html/template: document that it strips comments

[magical]

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

go1.11.1 (playground)

Does this issue reproduce with the latest release?

Yes.

What did you do?

package main

import (
	"fmt"
	"html/template"
	"os"
)

const templateSrc = `<style>/* one */</style> /* two */ <!-- three -->`

func main() {
	fmt.Println(templateSrc)
	tmpl := template.Must(template.New("").Parse(templateSrc))
	fmt.Println(tmpl.Tree.Root.String())
	tmpl.Execute(os.Stdout, nil)
}

https://play.golang.org/p/WPnEwLYTBkF

What did you expect to see?

Comments preserved in output.

<style>/* one */</style> /* two */ <!-- three -->
<style>/* one */</style> /* two */ <!-- three -->
<style>/* one */</style> /* two */ <!-- three -->

What did you see instead?

Comments are stripped.

<style>/* one */</style> /* two */ <!-- three -->
<style>/* one */</style> /* two */ <!-- three -->
<style> </style> /* two */ 

---

This behaviour is apparently intentional (#14256), but it is surprising and undocumented. Templates already have their own special comment syntax ({{/* */}}), so i didn't expect that they would gobble up HTML and CSS (and presumably JS) comments as well. This needs to be called out in the documentation, ideally with a rationale and workaround.

[hellozee]

If no one is on it, I would like to give it a try

[agnivade]

Go for it.

[gopherbot]

Change https://golang.org/cl/148833 mentions this issue: html/template: document that comments are stripped from html templates

[empijei]

I see this has been silent for a while, @hellozee do you have time to address the comments in cl/148833 ?😊

[hellozee]

I did update the patch accordingly, @empijei, please do drop anything that I may have missed, 😄

[jbpratt]

It seems this has been quiet. Reminder for @hellozee there are 3 unresolved comments on the patchset for this issue at cl/148833 😄

[gopherbot]

Change https://go.dev/cl/658115 mentions this issue: html/template: document comment stripping