zulip/help/add-a-custom-linkifier.md

Add a custom linkifier

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Linkifiers make it easy to refer to issues or tickets in third party issue trackers, like GitHub, Salesforce, Zendesk, and others. For instance, you can add a linkifier that automatically turns #2468 into a link to https://github.com/zulip/zulip/issues/2468.

If the pattern appears in a topic, Zulip adds an Open () button to the right of the topic in the message recipient bar that links to the appropriate URL.

If you have any trouble creating the linkifiers you want, please contact Zulip support with details on what you're trying to do.

Add a custom linkifier

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{settings_tab|linkifier-settings}

1. Under Add a new linkifier, enter a Pattern and URL template.

2. Click Add linkifier.

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Reorder linkifiers

Linkifiers are processed in order, and will not apply to text that already is linkified. One can thus configure multiple linkifiers with overlapping syntax, and only the first one whose regular expression matches a given part of a message will take effect. See the overlapping patterns section for examples.

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{settings_tab|linkifier-settings}

1. Under Linkifiers, click and drag existing linkifiers into the desired order.

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Common linkifier patterns

The following examples cover the most common types of linkifiers, with a focus on linkifiers for issues or tickets.

Link to an issue or ticket

This is a pattern that turns a # followed by a number into a link. It is often used to link to issues or tickets in third party issue trackers, like GitHub, Salesforce, Zendesk, and others.

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• Pattern: #(?P<id>[0-9]+)
• URL template: https://github.com/zulip/zulip/issues/{id}
• Original text: #2468
• Automatically links to: https://github.com/zulip/zulip/issues/2468

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Link to issues or tickets in multiple projects or apps

To set up linkifiers for issues or tickets in multiple projects, consider extending the #2468 format with project-specific variants. For example, the Zulip development community uses #M2468 for an issue in the repository for the Zulip mobile app, #D2468 and issue in the desktop app repository, etc.

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• Pattern: #M(?P<id>[0-9]+)
• URL template: https://github.com/zulip/zulip-mobile/issues/{id}
• Original text: #M2468
• Automatically links to: https://github.com/zulip/zulip-mobile/issues/2468

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Link to issues or tickets in multiple repositories

For organizations that commonly link to multiple GitHub repositories, this linkfier pattern turns org/repo#ID into an issue or pull request link.

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• Pattern: (?P<org>[a-zA-Z0-9_-]+)/(?P<repo>[a-zA-Z0-9_-]+)#(?P<id>[0-9]+)
• URL template: https://github.com/{org}/{repo}/issues/{id}
• Original text: zulip/zulip#2468
• Automatically links to: https://github.com/zulip/zulip/issues/2468

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Link to a hexadecimal issue or ticket number

The following pattern linkfies a string of hexadecimal digits between 7 and 40 characters long, such as a Git commit ID.

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• Pattern: (?P<id>[0-9a-f]{7,40})
• URL template: https://github.com/zulip/zulip/commit/{id}
• Original text: abdc123
• Automatically links to: https://github.com/zulip/zulip/commit/abcd123

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Advanced linkifier patterns

Linkifiers are a flexible system that can be used to construct rules for a wide variety of situations. Linkifier patterns are regular expressions, using the re2 regular expression engine.

Linkifiers use RFC 6570 compliant URL templates to describe how links should be generated. These templates support several expression types. The default expression type ({var}) will URL-encode special characters like / and &; this behavior is desired for the vast majority of linkifiers. Fancier URL template expression types can allow you to get the exact behavior you want in corner cases like optional URL query parameters. For example:

• Use {+var} when you want URL delimiter characters to not be URL-encoded.
• Use {?var} and {&var} for variables in URL query parameters.
• Use {#var} when generating # fragments in URLs.

The URL template specification has brief examples and detailed examples explaining the precise behavior of URL templates.

Linking to documentation pages

This example pattern is a shorthand for linking to pages on Zulip's ReadTheDocs site.

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• Pattern: RTD/(?P<article>[a-zA-Z0-9_/.#-]+)
• URL template: https://zulip.readthedocs.io/en/latest/{+article}
• Original text: RTD/overview/changelog.html
• Automatically links to: https://zulip.readthedocs.io/en/latest/overview/changelog.html

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!!! tip ""

This pattern uses the `{+var}` expression type. With the
default expression type (`{article}`), the `/` between `overview` and
`changelog` would incorrectly be URL-encoded.

Linking to Google search results

This example pattern allows linking to Google searches.

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• Pattern: google:(?P<q>\w+)?
• URL template: https://google.com/search{?q}
• Original text: google:foo or google:
• Automatically links to: https://google.com/search?q=foo or https://google.com/search

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!!! tip ""

This pattern uses the `{?var}` expression type. With the default expression
type (`{q}`), there would be no way to only include the `?` in the URL
if the optional `q` is present.

Overlapping patterns

In this example, a general linkifier is configured to make GitHub repository references like zulip-desktop#123 link to issues in that repository within the zulip GitHub organization. A more specific linkifier overrides that linkifier for a specific repository of interest (django/django) that is in a different organization.

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• Specific linkifier (ordered before the general linkifier)

  • Pattern: django#(?P<id>[0-9]+)
  • URL template: https://github.com/django/django/pull/{id}

• General linkifier

  • Pattern: (?P<repo>[a-zA-Z0-9_-]+)#(?P<id>[0-9]+)
  • URL template: https://github.com/zulip/{repo}/pull/{id}

• Example matching both linkifiers; specific linkifier takes precedence:

  • Original text: django#123
  • Automatically links to: https://github.com/django/django/pull/123

• Example matching only the general linkifier:

  • Original text: zulip-desktop#123
  • Automatically links to: https://github.com/zulip/zulip-desktop/pull/123

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!!! tip ""

This set of patterns has overlapping regular expressions. Note that
the general linkifier pattern would match `lorem#123` too. The specific
linkifier will only get prioritized over the general linkifier if it is
ordered before the more general pattern. This can be customized by
dragging and dropping existing linkifiers into the desired order. New
linkifiers will automatically be ordered last.