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@title Adding New Classes @title Adding New Classes

@group developer @group developer

Guide to adding new classes to extend Phabricator. Guide to adding new classes to extend Phorge.

Overview Overview

======== ========

Phabricator is highly modular, and many parts of it can be extended by adding Phorge is highly modular, and many parts of it can be extended by adding

new classes. This document explains how to write new classes to change or new classes. This document explains how to write new classes to change or

expand the behavior of Phabricator. expand the behavior of Phorge.

IMPORTANT: The upstream does not offer support with extension development. NOTE: The upstream offers limited support with extension development.

Fundamentals Fundamentals

============ ============

Phabricator primarily discovers functionality by looking at concrete subclasses Phorge primarily discovers functionality by looking at concrete subclasses

of some base class. For example, Phabricator determines which applications are of some base class. For example, Phorge determines which applications are

available by looking at all of the subclasses of available by looking at all of the subclasses of

@{class@phabricator:PhabricatorApplication}. It @{class@phabricator:PhabricatorApplication}. It

discovers available workflows in `arc` by looking at all of the subclasses of discovers available workflows in `arc` by looking at all of the subclasses of

@{class@arcanist:ArcanistWorkflow}. It discovers available locales @{class@arcanist:ArcanistWorkflow}. It discovers available locales

by looking at all of the subclasses of @{class@arcanist:PhutilLocale}. by looking at all of the subclasses of @{class@arcanist:PhutilLocale}.

This pattern holds in many cases, so you can often add functionality by adding This pattern holds in many cases, so you can often add functionality by adding

new classes with no other work. Phabricator will automatically discover and new classes with no other work. Phorge will automatically discover and

integrate the new capabilities or features at runtime. integrate the new capabilities or features at runtime.

There are two main ways to add classes: There are two main ways to add classes:

- **Extensions Directory**: This is a simple way to add new code. It is - **Extensions Directory**: This is a simple way to add new code. It is

less powerful, but takes a lot less work. This is good for quick changes, less powerful, but takes a lot less work. This is good for quick changes,

testing and development, or getting started on a larger project. testing and development, or getting started on a larger project.

- **Creating Libraries**: This is a more advanced and powerful way to - **Creating Libraries**: This is a more advanced and powerful way to

organize extension code. This is better for larger or longer-lived organize extension code. This is better for larger or longer-lived

projects, or any code which you plan to distribute. projects, or any code which you plan to distribute.

The next sections walk through these approaches in greater detail. The next sections walk through these approaches in greater detail.

Extensions Directory Extensions Directory

==================== ====================

The easiest way to extend Phabricator by adding new classes is to drop them The easiest way to extend Phorge by adding new classes is to drop them

into the extensions directory, at `phabricator/src/extensions/`. into the extensions directory, at `pohrge/src/extensions/`.

This is intended as a quick way to add small pieces of functionality, test new This is intended as a quick way to add small pieces of functionality, test new

features, or get started on a larger project. Extending Phabricator like this features, or get started on a larger project. Extending Phorge like this

imposes a small performance penalty compared to using a library. imposes a small performance penalty compared to using a library.

This directory exists in all libphutil libraries, so you can find a similar This directory also exists for Arcanist, so you can find a similar

directory in `arcanist/src/extensions/`. directory in `arcanist/src/extensions/`.

For example, to add a new application, create a file like this one and add it For example, to add a new application, create a file like this one and add it

to `phabricator/src/extensions/`. to `phorge/src/extensions/`.

```name=phabricator/src/extensions/ExampleApplication.php, lang=php ```name=phorge/src/extensions/ExampleApplication.php, lang=php

<?php <?php

final class ExampleApplication extends PhabricatorApplication { final class ExampleApplication extends PhabricatorApplication {

public function getName() { public function getName() {

return pht('Example'); return pht('Example');

} }

``` ```

If you load {nav Applications} in the web UI, you should now see your new If you load {nav Applications} in the web UI, you should now see your new

application in the list. It won't do anything yet since you haven't defined application in the list. It won't do anything yet since you haven't defined

any interesting behavior, but this is the basic building block of Phabricator any interesting behavior, but this is the basic building block of Phorge

extensions. extensions.

Creating Libraries Creating Libraries

================== ==================

A more powerful (but more complicated) way to extend Phabricator is to create A more powerful (but more complicated) way to extend Phorge is to create

a libphutil library. Libraries can organize a larger amount of code, are easier a library. Libraries can organize a larger amount of code, are easier

to work with and distribute, and have slightly better performance than loose to work with and distribute, and have slightly better performance than loose

source files in the extensions directory. source files in the extensions directory.

In general, you'll perform these one-time setup steps to create a library: In general, you'll perform these one-time setup steps to create a library:

- Create a new directory. - Create a new directory.

- Use `arc liberate` to initialize and name the library. - Use `arc liberate` to initialize and name the library.

- Configure Phabricator or Arcanist to load the library. - Configure Phorge or Arcanist to load the library.

Then, to add new code, you do this: Then, to add new code, you do this:

- Write or update classes. - Write or update classes.

- Update the library metadata by running `arc liberate` again. - Update the library metadata by running `arc liberate` again.

Initializing a Library Initializing a Library

====================== ======================

To create a new libphutil library, create a directory for it and run To create a new library, create a directory for it and run

`arc liberate` on the directory. This documentation will use a conventional `arc liberate` on the directory. This documentation will use a conventional

directory layout, which is recommended, but you are free to deviate from this. directory layout, which is recommended, but you are free to deviate from this.

``` ```

$ mkdir libcustom/ $ mkdir libcustom/

$ cd libcustom/ $ cd libcustom/

libcustom/ $ arc liberate src/ libcustom/ $ arc liberate src/

``` ```

Show All 31 Lines - `src/.phutil_module_cache` This is a cache which makes "arc liberate"

any time. If you check your library into version control, you can add this any time. If you check your library into version control, you can add this

file to ignore rules (like `.gitignore`). file to ignore rules (like `.gitignore`).

- `src/__phutil_library_init__.php` This records the name of the library and - `src/__phutil_library_init__.php` This records the name of the library and

tells libphutil that a library exists here. tells libphutil that a library exists here.

- `src/__phutil_library_map__.php` This is a map of all the symbols - `src/__phutil_library_map__.php` This is a map of all the symbols

(functions and classes) in the library, which allows them to be autoloaded (functions and classes) in the library, which allows them to be autoloaded

at runtime and dependencies to be statically managed by `arc liberate`. at runtime and dependencies to be statically managed by `arc liberate`.

Linking with Phabricator Linking with Phorge

======================== ===================

If you aren't using this library with Phabricator (e.g., you are only using it (NOTE) If you aren't using this library with Phorge (e.g., you are only using it

with Arcanist or are building something else on libphutil) you can skip this with Arcanist or are building something else) you can skip this

chrisUnsubmitted

Done

(NOTE) If you aren't using this library with Phorge (e.g., you are only using it

- with Arcanist or are building something else on libphutil) you can skip this

+ with Arcanist or are building something else) you can skip this

step.

Remove the libphutil reference while we're in here?

chris: Remove the `libphutil` reference while we're in here?

step. step.

But, if you intend to use this library with Phabricator, you need to define its But, if you intend to use this library with Phorge, you need to define its

dependency on Phabricator by creating a `.arcconfig` file which points at dependency on Phorge by creating a `.arcconfig` file which points at

Phabricator. For example, you might write this file to Phorge. For example, you might write this file to

`libcustom/.arcconfig`: `libcustom/.arcconfig`:

```lang=json ```lang=json

{ {

"load": [ "load": [

"phabricator/src/" "phorge/src/"

] ]

} }

``` ```

For details on creating a `.arcconfig`, see For details on creating a `.arcconfig`, see

@{article:Arcanist User Guide: Configuring a New Project}. In general, this @{article:Arcanist User Guide: Configuring a New Project}. In general, this

tells `arc liberate` that it should look for symbols in Phabricator when tells `arc liberate` that it should look for symbols in Phorge when

performing static analysis. performing static analysis.

NOTE: If Phabricator isn't located next to your custom library, specify a NOTE: If Phorge isn't located next to your custom library, specify a

path which actually points to the `phabricator/` directory. path which actually points to the `phorge/` directory.

You do not need to declare dependencies on `arcanist`, since `arc liberate` You do not need to declare dependencies on `arcanist`, since `arc liberate`

automatically loads them. automatically loads them.

Finally, edit your Phabricator config to tell it to load your library at Finally, edit your Phorge config to tell it to load your library at

runtime, by adding it to `load-libraries`: runtime, by adding it to `load-libraries`:

```lang=json ```lang=json

... ...

'load-libraries' => array( 'load-libraries' => array(

'libcustom' => 'libcustom/src/', 'libcustom' => 'libcustom/src/',

), ),

... ...

``` ```

Now, Phabricator will be able to load classes from your custom library. Now, Phorge will be able to load classes from your custom library.

Writing Classes Writing Classes

=============== ===============

To actually write classes, create a new module and put code in it: To actually write classes, create a new module and put code in it:

libcustom/ $ mkdir src/example/ libcustom/ $ mkdir src/example/

libcustom/ $ nano src/example/ExampleClass.php # Edit some code. libcustom/ $ nano src/example/ExampleClass.php # Edit some code.

Now, run `arc liberate` to regenerate the static resource map: Now, run `arc liberate` to regenerate the static resource map:

libcustom/ $ arc liberate src/ libcustom/ $ arc liberate src/

This will automatically regenerate the static map of the library. This will automatically regenerate the static map of the library.

What You Can Extend And Invoke What You Can Extend And Invoke

============================== ==============================

Arcanist and Phabricator are strict about extensibility of classes and Arcanist and Pohrge are strict about extensibility of classes and

visibility of methods and properties. Most classes are marked `final`, and visibility of methods and properties. Most classes are marked `final`, and

methods have the minimum required visibility (protected or private). The goal methods have the minimum required visibility (protected or private). The goal

of this strictness is to make it clear what you can safely extend, access, and of this strictness is to make it clear what you can safely extend, access, and

invoke, so your code will keep working as the upstream changes. invoke, so your code will keep working as the upstream changes.

IMPORTANT: We'll still break APIs frequently. The upstream does not support IMPORTANT: We'll still break APIs frequently. The upstream offers limited

extension development, and none of these APIs are stable. support for extension development, and none of these APIs are stable.

When developing libraries to work with Arcanist and Phabricator, you should When developing libraries to work with Arcanist and Phorge, you should

respect method and property visibility. respect method and property visibility.

If you want to add features but can't figure out how to do it without changing If you want to add features but can't figure out how to do it without changing

Phabricator code, here are some approaches you may be able to take: Phorge code, here are some approaches you may be able to take:

- {icon check, color=green} **Use Composition**: If possible, use composition - {icon check, color=green} **Use Composition**: If possible, use composition

rather than extension to build your feature. rather than extension to build your feature.

- {icon check, color=green} **Find Another Approach**: Check the - {icon check, color=green} **Find Another Approach**: Check the

documentation for a better way to accomplish what you're trying to do. documentation for a better way to accomplish what you're trying to do.

- {icon check, color=green} **File a Feature Request**: Let us know what your - {icon check, color=green} **File a Feature Request**: Let us know what your

use case is so we can make the class tree more flexible or configurable, or use case is so we can make the class tree more flexible or configurable, or

point you at the right way to do whatever you're trying to do, or explain point you at the right way to do whatever you're trying to do, or explain

why we don't let you do it. Note that we **do not support** extension why we don't let you do it.

development so you may have mixed luck with this one.

These approaches are **discouraged**, but also possible: These approaches are **discouraged**, but also possible:

- {icon times, color=red} **Fork**: Create an ad-hoc local fork and remove - {icon times, color=red} **Fork**: Create an ad-hoc local fork and remove

`final` in your copy of the code. This will make it more difficult for you `final` in your copy of the code. This will make it more difficult for you

to upgrade in the future, although it may be the only real way forward to upgrade in the future, although it may be the only real way forward

depending on what you're trying to do. depending on what you're trying to do.

- {icon times, color=red} **Use Reflection**: You can use - {icon times, color=red} **Use Reflection**: You can use

[[ http://php.net/manual/en/book.reflection.php | Reflection ]] to remove [[ http://php.net/manual/en/book.reflection.php | Reflection ]] to remove

modifiers at runtime. This is fragile and discouraged, but technically modifiers at runtime. This is fragile and discouraged, but technically

possible. possible.

- {icon times, color=red} **Remove Modifiers**: Send us a patch removing - {icon times, color=red} **Remove Modifiers**: Send us a patch removing

`final` (or turning `protected` or `private` into `public`). We will almost `final` (or turning `protected` or `private` into `public`). We will almost

never accept these patches unless there's a very good reason that the never accept these patches unless there's a very good reason that the

current behavior is wrong. current behavior is wrong.

Next Steps Next Steps

========== ==========

Continue by: Continue by:

- visiting the [[ https://secure.phabricator.com/w/community_resources/ | - visiting the [[ https://we.phorge.it/w/community_resources/ |

Community Resources ]] page to find or share extensions and libraries. Community Resources ]] page to find or share extensions and libraries.