[Field trial params] Getting field trial params by feature name in Java.

chrome/browser/android/chrome_feature_list.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/chrome_feature_list.h"
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/android/jni_string.h"
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial_params.h"
 #include "chrome/common/chrome_features.h"
 #include "components/autofill/core/browser/autofill_experiments.h"
 #include "components/ntp_snippets/features.h"
 #include "components/offline_pages/core/offline_page_feature.h"
 #include "components/password_manager/core/common/password_manager_features.h"
 #include "content/public/common/content_features.h"
 #include "jni/ChromeFeatureList_jni.h"
 
 using base::android::ConvertJavaStringToUTF8;
+using base::android::ConvertUTF8ToJavaString;
 using base::android::JavaParamRef;
+using base::android::ScopedJavaLocalRef;
 
 namespace chrome {
 namespace android {
 
 namespace {
 
 // Array of features exposed through the Java ChromeFeatureList API. Entries in
 // this array may either refer to features defined in the header of this file or
 // in other locations in the code base (e.g. chrome/, components/, etc).
 const base::Feature* kFeaturesExposedToJava[] = {
@@ skipping 30 matching lines @@
     &ntp_snippets::kIncreasedVisibility,
     &ntp_snippets::kForeignSessionsSuggestionsFeature,
     &ntp_snippets::kOfflineBadgeFeature,
     &ntp_snippets::kSaveToOfflineFeature,
     &offline_pages::kBackgroundLoaderForDownloadsFeature,
     &offline_pages::kOfflinePagesCTFeature,  // See crbug.com/620421.
     &offline_pages::kOfflinePagesSharingFeature,
     &password_manager::features::kViewPasswords,
 };
 
+const base::Feature* FindFeatureExposedToJava(const std::string& feature_name) {
+  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
+    if (kFeaturesExposedToJava[i]->name == feature_name)
+      return kFeaturesExposedToJava[i];
+  }
+  return nullptr;
+}
+
 }  // namespace
 
 // Alphabetical:
 const base::Feature kAndroidPayIntegrationV1{"AndroidPayIntegrationV1",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kAndroidPayIntegrationV2{"AndroidPayIntegrationV2",
                                              base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kAndroidPaymentApps{"AndroidPaymentApps",
@@ skipping 59 matching lines @@
 
 const base::Feature kWebPaymentsSingleAppUiSkip{
     "WebPaymentsSingleAppUiSkip", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kWebVRCardboardSupport{
     "WebVRCardboardSupport", base::FEATURE_ENABLED_BY_DEFAULT};
 
 static jboolean IsEnabled(JNIEnv* env,
                           const JavaParamRef<jclass>& clazz,
                           const JavaParamRef<jstring>& jfeature_name) {
-  const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
-  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
-    if (kFeaturesExposedToJava[i]->name == feature_name)
-      return base::FeatureList::IsEnabled(*kFeaturesExposedToJava[i]);
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr)
+    return base::FeatureList::IsEnabled(*feature);
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();

[Bernhard Bauer, 2017/02/09 17:04:29]

The NOTREACHED() made sense in the old version where the compiler requires a
return value, but here you have a check, and then code that handles when the
check fails, which is not allowed per the style guide. Just DCHECK(feature) and
return base::FeatureList::IsEnabled(*feature).

[jkrcal, 2017/02/09 19:10:40]

Ah, sure! Thanks!

I've moved the DCHECK into the helper function to make it even crisper.

+  return false;
+}
+
+static ScopedJavaLocalRef<jstring> GetFieldTrialParamByFeature(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name) {
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    std::string param_value =
+        base::GetFieldTrialParamValueByFeature(*feature, param_name);
+    return ConvertUTF8ToJavaString(env, param_value);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();
-  return false;
+  return ConvertUTF8ToJavaString(env, std::string());
 }
 
 static jint GetFieldTrialParamByFeatureAsInt(
     JNIEnv* env,
     const JavaParamRef<jclass>& clazz,
     const JavaParamRef<jstring>& jfeature_name,
     const JavaParamRef<jstring>& jparam_name,
     const jint jdefault_value) {
-  const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
-  const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
-  int default_value = static_cast<int>(jdefault_value);
-
-  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
-    if (kFeaturesExposedToJava[i]->name == feature_name)
-      return base::GetFieldTrialParamByFeatureAsInt(
-          *kFeaturesExposedToJava[i], param_name, default_value);
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsInt(*feature, param_name,
+                                                  jdefault_value);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();
+  return jdefault_value;
+}
+
+static jdouble GetFieldTrialParamByFeatureAsDouble(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name,
+    const jdouble jdefault_value) {
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsDouble(*feature, param_name,
+                                                     jdefault_value);
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
+  return jdefault_value;
+}
+
+static jboolean GetFieldTrialParamByFeatureAsBoolean(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name,
+    const jboolean jdefault_value) {
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsBool(*feature, param_name,
+                                                   jdefault_value);
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
   return jdefault_value;
 }
 
 bool RegisterChromeFeatureListJni(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace chrome