extends any[], R> extends Fn<T, A, R> {
   [MEMOISE_CACHE]: Cache;
 }

src/index.ts

@@ -1,6 +1,13 @@
 import type {Cache} from './cache';
 import type {Decorator, SerialiserFn} from './core';
-import {applyDecorator, defaultSerialiser, MEMOISE_CACHE, memoiseArglessFunction, memoiseFunction} from './core';
+import {
+  applyDecorator,
+  defaultSerialiser,
+  identitySerialiser,
+  MEMOISE_CACHE,
+  memoiseArglessFunction,
+  memoiseFunction
+} from './core';
 
 /**
  * Memoise the method's return value based on call arguments
@@ -15,7 +22,20 @@ function MemoiseAll<T, R>(): Decorator<T, [], R> {
   return applyDecorator(false);
 }
 
-export {Memoise, MemoiseAll, MEMOISE_CACHE, defaultSerialiser, memoiseArglessFunction, memoiseFunction};
+/** Memoise based on the 1st argument */
+function MemoiseIdentity<T, A, R>(): Decorator<T, [A], R> {
+  return applyDecorator(true, identitySerialiser);
+}
+
+export {
+  Memoise,
+  MemoiseAll,
+  MemoiseIdentity,
+  MEMOISE_CACHE,
+  defaultSerialiser,
+  memoiseArglessFunction,
+  memoiseFunction
+};
 export type {SerialiserFn, Cache};
 
 declare global {

src/test.ts

@@ -1,5 +1,6 @@
 import {expect} from 'chai';
 import type {Cache} from './index';
+import {MemoiseIdentity} from './index';
 import {Memoise, MEMOISE_CACHE, MemoiseAll, memoiseArglessFunction, memoiseFunction} from './index';
 
 /* eslint-disable @typescript-eslint/no-magic-numbers,class-methods-use-this,max-lines-per-function,no-new,max-lines */
@@ -664,3 +665,22 @@ describe('Memoised functions', () => {
     expect(r1).to.not.eq(r4, 'r1 !== r4');
   });
 });
+
+describe('identity', () => {
+  class Src {
+    @MemoiseIdentity()
+    static foo(x: number) {
+      return {x};
+    }
+  }
+
+  const c1 = Src.foo(1);
+  const c2 = Src.foo(1);
+  const c3 = Src.foo(0);
+  const c4 = Src.foo(0);
+
+  expect(c1).to.deep.eq({x: 1});
+  expect(c3).to.deep.eq({x: 0});
+  expect(c1).to.eq(c2, 'c1 === c2');
+  expect(c3).to.eq(c4, 'c3 === c4');
+});