fix: #3614 avoid unnecessary parentheses for complex values of a unit

Author: josdejong

src/type/unit/Unit.js

@@ -1,6 +1,7 @@
 import { isComplex, isUnit, typeOf } from '../../utils/is.js'
 import { factory } from '../../utils/factory.js'
 import { memoize } from '../../utils/function.js'
+import { nearlyEqual } from '../../utils/number.js'
 import { endsWith } from '../../utils/string.js'
 import { clone, hasOwnProperty } from '../../utils/object.js'
 import { createBigNumberPi as createPi } from '../../utils/bignumber/constants.js'
@@ -1175,7 +1176,12 @@ export const createUnitClass = /* #__PURE__ */ factory(name, dependencies, ({
   Unit.prototype.format = function (options) {
     const { simp, valueStr, unitStr } = formatBest(this, options)
     let str = valueStr
-    if (simp.value && isComplex(simp.value)) {
+    if (
+      simp.value &&
+      isComplex(simp.value) &&
+      !nearlyEqual(simp.value.re, 0) &&
+      !nearlyEqual(simp.value.im, 0)
+    ) {
       str = '(' + str + ')' // Surround complex values with ( ) to enable better parsing
     }
     if (unitStr.length > 0 && str.length > 0) {

test/unit-tests/type/unit/Unit.test.js

@@ -771,14 +771,17 @@ describe('Unit', function () {
 
     it('should format a Complex unit', function () {
       assert.strictEqual(new Unit(math.complex(-2, 4.5), 'mm').format(14), '(-2 + 4.5i) mm')
+      assert.strictEqual(new Unit(math.complex(1), 'kW').format(14), '1 kW')
+      assert.strictEqual(new Unit(math.complex(0, 1), 'kW').format(14), 'i kW')
+      assert.strictEqual(new Unit(math.complex(0, 2), 'kW').format(14), '2i kW')
     })
 
     it('should format units with VA and VAR correctly', function () {
       assert.strictEqual(math.evaluate('4000 VAR + 3000 VA').format(), '(3 + 4i) kVA')
       assert.strictEqual(math.evaluate('3000 VA + 4000 VAR').format(), '(3 + 4i) kVA')
-      assert.strictEqual(math.evaluate('4000 VAR').format(), '(4) kVAR')
-      assert.strictEqual(math.evaluate('4000i VA').format(), '(4) kVAR')
-      assert.strictEqual(math.evaluate('4000i VAR').format(), '(-4) kVA')
+      assert.strictEqual(math.evaluate('4000 VAR').format(), '4 kVAR')
+      assert.strictEqual(math.evaluate('4000i VA').format(), '4 kVAR')
+      assert.strictEqual(math.evaluate('4000i VAR').format(), '-4 kVA')
       assert.strictEqual(math.evaluate('abs(4000 VAR + 3000 VA)').format(), '5 kW')
       assert.strictEqual(math.evaluate('abs(3000 VA + 4000 VAR)').format(), '5 kW')
       assert.strictEqual(math.evaluate('abs(4000 VAR)').format(), '4 kW')