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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build ignore
// mkconsts generates const definition files for each GOEXPERIMENT.
package main
import (
"bytes"
"fmt"
"internal/goexperiment"
"log"
"os"
"reflect"
"strings"
)
func main() {
// Delete existing experiment constant files.
ents, err := os.ReadDir(".")
if err != nil {
log.Fatal(err)
}
for _, ent := range ents {
name := ent.Name()
if !strings.HasPrefix(name, "exp_") {
continue
}
// Check that this is definitely a generated file.
data, err := os.ReadFile(name)
if err != nil {
log.Fatalf("reading %s: %v", name, err)
}
if !bytes.Contains(data, []byte("Code generated by mkconsts")) {
log.Fatalf("%s: expected generated file", name)
}
if err := os.Remove(name); err != nil {
log.Fatal(err)
}
}
// Generate new experiment constant files.
rt := reflect.TypeOf(&goexperiment.Flags{}).Elem()
for i := 0; i < rt.NumField(); i++ {
f := rt.Field(i).Name
buildTag := "goexperiment." + strings.ToLower(f)
for _, val := range []bool{false, true} {
name := fmt.Sprintf("exp_%s_%s.go", strings.ToLower(f), pick(val, "off", "on"))
data := fmt.Sprintf(`// Code generated by mkconsts.go. DO NOT EDIT.
//go:build %s%s
package goexperiment
const %s = %v
const %sInt = %s
`, pick(val, "!", ""), buildTag, f, val, f, pick(val, "0", "1"))
if err := os.WriteFile(name, []byte(data), 0666); err != nil {
log.Fatalf("writing %s: %v", name, err)
}
}
}
}
func pick(v bool, f, t string) string {
if v {
return t
}
return f
}
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