initial

bang.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+	"text/template"
+
+	"github.com/pkg/errors"
+	"gopkg.in/yaml.v3"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Println("need 1 argument: <file.go:line>")
+		os.Exit(1)
+	}
+
+	bits := strings.SplitN(os.Args[1], ":", 2)
+	src, err := os.Open(bits[0])
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	defer func() { _ = src.Close() }()
+
+	start, err := strconv.Atoi(bits[1])
+	if err != nil {
+		fmt.Println("invalid line:", err)
+		os.Exit(1)
+	}
+
+	i := 0
+
+	var yamlData []byte
+	scanner := bufio.NewScanner(src)
+
+	for scanner.Scan() {
+		i++
+		if i <= start {
+			continue
+		}
+
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "//") {
+			break
+		}
+
+		if line == "//" {
+			line = ""
+		} else if strings.HasPrefix(line, "// ") {
+			line = strings.TrimPrefix(line, "// ")
+		} else if strings.HasPrefix(line, "//\t") {
+			line = strings.TrimPrefix(line, "//\t")
+		}
+
+		yamlData = append(yamlData, line...)
+		yamlData = append(yamlData, "\n"...)
+	}
+
+	if err := scanner.Err(); err != nil {
+		fmt.Println("scan fail:", err)
+		os.Exit(1)
+	}
+
+	log.Printf("yamlData:\n%s\n---", string(yamlData))
+
+	var j job
+	if err := yaml.Unmarshal(yamlData, &j); err != nil {
+		fmt.Println("format fail:", err)
+		os.Exit(1)
+	}
+
+	if err := j.do(); err != nil {
+		fmt.Println("job fail:", err)
+		os.Exit(1)
+	}
+}
+
+type job struct {
+	Dest     string                 `yaml:"dest"`
+	Vars     map[string]interface{} `yaml:"vars"`
+	Template string                 `yaml:"template"`
+}
+
+func (j job) do() error {
+	tpl, err := template.New(j.Dest).Parse(j.Template)
+	if err != nil {
+		return err
+	}
+
+	var buf bytes.Buffer
+	if err := tpl.Execute(&buf, j.Vars); err != nil {
+		return err
+	}
+
+	source := append([]byte("// Code generated by Bang.go DO NOT EDIT.\n\n"), buf.Bytes()...)
+	content, err := format.Source(source)
+	if err != nil {
+		return errors.Wrapf(err, "format fail: %s", string(source))
+	}
+
+	if err := os.WriteFile(j.Dest, content, 0644); err != nil {
+		return err
+	}
+
+	return nil
+}

example/example.go

@@ -0,0 +1,26 @@
+package main
+
+//go:generate bang $GOFILE:$GOLINE
+// dest: example_generated.go
+// vars:
+//   package: main
+//   items:
+//    - a
+//    - b
+//    - c
+// template: >
+//   package {{.package}}
+//
+//   func main() {
+//        println("123: {{.vars.items}}")
+//   }
+//
+//   {{range $k, $v := .items}}
+//       func f{{$k}}() {
+//        print("{{$v}}")
+//       }
+//   {{end}}
+
+func main() {
+	// noop
+}

example/run.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+set -ex
+cd $( dirname $0 )
+
+(
+  cd ..
+  go build
+  go install
+)
+
+go generate .

go.mod

@@ -0,0 +1,8 @@
+module github.com/tada-team/bang
+
+go 1.16
+
+require (
+	github.com/pkg/errors v0.9.1
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
+)

go.sum

@@ -0,0 +1,6 @@
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=