forgejo-federation/docs/content/doc/advanced/mail-templates-us.md
guillep2k 1f90147f39 Use templates for issue e-mail subject and body (#8329)
* Add template capability for issue mail subject

* Remove test string

* Fix trim subject length

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* Add information for the template

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* Fix mail tests

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advanced Mail templates 45 mail-templates

Mail templates

To craft the e-mail subject and contents for certain operations, Gitea can be customized by using templates. The templates for these functions are located under the custom directory. Gitea has an internal template that serves as default in case there's no custom alternative.

Custom templates are loaded when Gitea starts. Changes made to them are not recognized until Gitea is restarted again.

Mail notifications supporting templates

Currently, the following notification events make use of templates:

Action name Usage
new A new issue or pull request was created.
comment A new comment was created in an existing issue or pull request.
close An issue or pull request was closed.
reopen An issue or pull request was reopened.
review The head comment of a review in a pull request.
code A single comment on the code of a pull request.
assigned Used was assigned to an issue or pull request.
default Any action not included in the above categories, or when the corresponding category template is not present.

The path for the template of a particular message type is:

custom/templates/mail/{action type}/{action name}.tmpl

Where {action type} is one of issue or pull (for pull requests), and {action name} is one of the names listed above.

For example, the specific template for a mail regarding a comment in a pull request is:

custom/templates/mail/pull/comment.tmpl

However, creating templates for each and every action type/name combination is not required. A fallback system is used to choose the appropriate template for an event. The first existing template on this list is used:

  • The specific template for the desired action type and action name.
  • The template for action type issue and the desired action name.
  • The template for the desired action type, action name default.
  • The template for action type issue, action name default.

The only mandatory template is action type issue, action name default, which is already embedded in Gitea unless it's overridden by the user in the custom directory.

Template syntax

Mail templates are UTF-8 encoded text files that need to follow one of the following formats:

Text and macros for the subject line
------------
Text and macros for the mail body

or

Text and macros for the mail body

Specifying a subject section is optional (and therefore also the dash line separator). When used, the separator between subject and mail body templates requires at least three dashes; no other characters are allowed in the separator line.

Subject and mail body are parsed by Golang's template engine and are provided with a metadata context assembled for each notification. The context contains the following elements:

Name Type Available Usage
.FallbackSubject string Always A default subject line. See Below.
.Subject string Only in body The subject, once resolved.
.Body string Always The message of the issue, pull request or comment, parsed from Markdown into HTML and sanitized. Do not confuse with the mail body
.Link string Always The address of the originating issue, pull request or comment.
.Issue models.Issue Always The issue (or pull request) originating the notification. To get data specific to a pull request (e.g. HasMerged), .Issue.PullRequest can be used, but care should be taken as this field will be nil if the issue is not a pull request.
.Comment models.Comment If applicable If the notification is from a comment added to an issue or pull request, this will contain the information about the comment.
.IsPull bool Always true if the mail notification is associated with a pull request (i.e. .Issue.PullRequest is not nil).
.Repo string Always Name of the repository, including owner name (e.g. mike/stuff)
.User models.User Always Owner of the repository from which the event originated. To get the user name (e.g. mike),.User.Name can be used.
.Doer models.User Always User that executed the action triggering the notification event. To get the user name (e.g. rhonda), .Doer.Name can be used.
.IsMention bool Always true if this notification was only generated because the user was mentioned in the comment, while not being subscribed to the source. It will be false if the recipient was subscribed to the issue or repository.
.SubjectPrefix string Always Re: if the notification is about other than issue or pull request creation; otherwise an empty string.
.ActionType string Always "issue" or "pull". Will correspond to the actual action type independently of which template was selected.
.ActionName string Always It will be one of the action types described above (new, comment, etc.), and will correspond to the actual action name independently of which template was selected.

All names are case sensitive.

The subject part of the template

The template engine used for the mail subject is golang's text/template. Please refer to the linked documentation for details about its syntax.

The subject is built using the following steps:

  • A template is selected according to the type of notification and to what templates are present.
  • The template is parsed and resolved (e.g. {{.Issue.Index}} is converted to the number of the issue or pull request).
  • All space-like characters (e.g. TAB, LF, etc.) are converted to normal spaces.
  • All leading, trailing and redundant spaces are removed.
  • The string is truncated to its first 256 runes (characters).

If the end result is an empty string, or no subject template was available (i.e. the selected template did not include a subject part), Gitea's internal default will be used.

The internal default (fallback) subject is the equivalent of:

{{.SubjectPrefix}}[{{.Repo}}] {{.Issue.Title}} (#.Issue.Index)

For example: Re: [mike/stuff] New color palette (#38)

Gitea's default subject can also be found in the template metadata as .FallbackSubject from any of the two templates, even if a valid subject template is present.

The mail body part of the template

The template engine used for the mail body is golang's html/template. Please refer to the linked documentation for details about its syntax.

The mail body is parsed after the mail subject, so there is an additional metadata field which is the actual rendered subject, after all considerations.

The expected result is HTML (including structural elements like<html>, <body>, etc.). Styling through <style> blocks, class and style attributes is possible. However, html/template does some automatic escaping that should be considered.

Attachments (such as images or external style sheets) are not supported. However, other templates can be referenced too, for example to provide the contents of a <style> element in a centralized fashion. The external template must be placed under custom/mail and referenced relative to that directory. For example, custom/mail/styles/base.tmpl can be included using {{template styles/base}}.

The mail is sent with Content-Type: multipart/alternative, so the body is sent in both HTML and text formats. The latter is obtained by stripping the HTML markup.

Troubleshooting

How a mail is rendered is directly dependent on the capabilities of the mail application. Many mail clients don't even support HTML, so they show the text version included in the generated mail.

If the template fails to render, it will be noticed only at the moment the mail is sent. A default subject is used if the subject template fails, and whatever was rendered successfully from the the mail body is used, disregarding the rest.

Please check Gitea's logs for error messages in case of trouble.

Example

custom/templates/mail/issue/default.tmpl:

[{{.Repo}}] @{{.Doer.Name}}
{{if eq .ActionName "new"}}
    created
{{else if eq .ActionName "comment"}}
    commented on
{{else if eq .ActionName "close"}}
    closed
{{else if eq .ActionName "reopen"}}
    reopened
{{else}}
    updated
{{end}}
{{if eq .ActionType "issue"}}
    issue
{{else}}
    pull request
{{end}}
#{{.Issue.Index}}: {{.Issue.Title}}
------------
<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>{{.Subject}}</title>
</head>

<body>
    {{if .IsMention}}
    <p>
        You are receiving this because @{{.Doer.Name}} mentioned you.
    </p>
    {{end}}
    <p>
        <p>
        <a href="{{AppURL}}/{{.Doer.LowerName}}">@{{.Doer.Name}}</a>
        {{if not (eq .Doer.FullName "")}}
            ({{.Doer.FullName}})
        {{end}}
        {{if eq .ActionName "new"}}
            created
        {{else if eq .ActionName "close"}}
            closed
        {{else if eq .ActionName "reopen"}}
            reopened
        {{else}}
            updated
        {{end}}
        <a href="{{.Link}}">{{.Repo}}#{{.Issue.Index}}</a>.
        </p>
        {{if not (eq .Body "")}}
            <h3>Message content:</h3>
            <hr>
            {{.Body | Str2html}}
        {{end}}
    </p>
    <hr>
    <p>
        <a href="{{.Link}}">View it on Gitea</a>.
    </p>
</body>
</html>

This template produces something along these lines:

Subject

[mike/stuff] @rhonda commented on pull request #38: New color palette

Mail body

@rhonda (Rhonda Myers) updated mike/stuff#38.

Message content:

__________________________________________________________________

Mike, I think we should tone down the blues a little.
__________________________________________________________________

View it on Gitea.

Advanced

The template system contains several functions that can be used to further process and format the messages. Here's a list of some of them:

Name Parameters Available Usage
AppUrl - Any Gitea's URL
AppName - Any Set from app.ini, usually "Gitea"
AppDomain - Any Gitea's host name
EllipsisString string, int Any Truncates a string to the specified length; adds ellipsis as needed
Str2html string Body only Sanitizes text by removing any HTML tags from it.

These are functions, not metadata, so they have to be used:

Like this:         {{Str2html "Escape<my>text"}}
Or this:           {{"Escape<my>text" | Str2html}}
Or this:           {{AppUrl}}
But not like this: {{.AppUrl}}