Fix set utilities for explore section

Discovered implementation issues with the set utilities used in the
explore section after adding some tests. Added tests to reinforce the
expected behaviour of the utility functions.

Related: #13522

public/app/features/explore/utils/set.test.ts

+import { equal, intersect } from './set';
+
+describe('equal', () => {
+  it('returns false for two sets of differing sizes', () => {
+    const s1 = new Set([1, 2, 3]);
+    const s2 = new Set([4, 5, 6, 7]);
+    expect(equal(s1, s2)).toBe(false);
+  });
+  it('returns false for two sets where one is a subset of the other', () => {
+    const s1 = new Set([1, 2, 3]);
+    const s2 = new Set([1, 2, 3, 4]);
+    expect(equal(s1, s2)).toBe(false);
+  });
+  it('returns false for two sets with uncommon elements', () => {
+    const s1 = new Set([1, 2, 3, 4]);
+    const s2 = new Set([1, 2, 5, 6]);
+    expect(equal(s1, s2)).toBe(false);
+  });
+  it('returns false for two deeply equivalent sets', () => {
+    const s1 = new Set([{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]);
+    const s2 = new Set([{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]);
+    expect(equal(s1, s2)).toBe(false);
+  });
+  it('returns true for two sets with the same elements', () => {
+    const s1 = new Set([1, 2, 3, 4]);
+    const s2 = new Set([4, 3, 2, 1]);
+    expect(equal(s1, s2)).toBe(true);
+  });
+});
+
+describe('intersect', () => {
+  it('returns an empty set for two sets without any common elements', () => {
+    const s1 = new Set([1, 2, 3, 4]);
+    const s2 = new Set([5, 6, 7, 8]);
+    expect(intersect(s1, s2)).toEqual(new Set());
+  });
+  it('returns an empty set for two deeply equivalent sets', () => {
+    const s1 = new Set([{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]);
+    const s2 = new Set([{ a: 1 }, { b: 2 }, { c: 3 }, { d: 4 }]);
+    expect(intersect(s1, s2)).toEqual(new Set());
+  });
+  it('returns a set containing common elements between two sets of the same size', () => {
+    const s1 = new Set([1, 2, 3, 4]);
+    const s2 = new Set([5, 2, 7, 4]);
+    expect(intersect(s1, s2)).toEqual(new Set([2, 4]));
+  });
+  it('returns a set containing common elements between two sets of differing sizes', () => {
+    const s1 = new Set([1, 2, 3, 4]);
+    const s2 = new Set([5, 4, 3, 2, 1]);
+    expect(intersect(s1, s2)).toEqual(new Set([1, 2, 3, 4]));
+  });
+});

public/app/features/explore/utils/set.ts

@@ -8,27 +8,28 @@ export function equal<T>(a: Set<T>, b: Set<T>): boolean {
   const it = a.values();
   while (true) {
     const { value, done } = it.next();
-    if (b.has(value)) {
-      return false;
-    }
     if (done) {
       return true;
     }
+    if (!b.has(value)) {
+      return false;
+    }
   }
 }
 
 /**
- * Returns the first set with items in the second set through shallow comparison.
+ * Returns a new set with items in both sets using shallow comparison.
  */
 export function intersect<T>(a: Set<T>, b: Set<T>): Set<T> {
+  const result = new Set<T>();
   const it = b.values();
   while (true) {
     const { value, done } = it.next();
-    if (!a.has(value)) {
-      a.delete(value);
-    }
     if (done) {
-      return a;
+      return result;
+    }
+    if (a.has(value)) {
+      result.add(value);
     }
   }
 }