Add Forcing Flag Support to Fieldtrial Testing Configurations

This allows experiments to specify a command line that will override
the default experiment order and immediately select that experiment
instead.

BUG=637095

Review-Url: https://codereview.chromium.org/2420013003
Cr-Commit-Position: refs/heads/master@{#426005}

chrome/common/variations/fieldtrial_testing_config_schema.json

@@ -41,6 +41,10 @@
                 "field": "disable_features",
                 "type": "array",
                 "contents": { "type": "string"}
+              },
+              {
+                "field": "forcing_flag",
+                "type": "string"
               }
             ]
           }

chrome/common/variations/variations_util.cc

@@ -9,6 +9,7 @@
 #include <string>
 #include <vector>
 
+#include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_split.h"
@@ -61,6 +62,26 @@ void AssociateParamsFromExperiment(
   }
 }
 
+// Chooses an experiment taking into account the command line. Defaults to
+// picking the first experiment.
+const FieldTrialTestingExperiment& ChooseExperiment(
+    const FieldTrialTestingExperiment experiments[],
+    size_t experiment_size) {
+  DCHECK_GT(experiment_size, 0ul);
+  const auto& command_line = *base::CommandLine::ForCurrentProcess();
+  size_t chosen_index = 0;
+  for (size_t i = 1; i < experiment_size && chosen_index == 0; ++i) {
+    const auto& experiment = experiments[i];
+    if (experiment.forcing_flag &&
+        command_line.HasSwitch(experiment.forcing_flag)) {
+      chosen_index = i;
+      break;
+    }
+  }
+  DCHECK_GT(experiment_size, chosen_index);
+  return experiments[chosen_index];
+}
+
 } // namespace
 
 bool AssociateParamsFromString(const std::string& varations_string) {
@@ -116,7 +137,9 @@ void AssociateParamsFromFieldTrialConfig(const FieldTrialTestingConfig& config,
     const FieldTrialTestingStudy& study = config.studies[i];
     if (study.experiments_size > 0) {
       AssociateParamsFromExperiment(
-          study.name, study.experiments[0], feature_list);
+          study.name,
+          ChooseExperiment(study.experiments, study.experiments_size),
+          feature_list);
     } else {
       DLOG(ERROR) << "Unexpected empty study: " << study.name;
     }

chrome/common/variations/variations_util_unittest.cc

@@ -7,6 +7,7 @@
 #include <memory>
 #include <utility>
 
+#include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
@@ -18,7 +19,7 @@ namespace chrome_variations {
 
 class VariationsUtilTest : public ::testing::Test {
  public:
-  VariationsUtilTest() : field_trial_list_(NULL) {}
+  VariationsUtilTest() : field_trial_list_(nullptr) {}
 
   ~VariationsUtilTest() override {
     // Ensure that the maps are cleared between tests, since they are stored as
@@ -61,13 +62,16 @@ TEST_F(VariationsUtilTest, AssociateParamsFromFieldTrialConfig) {
   const FieldTrialTestingExperimentParams array_kFieldTrialConfig_params_0[] =
       {{"x", "1"}, {"y", "2"}};
   const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_0[] = {
-      {"TestGroup1", array_kFieldTrialConfig_params_0, 2, NULL, 0, NULL, 0},
+      {"TestGroup1", array_kFieldTrialConfig_params_0, 2, nullptr, 0,
+       nullptr, 0, nullptr},
   };
   const FieldTrialTestingExperimentParams array_kFieldTrialConfig_params_1[] =
       {{"x", "3"}, {"y", "4"}};
   const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_1[] = {
-      {"TestGroup2", array_kFieldTrialConfig_params_0, 2, NULL, 0, NULL, 0},
-      {"TestGroup2-2", array_kFieldTrialConfig_params_1, 2, NULL, 0, NULL, 0},
+      {"TestGroup2", array_kFieldTrialConfig_params_0, 2, nullptr, 0,
+       nullptr, 0, nullptr},
+      {"TestGroup2-2", array_kFieldTrialConfig_params_1, 2, nullptr, 0,
+       nullptr, 0, nullptr},
   };
   const FieldTrialTestingStudy array_kFieldTrialConfig_studies[] = {
       {"TestTrial1", array_kFieldTrialConfig_experiments_0, 1},
@@ -103,11 +107,11 @@ TEST_F(VariationsUtilTest, AssociateFeaturesFromFieldTrialConfig) {
   const char* disable_features[] = {"C", "D"};
 
   const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_0[] = {
-      {"TestGroup1", NULL, 0, enable_features, 2, NULL, 0},
+      {"TestGroup1", nullptr, 0, enable_features, 2, nullptr, 0, nullptr},
   };
   const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_1[] = {
-      {"TestGroup2", NULL, 0, NULL, 0, disable_features, 2},
-      {"TestGroup2-2", NULL, 0, NULL, 0, NULL, 0},
+      {"TestGroup2", nullptr, 0, nullptr, 0, disable_features, 2, nullptr},
+      {"TestGroup2-2", nullptr, 0, nullptr, 0, nullptr, 0, nullptr},
   };
 
   const FieldTrialTestingStudy array_kFieldTrialConfig_studies[] = {
@@ -137,4 +141,37 @@ TEST_F(VariationsUtilTest, AssociateFeaturesFromFieldTrialConfig) {
   EXPECT_TRUE(base::FieldTrialList::IsTrialActive("TestTrial2"));
 }
 
+TEST_F(VariationsUtilTest, AssociateForcingFlagsFromFieldTrialConfig) {
+  const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_0[] = {
+      {"TestGroup1", nullptr, 0, nullptr, 0, nullptr, 0, nullptr}
+  };
+  const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_1[] = {
+      {"TestGroup2", nullptr, 0, nullptr, 0, nullptr, 0, nullptr},
+      {"ForcedGroup2", nullptr, 0, nullptr, 0, nullptr, 0, "flag-2"},
+  };
+  const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_2[] = {
+      {"TestGroup3", nullptr, 0, nullptr, 0, nullptr, 0, nullptr},
+      {"ForcedGroup3", nullptr, 0, nullptr, 0, nullptr, 0, "flag-3"},
+      {"ForcedGroup3-2", nullptr, 0, nullptr, 0, nullptr, 0, "flag-3-2"},
+  };
+  const FieldTrialTestingStudy array_kFieldTrialConfig_studies[] = {
+      {"TestTrial1", array_kFieldTrialConfig_experiments_0, 1},
+      {"TestTrial2", array_kFieldTrialConfig_experiments_1, 2},
+      {"TestTrial3", array_kFieldTrialConfig_experiments_2, 3},
+  };
+  const FieldTrialTestingConfig kConfig = {
+      array_kFieldTrialConfig_studies, 3
+  };
+
+  base::CommandLine::ForCurrentProcess()->AppendSwitch("flag-2");
+  base::CommandLine::ForCurrentProcess()->AppendSwitch("flag-3");
+
+  base::FeatureList feature_list;
+  AssociateParamsFromFieldTrialConfig(kConfig, &feature_list);
+
+  EXPECT_EQ("TestGroup1", base::FieldTrialList::FindFullName("TestTrial1"));
+  EXPECT_EQ("ForcedGroup2", base::FieldTrialList::FindFullName("TestTrial2"));
+  EXPECT_EQ("ForcedGroup3", base::FieldTrialList::FindFullName("TestTrial3"));
+}
+
 }  // namespace chrome_variations

testing/variations/PRESUBMIT.py

@@ -14,6 +14,7 @@
 from collections import OrderedDict
 
 VALID_EXPERIMENT_KEYS = ['name',
+                         'forcing_flag',
                          'params',
                          'enable_features',
                          'disable_features',
@@ -50,6 +51,7 @@ def PrettyPrint(contents):
   #             'groups': [
   #                 {
   #                     name: ...
+  #                     forcing_flag: "forcing flag string"
   #                     params: {sorted dict}
   #                     enable_features: [sorted features]
   #                     disable_features: [sorted features]
@@ -78,6 +80,8 @@ def PrettyPrint(contents):
           if comment_key in experiment:
             ordered_experiment[comment_key] = experiment[comment_key]
         ordered_experiment['name'] = experiment['name']
+        if 'forcing_flag' in experiment:
+          ordered_experiment['forcing_flag'] = experiment['forcing_flag']
         if 'params' in experiment:
           ordered_experiment['params'] = OrderedDict(
               sorted(experiment['params'].items(), key=lambda t: t[0]))

tools/variations/fieldtrial_to_struct.py

@@ -37,6 +37,9 @@ def _LoadFieldTrialConfig(filename, platform):
 
 def _CreateExperiment(experiment_data):
   experiment = {'name': experiment_data['name']}
+  forcing_flags_data = experiment_data.get('forcing_flag')
+  if forcing_flags_data:
+    experiment['forcing_flag'] = forcing_flags_data
   params_data = experiment_data.get('params')
   if (params_data):
     experiment['params'] = [{'key': param, 'value': params_data[param]}

tools/variations/fieldtrial_to_struct_unittest.py

@@ -42,6 +42,17 @@ def test_FieldTrialToDescription(self):
           'platforms': ['win'],
           'experiments': [{'name': 'OtherGroup'}]
         }
+      ],
+      'TrialWithForcingFlag':  [
+        {
+          'platforms': ['win'],
+          'experiments': [
+            {
+              'name': 'ForcedGroup',
+              'forcing_flag': "my-forcing-flag"
+            }
+          ]
+        }
       ]
     }
     result = fieldtrial_to_struct._FieldTrialConfigToDescription(config, 'win')
@@ -76,6 +87,15 @@ def test_FieldTrialToDescription(self):
               'name': 'Trial2',
               'experiments': [{'name': 'OtherGroup'}]
             },
+            {
+              'name': 'TrialWithForcingFlag',
+              'experiments': [
+                  {
+                    'name': 'ForcedGroup',
+                    'forcing_flag': "my-forcing-flag"
+                  }
+              ]
+            },
           ]
         }
       }

tools/variations/unittest_data/expected_output.cc

@@ -10,6 +10,18 @@
 #include "test_output.h"
 
 
+const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_2[] = {
+    {
+      "ForcedGroup",
+      NULL,
+      0,
+      NULL,
+      0,
+      NULL,
+      0,
+      "my-forcing-flag",
+    },
+};
 const char* const array_kFieldTrialConfig_enable_features_1[] = {
       "X",
 };
@@ -22,6 +34,7 @@ const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_1[] = {
       1,
       NULL,
       0,
+      NULL,
     },
 };
 const char* const array_kFieldTrialConfig_disable_features_0[] = {
@@ -67,6 +80,7 @@ const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_0[] = {
       2,
       array_kFieldTrialConfig_disable_features,
       1,
+      NULL,
     },
     {
       "TestGroup2-2",
@@ -76,6 +90,7 @@ const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments_0[] = {
       2,
       array_kFieldTrialConfig_disable_features_0,
       1,
+      NULL,
     },
 };
 const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments[] = {
@@ -87,6 +102,7 @@ const FieldTrialTestingExperiment array_kFieldTrialConfig_experiments[] = {
       0,
       NULL,
       0,
+      NULL,
     },
 };
 const FieldTrialTestingStudy array_kFieldTrialConfig_studies[] = {
@@ -105,8 +121,13 @@ const FieldTrialTestingStudy array_kFieldTrialConfig_studies[] = {
     array_kFieldTrialConfig_experiments_1,
     1,
   },
+  {
+    "TrialWithForcingFlag",
+    array_kFieldTrialConfig_experiments_2,
+    1,
+  },
 };
 const FieldTrialTestingConfig kFieldTrialConfig = {
   array_kFieldTrialConfig_studies,
-  3,
+  4,
 };

tools/variations/unittest_data/expected_output.h

@@ -26,6 +26,7 @@ struct FieldTrialTestingExperiment {
   const size_t enable_features_size;
   const char* const * disable_features;
   const size_t disable_features_size;
+  const char* const forcing_flag;
 };
 
 struct FieldTrialTestingStudy {

tools/variations/unittest_data/test_config.json

@@ -35,5 +35,16 @@
       "platforms": ["win"],
       "experiments": [{"name": "TestGroup3", "enable_features": ["X"]}]
     }
+  ],
+  "TrialWithForcingFlag":  [
+    {
+      "platforms": ["win"],
+      "experiments": [
+        {
+          "name": "ForcedGroup",
+          "forcing_flag": "my-forcing-flag"
+        }
+      ]
+    }
   ]
 }