feat: ftl-language-go plugin (#3101)

#2452
Separates go support into `ftl-language-go`

Justfile

@@ -85,7 +85,18 @@ build-java *args:
   mvn -f jvm-runtime/ftl-runtime install {{args}}
 
 # Builds all language plugins
-build-language-plugins: build-python
+build-language-plugins: build-go build-python
+
+# Build ftl-language-go
+build-go: build-zips build-protos 
+  #!/bin/bash
+  shopt -s extglob
+
+  if [ "${FTL_DEBUG:-}" = "true" ]; then
+    go build -o "{{RELEASE}}/ftl-language-go" -tags release -gcflags=all="-N -l" -ldflags "-X github.com/TBD54566975/ftl.Version={{VERSION}} -X github.com/TBD54566975/ftl.Timestamp={{TIMESTAMP}}" "./go-runtime/cmd/ftl-language-go"
+  else
+    mk "{{RELEASE}}/ftl-language-go" : !(build|integration) -- go build -o "{{RELEASE}}/ftl-language-go" -tags release -ldflags "-X github.com/TBD54566975/ftl.Version={{VERSION}} -X github.com/TBD54566975/ftl.Timestamp={{TIMESTAMP}}" "./go-runtime/cmd/ftl-language-go"
+  fi
 
 # Build ftl-language-python
 build-python: build-zips build-protos

go-runtime/cmd/ftl-language-go/main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"context"
+	"os"
+
+	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/language/languagepbconnect"
+	"github.com/TBD54566975/ftl/common/plugin"
+	"github.com/TBD54566975/ftl/go-runtime/goplugin"
+)
+
+func main() {
+	plugin.Start(context.Background(),
+		os.Getenv("FTL_NAME"),
+		createService,
+		languagepbconnect.LanguageServiceName,
+		languagepbconnect.NewLanguageServiceHandler)
+}
+
+func createService(ctx context.Context, config any) (context.Context, *goplugin.Service, error) {
+	svc := goplugin.New()
+	return ctx, svc, nil
+}

go-runtime/compile/build.go

@@ -250,9 +250,9 @@ func buildDir(moduleDir string) string {
 }
 
 // Build the given module.
-func Build(ctx context.Context, projectRootDir, stubsRoot string, config moduleconfig.AbsModuleConfig, sch *schema.Schema, filesTransaction ModifyFilesTransaction, buildEnv []string, devMode bool) (moduleSch *schema.Module, buildErrors []builderrors.Error, err error) {
+func Build(ctx context.Context, projectRootDir, stubsRoot string, config moduleconfig.AbsModuleConfig, sch *schema.Schema, filesTransaction ModifyFilesTransaction, devMode bool) (moduleSch optional.Option[*schema.Module], buildErrors []builderrors.Error, err error) {
 	if err := filesTransaction.Begin(); err != nil {
-		return nil, nil, fmt.Errorf("could not start a file transaction: %w", err)
+		return moduleSch, nil, fmt.Errorf("could not start a file transaction: %w", err)
 	}
 	defer func() {
 		if terr := filesTransaction.End(); terr != nil {
@@ -262,7 +262,7 @@ func Build(ctx context.Context, projectRootDir, stubsRoot string, config modulec
 
 	replacements, goModVersion, err := updateGoModule(filepath.Join(config.Dir, "go.mod"))
 	if err != nil {
-		return nil, nil, err
+		return moduleSch, nil, err
 	}
 
 	goVersion := runtime.Version()[2:]
@@ -366,7 +366,7 @@ func Build(ctx context.Context, projectRootDir, stubsRoot string, config modulec
 	}
 	// We have seen lots of upstream HTTP/2 failures that make CI unstable.
 	// Disable HTTP/2 for now during the build. This can probably be removed later
-	buildEnv = append(buildEnv, "GODEBUG=http2client=0")
+	buildEnv := []string{"GODEBUG=http2client=0"}
 	err = exec.CommandWithEnv(ctx, log.Debug, mainDir, buildEnv, "go", args...).RunStderrError(ctx)
 	if err != nil {
 		return moduleSch, nil, fmt.Errorf("failed to compile: %w", err)
@@ -381,7 +381,7 @@ func Build(ctx context.Context, projectRootDir, stubsRoot string, config modulec
 	if err != nil {
 		return moduleSch, nil, fmt.Errorf("failed to write launch script: %w", err)
 	}
-	return result.Module, result.Errors, nil
+	return optional.Some(result.Module), result.Errors, nil
 }
 
 type mainModuleContextBuilder struct {

go-runtime/compile/stubs.go

@@ -84,7 +84,7 @@ func GenerateStubs(ctx context.Context, dir string, moduleSch *schema.Module, co
 	return nil
 }
 
-func SyncGeneratedStubReferences(ctx context.Context, config moduleconfig.ModuleConfig, stubsDir string, stubbedModules []string) error {
+func SyncGeneratedStubReferences(ctx context.Context, config moduleconfig.AbsModuleConfig, stubsDir string, stubbedModules []string) error {
 	sharedModulePaths := []string{}
 	for _, mod := range stubbedModules {
 		if mod == config.Module {
@@ -93,13 +93,13 @@ func SyncGeneratedStubReferences(ctx context.Context, config moduleconfig.Module
 		sharedModulePaths = append(sharedModulePaths, filepath.Join(stubsDir, mod))
 	}
 
-	_, goModVersion, err := updateGoModule(filepath.Join(config.Abs().Dir, "go.mod"))
+	_, goModVersion, err := updateGoModule(filepath.Join(config.Dir, "go.mod"))
 	if err != nil {
 		return err
 	}
 
 	funcs := maps.Clone(scaffoldFuncs)
-	if err := internal.ScaffoldZip(mainWorkTemplateFiles(), config.Abs().Dir, MainWorkContext{
+	if err := internal.ScaffoldZip(mainWorkTemplateFiles(), config.Dir, MainWorkContext{
 		GoVersion:          goModVersion,
 		SharedModulesPaths: sharedModulePaths,
 	}, scaffolder.Exclude("^go.mod$"), scaffolder.Functions(funcs)); err != nil {

internal/buildengine/languageplugin/go_plugin_integration_test.go → go-runtime/goplugin/integration_test.go

@@ -1,6 +1,6 @@
 //go:build integration
 
-package languageplugin
+package goplugin
 
 import (
 	"os"
@@ -14,7 +14,7 @@ import (
 func TestGoBuildClearsBuildDir(t *testing.T) {
 	file := "./another/.ftl/test-clear-build.tmp"
 	in.Run(t,
-		in.WithTestDataDir("../testdata"),
+		in.WithTestDataDir("testdata"),
 		in.CopyModule("another"),
 		in.Build("another"),
 		in.WriteFile(file, []byte{1}),
@@ -26,7 +26,7 @@ func TestGoBuildClearsBuildDir(t *testing.T) {
 
 func TestExternalType(t *testing.T) {
 	in.Run(t,
-		in.WithTestDataDir("../testdata"),
+		in.WithTestDataDir("testdata"),
 		in.CopyModule("external"),
 		in.ExpectError(in.Build("external"),
 			`unsupported type "time.Month" for field "Month"`,
@@ -43,7 +43,7 @@ func TestGeneratedTypeRegistry(t *testing.T) {
 	file := "other/.ftl/go/main/main.go"
 
 	in.Run(t,
-		in.WithTestDataDir("../testdata"),
+		in.WithTestDataDir("testdata"),
 		// Deploy dependency
 		in.CopyModule("another"),
 		in.Deploy("another"),

internal/buildengine/languageplugin/go_plugin_helpers.go → go-runtime/goplugin/replacements.go

@@ -1,6 +1,7 @@
-package languageplugin
+package goplugin
 
 import (
+	"errors"
 	"fmt"
 	"go/parser"
 	"go/token"
@@ -9,8 +10,6 @@ import (
 	"strings"
 
 	"golang.org/x/mod/modfile"
-
-	"github.com/TBD54566975/ftl/internal/errors"
 )
 
 func replacementWatches(moduleDir, deployDir string) ([]string, error) {