feat: Make isEmpty work for Sets (#31)

Author: crgwbr

src/utils/is-empty.ts

@@ -2,6 +2,7 @@ import { isArray } from './is-array';
 import { isString } from './is-string';
 import { isArguments } from './is-arguments';
 import { isUndefined } from './is-undefined';
+import { isSet } from './is-set';
 
 /**
  * Checks if `o` is an empty object. An object is "empty" if it:
@@ -19,6 +20,9 @@ export function isEmpty(o: unknown): boolean {
    if (isArray(o) || isString(o) || isArguments(o)) {
       return o.length === 0;
    }
+   if (isSet(o)) {
+      return o.size === 0;
+   }
    // Non-object arguments passed into Object.keys are coerced into objects (the only
    // exception being undefined or null, which is handled above). Therefore, it's ok to
    // assume the input is an object because it will be once passed through. See also:

tests/utils/is-empty.test.ts

@@ -6,6 +6,7 @@ describe('isEmpty', () => {
 
    it('correctly classifies empty things', () => {
       expect(t.isEmpty([])).to.strictlyEqual(true);
+      expect(t.isEmpty(new Set([]))).to.strictlyEqual(true);
       // eslint-disable-next-line
       expect(t.isEmpty(new Array())).to.strictlyEqual(true);
       expect(t.isEmpty({})).to.strictlyEqual(true);
@@ -41,6 +42,7 @@ describe('isEmpty', () => {
       expect(t.isEmpty({ length: 0 })).to.strictlyEqual(false);
       expect(t.isEmpty([ 1 ])).to.strictlyEqual(false);
       expect(t.isEmpty(new Array(10))).to.strictlyEqual(false);
+      expect(t.isEmpty(new Set([ 1 ]))).to.strictlyEqual(false);
    });
 
 });