Feature based code generation

codegen/features/cmd/cmd.go

@@ -0,0 +1,64 @@
+// Package gen/cmd allows to generate .go source files using the go:generate command.
+// Use with "cmd [templateFile] [outputFile] [typeName] [typeReceiver] [Features separated by space]".
+//
+// In the template the following are available:
+// - typeName as {{.Name}}
+// - typeReceiver as {{.Receiver}}
+// - Features are available via map and can be evaluated as {{if index .Features "extended"}}
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"os"
+	"strings"
+	"text/template"
+
+	"github.com/iotaledger/hive.go/lo"
+)
+
+func main() {
+	if len(os.Args) < 6 {
+		printUsage("not enough parameters")
+	}
+
+	templateFilePath := os.Args[1]
+	conf := newConfiguration(os.Args[2], os.Args[3], os.Args[4], os.Args[5])
+
+	funcs := template.FuncMap{
+		"firstLower": func(s string) string {
+			return strings.ToLower(s[0:1]) + s[1:]
+		},
+	}
+
+	tmplFile := lo.PanicOnErr(os.ReadFile(templateFilePath))
+
+	tmpl := template.Must(
+		template.New("gen").
+			Funcs(funcs).
+			Parse(string(tmplFile)),
+	)
+
+	buffer := new(bytes.Buffer)
+	panicOnError(tmpl.Execute(buffer, conf))
+
+	formattedOutput := lo.PanicOnErr(format.Source(buffer.Bytes()))
+
+	panicOnError(os.WriteFile(conf.FileName, formattedOutput, 0600))
+}
+
+// printUsage prints the usage of the variadic code generator in case of an error.
+func printUsage(errorMsg string) {
+	_, _ = fmt.Fprintf(os.Stderr, "Error:\t%s\n\n", errorMsg)
+	_, _ = fmt.Fprintf(os.Stderr, "Usage of gen/cmd:\n")
+	_, _ = fmt.Fprintf(os.Stderr, "\tcmd [templateFile] [outputFile] [typeName] [typeReceiver] [features separated by space]\n")
+
+	os.Exit(2)
+}
+
+func panicOnError(err error) {
+	if err != nil {
+		panic(err)
+	}
+}

codegen/features/cmd/configuration.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+type configuration struct {
+	FileName string
+	Name     string
+	Receiver string
+	Features map[string]bool
+}
+
+func newConfiguration(fileName, name, receiver, featuresStr string) *configuration {
+	features := make(map[string]bool)
+	for _, feature := range strings.Split(featuresStr, " ") {
+		features[feature] = true
+	}
+
+	return &configuration{
+		FileName: fileName,
+		Name:     name,
+		Receiver: strings.ToLower(receiver),
+		Features: features,
+	}
+}
+
+func (c *configuration) String() string {
+	return fmt.Sprintf("configuration{\n\tFileName:%s,\n\tName:%s,\n\tReceiver:%s,\n\tFeatures:%v,\n}\n", c.FileName, c.Name, c.Receiver, c.Features)
+}

codegen/features/example/example.tmpl

@@ -0,0 +1,21 @@
+package iotago
+
+// Code generated by go generate; DO NOT EDIT. Check gen/ directory instead.
+
+const (
+	// {{.Name}}Length defines the length of an {{.Name}}.
+    {{.Name}}Length = 32
+)
+
+var (
+	Empty{{.Name}} = {{.Name}}{}
+)
+
+// {{.Name}} is a 32 byte hash value.
+type {{.Name}} [{{.Name}}Length]byte
+
+{{if index .Features "example_feature"}}
+func ({{.Receiver}} {{.Name}}) ExampleFeature() string {
+    return "ExampleFeature"
+}
+{{end}}

codegen/features/example/identifier_gen.go

@@ -0,0 +1,5 @@
+//go:build ignore
+
+package gen
+
+//go:generate go run ../cmd example.tmpl example.gen.go ExampleName e "example_feature"