fix: remove afterPass throttling (#1901)

lighthouse-core/gather/driver.js

@@ -696,15 +696,16 @@ class Driver {
   }
 
   setThrottling(flags, passConfig) {
-    const p = [];
-    if (passConfig.useThrottling) {
-      if (!flags.disableNetworkThrottling) p.push(emulation.enableNetworkThrottling(this));
-      if (!flags.disableCpuThrottling) p.push(emulation.enableCPUThrottling(this));
-    } else {
-      p.push(emulation.disableNetworkThrottling(this));
-      p.push(emulation.disableCPUThrottling(this));
-    }
-    return Promise.all(p);
+    const throttleCpu = passConfig.useThrottling && !flags.disableCpuThrottling;
+    const throttleNetwork = passConfig.useThrottling && !flags.disableNetworkThrottling;
+    const cpuPromise = throttleCpu ?
+        emulation.enableCPUThrottling(this) :
+        emulation.disableCPUThrottling(this);
+    const networkPromise = throttleNetwork ?
+        emulation.enableNetworkThrottling(this) :
+        emulation.disableNetworkThrottling(this);
+
+    return Promise.all([cpuPromise, networkPromise]);
   }
 
   /**

lighthouse-core/gather/gather-runner.js

@@ -47,7 +47,7 @@ const URL = require('../lib/url-shim');
  *       c. navigate to options.url (and wait for onload)
  *     ii. all gatherer's pass()
  *   C. GatherRunner.afterPass()
- *     i. endTrace (if requested) & endNetworkCollect
+ *     i. endTrace (if requested) & endNetworkCollect & endThrottling
  *     ii. all gatherer's afterPass()
  *
  * 3. Teardown
@@ -244,6 +244,9 @@ class GatherRunner {
       log.verbose('statusEnd', status);
     });
 
+    // Disable throttling so the afterPass analysis isn't throttled
+    pass = pass.then(_ => driver.setThrottling(options.flags, {useThrottling: false}));
+
     pass = gatherers.reduce((chain, gatherer) => {
       const status = `Retrieving: ${gatherer.name}`;
       return chain.then(_ => {

lighthouse-core/test/gather/gather-runner-test.js

@@ -177,8 +177,8 @@ describe('GatherRunner', function() {
       calledNetworkEmulation: false,
       calledCpuEmulation: false,
     };
-    const createEmulationCheck = variable => () => {
-      tests[variable] = true;
+    const createEmulationCheck = variable => (...args) => {
+      tests[variable] = args;
       return true;
     };
     const driver = getMockedEmulationDriver(
@@ -192,9 +192,11 @@ describe('GatherRunner', function() {
         disableNetworkThrottling: true,
       }
     }).then(_ => {
-      assert.equal(tests.calledDeviceEmulation, true);
-      assert.equal(tests.calledNetworkEmulation, false);
-      assert.equal(tests.calledCpuEmulation, true);
+      assert.ok(tests.calledDeviceEmulation, 'called device emulation');
+      assert.deepEqual(tests.calledNetworkEmulation, [{
+        latency: 0, downloadThroughput: 0, uploadThroughput: 0, offline: false
+      }]);
+      assert.ok(tests.calledCpuEmulation, 'called CPU emulation');
     });
   });
 
@@ -204,8 +206,8 @@ describe('GatherRunner', function() {
       calledNetworkEmulation: false,
       calledCpuEmulation: false,
     };
-    const createEmulationCheck = variable => () => {
-      tests[variable] = true;
+    const createEmulationCheck = variable => (...args) => {
+      tests[variable] = args;
       return true;
     };
     const driver = getMockedEmulationDriver(
@@ -219,9 +221,9 @@ describe('GatherRunner', function() {
         disableCpuThrottling: true,
       }
     }).then(_ => {
-      assert.equal(tests.calledDeviceEmulation, true);
-      assert.equal(tests.calledNetworkEmulation, true);
-      assert.equal(tests.calledCpuEmulation, false);
+      assert.ok(tests.calledDeviceEmulation, 'called device emulation');
+      assert.ok(tests.calledNetworkEmulation, 'called network emulation');
+      assert.deepEqual(tests.calledCpuEmulation, [{rate: 1}]);
     });
   });