Add option to log a warning for unregistered field trials

Until now you only had the option to RTC_DCHECK for unregistered field
trials. This makes it possible to log a warning instead.

Bug: webrtc:14154
Change-Id: I8628054e3c9b5d690f241a93e61299126b732ed0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/295300
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Emil Lundmark <lndmrk@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39417}

BUILD.gn

@@ -276,10 +276,16 @@ config("common_config") {
     defines += [ "WEBRTC_ENABLE_PROTOBUF=0" ]
   }
 
-  if (rtc_strict_field_trials) {
+  if (rtc_strict_field_trials == "") {
-    defines += [ "WEBRTC_STRICT_FIELD_TRIALS=1" ]
-  } else {
     defines += [ "WEBRTC_STRICT_FIELD_TRIALS=0" ]
+  } else if (rtc_strict_field_trials == "dcheck") {
+    defines += [ "WEBRTC_STRICT_FIELD_TRIALS=1" ]
+  } else if (rtc_strict_field_trials == "warn") {
+    defines += [ "WEBRTC_STRICT_FIELD_TRIALS=2" ]
+  } else {
+    assert(false,
+           "Unsupported value for rtc_strict_field_trials: " +
+               "$rtc_strict_field_trials")
   }
 
   if (rtc_include_internal_audio_device) {

api/BUILD.gn

@@ -1499,6 +1499,7 @@ rtc_source_set("field_trials_registry") {
     ":field_trials_view",
     "../experiments:registered_field_trials",
     "../rtc_base:checks",
+    "../rtc_base:logging",
     "../rtc_base/containers:flat_set",
     "../rtc_base/system:rtc_export",
   ]

api/field_trials_registry.cc

@@ -16,14 +16,19 @@
 #include "experiments/registered_field_trials.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/containers/flat_set.h"
+#include "rtc_base/logging.h"
 
 namespace webrtc {
 
 std::string FieldTrialsRegistry::Lookup(absl::string_view key) const {
-#if WEBRTC_STRICT_FIELD_TRIALS
+#if WEBRTC_STRICT_FIELD_TRIALS == 1
   RTC_DCHECK(absl::c_linear_search(kRegisteredFieldTrials, key) ||
              test_keys_.contains(key))
-      << key << " is not registered.";
+      << key << " is not registered, see g3doc/field-trials.md.";
+#elif WEBRTC_STRICT_FIELD_TRIALS == 2
+  RTC_LOG_IF(LS_WARNING, !(absl::c_linear_search(kRegisteredFieldTrials, key) ||
+                           test_keys_.contains(key)))
+      << key << " is not registered, see g3doc/field-trials.md.";
 #endif
   return GetValue(key);
 }

system_wrappers/source/field_trial.cc

@@ -116,10 +116,15 @@ std::string MergeFieldTrialsStrings(absl::string_view first,
 
 #ifndef WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT
 std::string FindFullName(absl::string_view name) {
-#if WEBRTC_STRICT_FIELD_TRIALS
+#if WEBRTC_STRICT_FIELD_TRIALS == 1
   RTC_DCHECK(absl::c_linear_search(kRegisteredFieldTrials, name) ||
              TestKeys().contains(name))
-      << name << " is not registered.";
+      << 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) ||
+               TestKeys().contains(name)))
+      << name << " is not registered, see g3doc/field-trials.md.";
 #endif
 
   if (trials_init_string == NULL)

webrtc.gni

@@ -232,10 +232,16 @@ declare_args() {
   # Includes the dav1d decoder in the internal decoder factory when set to true.
   rtc_include_dav1d_in_internal_decoder_factory = true
 
-  # When set to true, a run-time check will make sure that all field trial keys
+  # When enabled, a run-time check will make sure that all field trial keys have
-  # have been registered in accordance with the field trial policy. The check
+  # been registered in accordance with the field trial policy, see
-  # will only run with builds that have RTC_DCHECKs enabled.
+  # g3doc/field-trials.md. The value can be set to the following:
-  rtc_strict_field_trials = false
+  #
+  #  "dcheck": RTC_DCHECKs that the field trial has been registered. RTC_DCHECK
+  #            must be enabled separately.
+  #
+  #  "warn": RTC_LOGs a message with LS_WARNING severity if the field trial
+  #          hasn't been registered.
+  rtc_strict_field_trials = ""
 }
 
 if (!build_with_mozilla) {