<p>On mobile development teams, code review is an essential part of the workflow. Teams are setting up rules to streamline and simplify their code review processes. Any time that&#8217;s wasted during code reviews is hindering the process. Did you know that you can set some rules for your code reviews and make sure the code author follows the rules before applying for a review? You can, by running Danger in CI.</p>
<p>Here&#8217;s an excerpt from their <a href="https://danger.systems" target="_blank" rel="noopener">website</a>:</p>
<blockquote><p>Danger runs during your CI process and gives teams the chance to automate common code review chores.</p>
<p>This provides another logical step in your build, through this Danger can help lint your rote tasks in daily code review.</p>
<p>You can use Danger to codify your team&#8217;s norms. Leaving humans to think about harder problems.</p></blockquote>
<p>Danger is a CI tool that allows you to automate code review comments such as</p>
<ul>
<li>This PR is too big</li>
<li>You forgot to update CHANGELOG</li>
</ul>
<p>Instead of writing the same comments again and again, you set the rules for Danger and it automatically adds comments to the pull request.</p>
<h2>Why should you use Danger?</h2>
<p>Danger not only help code reviewers but also the developers who send pull requests. Reviewer spends less time doing chores and spend more time efficiently reviewing the code.</p>
<p>Danger helps developers to get fast feedback about their pull requests. Developers can solve trivial errors by checking the comment that Danger leaves on the pull request. Since every pull request is checked by Danger code quality and code consistency will increase in the organization.</p>
<p>It&#8217;s not talked about much but getting a message from a human being and a bot has a different emotional impact. When you get a comment from a Danger, you know it is just software doing its job, nothing personal.</p>
<h2>Installing Danger</h2>
<p>Danger exists in different languages such as Ruby, JavaScript, Swift, Kotlin, and Python. In this guide, we will focus on the Ruby implementation which was the first implementation.</p>
<p>You can install the Danger directly by using <code>gem install danger</code> but this is not recommended. It&#8217;s better to install it by using a bundler. Create a Gemfile in your repository and fill it like below</p>
<pre><code class="language-ruby">source &quot;https://rubygems.org&quot;
git_source(:github) {|repo_name| &quot;https://github.com/#{repo_name}&quot; }

gem &#039;danger&#039;</code></pre>
<p>Running <code>bundle install</code> will install Danger. Using bundler is recommended way since it creates Gemfile.lock so that you can lock the version of Danger and its plugins.</p>
<h1>Using Danger</h1>
<p>Danger needs a rule set and credentials to operate. Danger will check your repository according to the rules you set and write a comment on your git repository with the given credentials.</p>
<h3>Creating Dangerfile</h3>
<p>Dangerfile is a Ruby file that can be easily edited. Since it&#8217;s a Ruby file, you can treat it as a Ruby script and can run any Ruby snippet code you want.</p>
<p>Example:</p>
<pre><code class="language-ruby">warn(&quot;PR is classed as Work in Progress&quot;) if github.pr_title.include? &quot;[WIP]&quot;</code></pre>
<p>If the title of your pull request includes <code>[WIP]</code>, Danger will add a warning to your pull request.</p>
<h3>Creating a Bot account</h3>
<p>Danger needs credentials to post comments on the issue. You need to create a bot account that can access your repositories. Give the least access level to the bot so that it can only comment on issues. Danger&#8217;s help document shows how to create bot tokens for your repository provider. In this guide, we will use GitHub. GitHub allows one bot per <a href="https://twitter.com/sebastiangrail/status/750844399563608065" target="_blank" rel="noopener">Github Account</a>.</p>
<p>To get started, create a new bot account in a private browser window and create a token by following <a href="https://github.com/settings/tokens/new" target="_blank" rel="noopener">this link</a>. Save this token to a secure place and treat it as confidential information. Anybody who has access to this token can act on behalf of this bot user.</p>
<h3>Setting up Danger on Appcircle CI/CD</h3>
<ul>
<li>Create environment groups and add your token as an environment variable. Since we&#8217;re doing it for GitHub, we will set <code>DANGER_GITHUB_API_TOKEN</code>. Different providers need different credentials, please check Danger&#8217;s website to learn more about them. Click the lock button to make your environment variable private.<img width="2560" height="727" class="aligncenter wp-image-4523 size-full" src="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-scaled.webp" alt="environment variables" srcset="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-scaled.webp 2560w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-300x85.webp 300w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-1030x292.webp 1030w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-768x218.webp 768w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-1536x436.webp 1536w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-2048x581.webp 2048w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-1500x426.webp 1500w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-environment-min-1-705x200.webp 705w" sizes="(max-width: 2560px) 100vw, 2560px" /></li>
</ul>
<ul>
<li>Edit your workflow and add the Danger component to your workflow. If your Dangerfile is in your main repository, you don&#8217;t need to change anything but if you want to configure the path of Dangerfile, and add extra command line options, you may edit the component. <strong>Do not</strong> set repository credentials directly to this component. Always use Environment Variables.<img width="2312" height="1404" class="aligncenter wp-image-4522 size-full" src="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1.webp" alt="workflow adding danger" srcset="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1.webp 2312w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-300x182.webp 300w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-1030x625.webp 1030w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-768x466.webp 768w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-1536x933.webp 1536w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-2048x1244.webp 2048w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-1500x911.webp 1500w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-workflow-min-1-705x428.webp 705w" sizes="(max-width: 2312px) 100vw, 2312px" /></li>
<li>Select the environment variable group in the build settings.<img width="1316" height="734" class="aligncenter wp-image-4521 size-full" src="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1.webp" alt="environment variable" srcset="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1.webp 1316w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1-300x167.webp 300w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1-1030x574.webp 1030w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1-768x428.webp 768w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-config-min-1-705x393.webp 705w" sizes="(max-width: 1316px) 100vw, 1316px" /></li>
</ul>
<ul>
<li style="list-style-type: none;"></li>
</ul>
<ul>
<li>Add a trigger to run this workflow. Our trigger will run our workflow when someone opens a Pull Request from <code>hotfix*</code>branch to <code>master</code> branch. You can follow our documentation to <a href="https://docs.appcircle.io/build/build-manually-or-with-triggers#managing-triggers-for-builds" target="_blank" rel="noopener">setup a trigger</a>.<img width="1320" height="942" class="aligncenter wp-image-4524 size-full" src="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min.webp" alt="triggers on merge" srcset="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min.webp 1320w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min-300x214.webp 300w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min-1030x735.webp 1030w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min-768x548.webp 768w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min-260x185.webp 260w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-trigger-min-min-705x503.webp 705w" sizes="(max-width: 1320px) 100vw, 1320px" /></li>
</ul>
<h3>Running Danger in CI</h3>
<p>If we open a pull request from <code>hotfix/myfeature</code> to <code>master</code> branch with a <code>[WIP]</code> title, Appcircle will start the build and your bot will comment on the pull request.</p>
<p><img width="2560" height="826" class="aligncenter wp-image-4525 size-full" src="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-scaled.webp" alt="pull request" srcset="https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-scaled.webp 2560w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-300x97.webp 300w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-1030x333.webp 1030w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-768x248.webp 768w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-1536x496.webp 1536w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-2048x661.webp 2048w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-1500x484.webp 1500w, https://ac.appcircle.io/wp-content/uploads/2022/11/AnyConv.com__danger-github-min-min-705x228.webp 705w" sizes="(max-width: 2560px) 100vw, 2560px" /></p>
<h2>Extending Danger</h2>
<p>Danger is much more capable than just writing comments. Its power comes from its plugins. For example, Danger can parse your test results with Junit, and code coverage with xcov. It can run your linter or code quality tool and pass the result to your pull request as a comment. You can warn developers to add a Jira Task id. You may even warn the developers when they open a pull request to the wrong branch.</p>
<h3>Example rules</h3>
<pre><code class="language-ruby"># Force rebase

if git.commits.any? { |c| c.message =~ /^Merge branch &#039;#{github.branch_for_base}&#039;/ }
    fail &quot;Please rebase first&quot;
  end

# Fail the PR if they didn&#039;t provide a description

if github.pr_body.length &lt; 10
    fail &quot;Please provide a description&quot;
end

# Warn if PR is too big

warn(&quot;This pull request is quite big (#{git.lines_of_code} lines changed), please consider splitting it into multiple pull requests.&quot;) if git.lines_of_code &gt; 200

# Run Xcov

xcov.report(
  scheme: ENV[&#039;AC_SCHEME&#039;]
  workspace: ENV[&#039;AC_PROJECT_PATH&#039;],
  xccov_file_direct_path: ENV[&#039;AC_TEST_RESULT_PATH&#039;],
  only_project_targets: true,
  markdown_report: true,
  html_report: false
)  
</code></pre>
<p>Please check Danger <a href="https://danger.systems/ruby/" target="_blank" rel="noopener">documentation</a> to learn more about the plugins.</p>
<h2>Summary</h2>
<p>Using Danger will greatly reduce the time you spend on code review chores. However, we don&#8217;t recommend putting lots of rules all at once. Instead, you should start with a simple rule set and add rules gradually according to your team&#8217;s needs.</p>


Save time, reduce costs and increase developer productivity now.

Danger in CI: Automate Your Mobile Code Reviews

Related Posts

Announcing Appcircle’s New Azure DevOps Integration Plugins

Announcing Appcircle’s New Fastlane Integration Plugins

Announcing Appcircle’s New GitHub Actions Integration Plugins

Top 5 Reasons Companies Choose Appcircle Over Microsoft App Center for Mobile