How to Render Newlines Correctly in HTML Templates?

Overcoming the Escaping Issue in html/templates with Newlines

In HTML templates, newlines encoded as n are rendered as HTML entities (
) rather than actual line breaks. This occurs when the n characters are escaped by the template instead of accepted as part of trusted data.

Solution: Sanitization and Pre-Escaping

To resolve this issue, follow these steps:

1. Sanitize the text: Use template.HTMLEscape() to remove any potentially harmful characters from the text file.
2. Substitute newlines: After sanitization, replace all occurrences of "n" with "
   ".
3. Use pre-escaped data: Pass the sanitized and substituted text to the template as template.HTML, which encapsulates safe HTML fragments.

Example Implementation:

The following code demonstrates the process:

<code class="go">package main

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

const page = `

  
  
  
    <p>{{.}}</p>
  
`

const text = `first line
<script>dangerous</script>
last line`

func main() {
    t := template.Must(template.New("page").Parse(page))
    safe := template.HTMLEscapeString(text)
    safe = strings.Replace(safe, "\n", "<br>", -1)
    t.Execute(os.Stdout, template.HTML(safe))
}</code>

This code sanitizes the text, replaces newlines with
, and passes it to the template as pre-escaped data. The rendered result will correctly display line breaks as intended without escaping issues.

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