Difference between revisions of "Starting as a Contributor"

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(feep tells me this is more sane cuz it avoids deleting someone else's data)
 
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This page contains a set of instructions that get anyone from having nothing D-related on their machine, to a full-blown development rig for the reference D compiler `dmd` and one or more of its paraphernalia: core runtime (aka <tt>druntime</tt>), standard library (aka <tt>phobos</tt>), website, and tools.
+
This page describes how to build D, put together a correct patch, and contribute it as a GitHub pull request.
  
=== 0. Prerequisites ===
+
==Existing tools==
  
This tutorial is written for a Posix system (Linux, OSX, FreeBSD etc) and assumes you have <tt>make</tt>, <tt>g++</tt>, <tt>libcurl4-openssl-dev</tt>, and <tt>git</tt> up and running on your system, as well as a working github account. To install the appropriate code on e.g. Ubuntu:
+
If you only want to build the latest and greatest DMD, there exist tools which can do this automatically:
  
<pre>
+
* [https://github.com/dlang/tools/blob/master/setup.sh tools/setup.sh] is a simple script that either installs a new or updates an existing D development tree. Just download the script and run.
sudo apt-get install git make g++ libcurl4-openssl-dev
+
<syntaxhighlight lang=bash>
</pre>
+
wget https://raw.githubusercontent.com/dlang/tools/master/setup.sh && bash setup.sh
 +
*** The following projects will be INSTALLED:                                                                                                                                                                   
 +
<YOUR-CURRENT-PATH>/dmd
 +
<YOUR-CURRENT-PATH>/druntime
 +
<YOUR-CURRENT-PATH>/phobos
 +
<YOUR-CURRENT-PATH>/dlang.org
 +
<YOUR-CURRENT-PATH>/tools
 +
<YOUR-CURRENT-PATH>/installer
 +
<YOUR-CURRENT-PATH>/dub
 +
Is this what you want? [y|n]                                                                                                                                                                                   
 +
y                       
 +
</syntaxhighlight>
  
To build the 32-bit phobos on a 64-bit machine, <tt>libc6-dev-i386</tt> and <tt>libcurl4-gnutls-dev:i386</tt> are also needed:
+
* [https://github.com/CyberShadow/Digger Digger] can download and build D from any point in its recent history.
 +
* [https://github.com/jacob-carlborg/dvm DVM] can build and locally install D from source code.
  
<pre>
+
There are also the [https://dlang.org/download.html#dmd-nightly dmd-nightly builds].
sudo apt-get install libc6-dev-i386 libcurl4-gnutls-dev:i386
 
</pre>
 
  
Other versions and variations of <tt>libcurl</tt> may work as well.
+
== Building from source ==
  
=== 1. Fetch <tt>dmd</tt> from github ===
+
The build information is split into Posix and Windows pages. Be sure to follow the instructions in the related guide and come back to this page once your setup is working.
  
Let's start by getting the current development (master) branch of dmd from github. Assume the root directory for everything D-related is <tt>~/code</tt> (replace appropriately). This is easily done by running at a command prompt:
+
* [[Building_under_Posix | Building under Posix (Linux, macOS, FreeBSD, ...)]]
 +
* [[Building_under_Windows | Building under Windows]]
  
<pre>
+
Once Druntime and Phobos are compiled, you can use your freshly compiled DMD compiler to compile programs:
cd ~/code
 
git clone https://github.com/D-Programming-Language/dmd
 
</pre>
 
  
After this step completes successfully, the directory <tt>~/code/dmd</tt> should be up and filled with good stuff.
+
<syntaxhighlight lang=bash>
 +
~/dlang/dmd/generated/linux/release/64/dmd mytest.d
 +
</syntaxhighlight>
  
=== 2. Bootstrap <tt>dmd</tt> ===
+
On a different OS, you will need to replace the OS name. For example for <tt>macOS</tt>:
  
This step is interesting because in order to build <tt>dmd</tt>, <tt>dmd</tt> is necessary. Fortunately, the steps of downloading and using a preexisting  <tt>dmd</tt> compiler are automated. All you need to do is run this command:
+
<syntaxhighlight lang=bash>
 +
~/dlang/dmd/generated/osx/release/64/dmd mytest.d
 +
</syntaxhighlight>
  
<pre>
+
== Development ==
cd ~/code/dmd
 
make -f posix.mak AUTO_BOOTSTRAP=1
 
</pre>
 
  
That's going to take a while. To make it faster, passing <tt>-j8</tt> accelerates things by running eight processes in parallel. The build produces the compiler binary <tt>~/code/dmd/src/dmd</tt>.
+
Depending on which part of the D ecosystem you want to dive in, there are separate guides which explain e.g. how unittests are run:
  
To make <tt>dmd</tt> builds faster in the future, you need to obviate the need for bootstrapping. Install <tt>dmd</tt> from the [http://dlang.org/download.html download page] or simply put the freshly built <tt>dmd</tt> binary in a place accessible through <tt>$PATH</tt> (a popular choice is <tt>~/bin</tt>).
+
* [[DMD_development | DMD Development]], [https://github.com/dlang/dmd/blob/master/CONTRIBUTING.md DMD Contribution Guide], and [[DMD_Source_Guide | DMD Source Guide]]
 +
* [[DRuntime_development | DRuntime development]]
 +
* [[Contributing_to_Phobos | Phobos development]]
 +
* [[Contributing_to_dlang.org | Dlang.org development]] (D documentation)
  
=== 3. Fetch and build <tt>druntime</tt> ===
+
There is also <tt>[https://github.com/dlang/tools tools]</tt> (typically cloned to the <tt>~/dlang/tools</tt> folder) where small helper programs live.
 +
For a full description of the tools provided, please see <tt>[https://github.com/dlang/tools tools]</tt>.
 +
If you are on Windows, {{code|dtab}} (transforms tabs into spaces in source code) and {{code|tolf}} (replaces line endings with LF) might prove helpful.
  
<tt>druntime</tt> is the core runtime library for D, needed for building most every D program, including the standard library itself. So it's the next step in the progression (note that it requires a properly built <tt>dmd</tt>, so make sure steps 1 and 2 have completed successfully). To fetch and build druntime, issue these commands:
+
Additionally, there are other repositories which are parts of the D ecosystem: <tt>[https://github.com/dlang/dconf.org dconf.org]</tt>, <tt>[https://github.com/dlang/dub dub]</tt>, <tt>[https://github.com/dlang/dub-registry dub-registry]</tt>, <tt>[https://github.com/dlang/installer installer]</tt>, <tt>[https://github.com/dlang/tools tools]</tt>, <tt>[https://github.com/dlang/visuald visuald]</tt>, <tt>[https://github.com/dlang/ci ci]</tt>, <tt>[https://github.com/dlang/undeaD undeaD]</tt> and more.
  
<pre>
+
These ancillary repositories are of somewhat specific interest. Their installation process mimics that of the repositories described above. If you get to the point where you need to work on one of these, chances are you're already versed in what needs doing. If not, [http://forum.dlang.org/group/digitalmars.D ask away].
cd ~/code
 
git clone https://github.com/D-Programming-Language/druntime
 
cd druntime
 
make -f posix.mak
 
</pre>
 
  
All that should go pretty fast. The somewhat anticlimactic result of the build is a library called <tt>libdruntime.a</tt> situated in an OS-dependent directory such as <tt>~/code/druntime/generated/linux/release/64/</tt>. Make sure it's there.
+
== Typical Contributor Workflow ==
 +
 
 +
There are many ways to use <tt>git</tt> and GitHub to contribute. Here's a typical one.
 +
 
 +
First, fork the github repository or repositories you'd like to contribute to (<tt>dmd</tt>, <tt>druntime</tt>, <tt>phobos</tt> etc) by navigating to their respective pages on <tt>github.com</tt> and clicking "Fork" (e.g. [https://github.com/dlang/dmd dmd], [https://github.com/dlang/druntime druntime], and [https://github.com/dlang/phobos phobos]). Then, set up your local git repository to reflect that. For example, consider you want to contribute to <tt>phobos</tt> and have forked it. Then run these commands:
 +
 
 +
<syntaxhighlight lang=bash>
 +
cd ~/dlang/phobos
 +
git remote set-url origin git@github.com:USERNAME/phobos.git
 +
</syntaxhighlight>
 +
 
 +
(Replace <tt>USERNAME</tt> with your actual github user name.)
  
=== 4. Fetch and build <tt>phobos</tt> ===
+
This sets your forked repository as origin.
 +
If you <b>don't have</b> the phobos repository, go back to the [[#Building from source|Building from source section]] or make a fresh clone from your fork:
  
Most D programs use D's standard library <tt>phobos</tt>. To get and build it, make sure you first fetch and build the latest <tt>dmd</tt> and <tt>druntime</tt>. Then:
+
<syntaxhighlight lang=bash>
 +
cd ~/dlang
 +
git clone git@github.com:username/phobos.git
 +
</syntaxhighlight>
  
<pre>
+
Now within your Phobos repository, setup the official Phobos repository as upstream remote node:
cd ~/code
 
git clone https://github.com/D-Programming-Language/phobos
 
cd phobos
 
make -f posix.mak
 
</pre>
 
  
The build produces (with similar anticlimacticity) static and shared libraries such as <tt>~/code/phobos/generated/linux/release/64/libphobos2.a</tt> and <tt>~/code/phobos/generated/linux/release/64/libphobos2.so</tt>.
+
<syntaxhighlight lang=bash>
 +
cd ~/dlang/phobos
 +
git remote add upstream https://github.com/dlang/phobos.git
 +
git fetch && git fetch upstream
 +
</syntaxhighlight>
  
==== 4.1. Unittest <tt>phobos</tt> ====
+
Then, it's best to work in branches as shown below:
  
If you want to work on phobos itself, you need to run unittests&mdash;either for the full library, a package, or a module. To unittest the entire library:
+
<syntaxhighlight lang=bash>
 +
git checkout -b awesome-new-feature
 +
# ... get some good work done here ...
 +
git commit -am "Awesome new feature ..."
 +
git push myfork
 +
</syntaxhighlight>
  
<pre>
+
With this, your work is in your github fork of the <tt>phobos</tt> (or whichever) repository. After that, visit your fork on <tt>github.com</tt>, which looks like <tt>https://github.com/username/phobos/tree/awesome-new-feature</tt>.
make -j16 -f posix.mak unittest
+
Also, you can always pull-in the latest, greatest Phobos changes:
</pre>
 
  
Adjust the parameter passed to <tt>-j</tt> depending on your machine (beefier machines support larger parameters). This command unittests <tt>phobos</tt> in both debug and release mode. To only test one of them, add <tt>BUILD=debug</tt> or <tt>BUILD=release</tt> to the command line, for example:
+
<syntaxhighlight lang=bash>
 +
git checkout master
 +
git fetch && git fetch upstream && git merge --ff-only upstream/master
 +
</syntaxhighlight>
  
<pre>
+
== Create a pull request ==
make -j16 -f posix.mak BUILD=debug unittest
 
</pre>
 
  
Specifying <tt>BUILD</tt> makes unittesting faster so it is recommended in iterative development. Just make sure both debug and release builds are tested before e.g. submitting a pull request.
+
Once you have tested all your changes and pushed them to your fork on GitHub, you are ready to submit a pull request.
 +
Navigate to <tt>[https://github.com/dlang/phobos phobos]</tt> GitHub page and you should already see your branch:
  
While changing one specific package or module, it's useful to be able to only unittest that particular entity. The following two commands only unittest (in debug mode) the <tt>std.algorithm</tt> package and the <tt>std.conv</tt> module, respectively:
+
[[File:Phobos_start_new_PR.png|800px]]
  
<pre>
+
Alternatively you can also click on the "New pull request" button, select "Compare across forks", select your repository as "head fork" and select the branch that you made your changes in, say issue_1234.
make -j16 -f posix.mak BUILD=debug std/algorithm.test
 
make -j16 -f posix.mak BUILD=debug std/conv.test
 
</pre>
 
  
Several modules, packages, or mix thereof may be specified for testing in the same command line. For example, this command also tests (and also in debug mode) the <tt>std.algorithm</tt> package and the <tt>std.conv</tt> module, with better parallelism:
+
[[File:PR_compare_across_changes.png|800px]]
  
<pre>
+
This will submit your changes for review by the D maintainers. If your changes are approved, they will be merged into the master branch. Otherwise, if the maintainers have some comments or feedback, you can refine your changes by editing and testing in your local workspace, and pushing the new changes to the same git branch. The new changes will be automatically included in your pull request.
make -j16 -f posix.mak BUILD=debug std/algorithm.test std/conv.test
 
</pre>
 
  
Also, it's important to test for trailing whitespace in your code before issuing a pull request, as the automated testing will fail if you have any:
+
=== How to choose a title for your Pull Request ===
  
<pre>
+
Choose a title for your pull request that clearly states what it does.  When fixing a bug, the usual thing to do is to use the title from the bugzilla report.  Eg a title like "Fix 3797" or "Issue 3797" contains much less information than "Fix Issue 3797 - Regression(2.038): Implicit conversion between incompatible function pointers" and requires a lot more effort for the reviewers to determine if it is something they are interested in.
make -j16 -f posix.mak checkwhitespace
 
</pre>
 
  
=== 5. Fetch and build <tt>dlang.org</tt> ===
+
If a pull request isn't a trivial bug, its description should explain the motivation for the change and briefly summarize the changes.
  
This step is optional but highly recommended. Significant changes to <tt>phobos</tt>' documentation require that the site (which includes automatically generated <tt>phobos</tt> documentation) builds successfully. So, without further ado:
+
=== Submitting a bug fix ===
  
<pre>
+
If the pull request is for a bug fix, the commit message should have the format "fix issue 1234". This allow the [https://github.com/dlang-bots/dlang-bot Dlang-Bot] to automatically pick up the issue from [[Bugzilla]] and post it as a comment on the PR.
cd ~/code
+
It's important the bot can link your commit message to the respective Bugzilla issue as it will then automatically close the issue on Bugzilla and otherwise the fixed issue won't appear in the changelog.
git clone https://github.com/D-Programming-Language/dlang.org
 
cd dlang.org
 
make -f posix.mak
 
</pre>
 
  
All of <tt>dmd</tt>, <tt>druntime</tt>, and <tt>phobos</tt> are needed for the site to build. Note that one of the first lines output during the <tt>make</tt> run looks like this:
+
If the PR is already open, then a <tt>git rebase</tt> is necessary followed by a force push. During the rebase, the commit message should be renamed to match the "Fix <copy bugzilla title>"
  
<pre>
+
[[File:Bugzilla_issue_title.png]]
LATEST=2.067.1 <-- place in the command line to skip network traffic.
 
</pre>
 
  
That's advice worth heeding because fetching <tt>LATEST</tt> automatically involves network traffic, which adds time to the build. So for future builds use this:
+
For [https://issues.dlang.org/show_bug.cgi?id=9582 Issue 9582], the commit message could be <tt>Fix Issue 9582 - std.algorithm.map!(T) cause CT error for fixed size arrays</tt>.
  
<pre>
+
After the pull request is created, don't forget to add a link to your pull request posted to the corresponding Bugzilla issue in a comment, so that future contributor are aware of your work and don't redo the fix.
make -f posix.mak LATEST=2.067.1
+
Hence, it's also helpful to add the 'pull' keyword to the Bugzilla issue.
</pre>
 
  
Of course, parallelizing with <tt>-j</tt> improves speed as well.
+
=== Characteristics of a good pull request ===
  
The build produces the entire site at <tt>~/code/dlang.org/web</tt>. To informally test it, open the appropriate HTML documents in that directory. Note that the currently released phobos has documentation in <tt>~/code/dlang.org/web/phobos</tt>, whereas the current (fresh) build of phobos has documentation in  <tt>~/code/dlang.org/web/phobos-prerelease</tt>. So, for example, if you change the embedded documentation in <tt>~/code/phobos/std/conv.d</tt>, the changes are visible in  <tt>~/code/dlang.org/web/phobos-prerelease/std_conv.html</tt>. (The build process replaces the slashes in submodules with underscores.)
+
* Addresses one topic only.
 +
* Refactorings should not be mixed in with bug fixes or enhancements.
 +
* Refactorings should be marked as such in the subject, and must not contain any behavior changes.
 +
* Larger refactorings need to broken up into smaller PRs.
  
=== 6. Ancillary stuff: <tt>[https://github.com/D-Programming-Language/dconf.org dconf.org]</tt>, <tt>[https://github.com/D-Programming-Language/dub dub]</tt>, <tt>[https://github.com/D-Programming-Language/dub-registry dub-registry]</tt>, <tt>[https://github.com/D-Programming-Language/installer installer]</tt>, <tt>[https://github.com/D-Programming-Language/tools tools]</tt>, and <tt>[https://github.com/D-Programming-Language/visuald visuald]</tt> ===
+
The problems with large PRs are:
  
These ancillary repositories are of somewhat specific interest. Their installation mimics that of the repositories described above. If you get to the point where you need to work on one of these, chances are you're already versed in what needs doing. If not, [http://forum.dlang.org/group/digitalmars.D ask away].
+
* They are hard to review.
 +
* github is very slow at serving pages with large diffs on them.
 +
* If the PR introduces a regression, a large diff is much harder to debug than a small one.
 +
* They imply an all or nothing view of it, when it actually may have good parts and bad parts.
  
== Typical Contributor Workflow ==
+
== Working on an pull request ==
 +
 
 +
=== Autotester ===
 +
 
 +
Pull requests are automatically picked up by the [[Git Commit Tester|autotester]], which compiles the code in the pull request and runs it through the dmd, druntime, and phobos unittests on all supported platforms. Generally, pull requests must pass all tests before they will be merged. The status of the tests can be monitored through the pull request page.
 +
 
 +
Every user must be manually approved before the autotester will start testing their pull requests.  Users can be approved by anyone with commit access.
 +
 
 +
=== Rebasing ===
 +
 
 +
Sometimes, if a particular change you are working on is taking a long time, or if you encounter a problem that is fixed by a new commit upstream, you may need to sync your local branch with master in order to keep the code up-to-date. In this case, it is recommended that you use git rebase to apply your changes ''on top of'' the latest git master, so that when you submit a pull request, the change history will be easier for the reviewers to follow. git merge should <b>not</b> be used, as it may produce a lot of merge commits that may not be relevant to your changes.
 +
 
 +
For example, you may be working on your changes:
 +
 
 +
<syntaxhighlight lang=bash>
 +
cd ~/dlang/phobos
 +
git checkout mybranch
 +
vim std/algorithm.d  # apply lots of cool changes here
 +
</syntaxhighlight>
 +
 
 +
First, before you resync with master, make sure all your changes are checked in (or stashed):
 +
 
 +
<syntaxhighlight lang=bash>
 +
git commit --ammend
 +
</syntaxhighlight>
 +
 
 +
If you forked from the official D programming language repositories you may need to add an upstream remote to pull in the latest official changes. If this is the case you can add an upstream remote like this:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git remote add upstream git@github.com:dlang/phobos
 +
</syntaxhighlight>
 +
 +
This adds another remote to your repository called upstream and only needs to be done once. Once the upstream remote is added, you can update your repository's master branch by running the following:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git checkout master
 +
git pull --ff-only upstream master
 +
</syntaxhighlight>
 +
 
 +
The <tt>--ff-only</tt> option is to ensure that your master branch is identical to the official D sources' master branch, since otherwise you will end up with a very messy history that will be hard to clean up (and the reviewers will probably reject your pull request due to having unrelated merge commits).
 +
 
 +
Now go back to your branch and rebase it:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git checkout mybranch
 +
git rebase master
 +
</syntaxhighlight>
 +
 
 +
Now your sources should be up-to-date. Recompile and test everything to make sure it all works.
 +
 
 +
Note that after rebasing, you will need to force an update to your fork on GitHub with the --force-with-lease flag, otherwise it will fail because the histories don't match anymore:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git push --force-with-lease origin mybranch
 +
</syntaxhighlight>
 +
 
 +
You may wish to read up on [http://git-scm.com/book/en/Git-Branching-Rebasing how git rebase works] if you're not familiar with the concept.
 +
 
 +
If, during the 'git rebase' command, you encounter conflicts, you may want to learn [http://stackoverflow.com/questions/8780257/git-rebase-a-branch-onto-master-failed-how-to-resolve how to resolve a conflict during git rebase].
 +
 
 +
=== Squashing ===
 +
 
 +
After receiving feedback on your PR, it's common for it to have lots of commits that don't add much by being separate. For example, consider the following git history on a PR:
 +
 
 +
commit [ffffff] Added new function: foobar
 +
commit [aaaaaa] Spelling error fix in foobar docs
 +
commit [cccccc] Clarified Docs for foobar
 +
 
 +
Nothing is gained from having these as three separate commits as they are all focused on one feature. Instead, they should be one commit so the history looks like this
 +
 
 +
commit [333333] Added new function: foobar
 +
 
 +
while still retaining all of your changes. In order to perform this, please consult this [https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History#Squashing-Commits guide]
 +
 
 +
You can also directly append to your last commit and force an update of your PR:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git commit --amend
 +
git push --force-with-lease
 +
</syntaxhighlight>
 +
 
 +
=== Stable Branch ===
 +
 
 +
If you are working on a fix for a regression, chances are it should go into the next point release, and not the next major version (e.g. 2.067.1 instead of 2.068). In this case, you should check out the stable branch of each subproject BEFORE you create your topic branch:
 +
 
 +
<syntaxhighlight lang=bash>
 +
cd dmd
 +
git checkout stable
 +
cd ../druntime
 +
git checkout stable
 +
cd ../phobos
 +
git checkout stable
 +
</syntaxhighlight>
 +
 
 +
Then follow the instructions for [[#Make your changes in a branch|making a branch]].
 +
 
 +
Unfortunately, it's not possible to simply re-target your branch for pulling into the stable branch. GitHub will let you do this, but your branch will include many of the changes from the unstable branch!
 +
 
 +
In order to fix such a problem, you can [[#Rebasing|rebase]] your changes from master on top of the stable branch. First you need to pull in the stable branch from your fork on github:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git checkout stable
 +
</syntaxhighlight>
 +
 
 +
Then, you go back to your branch, and replay the changes from master using rebase:
 +
 
 +
<syntaxhighlight lang=bash>
 +
git checkout mybranch
 +
git fetch upstream
 +
git rebase --onto upstream/stable upstream/master mybranch
 +
</syntaxhighlight>
 +
 
 +
You may have to follow the instructions in the [[#Rebasing|Rebasing section]] on adding the upstream branch, substituting stable for master, if you need to update to the latest stable changes.
 +
 
 +
This sometimes may not work, as the changes between the stable and master are too drastic. In this case, you may have to re-create your changes after a clean checkout of the stable branch.
 +
 
 +
When creating a pull request, you need to tell github to target the stable branch instead of master on the upstream repository. This is done via a drop-down at the top of the page, make sure to do this before submitting your pull request as this cannot be changed after the PR is created (you will have to close the PR and create a new one).
 +
 
 +
If you notice in your PR a whole slew of changes that seem to have nothing to do with your changes, it's likely because you forgot one of these steps.
 +
 
 +
=== Reviews ===
 +
 
 +
Any pull requests that make language changes must be approved by Walter and Andrei. This includes druntime changes that implement the specification.
 +
 
 +
Any pull requests that make significant changes to code should be reviewed by more than one person. This means that at least two people need to approve the pull request before it is merged. One person must be a person with commit rights, but the other need not be, as long as that person is trusted within the developer community.
 +
 
 +
Pull requests that are trivial (typos, obvious minor bug fixes, etc.) may be pulled without a second review.
 +
 
 +
Please note that any updates pushed to the candidate branch do not automatically notify a subscribed person. If you update your branch to correct an issue, please also put in a comment indicating it.
 +
 
 +
== Contributing FAQ ==
 +
 
 +
=== A file that I made a change on was modified by a different merged PR, and now my PR can't be merged, now what? ===
 +
 
 +
What you need to do is rebase your git branch on the master branch. What this does is rewrite the history of your git branch to make it seem like it was merged off of the head of master rather than the older commit where you actually branched. This will include the new commits in your PR so your PR no longer conflicts. See [https://github.com/edx/edx-platform/wiki/How-to-Rebase-a-Pull-Request this tutorial] for more details.
 +
 
 +
=== I would like to help but I don't know how. What is the best way? ===
 +
 
 +
Anyone is welcome to contribute as D is very much a volunteer effort!
 +
The best place to look for ideas to contribute is the [[Get involved|get involved]] guide.
 +
Please also don't hesitate to point out (or even fix) any stumbling blocks you may encounter when starting out.
 +
 
 +
=== CodeCov shows a red cross ===
 +
 
 +
[[File:CI_CodeCov_failed.png]]
 +
 
 +
On every build the generated coverage files are sent to CodeCov for further processing.
 +
You can see the non-covered lines by clicking on the link or for further convenience in the future by installing the [https://github.com/codecov/browser-extension CodeCov browser extension].
 +
 
 +
=== CircleCi shows a red cross ===
 +
 
 +
[[File:CI_CircleCI_failed.png]]
 +
 
 +
On CircleCi static code analysis is run. For example it lints the Phobos codebase after [https://dlang.org/dstyle.html the DStyle].
 +
Moreover, checks are run to ensure that every example on dlang.org is runnable. On Posix, you can run this locally by executing the <tt>style</tt> target:
 +
 
 +
<syntaxhighlight lang=bash>
 +
make -f posix.mak style
 +
</syntaxhighlight>
 +
 
 +
=== The auto-tester shows a red cross ===
 +
 
 +
[[File:CI_auto-tester_failed.png]]
 +
 
 +
The [https://auto-tester.puremagic.com auto-tester] tests every PR on all supported platforms (Windows, Linux, macOS, and Linux) for 32 and 64-bit builds.
 +
Please click on the link of your PR to find out more about the error.
  
There are many ways to use <tt>git</tt> and <tt>github</tt> to contribute. Here's a typical one.
+
=== The Jenkins Project Tester shows a red cross ===
  
First, fork the github repository or repositories you'd like to contribute to (<tt>dmd</tt>, <tt>druntime</tt>, <tt>phobos</tt> etc) by navigating to their respective pages on <tt>github.com</tt> and clicking "Fork". Then, set up your local git repository to reflect that. For example, consider you want to contribute to <tt>phobos</tt> and have forked it. Then run these commands:
+
[[File:CI_project_tester.png]]
  
<pre>
+
The Project Tester tests every PR on all supported platforms (Windows, Linux, macOS, and Linux) for 32 and 64-bit builds.
cd ~/code/phobos
+
Please click on the link of your PR to find out more about the error.
git remote add myfork https://github.com/username/phobos.git
 
git remote update
 
</pre>
 
  
(Replace <tt>username</tt> with your actual github user name.) This adds the "myfork" repository and makes sure everything is synchronized between your local copy and the remote repositories. Then, it's best to work in branches as shown below:
+
=== How can I link a PR with Bugzilla? ===
  
<pre>
+
[[File:DLang_Bot_comment.png]]
git checkout -b awesome-new-feature
 
# ... get some good work done here ...
 
git commit -am "Awesome new feature ..."
 
git push -f myfork
 
</pre>
 
  
With this, your work is in your github fork of the <tt>phobos</tt> (or whichever) repository. After that, visit your fork on <tt>github.com</tt>, which looks like <tt>https://github.com/username/phobos/tree/awesome-new-feature</tt>. Then, github detects the new code and offers assistance to create a pull request with just a couple of clicks.
+
The integration is handled by [https://github.com/dlang-bots/dlang-bot Dlang-Bot].
 +
If you mention a bugzilla issue in your git commit message, you will get linked to the Bugzilla issue.
 +
For more information, please visit [https://github.com/dlang-bots/dlang-bot Dlang-Bot's documentation].
  
==More Information==
+
== See Also ==
  
You're all set! More information about contributing on a regular basis can be found [http://wiki.dlang.org/Pull_Requests here].
+
* [https://github.com/dlang/dmd/blob/master/CONTRIBUTING.md Contributing to DMD]
 +
* [[DMD Source Guide]]
 +
* [[Contributing_to_Phobos| Contributing to Phobos]]
 +
* [[Contributing_to_dlang.org| Contributing to dlang.org]]
 +
* [[Guidelines for maintainers]]
 +
* [[Get involved]]
  
 
[[Category: Contribution Guidelines]]
 
[[Category: Contribution Guidelines]]

Latest revision as of 18:28, 11 December 2019

This page describes how to build D, put together a correct patch, and contribute it as a GitHub pull request.

Existing tools

If you only want to build the latest and greatest DMD, there exist tools which can do this automatically:

  • tools/setup.sh is a simple script that either installs a new or updates an existing D development tree. Just download the script and run.
wget https://raw.githubusercontent.com/dlang/tools/master/setup.sh && bash setup.sh
*** The following projects will be INSTALLED:                                                                                                                                                                    
<YOUR-CURRENT-PATH>/dmd
<YOUR-CURRENT-PATH>/druntime
<YOUR-CURRENT-PATH>/phobos
<YOUR-CURRENT-PATH>/dlang.org
<YOUR-CURRENT-PATH>/tools
<YOUR-CURRENT-PATH>/installer
<YOUR-CURRENT-PATH>/dub
Is this what you want? [y|n]                                                                                                                                                                                     
y
  • Digger can download and build D from any point in its recent history.
  • DVM can build and locally install D from source code.

There are also the dmd-nightly builds.

Building from source

The build information is split into Posix and Windows pages. Be sure to follow the instructions in the related guide and come back to this page once your setup is working.

Once Druntime and Phobos are compiled, you can use your freshly compiled DMD compiler to compile programs:

~/dlang/dmd/generated/linux/release/64/dmd mytest.d

On a different OS, you will need to replace the OS name. For example for macOS:

~/dlang/dmd/generated/osx/release/64/dmd mytest.d

Development

Depending on which part of the D ecosystem you want to dive in, there are separate guides which explain e.g. how unittests are run:

There is also tools (typically cloned to the ~/dlang/tools folder) where small helper programs live. For a full description of the tools provided, please see tools. If you are on Windows, dtab (transforms tabs into spaces in source code) and tolf (replaces line endings with LF) might prove helpful.

Additionally, there are other repositories which are parts of the D ecosystem: dconf.org, dub, dub-registry, installer, tools, visuald, ci, undeaD and more.

These ancillary repositories are of somewhat specific interest. Their installation process mimics that of the repositories described above. If you get to the point where you need to work on one of these, chances are you're already versed in what needs doing. If not, ask away.

Typical Contributor Workflow

There are many ways to use git and GitHub to contribute. Here's a typical one.

First, fork the github repository or repositories you'd like to contribute to (dmd, druntime, phobos etc) by navigating to their respective pages on github.com and clicking "Fork" (e.g. dmd, druntime, and phobos). Then, set up your local git repository to reflect that. For example, consider you want to contribute to phobos and have forked it. Then run these commands:

cd ~/dlang/phobos
git remote set-url origin git@github.com:USERNAME/phobos.git

(Replace USERNAME with your actual github user name.)

This sets your forked repository as origin. If you don't have the phobos repository, go back to the Building from source section or make a fresh clone from your fork:

cd ~/dlang
git clone git@github.com:username/phobos.git

Now within your Phobos repository, setup the official Phobos repository as upstream remote node:

cd ~/dlang/phobos
git remote add upstream https://github.com/dlang/phobos.git
git fetch && git fetch upstream

Then, it's best to work in branches as shown below:

git checkout -b awesome-new-feature
# ... get some good work done here ...
git commit -am "Awesome new feature ..."
git push myfork

With this, your work is in your github fork of the phobos (or whichever) repository. After that, visit your fork on github.com, which looks like https://github.com/username/phobos/tree/awesome-new-feature. Also, you can always pull-in the latest, greatest Phobos changes:

git checkout master
git fetch && git fetch upstream && git merge --ff-only upstream/master

Create a pull request

Once you have tested all your changes and pushed them to your fork on GitHub, you are ready to submit a pull request. Navigate to phobos GitHub page and you should already see your branch:

Phobos start new PR.png

Alternatively you can also click on the "New pull request" button, select "Compare across forks", select your repository as "head fork" and select the branch that you made your changes in, say issue_1234.

PR compare across changes.png

This will submit your changes for review by the D maintainers. If your changes are approved, they will be merged into the master branch. Otherwise, if the maintainers have some comments or feedback, you can refine your changes by editing and testing in your local workspace, and pushing the new changes to the same git branch. The new changes will be automatically included in your pull request.

How to choose a title for your Pull Request

Choose a title for your pull request that clearly states what it does. When fixing a bug, the usual thing to do is to use the title from the bugzilla report. Eg a title like "Fix 3797" or "Issue 3797" contains much less information than "Fix Issue 3797 - Regression(2.038): Implicit conversion between incompatible function pointers" and requires a lot more effort for the reviewers to determine if it is something they are interested in.

If a pull request isn't a trivial bug, its description should explain the motivation for the change and briefly summarize the changes.

Submitting a bug fix

If the pull request is for a bug fix, the commit message should have the format "fix issue 1234". This allow the Dlang-Bot to automatically pick up the issue from Bugzilla and post it as a comment on the PR. It's important the bot can link your commit message to the respective Bugzilla issue as it will then automatically close the issue on Bugzilla and otherwise the fixed issue won't appear in the changelog.

If the PR is already open, then a git rebase is necessary followed by a force push. During the rebase, the commit message should be renamed to match the "Fix <copy bugzilla title>"

Bugzilla issue title.png

For Issue 9582, the commit message could be Fix Issue 9582 - std.algorithm.map!(T) cause CT error for fixed size arrays.

After the pull request is created, don't forget to add a link to your pull request posted to the corresponding Bugzilla issue in a comment, so that future contributor are aware of your work and don't redo the fix. Hence, it's also helpful to add the 'pull' keyword to the Bugzilla issue.

Characteristics of a good pull request

  • Addresses one topic only.
  • Refactorings should not be mixed in with bug fixes or enhancements.
  • Refactorings should be marked as such in the subject, and must not contain any behavior changes.
  • Larger refactorings need to broken up into smaller PRs.

The problems with large PRs are:

  • They are hard to review.
  • github is very slow at serving pages with large diffs on them.
  • If the PR introduces a regression, a large diff is much harder to debug than a small one.
  • They imply an all or nothing view of it, when it actually may have good parts and bad parts.

Working on an pull request

Autotester

Pull requests are automatically picked up by the autotester, which compiles the code in the pull request and runs it through the dmd, druntime, and phobos unittests on all supported platforms. Generally, pull requests must pass all tests before they will be merged. The status of the tests can be monitored through the pull request page.

Every user must be manually approved before the autotester will start testing their pull requests. Users can be approved by anyone with commit access.

Rebasing

Sometimes, if a particular change you are working on is taking a long time, or if you encounter a problem that is fixed by a new commit upstream, you may need to sync your local branch with master in order to keep the code up-to-date. In this case, it is recommended that you use git rebase to apply your changes on top of the latest git master, so that when you submit a pull request, the change history will be easier for the reviewers to follow. git merge should not be used, as it may produce a lot of merge commits that may not be relevant to your changes.

For example, you may be working on your changes:

cd ~/dlang/phobos
git checkout mybranch
vim std/algorithm.d   # apply lots of cool changes here

First, before you resync with master, make sure all your changes are checked in (or stashed):

git commit --ammend

If you forked from the official D programming language repositories you may need to add an upstream remote to pull in the latest official changes. If this is the case you can add an upstream remote like this:

git remote add upstream git@github.com:dlang/phobos

This adds another remote to your repository called upstream and only needs to be done once. Once the upstream remote is added, you can update your repository's master branch by running the following:

git checkout master
git pull --ff-only upstream master

The --ff-only option is to ensure that your master branch is identical to the official D sources' master branch, since otherwise you will end up with a very messy history that will be hard to clean up (and the reviewers will probably reject your pull request due to having unrelated merge commits).

Now go back to your branch and rebase it:

git checkout mybranch
git rebase master

Now your sources should be up-to-date. Recompile and test everything to make sure it all works.

Note that after rebasing, you will need to force an update to your fork on GitHub with the --force-with-lease flag, otherwise it will fail because the histories don't match anymore:

git push --force-with-lease origin mybranch

You may wish to read up on how git rebase works if you're not familiar with the concept.

If, during the 'git rebase' command, you encounter conflicts, you may want to learn how to resolve a conflict during git rebase.

Squashing

After receiving feedback on your PR, it's common for it to have lots of commits that don't add much by being separate. For example, consider the following git history on a PR:

commit [ffffff] Added new function: foobar
commit [aaaaaa] Spelling error fix in foobar docs
commit [cccccc] Clarified Docs for foobar

Nothing is gained from having these as three separate commits as they are all focused on one feature. Instead, they should be one commit so the history looks like this

commit [333333] Added new function: foobar

while still retaining all of your changes. In order to perform this, please consult this guide

You can also directly append to your last commit and force an update of your PR:

git commit --amend
git push --force-with-lease

Stable Branch

If you are working on a fix for a regression, chances are it should go into the next point release, and not the next major version (e.g. 2.067.1 instead of 2.068). In this case, you should check out the stable branch of each subproject BEFORE you create your topic branch:

cd dmd
git checkout stable
cd ../druntime
git checkout stable
cd ../phobos
git checkout stable

Then follow the instructions for making a branch.

Unfortunately, it's not possible to simply re-target your branch for pulling into the stable branch. GitHub will let you do this, but your branch will include many of the changes from the unstable branch!

In order to fix such a problem, you can rebase your changes from master on top of the stable branch. First you need to pull in the stable branch from your fork on github:

git checkout stable

Then, you go back to your branch, and replay the changes from master using rebase:

git checkout mybranch
git fetch upstream
git rebase --onto upstream/stable upstream/master mybranch

You may have to follow the instructions in the Rebasing section on adding the upstream branch, substituting stable for master, if you need to update to the latest stable changes.

This sometimes may not work, as the changes between the stable and master are too drastic. In this case, you may have to re-create your changes after a clean checkout of the stable branch.

When creating a pull request, you need to tell github to target the stable branch instead of master on the upstream repository. This is done via a drop-down at the top of the page, make sure to do this before submitting your pull request as this cannot be changed after the PR is created (you will have to close the PR and create a new one).

If you notice in your PR a whole slew of changes that seem to have nothing to do with your changes, it's likely because you forgot one of these steps.

Reviews

Any pull requests that make language changes must be approved by Walter and Andrei. This includes druntime changes that implement the specification.

Any pull requests that make significant changes to code should be reviewed by more than one person. This means that at least two people need to approve the pull request before it is merged. One person must be a person with commit rights, but the other need not be, as long as that person is trusted within the developer community.

Pull requests that are trivial (typos, obvious minor bug fixes, etc.) may be pulled without a second review.

Please note that any updates pushed to the candidate branch do not automatically notify a subscribed person. If you update your branch to correct an issue, please also put in a comment indicating it.

Contributing FAQ

A file that I made a change on was modified by a different merged PR, and now my PR can't be merged, now what?

What you need to do is rebase your git branch on the master branch. What this does is rewrite the history of your git branch to make it seem like it was merged off of the head of master rather than the older commit where you actually branched. This will include the new commits in your PR so your PR no longer conflicts. See this tutorial for more details.

I would like to help but I don't know how. What is the best way?

Anyone is welcome to contribute as D is very much a volunteer effort! The best place to look for ideas to contribute is the get involved guide. Please also don't hesitate to point out (or even fix) any stumbling blocks you may encounter when starting out.

CodeCov shows a red cross

CI CodeCov failed.png

On every build the generated coverage files are sent to CodeCov for further processing. You can see the non-covered lines by clicking on the link or for further convenience in the future by installing the CodeCov browser extension.

CircleCi shows a red cross

CI CircleCI failed.png

On CircleCi static code analysis is run. For example it lints the Phobos codebase after the DStyle. Moreover, checks are run to ensure that every example on dlang.org is runnable. On Posix, you can run this locally by executing the style target:

make -f posix.mak style

The auto-tester shows a red cross

CI auto-tester failed.png

The auto-tester tests every PR on all supported platforms (Windows, Linux, macOS, and Linux) for 32 and 64-bit builds. Please click on the link of your PR to find out more about the error.

The Jenkins Project Tester shows a red cross

CI project tester.png

The Project Tester tests every PR on all supported platforms (Windows, Linux, macOS, and Linux) for 32 and 64-bit builds. Please click on the link of your PR to find out more about the error.

How can I link a PR with Bugzilla?

DLang Bot comment.png

The integration is handled by Dlang-Bot. If you mention a bugzilla issue in your git commit message, you will get linked to the Bugzilla issue. For more information, please visit Dlang-Bot's documentation.

See Also