Why Are My Go HTML Comments Disappearing in Rendered Pages?

Go HTML Comments Not Rendering: A Solution with template.HTML

In a Go web application, the disappearance of HTML comments in rendered pages can be a frustrating issue. This is especially problematic for KnockoutJS code that relies on containerless control flow syntax.

The reason behind this behavior is that by default, Go's html/template package escapes HTML content for security reasons. This means that HTML comments, which are wrapped in , are rendered as escaped text instead of being displayed as comments.

To resolve this issue, the html/template package provides a special type called template.HTML. Values of this type are not escaped when rendered.

Custom Function Approach

One effective solution is to create a custom function for your templates that wraps your HTML comments in template.HTML. Here's how you can do it:

<code class="go">func main() {
    t := template.Must(template.New("").Funcs(template.FuncMap{
        "safe": func(s string) template.HTML { return template.HTML(s) },
    }).Parse(src))
    t.Execute(os.Stdout, nil)
}

const src = `
{{safe "<!-- This is a comment -->"}}
<div>Some <b>HTML</b> content</div>
`</code>

In this example, we define a safe() function that takes a string argument and returns it as template.HTML. Within the template, we can pass HTML comments to this function using {{safe ""}}. This ensures that the comments are not escaped.

Usage

To use this technique, simply transform your HTML comments to the following format:

<code class="html">{{safe "<!-- Your comment -->"}}</code>

or

<code class="html">{{"<!-- Your comment -->" | safe}}</code>

By using this approach, your HTML comments will be retained in the rendered output.

Note:

• If your HTML comments contain quotation marks, be sure to escape them properly, e.g., {{safe ""}}.
• Avoid using conditional HTML comments as they can interfere with the context-sensitive escaping mechanism.

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