1============================= 2Code Reviews with Phabricator 3============================= 4 5.. contents:: 6 :local: 7 8If you prefer to use a web user interface for code reviews, you can now submit 9your patches for Clang and LLVM at `LLVM's Phabricator`_ instance. 10 11While Phabricator is a useful tool for some, the relevant -commits mailing list 12is the system of record for all LLVM code review. The mailing list should be 13added as a subscriber on all reviews, and Phabricator users should be prepared 14to respond to free-form comments in mail sent to the commits list. 15 16Sign up 17------- 18 19To get started with Phabricator, navigate to `http://reviews.llvm.org`_ and 20click the power icon in the top right. You can register with a GitHub account, 21a Google account, or you can create your own profile. 22 23Make *sure* that the email address registered with Phabricator is subscribed 24to the relevant -commits mailing list. If you are not subscribed to the commit 25list, all mail sent by Phabricator on your behalf will be held for moderation. 26 27Note that if you use your Subversion user name as Phabricator user name, 28Phabricator will automatically connect your submits to your Phabricator user in 29the `Code Repository Browser`_. 30 31Requesting a review via the command line 32---------------------------------------- 33 34Phabricator has a tool called *Arcanist* to upload patches from 35the command line. To get you set up, follow the 36`Arcanist Quick Start`_ instructions. 37 38You can learn more about how to use arc to interact with 39Phabricator in the `Arcanist User Guide`_. 40 41.. _phabricator-request-review-web: 42 43Requesting a review via the web interface 44----------------------------------------- 45 46The tool to create and review patches in Phabricator is called 47*Differential*. 48 49Note that you can upload patches created through various diff tools, 50including git and svn. To make reviews easier, please always include 51**as much context as possible** with your diff! Don't worry, Phabricator 52will automatically send a diff with a smaller context in the review 53email, but having the full file in the web interface will help the 54reviewer understand your code. 55 56To get a full diff, use one of the following commands (or just use Arcanist 57to upload your patch): 58 59* ``git show HEAD -U999999 > mypatch.patch`` 60* ``git format-patch -U999999 @{u}`` 61* ``svn diff --diff-cmd=diff -x -U999999`` 62 63To upload a new patch: 64 65* Click *Differential*. 66* Click *+ Create Diff*. 67* Paste the text diff or browse to the patch file. Click *Create Diff*. 68* Leave this first Repository field blank. (We'll fill in the Repository 69 later, when sending the review.) 70* Leave the drop down on *Create a new Revision...* and click *Continue*. 71* Enter a descriptive title and summary. The title and summary are usually 72 in the form of a :ref:`commit message <commit messages>`. 73* Add reviewers (see below for advice). (If you set the Repository field 74 correctly, llvm-commits or cfe-commits will be subscribed automatically; 75 otherwise, you will have to manually subscribe them.) 76* In the Repository field, enter the name of the project (LLVM, Clang, 77 etc.) to which the review should be sent. 78* Click *Save*. 79 80To submit an updated patch: 81 82* Click *Differential*. 83* Click *+ Create Diff*. 84* Paste the updated diff or browse to the updated patch file. Click *Create Diff*. 85* Select the review you want to from the *Attach To* dropdown and click 86 *Continue*. 87* Leave the Repository field blank. (We previously filled out the Repository 88 for the review request.) 89* Add comments about the changes in the new diff. Click *Save*. 90 91Choosing reviewers: You typically pick one or two people as initial reviewers. 92This choice is not crucial, because you are merely suggesting and not requiring 93them to participate. Many people will see the email notification on cfe-commits 94or llvm-commits, and if the subject line suggests the patch is something they 95should look at, they will. 96 97Here are a couple of ways to pick the initial reviewer(s): 98 99* Use ``svn blame`` and the commit log to find names of people who have 100 recently modified the same area of code that you are modifying. 101* Look in CODE_OWNERS.TXT to see who might be responsible for that area. 102* If you've discussed the change on a dev list, the people who participated 103 might be appropriate reviewers. 104 105Even if you think the code owner is the busiest person in the world, it's still 106okay to put them as a reviewer. Being the code owner means they have accepted 107responsibility for making sure the review happens. 108 109Reviewing code with Phabricator 110------------------------------- 111 112Phabricator allows you to add inline comments as well as overall comments 113to a revision. To add an inline comment, select the lines of code you want 114to comment on by clicking and dragging the line numbers in the diff pane. 115When you have added all your comments, scroll to the bottom of the page and 116click the Submit button. 117 118You can add overall comments in the text box at the bottom of the page. 119When you're done, click the Submit button. 120 121Phabricator has many useful features, for example allowing you to select 122diffs between different versions of the patch as it was reviewed in the 123*Revision Update History*. Most features are self descriptive - explore, and 124if you have a question, drop by on #llvm in IRC to get help. 125 126Note that as e-mail is the system of reference for code reviews, and some 127people prefer it over a web interface, we do not generate automated mail 128when a review changes state, for example by clicking "Accept Revision" in 129the web interface. Thus, please type LGTM into the comment box to accept 130a change from Phabricator. 131 132Committing a change 133------------------- 134 135Once a patch has been reviewed and approved on Phabricator it can then be 136committed to trunk. If you do not have commit access, someone has to 137commit the change for you (with attribution). It is sufficient to add 138a comment to the approved review indicating you cannot commit the patch 139yourself. If you have commit access, there are multiple workflows to commit the 140change. Whichever method you follow it is recommended that your commit message 141ends with the line: 142 143:: 144 145 Differential Revision: <URL> 146 147where ``<URL>`` is the URL for the code review, starting with 148``http://reviews.llvm.org/``. 149 150This allows people reading the version history to see the review for 151context. This also allows Phabricator to detect the commit, close the 152review, and add a link from the review to the commit. 153 154Note that if you use the Arcanist tool the ``Differential Revision`` line will 155be added automatically. If you don't want to use Arcanist, you can add the 156``Differential Revision`` line (as the last line) to the commit message 157yourself. 158 159Using the Arcanist tool can simplify the process of committing reviewed code 160as it will retrieve reviewers, the ``Differential Revision``, etc from the review 161and place it in the commit message. Several methods of using Arcanist to commit 162code are given below. If you do not wish to use Arcanist then simply commit 163the reviewed patch as you would normally. 164 165Note that if you commit the change without using Arcanist and forget to add the 166``Differential Revision`` line to your commit message then it is recommended 167that you close the review manually. In the web UI, under "Leap Into Action" put 168the SVN revision number in the Comment, set the Action to "Close Revision" and 169click Submit. Note the review must have been Accepted first. 170 171Subversion and Arcanist 172^^^^^^^^^^^^^^^^^^^^^^^ 173 174On a clean Subversion working copy run the following (where ``<Revision>`` is 175the Phabricator review number): 176 177:: 178 179 arc patch D<Revision> 180 arc commit --revision D<Revision> 181 182The first command will take the latest version of the reviewed patch and apply it to the working 183copy. The second command will commit this revision to trunk. 184 185git-svn and Arcanist 186^^^^^^^^^^^^^^^^^^^^ 187 188This presumes that the git repository has been configured as described in :ref:`developers-work-with-git-svn`. 189 190On a clean Git repository on an up to date ``master`` branch run the 191following (where ``<Revision>`` is the Phabricator review number): 192 193:: 194 195 arc patch D<Revision> 196 197 198This will create a new branch called ``arcpatch-D<Revision>`` based on the 199current ``master`` and will create a commit corresponding to ``D<Revision>`` with a 200commit message derived from information in the Phabricator review. 201 202Check you are happy with the commit message and amend it if necessary. Now switch to 203the ``master`` branch and add the new commit to it and commit it to trunk. This 204can be done by running the following: 205 206:: 207 208 git checkout master 209 git merge --ff-only arcpatch-D<Revision> 210 git svn dcommit 211 212 213 214Abandoning a change 215------------------- 216 217If you decide you should not commit the patch, you should explicitly abandon 218the review so that reviewers don't think it is still open. In the web UI, 219scroll to the bottom of the page where normally you would enter an overall 220comment. In the drop-down Action list, which defaults to "Comment," you should 221select "Abandon Revision" and then enter a comment explaining why. Click the 222Submit button to finish closing the review. 223 224Status 225------ 226 227Please let us know whether you like it and what could be improved! We're still 228working on setting up a bug tracker, but you can email klimek-at-google-dot-com 229and chandlerc-at-gmail-dot-com and CC the llvm-dev mailing list with questions 230until then. We also could use help implementing improvements. This sadly is 231really painful and hard because the Phabricator codebase is in PHP and not as 232testable as you might like. However, we've put exactly what we're deploying up 233on an `llvm-reviews GitHub project`_ where folks can hack on it and post pull 234requests. We're looking into what the right long-term hosting for this is, but 235note that it is a derivative of an existing open source project, and so not 236trivially a good fit for an official LLVM project. 237 238.. _LLVM's Phabricator: http://reviews.llvm.org 239.. _`http://reviews.llvm.org`: http://reviews.llvm.org 240.. _Code Repository Browser: http://reviews.llvm.org/diffusion/ 241.. _Arcanist Quick Start: https://secure.phabricator.com/book/phabricator/article/arcanist_quick_start/ 242.. _Arcanist User Guide: https://secure.phabricator.com/book/phabricator/article/arcanist/ 243.. _llvm-reviews GitHub project: https://github.com/r4nt/llvm-reviews/ 244