knadh/listmonk · error

error compiling message: %v

Error message

error compiling message: %v

What it means

Compilation of an individual message body from the campaign template failed while preparing the campaign for sending.

Source

Thrown at models/campaigns.go:191

	// If the format is markdown, convert Markdown to HTML.
	if c.ContentType == CampaignContentTypeMarkdown {
		var b bytes.Buffer
		if err := markdown.Convert([]byte(c.Body), &b); err != nil {
			return err
		}
		body = b.String()
	} else {
		body = c.Body
	}

	// Compile the campaign message.
	for _, r := range regTplFuncs {
		body = r.regExp.ReplaceAllString(body, r.replace)
	}

	msgTpl, err := template.New(ContentTpl).Funcs(f).Parse(body)
	if err != nil {
		return fmt.Errorf("error compiling message: %v", err)
	}

	out, err := baseTPL.AddParseTree(ContentTpl, msgTpl.Tree)
	if err != nil {
		return fmt.Errorf("error inserting child template: %v", err)
	}
	c.Tpl = out

	if hasTplExpr(c.AltBody.String) {
		b := c.AltBody.String
		for _, r := range regTplFuncs {
			b = r.regExp.ReplaceAllString(b, r.replace)
		}
		bTpl, err := template.New(ContentTpl).Funcs(f).Parse(b)
		if err != nil {
			return fmt.Errorf("error compiling alt plaintext message: %v", err)
		}
		c.AltBodyTpl = bTpl

View on GitHub (pinned to 670c01717d)

Solutions

1. Fix the invalid template expression reported in the wrapped error
2. Escape literal braces using {{"{{"}}"
3. Ensure functions used are in the func map f registered with the template
4. Use previewTemplate to smoke-test the body before saving

Example fix

// before
{{ .TrackLink | urlquery extraArg }}
// after
{{ .TrackLink | urlquery }}

if _, err := template.New("msg").Funcs(funcMap).Parse(body); err != nil {
    return fmt.Errorf("invalid message template: %v", err)
}

if err := c.CompileTemplate(); err != nil {
    if strings.Contains(err.Error(), "error compiling message") {
        // surface the wrapped parse error to the content editor
    }
}

When it happens

Trigger: CompileTemplate is called and template.New(ContentTpl).Funcs(f).Parse(body) fails because the campaign message body has invalid template actions or references unknown functions/fields.

Common situations: Same family as subject/base errors: stray "{{", misspelled function, wrong argument types to template funcs; often introduced after editing campaign content in the UI or via API import.

Related errors

• error compiling subject: %v
• error compiling base template: %v
• error inserting child template: %v
• error compiling alt plaintext message: %v
• campaigns.fieldInvalidSubject

AI-assisted analysis of knadh/listmonk@670c01717d (2026-09-01). Data as JSON: /api/errors/6815615feefc0606. Report an issue: GitHub.