fix #2589: avoid invoking getter as side-effect (#2592)

of creating restorerer function. Check for the odd case
where we actually force setting a value through accessor
functions and only look up the value at that time.

The alternative would be more elaborate, check if the
descriptor had a `get` or a `value` field, and then
decide, but this should do the trick.

Author: fatso83

lib/sinon/sandbox.js

@@ -243,7 +243,7 @@ function Sandbox(opts = {}) {
      */
     function getFakeRestorer(object, property, forceAssignment = false) {
         const descriptor = getPropertyDescriptor(object, property);
-        const value = object[property];
+        const value = forceAssignment && object[property];
 
         function restorer() {
             if (forceAssignment) {

test/sandbox-test.js

@@ -1296,6 +1296,20 @@ describe("Sandbox", function () {
                 },
             );
         });
+
+        it("do not call getter whilst replacing getter", function () {
+            const sandbox = this.sandbox;
+            const fake = sandbox.fake.returns("bar");
+            const object = {
+                get foo() {
+                    return fake();
+                },
+            };
+
+            sandbox.replaceGetter(object, "foo", () => "replacement");
+
+            refute(fake.called);
+        });
     });
 
     describe(".replaceSetter", function () {