text/template: incorrect error line number reporting after multiline comments #69526
Description
Go version
go version go1.23.0 darwin/amd64
Output of go env in your module/workspace:
GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/dev/Library/Caches/go-build'
GOENV='/Users/dev/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOMODCACHE='/Users/dev/pkg/mod'
GOOS='darwin'
GOPATH='/Users/dev'
GOPROXY='https://goproxy.cn,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.23.0'
GODEBUG='gotypesalias=1'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/dev/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='0'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/2f/7bsk573j6bd1b949y1mq2stm0000gn/T/go-build3492055087=/tmp/go-build -gno-record-gcc-switches -fno-common'What did you do?
I encountered a problem with incorrect error line number reporting when using the text/template package. Specifically, if a template has a multiline comment (e.g., {{/* ... */}}), and an error occurs (such as an undefined function) on a line immediately after the comment, the reported error line is incorrect and points to the start of the comment block or earlier.
Example code https://go.dev/play/p/YVbgdA-Sj1Z:
package main
import (
"os"
"text/template"
"log"
)
func main() {
tmpl := `{{/*
This is a multiline comment.
It spans multiple lines.
*/}}
{{undefinedFunction "test"}}
`
t, err := template.New("test").Parse(tmpl)
if err != nil {
log.Fatalf("Template parse error: %v", err)
}
err = t.Execute(os.Stdout, nil)
if err != nil {
log.Printf("Template execution error: %v", err)
}
}What did you see happen?
The error reported the wrong line number):
Template parse error: template: test:2: function "undefinedFunction" not defined
What did you expect to see?
I expected the error to report the correct line where the undefined function is used:
Template parse error: template: test:5: function "undefinedFunction" not defined