1.. _phabricator-reviews: 2 3============================= 4Code Reviews with Phabricator 5============================= 6 7.. contents:: 8 :local: 9 10If you prefer to use a web user interface for code reviews, you can now submit 11your patches for Clang and LLVM at `LLVM's Phabricator`_ instance. 12 13While Phabricator is a useful tool for some, the relevant -commits mailing list 14is the system of record for all LLVM code review. The mailing list should be 15added as a subscriber on all reviews, and Phabricator users should be prepared 16to respond to free-form comments in mail sent to the commits list. 17 18Sign up 19------- 20 21To get started with Phabricator, navigate to `https://reviews.llvm.org`_ and 22click the power icon in the top right. You can register with a GitHub account, 23a Google account, or you can create your own profile. 24 25Make *sure* that the email address registered with Phabricator is subscribed 26to the relevant -commits mailing list. If you are not subscribed to the commit 27list, all mail sent by Phabricator on your behalf will be held for moderation. 28 29Note that if you use your git user name as Phabricator user name, 30Phabricator will automatically connect your submits to your Phabricator user in 31the `Code Repository Browser`_. 32 33Requesting a review via the command line 34---------------------------------------- 35 36Phabricator has a tool called *Arcanist* to upload patches from 37the command line. To get you set up, follow the 38`Arcanist Quick Start`_ instructions. 39 40You can learn more about how to use arc to interact with 41Phabricator in the `Arcanist User Guide`_. 42The basic way of creating a revision for the current commit in your local 43repository is to run: 44 45:: 46 47 arc diff HEAD~ 48 49 50If you later update your commit message, you need to add the `--verbatim` 51option to have `arc` update the description on Phabricator: 52 53:: 54 55 arc diff --edit --verbatim 56 57 58.. _phabricator-request-review-web: 59 60Requesting a review via the web interface 61----------------------------------------- 62 63The tool to create and review patches in Phabricator is called 64*Differential*. 65 66Note that you can upload patches created through git, but using `arc` on the 67command line (see previous section) is preferred: it adds more metadata to 68Phabricator which are useful for the pre-merge testing system and for 69propagating attribution on commits when someone else has to push it for you. 70 71To make reviews easier, please always include **as much context as 72possible** with your diff! Don't worry, Phabricator 73will automatically send a diff with a smaller context in the review 74email, but having the full file in the web interface will help the 75reviewer understand your code. 76 77To get a full diff, use one of the following commands (or just use Arcanist 78to upload your patch): 79 80* ``git show HEAD -U999999 > mypatch.patch`` 81* ``git diff -U999999 @{u} > mypatch.patch`` 82* ``git diff HEAD~1 -U999999 > mypatch.patch`` 83 84Before uploading your patch, please make sure it is formatted properly, as 85described in :ref:`How to Submit a Patch <format patches>`. 86 87To upload a new patch: 88 89* Click *Differential*. 90* Click *+ Create Diff*. 91* Paste the text diff or browse to the patch file. Click *Create Diff*. 92* Leave this first Repository field blank. (We'll fill in the Repository 93 later, when sending the review.) 94* Leave the drop down on *Create a new Revision...* and click *Continue*. 95* Enter a descriptive title and summary. The title and summary are usually 96 in the form of a :ref:`commit message <commit messages>`. 97* Add reviewers (see below for advice). (If you set the Repository field 98 correctly, llvm-commits or cfe-commits will be subscribed automatically; 99 otherwise, you will have to manually subscribe them.) 100* In the Repository field, enter "rG LLVM Github Monorepo". 101* Click *Save*. 102 103To submit an updated patch: 104 105* Click *Differential*. 106* Click *+ Create Diff*. 107* Paste the updated diff or browse to the updated patch file. Click *Create Diff*. 108* Select the review you want to from the *Attach To* dropdown and click 109 *Continue*. 110* Leave the Repository field blank. (We previously filled out the Repository 111 for the review request.) 112* Add comments about the changes in the new diff. Click *Save*. 113 114Choosing reviewers: You typically pick one or two people as initial reviewers. 115This choice is not crucial, because you are merely suggesting and not requiring 116them to participate. Many people will see the email notification on cfe-commits 117or llvm-commits, and if the subject line suggests the patch is something they 118should look at, they will. 119 120 121.. _finding-potential-reviewers: 122 123Finding potential reviewers 124--------------------------- 125 126Here are a couple of ways to pick the initial reviewer(s): 127 128* Use ``git blame`` and the commit log to find names of people who have 129 recently modified the same area of code that you are modifying. 130* Look in CODE_OWNERS.TXT to see who might be responsible for that area. 131* If you've discussed the change on a dev list, the people who participated 132 might be appropriate reviewers. 133 134Even if you think the code owner is the busiest person in the world, it's still 135okay to put them as a reviewer. Being the code owner means they have accepted 136responsibility for making sure the review happens. 137 138Reviewing code with Phabricator 139------------------------------- 140 141Phabricator allows you to add inline comments as well as overall comments 142to a revision. To add an inline comment, select the lines of code you want 143to comment on by clicking and dragging the line numbers in the diff pane. 144When you have added all your comments, scroll to the bottom of the page and 145click the Submit button. 146 147You can add overall comments in the text box at the bottom of the page. 148When you're done, click the Submit button. 149 150Phabricator has many useful features, for example allowing you to select 151diffs between different versions of the patch as it was reviewed in the 152*Revision Update History*. Most features are self descriptive - explore, and 153if you have a question, drop by on #llvm in IRC to get help. 154 155Note that as e-mail is the system of reference for code reviews, and some 156people prefer it over a web interface, we do not generate automated mail 157when a review changes state, for example by clicking "Accept Revision" in 158the web interface. Thus, please type LGTM into the comment box to accept 159a change from Phabricator. 160 161Committing a change 162------------------- 163 164Once a patch has been reviewed and approved on Phabricator it can then be 165committed to trunk. If you do not have commit access, someone has to 166commit the change for you (with attribution). It is sufficient to add 167a comment to the approved review indicating you cannot commit the patch 168yourself. If you have commit access, there are multiple workflows to commit the 169change. Whichever method you follow it is recommended that your commit message 170ends with the line: 171 172:: 173 174 Differential Revision: <URL> 175 176where ``<URL>`` is the URL for the code review, starting with 177``https://reviews.llvm.org/``. 178 179This allows people reading the version history to see the review for 180context. This also allows Phabricator to detect the commit, close the 181review, and add a link from the review to the commit. 182 183Note that if you use the Arcanist tool the ``Differential Revision`` line will 184be added automatically. If you don't want to use Arcanist, you can add the 185``Differential Revision`` line (as the last line) to the commit message 186yourself. 187 188Using the Arcanist tool can simplify the process of committing reviewed code as 189it will retrieve reviewers, the ``Differential Revision``, etc from the review 190and place it in the commit message. You may also commit an accepted change 191directly using ``git push``, per the section in the :ref:`getting started 192guide <commit_from_git>`. 193 194Note that if you commit the change without using Arcanist and forget to add the 195``Differential Revision`` line to your commit message then it is recommended 196that you close the review manually. In the web UI, under "Leap Into Action" put 197the git revision number in the Comment, set the Action to "Close Revision" and 198click Submit. Note the review must have been Accepted first. 199 200Committing someone's change from Phabricator 201^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 202 203On a clean Git repository on an up to date ``master`` branch run the 204following (where ``<Revision>`` is the Phabricator review number): 205 206:: 207 208 arc patch D<Revision> 209 210 211This will create a new branch called ``arcpatch-D<Revision>`` based on the 212current ``master`` and will create a commit corresponding to ``D<Revision>`` with a 213commit message derived from information in the Phabricator review. 214 215Check you are happy with the commit message and amend it if necessary. 216For example, ensure the 'Author' property of the commit is set to the original author. 217You can use a command to correct the author property if it is incorrect: 218 219:: 220 221 git commit --amend --author="John Doe <jdoe@llvm.org>" 222 223Then, make sure the commit is up-to-date, and commit it. This can be done by running 224the following: 225 226:: 227 228 git pull --rebase https://github.com/llvm/llvm-project.git master 229 git show # Ensure the patch looks correct. 230 ninja check-$whatever # Rerun the appropriate tests if needed. 231 git push https://github.com/llvm/llvm-project.git HEAD:master 232 233 234Abandoning a change 235------------------- 236 237If you decide you should not commit the patch, you should explicitly abandon 238the review so that reviewers don't think it is still open. In the web UI, 239scroll to the bottom of the page where normally you would enter an overall 240comment. In the drop-down Action list, which defaults to "Comment," you should 241select "Abandon Revision" and then enter a comment explaining why. Click the 242Submit button to finish closing the review. 243 244Status 245------ 246 247Please let us know whether you like it and what could be improved! We're still 248working on setting up a bug tracker, but you can email klimek-at-google-dot-com 249and chandlerc-at-gmail-dot-com and CC the llvm-dev mailing list with questions 250until then. We also could use help implementing improvements. This sadly is 251really painful and hard because the Phabricator codebase is in PHP and not as 252testable as you might like. However, we've put exactly what we're deploying up 253on an `llvm-reviews GitHub project`_ where folks can hack on it and post pull 254requests. We're looking into what the right long-term hosting for this is, but 255note that it is a derivative of an existing open source project, and so not 256trivially a good fit for an official LLVM project. 257 258.. _LLVM's Phabricator: https://reviews.llvm.org 259.. _`https://reviews.llvm.org`: https://reviews.llvm.org 260.. _Code Repository Browser: https://reviews.llvm.org/diffusion/ 261.. _Arcanist Quick Start: https://secure.phabricator.com/book/phabricator/article/arcanist_quick_start/ 262.. _Arcanist User Guide: https://secure.phabricator.com/book/phabricator/article/arcanist/ 263.. _llvm-reviews GitHub project: https://github.com/r4nt/llvm-reviews/ 264