html/template: reflect Seq/CanSeq/CanSeq2 undefined with go1.24.1; works with go1.23.4 #4807
Description
Getting reflect compile errors on code using html/template after upgrading to go1.24.1.
$ go version
go version go1.24.1 linux/amd64
$ tinygo version
tinygo version 0.37.0-dev-4f7c64cb linux/amd64 (using go version go1.24.1 and LLVM version 17.0.6)
$ tinygo build -target nano-rp2040 ./main.go
# text/template
/usr/local/go/src/text/template/exec.go:405:22: val.Seq undefined (type reflect.Value has no field or method Seq)
/usr/local/go/src/text/template/exec.go:454:17: val.Type().CanSeq undefined (type reflect.Type has no field or method CanSeq)
/usr/local/go/src/text/template/exec.go:460:23: val.Seq undefined (type reflect.Value has no field or method Seq)
/usr/local/go/src/text/template/exec.go:471:17: val.Type().CanSeq2 undefined (type reflect.Type has no field or method CanSeq2)
/usr/local/go/src/text/template/exec.go:473:26: val.Seq2 undefined (type reflect.Value has no field or method Seq2)
If I revert back to go1.23.4, then compile works:
$ go version
go version go1.23.4 linux/amd64
$ tinygo build -target nano-rp2040 ./main.go
Test program is:
package main
import (
"log"
"os"
"text/template"
"time"
)
type PageData struct {
Title string
Message string
Name string
}
const htmlTemplate = `
<!DOCTYPE html>
<html>
<head>
<title>{{.Title}}</title>
</head>
<body>
<h1>{{.Title}}</h1>
<div class="message">
{{.Message}}
{{if .Name}}
<p>Welcome, {{.Name}}!</p>
{{else}}
<p>Please provide a name in the URL query!</p>
{{end}}
</div>
</body>
</html>
`
func main() {
time.Sleep(2 * time.Second)
// Parse the template
tmpl, err := template.New("webpage").Parse(htmlTemplate)
if err != nil {
log.Fatal("Error parsing template:", err)
}
// Create data for the template
data := PageData{
Title: "Template Demo",
Message: "This is a demonstration of Go's html/template package",
Name: "Joe",
}
// Execute the template with the data
err = tmpl.Execute(os.Stdout, data)
if err != nil {
log.Println("Error executing template:", err)
return
}
for {
time.Sleep(time.Second)
}
}