chore: remove redundant log messages in language plugin proto (#3212)

We will use stdout with the json log format instead, as this matches
what we do elsewhere.

backend/protos/xyz/block/ftl/v1/language/language.proto

@@ -233,26 +233,12 @@ message BuildFailure {
   bool invalidate_dependencies = 4;
 }
 
-// Log message from the language service.
-message LogMessage {
-  enum LogLevel {
-    DEBUG = 0;
-    INFO = 1;
-    WARN = 2;
-    ERROR = 3;
-  }
-
-  string message = 1;
-  LogLevel level = 2;
-}
-
 // Every type of message that can be streamed from the language plugin for a build.
 message BuildEvent {
   oneof event {
     AutoRebuildStarted auto_rebuild_started = 2;
     BuildSuccess build_success = 3;
     BuildFailure build_failure = 4;
-    LogMessage log_message = 5;
   }
 }
 
@@ -320,6 +306,9 @@ service LanguageService {
   //
   // Each time this call is made, the Build call must send back a corresponding BuildSuccess or BuildFailure
   // event with the updated build context id with "is_automatic_rebuild" as false.
+  //
+  // If the plugin will not be able to return a BuildSuccess or BuildFailure, such as when there is no active
+  // build stream, it must fail the BuildContextUpdated call.
   rpc BuildContextUpdated(BuildContextUpdatedRequest) returns (BuildContextUpdatedResponse);
 
   // Generate stubs for a module.

backend/protos/xyz/block/ftl/v1/language/mixins.go

@@ -7,7 +7,6 @@ import (
 	structpb "google.golang.org/protobuf/types/known/structpb"
 
 	"github.com/TBD54566975/ftl/internal/builderrors"
-	"github.com/TBD54566975/ftl/internal/log"
 	"github.com/TBD54566975/ftl/internal/moduleconfig"
 	"github.com/TBD54566975/ftl/internal/projectconfig"
 	"github.com/TBD54566975/ftl/internal/slices"
@@ -86,36 +85,6 @@ func PosFromProto(pos *Position) optional.Option[builderrors.Position] {
 	})
 }
 
-func LogLevelFromProto(level LogMessage_LogLevel) log.Level {
-	switch level {
-	case LogMessage_INFO:
-		return log.Info
-	case LogMessage_DEBUG:
-		return log.Debug
-	case LogMessage_WARN:
-		return log.Warn
-	case LogMessage_ERROR:
-		return log.Error
-	default:
-		panic(fmt.Sprintf("unhandled log level %v", level))
-	}
-}
-
-func LogLevelToProto(level log.Level) LogMessage_LogLevel {
-	switch level {
-	case log.Info:
-		return LogMessage_INFO
-	case log.Debug:
-		return LogMessage_DEBUG
-	case log.Warn:
-		return LogMessage_WARN
-	case log.Error:
-		return LogMessage_ERROR
-	default:
-		panic(fmt.Sprintf("unhandled log level %v", level))
-	}
-}
-
 // ModuleConfigToProto converts a moduleconfig.AbsModuleConfig to a protobuf ModuleConfig.
 //
 // Absolute configs are used because relative paths may change resolve differently between parties.

common/plugin/serve.go

@@ -112,7 +112,7 @@ func Start[Impl any, Iface any, Config any](
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
-	// Configure logging to JSON on stdout. This will be read by the parent process.
+	// Configure logging to JSON on stderr. This will be read by the parent process.
 	logConfig := cli.LogConfig
 	logConfig.JSON = true
 	logger := log.Configure(os.Stderr, logConfig)

internal/buildengine/languageplugin/external_integration_test.go

@@ -421,8 +421,6 @@ func waitForAutoRebuildToStart(contextId string) in.Action {
 				} else {
 					logger.Warnf("ignoring build failure for unexpected context %q while waiting for auto rebuild started event for %q", event.BuildFailure.ContextId, contextId)
 				}
-			case *langpb.BuildEvent_LogMessage:
-				logger.Debugf("plugin: %s", event.LogMessage.Message)
 			}
 		}
 	}
@@ -484,9 +482,6 @@ func waitForBuildToEnd(success BuildResultType, contextId string, automaticRebui
 					additionalChecks(t, ic, e)
 				}
 				return
-
-			case *langpb.BuildEvent_LogMessage:
-				logger.Infof("plugin log: %v", event.LogMessage.Message)
 			}
 		}
 	}
@@ -495,7 +490,6 @@ func waitForBuildToEnd(success BuildResultType, contextId string, automaticRebui
 func checkForNoEvents(duration time.Duration) in.Action {
 	return func(t testing.TB, ic in.TestContext) {
 		in.Infof("Checking for no events for %v", duration)
-		logger := log.FromContext(ic.Context)
 		for {
 			select {
 			case result := <-buildChan:
@@ -508,9 +502,6 @@ func checkForNoEvents(duration time.Duration) in.Action {
 					panic(fmt.Sprintf("build success event when expecting no events: %v", event))
 				case *langpb.BuildEvent_BuildFailure:
 					panic(fmt.Sprintf("build failure event when expecting no events: %v", event))
-				case *langpb.BuildEvent_LogMessage:
-					logger.Infof("plugin log: %v", event.LogMessage.Message)
-					continue
 				}
 			case <-time.After(duration):
 				return

internal/buildengine/languageplugin/external_plugin.go

@@ -366,9 +366,7 @@ func (p *externalPlugin) run(ctx context.Context) {
 				continue
 			}
 
-			switch event := e.Event.(type) {
-			case *langpb.BuildEvent_LogMessage:
-				logger.Logf(langpb.LogLevelFromProto(event.LogMessage.Level), "%s", event.LogMessage.Message)
+			switch e.Event.(type) {
 			case *langpb.BuildEvent_AutoRebuildStarted:
 				if _, ok := activeBuildCmd.Get(); ok {
 					logger.Debugf("ignoring automatic rebuild started during explicit build")

python-runtime/python-plugin/service.go

@@ -105,8 +105,6 @@ func (s *Service) Build(ctx context.Context, req *connect.Request[langpb.BuildRe
 	logger := log.FromContext(ctx)
 	logger.Infof("Do python build")
 
-	ctx = log.ContextWithLogger(ctx, newLoggerForStream(log.Debug, stream))
-
 	buildCtx, err := buildContextFromProto(req.Msg.BuildContext)
 	if err != nil {
 		return err