feat: Implement basic general folder support (#2051)

- Related: #1748

tests/cache/equality-cache.test.ts

@@ -0,0 +1,88 @@
+import { describe, expect, it } from 'vitest';
+import { EqualityCache } from '../../src/cache/equality-cache';
+
+interface TestCacheValue {
+  val: number;
+}
+
+describe('EqualityCache', () => {
+  describe('has', () => {
+    it('positive', () => {
+      const cache = new EqualityCache<string, TestCacheValue>();
+      cache.set('test', { val: 2 });
+      expect(cache.has('test')).toBeTruthy();
+    });
+
+    it('negative', () => {
+      const cache = new EqualityCache<string, TestCacheValue>();
+      expect(cache.has('absent')).toBeFalsy();
+    });
+  });
+
+  describe('get', () => {
+    it('positive', () => {
+      const cache = new EqualityCache<string, TestCacheValue>();
+      const original = { val: 2 };
+      cache.set('test', original);
+
+      const replacement = { val: 2 };
+      cache.set('test', replacement);
+
+      expect(cache.get('test')).not.toBe(original);
+      expect(cache.get('test')).toBe(replacement);
+    });
+
+    it('negative', () => {
+      const cache = new EqualityCache<string, TestCacheValue>();
+      expect(cache.get('absent')).toBeNull();
+    });
+  });
+
+  it('delete', () => {
+    const cache = new EqualityCache<string, TestCacheValue>();
+    cache.set('test-1', { val: 1 });
+    cache.set('test-2', { val: 2 });
+    cache.set('test-3', { val: 3 });
+
+    cache.delete('test-2');
+
+    expect(cache.get('test-2')).toBeNull();
+    expect(cache.get('test-1')).toEqual({ val: 1 });
+    expect(cache.get('test-3')).toEqual({ val: 3 });
+  });
+
+  it('clear', () => {
+    const cache = new EqualityCache<string, TestCacheValue>();
+    cache.set('test-1', { val: 1 });
+    cache.set('test-2', { val: 2 });
+    cache.set('test-3', { val: 3 });
+
+    cache.clear();
+
+    expect(cache.get('test-1')).toBeNull();
+    expect(cache.get('test-2')).toBeNull();
+    expect(cache.get('test-3')).toBeNull();
+  });
+
+  it('getMatches', () => {
+    const cache = new EqualityCache<string, TestCacheValue>();
+    cache.set('test-1', { val: 1 });
+    cache.set('test-2', { val: 2 });
+    cache.set('test-3', { val: 3 });
+
+    expect(cache.getMatches((obj) => obj.val >= 2)).toEqual([{ val: 2 }, { val: 3 }]);
+  });
+
+  it('entries', () => {
+    const cache = new EqualityCache<string, TestCacheValue>();
+    cache.set('test-1', { val: 1 });
+    cache.set('test-2', { val: 2 });
+    cache.set('test-3', { val: 3 });
+
+    expect([...cache.entries()]).toEqual([
+      ['test-1', { val: 1 }],
+      ['test-2', { val: 2 }],
+      ['test-3', { val: 3 }],
+    ]);
+  });
+});