feat: Add LSP for FTL (#1150)

Add an LSP that produces document highlights when FTL outputs build
errors

this is a work in progress

---------

Co-authored-by: Wes <[email protected]>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

go-runtime/compile/errors.go → backend/schema/errors.go

@@ -1,41 +1,37 @@
-package compile
+package schema
 
 import (
 	"errors"
 	"fmt"
-	"go/ast"
-	"go/token"
-
-	"github.com/TBD54566975/ftl/backend/schema"
 )
 
 type Error struct {
 	Msg string
-	Pos schema.Position
+	Pos Position
 	Err error // Wrapped error, if any
 }
 
 func (e Error) Error() string { return fmt.Sprintf("%s: %s", e.Pos, e.Msg) }
 func (e Error) Unwrap() error { return e.Err }
 
-func errorf(pos token.Pos, format string, args ...any) Error {
-	return Error{Msg: fmt.Sprintf(format, args...), Pos: goPosToSchemaPos(pos)}
+func Errorf(pos Position, format string, args ...any) Error {
+	return Error{Msg: fmt.Sprintf(format, args...), Pos: pos}
 }
 
-func wrapf(node ast.Node, err error, format string, args ...any) Error {
+func Wrapf(pos Position, err error, format string, args ...any) Error {
 	if format == "" {
 		format = "%s"
 	} else {
 		format += ": %s"
 	}
 	// Propagate existing error position if available
-	var pos schema.Position
+	var newPos Position
 	if perr := (Error{}); errors.As(err, &perr) {
-		pos = perr.Pos
+		newPos = perr.Pos
 		args = append(args, perr.Msg)
 	} else {
-		pos = goPosToSchemaPos(node.Pos())
+		newPos = pos
 		args = append(args, err)
 	}
-	return Error{Msg: fmt.Sprintf(format, args...), Pos: pos, Err: err}
+	return Error{Msg: fmt.Sprintf(format, args...), Pos: newPos, Err: err}
 }

buildengine/engine.go

@@ -29,6 +29,11 @@ type schemaChange struct {
 	*schema.Module
 }
 
+type Listener struct {
+	OnBuildComplete  func(project Project, err error)
+	OnDeployComplete func(project Project, err error)
+}
+
 // Engine for building a set of modules.
 type Engine struct {
 	client           ftlv1connect.ControllerServiceClient
@@ -39,6 +44,7 @@ type Engine struct {
 	schemaChanges    *pubsub.Topic[schemaChange]
 	cancel           func()
 	parallelism      int
+	listener         *Listener
 }
 
 type Option func(o *Engine)
@@ -49,6 +55,13 @@ func Parallelism(n int) Option {
 	}
 }
 
+// WithListener sets the event listener for the Engine.
+func WithListener(listener *Listener) Option {
+	return func(o *Engine) {
+		o.listener = listener
+	}
+}
+
 // New constructs a new [Engine].
 //
 // Completely offline builds are possible if the full dependency graph is
@@ -356,7 +369,11 @@ func (e *Engine) buildAndDeploy(ctx context.Context, replicas int32, waitForDepl
 						return nil
 					}
 					if module, ok := project.(Module); ok {
-						if err := Deploy(ctx, module, replicas, waitForDeployOnline, e.client); err != nil {
+						err := Deploy(ctx, module, replicas, waitForDeployOnline, e.client)
+						if e.listener != nil && e.listener.OnDeployComplete != nil {
+							e.listener.OnDeployComplete(project, err)
+						}
+						if err != nil {
 							return err
 						}
 					}
@@ -457,8 +474,10 @@ func (e *Engine) build(ctx context.Context, key ProjectKey, builtModules map[str
 	sch := &schema.Schema{Modules: maps.Values(combined)}
 
 	err := Build(ctx, sch, project)
+	if e.listener != nil && e.listener.OnBuildComplete != nil {
+		e.listener.OnBuildComplete(project, err)
+	}
 	if err != nil {
-
 		return err
 	}
 	if module, ok := project.(Module); ok {

cmd/ftl/cmd_dev.go

@@ -11,15 +11,18 @@ import (
 	"github.com/TBD54566975/ftl/buildengine"
 	"github.com/TBD54566975/ftl/common/projectconfig"
 	"github.com/TBD54566975/ftl/internal/rpc"
+	"github.com/TBD54566975/ftl/lsp"
 )
 
 type devCmd struct {
-	Parallelism int           `short:"j" help:"Number of modules to build in parallel." default:"${numcpu}"`
-	Dirs        []string      `arg:"" help:"Base directories containing modules." type:"existingdir" optional:""`
-	External    []string      `help:"Directories for libraries that require FTL module stubs." type:"existingdir" optional:""`
-	Watch       time.Duration `help:"Watch template directory at this frequency and regenerate on change." default:"500ms"`
-	NoServe     bool          `help:"Do not start the FTL server." default:"false"`
-	ServeCmd    serveCmd      `embed:""`
+	Parallelism    int           `short:"j" help:"Number of modules to build in parallel." default:"${numcpu}"`
+	Dirs           []string      `arg:"" help:"Base directories containing modules." type:"existingdir" optional:""`
+	External       []string      `help:"Directories for libraries that require FTL module stubs." type:"existingdir" optional:""`
+	Watch          time.Duration `help:"Watch template directory at this frequency and regenerate on change." default:"500ms"`
+	NoServe        bool          `help:"Do not start the FTL server." default:"false"`
+	RunLsp         bool          `help:"Run the language server." default:"false"`
+	ServeCmd       serveCmd      `embed:""`
+	languageServer *lsp.Server
 }
 
 func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error {
@@ -56,7 +59,19 @@ func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error
 			return err
 		}
 
-		engine, err := buildengine.New(ctx, client, d.Dirs, d.External, buildengine.Parallelism(d.Parallelism))
+		var listener *buildengine.Listener
+		if d.RunLsp {
+			d.languageServer = lsp.NewServer(ctx)
+			listener = &buildengine.Listener{
+				OnBuildComplete:  d.OnBuildComplete,
+				OnDeployComplete: d.OnDeployComplete,
+			}
+			g.Go(func() error {
+				return d.languageServer.Run()
+			})
+		}
+
+		engine, err := buildengine.New(ctx, client, d.Dirs, d.External, buildengine.Parallelism(d.Parallelism), buildengine.WithListener(listener))
 		if err != nil {
 			return err
 		}
@@ -65,3 +80,11 @@ func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error
 
 	return g.Wait()
 }
+
+func (d *devCmd) OnBuildComplete(project buildengine.Project, err error) {
+	d.languageServer.BuildComplete(project.Config().Dir, err)
+}
+
+func (d *devCmd) OnDeployComplete(project buildengine.Project, err error) {
+	d.languageServer.DeployComplete(project.Config().Dir, err)
+}

go-runtime/compile/schema.go

@@ -44,6 +44,14 @@ type NativeNames map[schema.Decl]string
 
 type enums map[string]*schema.Enum
 
+func errorf(pos token.Pos, format string, args ...interface{}) schema.Error {
+	return schema.Errorf(goPosToSchemaPos(pos), format, args...)
+}
+
+func wrapf(pos token.Pos, err error, format string, args ...interface{}) schema.Error {
+	return schema.Wrapf(goPosToSchemaPos(pos), err, format, args...)
+}
+
 // ExtractModuleSchema statically parses Go FTL module source into a schema.Module.
 func ExtractModuleSchema(dir string) (NativeNames, *schema.Module, error) {
 	pkgs, err := packages.Load(&packages.Config{
@@ -70,7 +78,7 @@ func ExtractModuleSchema(dir string) (NativeNames, *schema.Module, error) {
 		if len(pkg.Errors) > 0 {
 			for _, perr := range pkg.Errors {
 				if len(pkg.Syntax) > 0 {
-					merr = append(merr, wrapf(pkg.Syntax[0], perr, "%s", pkg.PkgPath))
+					merr = append(merr, wrapf(pkg.Syntax[0].Pos(), perr, "%s", pkg.PkgPath))
 				} else {
 					merr = append(merr, fmt.Errorf("%s: %w", pkg.PkgPath, perr))
 				}
@@ -81,7 +89,7 @@ func ExtractModuleSchema(dir string) (NativeNames, *schema.Module, error) {
 			err := goast.Visit(file, func(node ast.Node, next func() error) (err error) {
 				defer func() {
 					if err != nil {
-						err = wrapf(node, err, "")
+						err = wrapf(node.Pos(), err, "")
 					}
 				}()
 				switch node := node.(type) {
@@ -188,7 +196,7 @@ func parseConfigDecl(pctx *parseContext, node *ast.CallExpr, fn *types.Func) err
 			var err error
 			name, err = strconv.Unquote(literal.Value)
 			if err != nil {
-				return wrapf(node, err, "")
+				return wrapf(node.Pos(), err, "")
 			}
 		}
 	}
@@ -445,7 +453,7 @@ func visitFuncDecl(pctx *parseContext, node *ast.FuncDecl) (verb *schema.Verb, e
 	results := sig.Results()
 	reqt, respt, err := checkSignature(sig)
 	if err != nil {
-		return nil, wrapf(node, err, "")
+		return nil, wrapf(node.Pos(), err, "")
 	}
 	var req schema.Type
 	if reqt != nil {
@@ -602,12 +610,12 @@ func visitStruct(pctx *parseContext, pos token.Pos, tnode types.Type) (*schema.R
 		f := s.Field(i)
 		ft, err := visitType(pctx, f.Pos(), f.Type())
 		if err != nil {
-			return nil, errorf(pos, "field %s: %v", f.Name(), err)
+			return nil, errorf(f.Pos(), "field %s: %v", f.Name(), err)
 		}
 
 		// Check if field is exported
 		if len(f.Name()) > 0 && unicode.IsLower(rune(f.Name()[0])) {
-			return nil, errorf(pos, "params field %s must be exported by starting with an uppercase letter", f.Name())
+			return nil, errorf(f.Pos(), "params field %s must be exported by starting with an uppercase letter", f.Name())
 		}
 
 		// Extract the JSON tag and split it to get just the field name
@@ -621,13 +629,13 @@ func visitStruct(pctx *parseContext, pos token.Pos, tnode types.Type) (*schema.R
 		var metadata []schema.Metadata
 		if jsonFieldName != "" {
 			metadata = append(metadata, &schema.MetadataAlias{
-				Pos:   goPosToSchemaPos(pos),
+				Pos:   goPosToSchemaPos(f.Pos()),
 				Kind:  schema.AliasKindJSON,
 				Alias: jsonFieldName,
 			})
 		}
 		out.Fields = append(out.Fields, &schema.Field{
-			Pos:      goPosToSchemaPos(pos),
+			Pos:      goPosToSchemaPos(f.Pos()),
 			Name:     strcase.ToLowerCamel(f.Name()),
 			Type:     ft,
 			Metadata: metadata,
@@ -746,7 +754,7 @@ func visitType(pctx *parseContext, pos token.Pos, tnode types.Type) (schema.Type
 		if underlying.String() == "any" {
 			return &schema.Any{Pos: goPosToSchemaPos(pos)}, nil
 		}
-		return nil, errorf(pos, "unsupported type %T", tnode)
+		return nil, errorf(pos, "unsupported type %q", tnode)
 
 	default:
 		return nil, errorf(pos, "unsupported type %T", tnode)

go.mod

@@ -35,6 +35,9 @@ require (
 	github.com/santhosh-tekuri/jsonschema/v5 v5.3.1
 	github.com/swaggest/jsonschema-go v0.3.70
 	github.com/titanous/json5 v1.0.0
+	github.com/tliron/commonlog v0.2.17
+	github.com/tliron/glsp v0.2.2
+	github.com/tliron/kutil v0.3.24
 	github.com/tmc/langchaingo v0.1.8
 	github.com/zalando/go-keyring v0.2.4
 	go.opentelemetry.io/otel v1.24.0
@@ -56,10 +59,22 @@ require (
 )
 
 require (
+	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/gorilla/websocket v1.5.1 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
+	github.com/iancoleman/strcase v0.3.0 // indirect
+	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
+	github.com/mattn/go-runewidth v0.0.14 // indirect
+	github.com/muesli/termenv v0.15.2 // indirect
 	github.com/ncruces/go-strftime v0.1.9 // indirect
+	github.com/petermattis/goid v0.0.0-20180202154549-b0b1615b78e5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pkoukk/tiktoken-go v0.1.6 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
+	github.com/sasha-s/go-deadlock v0.3.1 // indirect
+	github.com/segmentio/ksuid v1.0.4 // indirect
+	github.com/sourcegraph/jsonrpc2 v0.2.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.1.0 // indirect
 	modernc.org/gc/v3 v3.0.0-20240107210532-573471604cb6 // indirect
 )