Delete field_trial::FindFullName

Thus remove support for providing field trials implementation link-time.

Bug: webrtc:42220378
Change-Id: Ifd1240d81485820831195ebb915a3037d7dd8986
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/396880
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#45273}

api/transport/field_trial_based_config.cc

@@ -9,6 +9,7 @@
  */
 #include "api/transport/field_trial_based_config.h"
 
+#include <cstddef>
 #include <string>
 
 #include "absl/strings/string_view.h"
@@ -18,7 +19,35 @@ namespace webrtc {
 std::string FieldTrialBasedConfig::GetValue(absl::string_view key) const {
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
-  return field_trial::FindFullName(std::string(key));
+  const char* global_field_trial_string = field_trial::GetFieldTrialString();
 #pragma clang diagnostic pop
+
+  if (global_field_trial_string == nullptr)
+    return std::string();
+
+  absl::string_view trials_string(global_field_trial_string);
+  if (trials_string.empty())
+    return std::string();
+
+  size_t next_item = 0;
+  while (next_item < trials_string.length()) {
+    // Find next name/value pair in field trial configuration string.
+    size_t field_name_end = trials_string.find('/', next_item);
+    if (field_name_end == trials_string.npos || field_name_end == next_item)
+      break;
+    size_t field_value_end = trials_string.find('/', field_name_end + 1);
+    if (field_value_end == trials_string.npos ||
+        field_value_end == field_name_end + 1)
+      break;
+    absl::string_view field_name =
+        trials_string.substr(next_item, field_name_end - next_item);
+    absl::string_view field_value = trials_string.substr(
+        field_name_end + 1, field_value_end - field_name_end - 1);
+    next_item = field_value_end + 1;
+
+    if (key == field_name)
+      return std::string(field_value);
+  }
+  return std::string();
 }
 }  // namespace webrtc

native-api.md

@@ -84,18 +84,6 @@ You can achieve this by defining the preprocessor macro
 argument `rtc_builtin_ssl_root_certificates` to false and GN will define the
 macro for you.
 
-## `WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT`
-If you want to provide your own implementation of `webrtc::field_trial` functions
-(more info [here][field_trial_h]) you will have to exclude WebRTC's default
-implementation.
-
-You can achieve this by defining the preprocessor macro
-`WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT`. If you use GN, you can just set the GN
-argument `rtc_exclude_field_trial_default` to true and GN will define the
-macro for you.
-
-[field_trial_h]: https://webrtc.googlesource.com/src/+/main/system_wrappers/include/field_trial.h
-
 ## `WEBRTC_EXCLUDE_METRICS_DEFAULT`
 If you want to provide your own implementation of `webrtc::metrics` functions
 (more info [here][metrics_h]) you will have to exclude WebRTC's default

system_wrappers/BUILD.gn

@@ -51,16 +51,10 @@ rtc_library("field_trial") {
     "include/field_trial.h",
     "source/field_trial.cc",
   ]
-  if (rtc_exclude_field_trial_default) {
-    defines = [ "WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT" ]
-  }
   deps = [
-    "../experiments:registered_field_trials",
     "../rtc_base:checks",
     "../rtc_base:logging",
     "../rtc_base:stringutils",
-    "../rtc_base/containers:flat_set",
-    "//third_party/abseil-cpp/absl/algorithm:container",
     "//third_party/abseil-cpp/absl/strings:string_view",
   ]
 }

system_wrappers/include/field_trial.h

@@ -25,14 +25,6 @@
 namespace webrtc {
 namespace field_trial {
 
-// Returns the group name chosen for the named trial, or the empty string
-// if the trial does not exists.
-//
-// Note: To keep things tidy append all the trial names with WebRTC.
-// TODO: bugs.webrtc.org/42220378 - Remove from api after August 1, 2025.
-[[deprecated]]
-std::string FindFullName(absl::string_view name);
-
 // Optionally initialize field trial from a string.
 // This method can be called at most once before any other call into webrtc.
 // E.g. before the peer connection factory is constructed.

system_wrappers/source/field_trial.cc

@@ -15,15 +15,11 @@
 #include <utility>
 #include <vector>
 
-#include "absl/algorithm/container.h"  // IWYU pragma: keep
 #include "absl/strings/string_view.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/string_encode.h"
 
-// Generated file.
-#include "experiments/registered_field_trials.h"  // IWYU pragma: keep
-
 // Simple field trial implementation, which allows client to
 // specify desired flags in InitFieldTrialsFromString.
 namespace webrtc {
@@ -110,48 +106,6 @@ std::string MergeFieldTrialsStrings(absl::string_view first,
   return merged;
 }
 
-#ifndef WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT
-std::string FindFullName(absl::string_view name) {
-#if WEBRTC_STRICT_FIELD_TRIALS == 1
-  RTC_DCHECK(absl::c_linear_search(kRegisteredFieldTrials, name))
-      << name << " is not registered, see g3doc/field-trials.md.";
-#elif WEBRTC_STRICT_FIELD_TRIALS == 2
-  RTC_LOG_IF(LS_WARNING, !absl::c_linear_search(kRegisteredFieldTrials, name))
-      << name << " is not registered, see g3doc/field-trials.md.";
-#endif
-
-  if (trials_init_string == nullptr)
-    return std::string();
-
-  absl::string_view trials_string(trials_init_string);
-  if (trials_string.empty())
-    return std::string();
-
-  size_t next_item = 0;
-  while (next_item < trials_string.length()) {
-    // Find next name/value pair in field trial configuration string.
-    size_t field_name_end =
-        trials_string.find(kPersistentStringSeparator, next_item);
-    if (field_name_end == trials_string.npos || field_name_end == next_item)
-      break;
-    size_t field_value_end =
-        trials_string.find(kPersistentStringSeparator, field_name_end + 1);
-    if (field_value_end == trials_string.npos ||
-        field_value_end == field_name_end + 1)
-      break;
-    absl::string_view field_name =
-        trials_string.substr(next_item, field_name_end - next_item);
-    absl::string_view field_value = trials_string.substr(
-        field_name_end + 1, field_value_end - field_name_end - 1);
-    next_item = field_value_end + 1;
-
-    if (name == field_name)
-      return std::string(field_value);
-  }
-  return std::string();
-}
-#endif  // WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT
-
 // Optionally initialize field trial from a string.
 void InitFieldTrialsFromString(const char* trials_string) {
   RTC_LOG(LS_INFO) << "Setting field trial string:" << trials_string;

test/fuzzers/BUILD.gn

@@ -19,10 +19,9 @@ rtc_library("webrtc_fuzzer_main") {
   ]
 
   # When WebRTC fuzzer tests are built on Chromium bots they need to link
-  # with Chromium's implementation of metrics, field trial, and system time.
+  # with Chromium's implementation of metrics and system time.
   if (build_with_chromium) {
     deps += [
-      "../../../webrtc_overrides:field_trial",
       "../../../webrtc_overrides:metrics",
       "../../../webrtc_overrides:system_time",
     ]

webrtc.gni

@@ -69,18 +69,9 @@ declare_args() {
   # annotated symbols.
   rtc_enable_objc_symbol_export = rtc_enable_symbol_export
 
-  # Setting this to true will define WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT which
-  # will tell the pre-processor to remove the default definition of symbols
-  # needed to use field_trial. In that case a new implementation needs to be
-  # provided.
-  if (build_with_chromium) {
-    # When WebRTC is built as part of Chromium it should exclude the default
-    # implementation of field_trial unless it is building for NACL or
-    # Chromecast.
-    rtc_exclude_field_trial_default = !is_nacl && !is_castos && !is_cast_android
-  } else {
-    rtc_exclude_field_trial_default = false
-  }
+  # Deprecated, this flag has no effect.
+  # TODO: bugs.webrtc.org/42220378 - Delete after August 15, 2025.
+  rtc_exclude_field_trial_default = false
 
   # Setting this to true will define WEBRTC_EXCLUDE_METRICS_DEFAULT which
   # will tell the pre-processor to remove the default definition of symbols