feat(go-scaffolding): simplify Go layout (#521)

Also added a README to the template to explain the directory structure.

cmd/ftl/cmd_init.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"archive/zip"
 	"os"
 	"path/filepath"
 
@@ -18,28 +19,15 @@ type initCmd struct {
 }
 
 type initGoCmd struct {
-	Dir      string `arg:"" default:"." type:"dir" help:"Directory to initialize the module in."`
-	Name     string `short:"n" help:"Name of the FTL module (defaults to name of directory)."`
-	GoModule string `short:"G" required:"" help:"Go module import path."`
+	Dir  string `arg:"" default:"." type:"dir" help:"Directory to initialize the module in."`
+	Name string `short:"n" help:"Name of the FTL module (defaults to name of directory)."`
 }
 
 func (i initGoCmd) Run(parent *initCmd) error {
 	if i.Name == "" {
 		i.Name = filepath.Base(i.Dir)
 	}
-	err := internal.UnzipDir(goruntime.Files, i.Dir)
-	if err != nil {
-		return errors.WithStack(err)
-	}
-	if err := internal.Scaffold(i.Dir, i); err != nil {
-		return errors.WithStack(err)
-	}
-	if !parent.Hermit {
-		if err := os.RemoveAll(filepath.Join(i.Dir, "bin")); err != nil {
-			return errors.WithStack(err)
-		}
-	}
-	return nil
+	return errors.WithStack(scaffold(goruntime.Files, parent.Hermit, i.Dir, i))
 }
 
 type initKotlinCmd struct {
@@ -51,15 +39,22 @@ func (i *initKotlinCmd) Run(parent *initCmd) error {
 	if i.Name == "" {
 		i.Name = filepath.Base(i.Dir)
 	}
-	err := internal.UnzipDir(kotlinruntime.Files, i.Dir)
+	return errors.WithStack(scaffold(kotlinruntime.Files, parent.Hermit, i.Dir, i))
+}
+
+func scaffold(reader *zip.Reader, hermit bool, dir string, ctx any) error {
+	err := internal.UnzipDir(reader, dir)
 	if err != nil {
 		return errors.WithStack(err)
 	}
-	if err := internal.Scaffold(i.Dir, i); err != nil {
+	if err := os.Remove(filepath.Join(dir, "go.mod")); err != nil {
+		return errors.WithStack(err)
+	}
+	if err := internal.Scaffold(dir, ctx); err != nil {
 		return errors.WithStack(err)
 	}
-	if !parent.Hermit {
-		if err := os.RemoveAll(filepath.Join(i.Dir, "bin")); err != nil {
+	if !hermit {
+		if err := os.RemoveAll(filepath.Join(dir, "bin")); err != nil {
 			return errors.WithStack(err)
 		}
 	}

go-runtime/scaffolding/README.md

@@ -0,0 +1,17 @@
+# FTL modules
+
+Each subdirectory represents an FTL module. Remote modules will be
+code-generated into their own directories, one module per directory. Note that
+this is a temporary solution.
+
+For example given an `echo` module written in Go that calls a `time` module
+written in Kotlin, the filesystem might look like this once the FTL tooling is
+started:
+
+```
+README.md
+go.mod
+echo/ftl.toml
+echo/echo.go
+time/generated_ftl_module.go
+```

go-runtime/scaffolding/go.mod.tmpl

@@ -1,4 +1,4 @@
-module {{ .GoModule }}
+module ftl
 
 go 1.21.0
 

go-runtime/scaffolding/{{ .Name | camel | lower }}/ftl.toml

@@ -0,0 +1,3 @@
+module = "{{ .Name }}"
+language = "go"
+deploy = ["build/main", "build/schema.pb"]

go-runtime/scaffolding/{{ .Name | camel | lower }}/go.mod

@@ -0,0 +1,5 @@
+module ftl/{{ .Name | camel | lower }}
+
+go 1.21.0
+
+require github.com/TBD54566975/ftl latest

go-runtime/scaffolding/{{ .Name | camel | lower }}/{{ .Name | camel | lower }}.go.tmpl

@@ -0,0 +1,21 @@
+package {{ .Name | camel | lower }}
+
+import (
+	"context"
+	"fmt"
+
+	_ "github.com/TBD54566975/ftl/go-runtime/sdk" // Import the FTL SDK.
+)
+
+type EchoRequest struct {
+	Name string `json:"name'`
+}
+
+type EchoResponse struct {
+	Message string `json:"message"`
+}
+
+//ftl:verb
+func echo(ctx context.Context, req EchoRequest) (EchoResponse, error) {
+	return EchoResponse{Message: fmt.Sprintf("Hello, %s!", req.Name)}, nil
+}

internal/scaffolder.go

@@ -21,6 +21,10 @@ import (
 //
 // The functions "snake", "camel", "lowerCamel", "kebab", "upper", and "lower"
 // are available.
+//
+// This is inspired by [cookiecutter].
+//
+// [cookiecutter]: https://github.com/cookiecutter/cookiecutter
 func Scaffold(destination string, ctx any) error {
 	return errors.WithStack(walkDir(destination, func(path string, d fs.DirEntry) error {
 		info, err := d.Info()
@@ -98,12 +102,15 @@ func walkDir(dir string, fn func(path string, d fs.DirEntry) error) error {
 func evaluate(tmpl string, ctx any) (string, error) {
 	t, err := template.New("scaffolding").Funcs(
 		template.FuncMap{
-			"snake":      strcase.ToSnake,
-			"camel":      strcase.ToCamel,
-			"lowerCamel": strcase.ToLowerCamel,
-			"kebab":      strcase.ToKebab,
-			"upper":      strings.ToUpper,
-			"lower":      strings.ToLower,
+			"snake":          strcase.ToSnake,
+			"screamingSnake": strcase.ToScreamingSnake,
+			"camel":          strcase.ToCamel,
+			"lowerCamel":     strcase.ToLowerCamel,
+			"kebab":          strcase.ToKebab,
+			"screamingKebab": strcase.ToScreamingKebab,
+			"upper":          strings.ToUpper,
+			"lower":          strings.ToLower,
+			"title":          strings.Title,
 			"typename": func(v any) string {
 				return reflect.Indirect(reflect.ValueOf(v)).Type().Name()
 			},