Golang text/template: Unable to set zero value for fields in template

Go version

go1.24.0

Output of go env in your module/workspace:

set AR=ar
set CC=gcc
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_ENABLED=0
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set CXX=g++
set GCCGO=gccgo
set GO111MODULE=
set GOAMD64=v1
set GOARCH=amd64
set GOAUTH=netrc
set GOBIN=
set GOCACHE=C:\Users\xxx\AppData\Local\go-build
set GOCACHEPROG=
set GODEBUG=
set GOENV=C:\Users\xxx\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFIPS140=off
set GOFLAGS=
set GOGCCFLAGS=-m64 -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\xxx\AppData\Local\Temp\go-build2279385750=/tmp/go-build -gno-record-gcc-switches
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMOD=NUL
set GOMODCACHE=C:\Users\xx\go\pkg\mod
set GONOPROXY=gitlab.com/xxx/*
set GONOSUMDB=gitlab.com/xxx/*
set GOOS=windows
set GOPATH=C:\Users\xxx\go
set GOPRIVATE=gitlab.com/xxx/*
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTELEMETRY=local
set GOTELEMETRYDIR=C:\Users\xxx\AppData\Roaming\go\telemetry
set GOTMPDIR=
set GOTOOLCHAIN=auto
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.24.0
set GOWORK=
set PKG_CONFIG=pkg-config

What did you do?

I am trying to parse template using text/template package. My input payload has few fields and which are optional in certain cases. So i was trying to set them with their zero value when missing in input payload.

To achieve this, I took help of Options and set missingkey=zero option while parsing template. The expected behavior was to set empty string value for missing fields with string data type but it was showing <no value>

Below is the code snippet I used to test this issue.

package main

import (
    "bytes"
    "fmt"
    "strings"
    "text/template"
)

func main() {
    payload := map[string]interface{}{
        //"PackagerType" is intentionally missing
        "Name": "Checkout",
    }

    tmpl, err := template.New("test").
        //Option("missingkey=zero").
        Parse(`Name:         {{.Name}}
PackagerType: {{.PackagerType}}
UnknownKey:   {{.DoesNotExist}}
`)
    if err != nil {
        panic(err)
    }

    var buf bytes.Buffer
    if err := tmpl.Execute(&buf, payload); err != nil {
        panic(err)
    }

    fmt.Println("OUTPUT:")
    fmt.Println(buf.String())
}

What did you see happen?

I used feature of Options to set missingkey=zero option while parsing template. The expected behavior was to set empty string value for missing fields with string data type but it was showing <no value>

Sample output:

$ go run main.go
OUTPUT:
Name:         Checkout
PackagerType: <no value>
UnknownKey:   <no value>

What did you expect to see?

I was expecting below output to be displayed.

OUTPUT:
Name:         Checkout
PackagerType: 
UnknownKey:   

Comment From: seankhliao

The type for the values of map[string]any is any, represented as a nil pointer, printed as <no value>. It is not a string.

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