Fix exception on older browsers

lib/callable-instance.js

@@ -30,7 +30,9 @@ export const CallableInstance =
 
         for (const p of names) {
           const descriptor = Object.getOwnPropertyDescriptor(value, p)
-          if (descriptor) Object.defineProperty(apply, p, descriptor)
+          if (descriptor && descriptor.configurable) {
+            Object.defineProperty(apply, p, descriptor)
+          }
         }
 
         return apply

package.json

@@ -96,7 +96,10 @@
     "atLeast": 100,
     "detail": true,
     "ignoreCatch": true,
-    "strict": true
+    "strict": true,
+    "ignoreFiles": [
+      "test/*.js"
+    ]
   },
   "xo": {
     "overrides": [

test/callable-instance.js

@@ -0,0 +1,61 @@
+// @ts-nocheck
+import assert from 'node:assert/strict'
+import test from 'node:test'
+import {CallableInstance} from '../lib/callable-instance.js'
+
+test('callable-instance', async function (t) {
+  await t.test('can invoke ES6 class', async function () {
+    class Es6Class extends CallableInstance {
+      constructor() {
+        super('copy')
+
+        this.foo = 42
+        this.bar = 0
+      }
+
+      copy() {
+        const destination = new Es6Class()
+        destination.foo = this.foo
+        destination.bar = this.bar
+        return destination
+      }
+    }
+
+    const instance = new Es6Class()
+    assert.strictEqual(instance.foo, 42)
+
+    instance.bar = 100
+
+    // Instance is callable
+    const copied = instance()
+    assert.strictEqual(copied.foo, 42)
+    assert.strictEqual(copied.bar, 100)
+  })
+
+  await t.test('can invoke new (ES5 class)', async function () {
+    function Es5Class() {
+      const _this = CallableInstance.call(this, ['copy'])
+      return _this
+    }
+
+    Es5Class.prototype.foo = 42
+    Es5Class.prototype.bar = 0
+
+    Es5Class.prototype.copy = function () {
+      const destination = new Es5Class()
+      destination.foo = this.foo
+      destination.bar = this.bar
+      return destination
+    }
+
+    const instance = new Es5Class()
+    assert.strictEqual(instance.foo, 42)
+
+    instance.bar = 100
+
+    // Instance is callable
+    const copied = instance()
+    assert.strictEqual(copied.foo, 42)
+    assert.strictEqual(copied.bar, 100)
+  })
+})

test/index.js

@@ -1,4 +1,5 @@
 /* eslint-disable import/no-unassigned-import */
+import './callable-instance.js'
 import './core.js'
 import './data.js'
 import './freeze.js'