improve embed tool

Makefile

@@ -230,16 +230,16 @@ frontend/out/index.html: frontend/node_modules
 	cd frontend && yarn export
 
 pkg/server/assets.go: frontend/out/index.html
-	go run ./util/embed -package server -output $@ $(FRONTEND_EXPORT_DIR)
+	go run ./util/embed -package server -tag web -output $@ $(FRONTEND_EXPORT_DIR)
 
 $(BACKTEST_REPORT_APP_DIR)/node_modules:
 	cd $(BACKTEST_REPORT_APP_DIR) && yarn install
 
-$(BACKTEST_REPORT_APP_DIR)/out/index.html: $(BACKTEST_REPORT_APP_DIR)/node_modules
+$(BACKTEST_REPORT_APP_DIR)/out/index.html: .FORCE $(BACKTEST_REPORT_APP_DIR)/node_modules
 	cd $(BACKTEST_REPORT_APP_DIR) && yarn build && yarn export
 
 pkg/backtest/assets.go: $(BACKTEST_REPORT_APP_DIR)/out/index.html
-	go run ./util/embed -package backtest -output $@ $(BACKTEST_REPORT_EXPORT_DIR)
+	go run ./util/embed -package backtest -tag web -output $@ $(BACKTEST_REPORT_EXPORT_DIR)
 
 embed: pkg/server/assets.go pkg/backtest/assets.go
 

pkg/backtest/assets_dummy.go

@@ -0,0 +1,65 @@
+//go:build !web
+// +build !web
+
+package backtest
+
+import (
+	"bytes"
+	"errors"
+	"net/http"
+	"os"
+	"time"
+)
+
+var assets = map[string][]byte{}
+
+var FS = &fs{}
+
+type fs struct{}
+
+func (fs *fs) Open(name string) (http.File, error) {
+	if name == "/" {
+		return fs, nil
+	}
+	b, ok := assets[name]
+	if !ok {
+		return nil, os.ErrNotExist
+	}
+	return &file{name: name, size: len(b), Reader: bytes.NewReader(b)}, nil
+}
+
+func (fs *fs) Close() error                                 { return nil }
+func (fs *fs) Read(p []byte) (int, error)                   { return 0, nil }
+func (fs *fs) Seek(offset int64, whence int) (int64, error) { return 0, nil }
+func (fs *fs) Stat() (os.FileInfo, error)                   { return fs, nil }
+func (fs *fs) Name() string                                 { return "/" }
+func (fs *fs) Size() int64                                  { return 0 }
+func (fs *fs) Mode() os.FileMode                            { return 0755 }
+func (fs *fs) ModTime() time.Time                           { return time.Time{} }
+func (fs *fs) IsDir() bool                                  { return true }
+func (fs *fs) Sys() interface{}                             { return nil }
+func (fs *fs) Readdir(count int) ([]os.FileInfo, error) {
+	files := []os.FileInfo{}
+	for name, data := range assets {
+		files = append(files, &file{name: name, size: len(data), Reader: bytes.NewReader(data)})
+	}
+	return files, nil
+}
+
+type file struct {
+	name string
+	size int
+	*bytes.Reader
+}
+
+func (f *file) Close() error { return nil }
+func (f *file) Readdir(count int) ([]os.FileInfo, error) {
+	return nil, errors.New("readdir is not supported")
+}
+func (f *file) Stat() (os.FileInfo, error) { return f, nil }
+func (f *file) Name() string               { return f.name }
+func (f *file) Size() int64                { return int64(f.size) }
+func (f *file) Mode() os.FileMode          { return 0644 }
+func (f *file) ModTime() time.Time         { return time.Time{} }
+func (f *file) IsDir() bool                { return false }
+func (f *file) Sys() interface{}           { return nil }

util/embed/main.go

@@ -17,9 +17,9 @@ var funcs = map[string]interface{}{
 }
 
 var (
-	tmpl = template.Must(template.New("").Funcs(funcs).Parse(`// +build web
+	tmpl = template.Must(template.New("").Funcs(funcs).Parse(`{{- if .Tag -}} // +build {{ .Tag }} {{- end }}
 
-// code is generated by embed. DO NOT EDIT.
+// Code generated by "embed"; DO NOT EDIT.
 package {{ .Package }}
 
 import (
@@ -81,19 +81,22 @@ func (f *file) ModTime() time.Time{ return time.Time{} }
 func (f *file) IsDir() bool { return false }
 func (f *file) Sys() interface{} { return nil }
 
-`)))
+`))
+)
 
 // Embed is a helper function that embeds assets from the given directories
 // into a Go source file. It is designed to be called from some generator
 // script, see example project to find out how it can be used.
-func Embed(packageName, file string, dirs ...string) error {
+func Embed(file string, dirs ...string) error {
 	var buf bytes.Buffer
 
 	// Execute template
-	if err := tmpl.Execute(&buf, struct{
+	if err := tmpl.Execute(&buf, struct {
 		Package string
+		Tag     string
 	}{
 		Package: packageName,
+		Tag:     tag,
 	}); err != nil {
 		return err
 	}
@@ -142,16 +145,17 @@ func formatBytes(s []byte) string {
 	return builder.String()
 }
 
+var packageName string
+var outputFile string
+var tag string
 
 func main() {
-	var packageName string
-	var outputFile string
-
-	flag.StringVar(&packageName,"package", "", "package name")
-	flag.StringVar(&outputFile,"output", "assets.go", "output filename")
+	flag.StringVar(&packageName, "package", "", "package name")
+	flag.StringVar(&tag, "tag", "", "build tag in the generated file")
+	flag.StringVar(&outputFile, "output", "assets.go", "output filename")
 	flag.Parse()
 	args := flag.Args()
-	if err := Embed(packageName, outputFile, args...) ; err != nil {
+	if err := Embed(outputFile, args...); err != nil {
 		log.Fatal(err)
 	}
 }