<chapter xmlns="http://docbook.org/ns/docbook"
        xmlns:xlink="http://www.w3.org/1999/xlink"
        xmlns:xi="http://www.w3.org/2001/XInclude"
        version="5.0"
        xml:id="sec-reviewing-contributions">

<title>Reviewing contributions</title>

<warning>
  <para>The following section is a draft and reviewing policy is still being 
    discussed.</para>
</warning>

<para>The nixpkgs projects receives a fairly high number of contributions via 
  GitHub pull-requests. Reviewing and approving these is an important task and a 
  way to contribute to the project.</para>

<para>The high change rate of nixpkgs make any pull request that is open for 
  long enough subject to conflicts that will require extra work from the 
  submitter or the merger. Reviewing pull requests in a timely manner and being 
  responsive to the comments is the key to avoid these. GitHub provides sort 
  filters that can be used to see the <link 
    xlink:href="https://github.com/NixOS/nixpkgs/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-desc">most 
    recently</link> and the <link 
    xlink:href="https://github.com/NixOS/nixpkgs/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-asc">least 
    recently</link> updated pull-requests.</para>

<para>When reviewing a pull request, please always be nice and polite. 
  Controversial changes can lead to controversial opinions, but it is important 
  to respect every community members and their work.</para>

<para>GitHub provides reactions, they are a simple and quick way to provide 
  feedback to pull-requests or any comments. The thumb-down reaction should be 
  used with care and if possible accompanied with some explanations so the 
  submitter has directions to improve his contribution.</para>

<para>Pull-requests reviews should include a list of what has been reviewed in a 
  comment, so other reviewers and mergers can know the state of the 
  review.</para>

<para>All the review template samples provided in this section are generic and 
  meant as examples. Their usage is optional and the reviewer is free to adapt 
  them to his liking.</para>

<section><title>Package updates</title>

<para>A package update is the most trivial and common type of pull-request. 
  These pull-requests mainly consist in updating the version part of the package 
  name and the source hash.</para>
<para>It can happen that non trivial updates include patches or more complex 
  changes.</para>

<para>Reviewing process:</para>

<itemizedlist>
  <listitem><para>Add labels to the pull-request. (Requires commit 
      rights)</para>
    <itemizedlist>
      <listitem><para><literal>8.has: package (update)</literal> and any topic 
          label that fit the updated package.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the package versioning is fitting the 
      guidelines.</para></listitem>
  <listitem><para>Ensure that the commit text is fitting the 
      guidelines.</para></listitem>
  <listitem><para>Ensure that the package maintainers are notified.</para>
    <itemizedlist>
      <listitem><para>mention-bot usually notify GitHub users based on the 
          submitted changes, but it can happen that it misses some of the 
          package maintainers.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the meta field contains correct 
      information.</para>
    <itemizedlist>
      <listitem><para>License can change with version updates, so it should be 
          checked to be fitting upstream license.</para></listitem>
      <listitem><para>If the package has no maintainer, a maintainer must be 
          set. This can be the update submitter or a community member that 
          accepts to take maintainership of the package.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the code contains no typos.</para></listitem>
  <listitem><para>Building the package locally.</para>
    <itemizedlist>
      <listitem><para>Pull-requests are often targeted to the master or staging 
          branch so building the pull-request locally as it is submitted can 
          trigger a large amount of source builds.</para>
        <para>It is possible to rebase the changes on nixos-unstable or 
          nixpkgs-unstable for easier review by running the following commands 
          from a nixpkgs clone.
<screen>
$ git remote add channels https://github.com/NixOS/nixpkgs-channels.git <co 
  xml:id='reviewing-rebase-1' />
$ git fetch channels nixos-unstable <co xml:id='reviewing-rebase-2' />
$ git fetch origin pull/PRNUMBER/head <co xml:id='reviewing-rebase-3' />
$ git rebase --onto nixos-unstable BASEBRANCH FETCH_HEAD <co 
  xml:id='reviewing-rebase-4' />
</screen>
        <calloutlist>
          <callout arearefs='reviewing-rebase-1'>
            <para>This should be done only once to be able to fetch channel 
              branches from the nixpkgs-channels repository.</para>
          </callout>
          <callout arearefs='reviewing-rebase-2'>
            <para>Fetching the nixos-unstable branch.</para>
          </callout>
          <callout arearefs='reviewing-rebase-3'>
            <para>Fetching the pull-request changes, <varname>PRNUMBER</varname> 
              is the number at the end of the pull-request title and 
              <varname>BASEBRANCH</varname> the base branch of the 
              pull-request.</para>
          </callout>
          <callout arearefs='reviewing-rebase-3'>
            <para>Rebasing the pull-request changes to the nixos-unstable 
              branch.</para>
          </callout>
        </calloutlist>
        </para>
      </listitem>
      <listitem>
        <para>The <link xlink:href="https://github.com/madjar/nox">nox</link> 
          tool can be used to review a pull-request content in a single command. 
          It doesn't rebase on a channel branch so it might trigger multiple 
          source builds. <varname>PRNUMBER</varname> should be replaced by the 
          number at the end of the pull-request title.</para>
<screen>
$ nix-shell -p nox --run "nox-review -k pr PRNUMBER"
</screen>
      </listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Running every binary.</para></listitem>
</itemizedlist>

<example><title>Sample template for a package update review</title>
<screen>
##### Reviewed points

- [ ] package name fits guidelines
- [ ] package version fits guidelines
- [ ] package build on ARCHITECTURE
- [ ] executables tested on ARCHITECTURE
- [ ] all depending packages build

##### Possible improvements

##### Comments

</screen></example>
</section>

<section><title>New packages</title>

<para>New packages are a common type of pull-requests. These pull requests 
  consists in adding a new nix-expression for a package.</para>

<para>Reviewing process:</para>

<itemizedlist>
  <listitem><para>Add labels to the pull-request. (Requires commit 
      rights)</para>
    <itemizedlist>
      <listitem><para><literal>8.has: package (new)</literal> and any topic 
          label that fit the new package.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the package versioning is fitting the 
      guidelines.</para></listitem>
  <listitem><para>Ensure that the commit name is fitting the 
      guidelines.</para></listitem>
  <listitem><para>Ensure that the meta field contains correct 
      information.</para>
    <itemizedlist>
      <listitem><para>License must be checked to be fitting upstream 
          license.</para></listitem>
      <listitem><para>Platforms should be set or the package will not get binary 
          substitutes.</para></listitem>
      <listitem><para>A maintainer must be set, this can be the package 
          submitter or a community member that accepts to take maintainership of 
          the package.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the code contains no typos.</para></listitem>
  <listitem><para>Ensure the package source.</para>
    <itemizedlist>
      <listitem><para>Mirrors urls should be used when 
          available.</para></listitem>
      <listitem><para>The most appropriate function should be used (e.g. 
          packages from GitHub should use 
          <literal>fetchFromGitHub</literal>).</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Building the package locally.</para></listitem>
  <listitem><para>Running every binary.</para></listitem>
</itemizedlist>

<example><title>Sample template for a new package review</title>
<screen>
##### Reviewed points

- [ ] package path fits guidelines
- [ ] package name fits guidelines
- [ ] package version fits guidelines
- [ ] package build on ARCHITECTURE
- [ ] executables tested on ARCHITECTURE
- [ ] `meta.description` is set and fits guidelines
- [ ] `meta.license` fits upstream license
- [ ] `meta.platforms` is set
- [ ] `meta.maintainers` is set
- [ ] build time only dependencies are declared in `nativeBuildInputs`
- [ ] source is fetched using the appropriate function
- [ ] phases are respected
- [ ] patches that are remotely available are fetched with `fetchpatch`

##### Possible improvements

##### Comments

</screen></example>
</section>

<section><title>Module updates</title>

<para>Module updates are submissions changing modules in some ways. These often 
  contains changes to the options or introduce new options.</para>

<para>Reviewing process</para>

<itemizedlist>
  <listitem><para>Add labels to the pull-request. (Requires commit 
      rights)</para>
    <itemizedlist>
      <listitem><para><literal>8.has: module (update)</literal> and any topic 
          label that fit the module.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the module maintainers are notified.</para>
    <itemizedlist>
      <listitem><para>Mention-bot notify GitHub users based on the submitted 
          changes, but it can happen that it miss some of the package 
          maintainers.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the module tests, if any, are 
      succeeding.</para></listitem>
  <listitem><para>Ensure that the introduced options are correct.</para>
    <itemizedlist>
      <listitem><para>Type should be appropriate (string related types differs 
          in their merging capabilities, <literal>optionSet</literal> and 
          <literal>string</literal> types are deprecated).</para></listitem>
      <listitem><para>Description, default and example should be 
          provided.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that option changes are backward compatible.</para>
    <itemizedlist>
      <listitem><para><literal>mkRenamedOptionModule</literal> and 
          <literal>mkAliasOptionModule</literal> functions provide way to make 
          option changes backward compatible.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that removed options are declared with 
      <literal>mkRemovedOptionModule</literal></para></listitem>
  <listitem><para>Ensure that changes that are not backward compatible are 
      mentioned in release notes.</para></listitem>
  <listitem><para>Ensure that documentations affected by the change is 
      updated.</para></listitem>
</itemizedlist>

<example><title>Sample template for a module update review</title>
<screen>
##### Reviewed points

- [ ] changes are backward compatible
- [ ] removed options are declared with `mkRemovedOptionModule`
- [ ] changes that are not backward compatible are documented in release notes
- [ ] module tests succeed on ARCHITECTURE
- [ ] options types are appropriate
- [ ] options description is set
- [ ] options example is provided
- [ ] documentation affected by the changes is updated

##### Possible improvements

##### Comments

</screen></example>
</section>

<section><title>New modules</title>

<para>New modules submissions introduce a new module to NixOS.</para>

<itemizedlist>
  <listitem><para>Add labels to the pull-request. (Requires commit 
      rights)</para>
    <itemizedlist>
      <listitem><para><literal>8.has: module (new)</literal> and any topic label 
          that fit the module.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the module tests, if any, are 
      succeeding.</para></listitem>
  <listitem><para>Ensure that the introduced options are correct.</para>
    <itemizedlist>
      <listitem><para>Type should be appropriate (string related types differs 
          in their merging capabilities, <literal>optionSet</literal> and 
          <literal>string</literal> types are deprecated).</para></listitem>
      <listitem><para>Description, default and example should be 
          provided.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that module <literal>meta</literal> field is 
      present</para>
    <itemizedlist>
      <listitem><para>Maintainers should be declared in 
          <literal>meta.maintainers</literal>.</para></listitem>
      <listitem><para>Module documentation should be declared with 
          <literal>meta.doc</literal>.</para></listitem>
    </itemizedlist>
  </listitem>
  <listitem><para>Ensure that the module respect other modules 
      functionality.</para>
    <itemizedlist>
      <listitem><para>For example, enabling a module should not open firewall 
          ports by default.</para></listitem>
    </itemizedlist>
  </listitem>
</itemizedlist>

<example><title>Sample template for a new module review</title>
<screen>
##### Reviewed points

- [ ] module path fits the guidelines
- [ ] module tests succeed on ARCHITECTURE
- [ ] options have appropriate types
- [ ] options have default
- [ ] options have example
- [ ] options have descriptions
- [ ] No unneeded package is added to system.environmentPackages
- [ ] meta.maintainers is set
- [ ] module documentation is declared in meta.doc

##### Possible improvements

##### Comments

</screen></example>
</section>

<section><title>Other submissions</title>

<para>Other type of submissions requires different reviewing steps.</para>

<para>If you consider having enough knowledge and experience in a topic and 
  would like to be a long-term reviewer for related submissions, please contact 
  the current reviewers for that topic. They will give you information about the 
  reviewing process.
The main reviewers for a topic can be hard to find as there is no list, but 
checking past pull-requests to see who reviewed or git-blaming the code to see 
who committed to that topic can give some hints.</para>

<para>Container system, boot system and library changes are some examples of the 
  pull requests fitting this category.</para>

</section>

<section><title>Merging pull-requests</title>

<para>It is possible for community members that have enough knowledge and 
  experience on a special topic to contribute by merging pull requests.</para>

<para>TODO: add the procedure to request merging rights.</para>

<!--
The following paragraph about how to deal with unactive contributors is just a
proposition and should be modified to what the community agrees to be the right
policy.

<para>Please note that contributors with commit rights unactive for more than 
  three months will have their commit rights revoked.</para>
-->

<para>In a case a contributor leaves definitively the Nix community, he should 
  create an issue or notify the mailing list with references of packages and 
  modules he maintains so the maintainership can be taken over by other 
  contributors.</para>

</section>
</chapter>
