warnings for flags due for deprecation (#14856)

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

changelog/kasey_warn-hist-state-rep.md

@@ -0,0 +1,2 @@
+### Added
+- WARN log message on node startup advising of the upcoming deprecation of the --enable-historical-state-representation feature flag.

config/features/config.go

@@ -166,6 +166,7 @@ func applyHoleskyFeatureFlags(ctx *cli.Context) {
 // ConfigureBeaconChain sets the global config based
 // on what flags are enabled for the beacon-chain client.
 func ConfigureBeaconChain(ctx *cli.Context) error {
+	warnDeprecationUpcoming(ctx)
 	complainOnDeprecatedFlags(ctx)
 	cfg := &Flags{}
 	if ctx.Bool(devModeFlag.Name) {
@@ -336,6 +337,22 @@ func complainOnDeprecatedFlags(ctx *cli.Context) {
 	}
 }
 
+var upcomingDeprecationExtra = map[string]string{
+	enableHistoricalSpaceRepresentation.Name: "The node needs to be resynced after flag removal.",
+}
+
+func warnDeprecationUpcoming(ctx *cli.Context) {
+	for _, f := range upcomingDeprecation {
+		if ctx.IsSet(f.Names()[0]) {
+			extra := "Please remove this flag from your configuration."
+			if special, ok := upcomingDeprecationExtra[f.Names()[0]]; ok {
+				extra += " " + special
+			}
+			log.Warnf("--%s is pending deprecation and will be removed in the next release. %s", f.Names()[0], extra)
+		}
+	}
+}
+
 func logEnabled(flag cli.DocGenerationFlag) {
 	var name string
 	if names := flag.Names(); len(names) > 0 {

config/features/deprecated_flags.go

@@ -120,6 +120,10 @@ var deprecatedFlags = []cli.Flag{
 	deprecatedEnableQuic,
 }
 
+var upcomingDeprecation = []cli.Flag{
+	enableHistoricalSpaceRepresentation,
+}
+
 // deprecatedBeaconFlags contains flags that are still used by other components
 // and therefore cannot be added to deprecatedFlags
 var deprecatedBeaconFlags = []cli.Flag{

config/features/flags.go

@@ -205,7 +205,7 @@ var E2EValidatorFlags = []string{
 }
 
 // BeaconChainFlags contains a list of all the feature flags that apply to the beacon-chain client.
-var BeaconChainFlags = append(deprecatedBeaconFlags, append(deprecatedFlags, []cli.Flag{
+var BeaconChainFlags = combinedFlags([]cli.Flag{
 	devModeFlag,
 	disableExperimentalState,
 	writeSSZStateTransitionsFlag,
@@ -218,7 +218,6 @@ var BeaconChainFlags = append(deprecatedBeaconFlags, append(deprecatedFlags, []c
 	disablePeerScorer,
 	disableBroadcastSlashingFlag,
 	enableSlasherFlag,
-	enableHistoricalSpaceRepresentation,
 	disableStakinContractCheck,
 	SaveFullExecutionPayloads,
 	enableStartupOptimistic,
@@ -236,7 +235,18 @@ var BeaconChainFlags = append(deprecatedBeaconFlags, append(deprecatedFlags, []c
 	DisableCommitteeAwarePacking,
 	EnableDiscoveryReboot,
 	enableExperimentalAttestationPool,
-}...)...)
+}, deprecatedBeaconFlags, deprecatedFlags, upcomingDeprecation)
+
+func combinedFlags(flags ...[]cli.Flag) []cli.Flag {
+	if len(flags) == 0 {
+		return []cli.Flag{}
+	}
+	collected := flags[0]
+	for _, f := range flags[1:] {
+		collected = append(collected, f...)
+	}
+	return collected
+}
 
 // E2EBeaconChainFlags contains a list of the beacon chain feature flags to be tested in E2E.
 var E2EBeaconChainFlags = []string{