html/template: user-defined function is not parsed via ParseFiles

[gkarthiks]

What version of Go are you using (go version)?

$ go version
go version go1.12.6 darwin/amd64

Does this issue reproduce with the latest release?

Yes, its with 1.12 release

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/kagovind/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/kagovind/GODeveloper"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/kagovind/GODeveloper/data-fabric-reconcile-alerter/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/yz/mp010ls16zdcnm10w218zywxvykr04/T/go-build353080250=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I have a HTML template; Along with all the CSS and HTML tags, below is the template I want to iterate over. I have stored this as a file in HTML format.

    <tr>
        <td style="padding: 30px 0 20px 0;" bgcolor="#dad8e6">
            <table bgcolor="#e1effc" cellspacing="0" class="buttonwrapper" cellspacing="0" celpadding="0" border=".5">
                <tr bgcolor="#3662d1" style="color: white">
                    <th>S No</th>
                    <th>Unused </th>
                </tr>
                {{ range $index, $element := .UnUsed }}
                    <tr>
                        <td>
                            {{ $index | inc }}
                        </td>
                        <td>
                            {{ $element }}
                        </td>
                    </tr>
                {{ end }}
            </table>
        </td>
    </tr>

Now I have the following snippet of code for incrementing the Index in the template.

func inc(i int) int {
    return i + 1
}

funcMap := template.FuncMap{
    "inc": inc,
}

tmpl = template.New("email").Funcs(funcMap)
tmpl, err = tmpl.ParseFiles(templateFileName)

if err != nil {
    log.Fatalf("Error occurred while parsing the template %s ", err)
} else {
    log.Debug("Parsing the html template completed")
}
buffer := new(bytes.Buffer)
if err = tmpl.Execute(buffer, data); err != nil {
    log.Fatalf("Error occurred while parsing the template %s ", err)
}

When I execute the above code, nothing is getting parsed. But if I parse the same template passed to the template as a string like below

fileBytes, err := ioutil.ReadFile(templateFileName)
if err != nil {
    log.Fatalf("Error while reading file data into byte array %s ",err)
}

funcMap := template.FuncMap{
    "inc": inc,
}
tmpl, err := template.New("email").Funcs(funcMap).Parse(string(fileBytes))

this later one via []byte is working.

What did you expect to see?

Should have the index incremented with +1

What did you see instead?

The template file was not parsed.

[bcmills]

When possible, please post code examples as runnable links to https://play.golang.org rather than isolated snippets.

[bcmills]

Note that both of your log.Fatalf calls have the same error message. Correcting that (as https://play.golang.org/p/wgWilb_xu0m), I see:

2009/11/10 23:00:00 Parsing the html template completed
2009/11/10 23:00:00 Error occurred while executing the template: template: email: "email" is an incomplete or empty template

[bcmills]

Please provide a complete example that illustrates the problem.

[gkarthiks]

@bcmills will be updating the complete data shortly.

[ALTree]

This has been in waiting for info for 2 years, it was reported against a version of Go that is no longer supported, and we still don't have an auto-contained reproducer, so let's archive this. If it comes out again on a recent Go version we can open a new issue.