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