faking performance when it is not present throws

sinonjs · Sep 16, 2021 · 227160c · 227160c
1 parent aaa8153
commit 227160c
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Showing 2 changed files with 34 additions and 14 deletions.
diff --git a/src/fake-timers-src.js b/src/fake-timers-src.js
@@ -1525,20 +1525,6 @@ function withGlobal(_global) {
 
         if (performancePresent) {
             clock.performance = Object.create(null);
-
-            if (hasPerformancePrototype) {
-                const proto = _global.Performance.prototype;
-
-                Object.getOwnPropertyNames(proto).forEach(function (name) {
-                    if (name.indexOf("getEntries") === 0) {
-                        // match expected return type for getEntries functions
-                        clock.performance[name] = NOOP_ARRAY;
-                    } else {
-                        clock.performance[name] = NOOP;
-                    }
-                });
-            }
-
             clock.performance.now = function FakeTimersNow() {
                 const hrt = hrtime();
                 const millis = hrt[0] * 1000 + hrt[1] / 1e6;
@@ -1613,6 +1599,25 @@ function withGlobal(_global) {
             clock.attachedInterval = intervalId;
         }
 
+        if (clock.methods.includes("performance")) {
+            if (hasPerformancePrototype) {
+                var proto = _global.Performance.prototype;
+                Object.getOwnPropertyNames(proto).forEach(function (name) {
+                    if (name !== "now") {
+                        clock.performance[name] =
+                            name.indexOf("getEntries") === 0
+                                ? NOOP_ARRAY
+                                : NOOP;
+                    }
+                });
+            } else if (config.toFake.includes("performance")) {
+                // user explicitly tried to fake performance when not present
+                throw new ReferenceError(
+                    "non-existent performance object cannot be faked"
+                );
+            }
+        }
+
         for (i = 0, l = clock.methods.length; i < l; i++) {
             const nameOfMethodToReplace = clock.methods[i];
             if (nameOfMethodToReplace === "hrtime") {

diff --git a/test/fake-timers-test.js b/test/fake-timers-test.js
@@ -3700,6 +3700,21 @@ describe("FakeTimers", function () {
             });
         }
 
+        if (!performanceNowPresent) {
+            it("throws when adding performance to tofake array when performance not present", function () {
+                try {
+                    this.clock = FakeTimers.install({
+                        toFake: ["performance"],
+                    });
+                } catch (e) {
+                    const expectedMsg =
+                        "non-existent performance object cannot be faked";
+                    assert(e instanceof ReferenceError);
+                    assert.equals(e.message, expectedMsg);
+                }
+            });
+        }
+
         if (performanceNowPresent) {
             it("replaces global performance.now", function () {
                 this.clock = FakeTimers.install();