.define method (#2539)

* Restore sandbox after each .replace test

Otherwise a failed test may not restore it.

* .define method for temporarily defining new properties during the tests

* better comment

* detailed exception messages

* properly delete the property during the cleanup

* Add .define to more places

* Document .define

* Fix test

* Code review suggestions

* prettier --write

Author: gukoff

docs/release-source/release/sandbox.md

@@ -4,7 +4,7 @@ title: Sandboxes - Sinon.JS
 breadcrumb: sandbox
 ---
 
-Sandboxes removes the need to keep track of every fake created, which greatly simplifies cleanup.
+Sandboxes remove the need to keep track of every fake created, which greatly simplifies cleanup.
 
 ```javascript
 var sandbox = require("sinon").createSandbox();
@@ -181,6 +181,40 @@ A convenience reference for [`sinon.assert`](./assertions)
 
 _Since `[email protected]`_
 
+#### `sandbox.define(object, property, value);`
+
+Defines the `property` on `object` with the value `value`. Attempts to define an already defined value cause an exception.
+
+`value` can be any value except `undefined`, including `spies`, `stubs` and `fakes`.
+
+```js
+var myObject = {};
+
+sandbox.define(myObject, "myValue", function () {
+  return "blackberry";
+});
+
+sandbox.define(myObject, "myMethod", function () {
+  return "strawberry";
+});
+
+console.log(myObject.myValue);
+// blackberry
+
+console.log(myObject.myMethod());
+// strawberry
+
+sandbox.restore();
+
+console.log(myObject.myValue);
+// undefined
+
+console.log(myObject.myMethod);
+// undefined
+```
+
+_Since `[email protected]`_
+
 #### `sandbox.replace(object, property, replacement);`
 
 Replaces `property` on `object` with `replacement` argument. Attempts to replace an already replaced value cause an exception. Returns the `replacement`.

lib/sinon/sandbox.js

@@ -106,6 +106,10 @@ function Sandbox() {
             return sandbox.fake.apply(null, arguments);
         };
 
+        obj.define = function () {
+            return sandbox.define.apply(null, arguments);
+        };
+
         obj.replace = function () {
             return sandbox.replace.apply(null, arguments);
         };
@@ -196,7 +200,7 @@ function Sandbox() {
         const descriptor = getPropertyDescriptor(object, property);
 
         function restorer() {
-            if (descriptor.isOwn) {
+            if (descriptor?.isOwn) {
                 Object.defineProperty(object, property, descriptor);
             } else {
                 delete object[property];
@@ -228,7 +232,7 @@ function Sandbox() {
             throw new TypeError(
                 `Cannot replace non-existent property ${valueToString(
                     property
-                )}`
+                )}. Perhaps you meant sandbox.define()?`
             );
         }
 
@@ -262,6 +266,31 @@ function Sandbox() {
         return replacement;
     };
 
+    sandbox.define = function define(object, property, value) {
+        const descriptor = getPropertyDescriptor(object, property);
+
+        if (descriptor) {
+            throw new TypeError(
+                `Cannot define the already existing property ${valueToString(
+                    property
+                )}. Perhaps you meant sandbox.replace()?`
+            );
+        }
+
+        if (typeof value === "undefined") {
+            throw new TypeError("Expected value argument to be defined");
+        }
+
+        verifyNotReplaced(object, property);
+
+        // store a function for restoring the defined property
+        push(fakeRestorers, getFakeRestorer(object, property));
+
+        object[property] = value;
+
+        return value;
+    };
+
     sandbox.replaceGetter = function replaceGetter(
         object,
         property,

lib/sinon/util/core/default-config.js

@@ -10,6 +10,7 @@ module.exports = {
         "server",
         "requests",
         "fake",
+        "define",
         "replace",
         "replaceSetter",
         "replaceGetter",

test/sandbox-test.js

@@ -807,11 +807,96 @@ describe("Sandbox", function () {
         });
     });
 
+    describe(".define", function () {
+        beforeEach(function () {
+            this.sandbox = createSandbox();
+        });
+
+        afterEach(function () {
+            this.sandbox.restore();
+        });
+
+        it("should define a function property", function () {
+            function newFunction() {
+                return;
+            }
+
+            const object = {};
+
+            this.sandbox.define(object, "property", newFunction);
+
+            assert.equals(object.property, newFunction);
+
+            this.sandbox.restore();
+
+            assert.isUndefined(object.property);
+        });
+
+        it("should define a non-function property", function () {
+            const newValue = "some-new-value";
+            const object = {};
+
+            this.sandbox.define(object, "property", newValue);
+
+            assert.equals(object.property, newValue);
+
+            this.sandbox.restore();
+
+            assert.isUndefined(object.property);
+        });
+
+        it("should error on existing descriptor", function () {
+            const sandbox = this.sandbox;
+
+            const existingValue = "123";
+            const existingFunction = () => "abcd";
+
+            const object = {
+                existingValue: existingValue,
+                existingFunction: existingFunction,
+            };
+
+            assert.exception(
+                function () {
+                    sandbox.define(object, "existingValue", "new value");
+                },
+                {
+                    message:
+                        "Cannot define the already existing property existingValue. Perhaps you meant sandbox.replace()?",
+                    name: "TypeError",
+                }
+            );
+
+            assert.exception(
+                function () {
+                    sandbox.define(
+                        object,
+                        "existingFunction",
+                        () => "new function"
+                    );
+                },
+                {
+                    message:
+                        "Cannot define the already existing property existingFunction. Perhaps you meant sandbox.replace()?",
+                    name: "TypeError",
+                }
+            );
+
+            // Verify that the methods above, even though they failed, did not replace the values
+            assert.equals(object.existingValue, existingValue);
+            assert.equals(object.existingFunction, existingFunction);
+        });
+    });
+
     describe(".replace", function () {
         beforeEach(function () {
             this.sandbox = createSandbox();
         });
 
+        afterEach(function () {
+            this.sandbox.restore();
+        });
+
         it("should replace a function property", function () {
             const replacement = function replacement() {
                 return;
@@ -873,7 +958,7 @@ describe("Sandbox", function () {
                 },
                 {
                     message:
-                        "Cannot replace non-existent property i-dont-exist",
+                        "Cannot replace non-existent property i-dont-exist. Perhaps you meant sandbox.define()?",
                     name: "TypeError",
                 }
             );