From b1c64c753f0d3143dd0630c148b526e9b549c81b Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Sat, 6 Sep 2025 13:44:56 +0200
Subject: [PATCH] chore: enable multi-line decorators (#23431)

---
 cmd/decorate/decorate.go | 66 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 58 insertions(+), 8 deletions(-)

diff --git a/cmd/decorate/decorate.go b/cmd/decorate/decorate.go
index c8ac3101b..b1beba1d2 100644
--- a/cmd/decorate/decorate.go
+++ b/cmd/decorate/decorate.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	_ "embed"
 	"fmt"
@@ -20,7 +21,13 @@ import (
 	"golang.org/x/tools/imports"
 )
 
-//go:generate go tool decorate -f decorateTest -b api.Charger -t "api.MeterEnergy,TotalEnergy,func() (float64, error)" -t "api.PhaseSwitcher,Phases1p3p,func(int) error" -t "api.PhaseGetter,GetPhases,func() (int, error)"
+// go:generate go tool decorate -f decorateTest -b api.Charger -t "api.MeterEnergy,TotalEnergy,func() (float64, error)" -t "api.PhaseSwitcher,Phases1p3p,func(int) error" -t "api.PhaseGetter,GetPhases,func() (int, error)"
+//go:generate go tool decorate
+//evcc:function decorateTest
+//evcc:basetype api.Charger
+//evcc:type api.MeterEnergy,TotalEnergy,func() (float64, error)
+//evcc:type api.PhaseSwitcher,Phases1p3p,func(int) error
+//evcc:type api.PhaseGetter,GetPhases,func() (int, error)
 
 //go:embed decorate.tpl
 var srcTmpl string
@@ -198,7 +205,7 @@ COMBO:
 var (
 	target   = pflag.StringP("out", "o", "", "output file")
 	pkg      = pflag.StringP("package", "p", "", "package name")
-	function = pflag.StringP("function", "f", "decorate", "function name")
+	function = pflag.StringP("function", "f", "", "function name")
 	base     = pflag.StringP("base", "b", "", "base type")
 	ret      = pflag.StringP("return", "r", "", "return type")
 	types    = pflag.StringArrayP("type", "t", nil, "comma-separated list of type definitions")
@@ -212,15 +219,64 @@ func Usage() {
 	pflag.PrintDefaults()
 }
 
+func parseFile(file string, function, basetype, returntype *string, types *[]string) error {
+	f, err := os.Open(file)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if s, ok := strings.CutPrefix(line, "//evcc:"); ok {
+			segs := strings.SplitN(s, " ", 2)
+			if len(segs) != 2 {
+				panic("invalid segments: " + s)
+			}
+
+			switch segs[0] {
+			case "function":
+				*function = segs[1]
+			case "basetype":
+				*basetype = segs[1]
+			case "returntype":
+				*returntype = segs[1]
+			case "type":
+				*types = append(*types, segs[1])
+			default:
+				panic("invalid directive //evcc:" + segs[0])
+			}
+		}
+	}
+
+	return scanner.Err()
+}
+
 func main() {
 	pflag.Usage = Usage
 	pflag.Parse()
 
+	// read target from go:generate
+	gofile, ok := os.LookupEnv("GOFILE")
+	if *target == "" && ok {
+		gofile := strings.TrimSuffix(gofile, ".go") + "_decorators.go"
+		target = &gofile
+	}
+
 	// read target from go:generate
 	if gopkg, ok := os.LookupEnv("GOPACKAGE"); *pkg == "" && ok {
 		pkg = &gopkg
 	}
 
+	if *function == "" {
+		if err := parseFile(gofile, function, base, ret, types); err != nil {
+			fmt.Println(err)
+			os.Exit(2)
+		}
+	}
+
 	if *base == "" || *pkg == "" || len(*types) == 0 {
 		Usage()
 		os.Exit(2)
@@ -242,12 +298,6 @@ func main() {
 
 	var out io.Writer = os.Stdout
 
-	// read target from go:generate
-	if gofile, ok := os.LookupEnv("GOFILE"); *target == "" && ok {
-		gofile = strings.TrimSuffix(gofile, ".go") + "_decorators.go"
-		target = &gofile
-	}
-
 	var name string
 	if target != nil {
 		name = *target