Code Quality

Ensuring your project’s code stays simple, readable and easy to contribute to can be problematic. With the help of GitLab CI/CD, you can analyze your source code quality using GitLab Code Quality.

Code Quality:

Going a step further, GitLab can show the Code Quality report right in the merge request widget area:

Code Quality Widget

Watch a quick walkthrough of Code Quality in action:

See the video: Code Quality: Speed Run.
Note: For one customer, the auditor found that having Code Quality, SAST, and Container Scanning all automated in GitLab CI/CD was almost better than a manual review! Read more.

See also the Code Climate list of Supported Languages for Maintainability.

Use cases

For instance, consider the following workflow:

  1. Your backend team member starts a new implementation for making a certain feature in your app faster.
  2. With Code Quality reports, they analyze how their implementation is impacting the code quality.
  3. The metrics show that their code degrades the quality by 10 points.
  4. You ask a co-worker to help them with this modification.
  5. They both work on the changes until Code Quality report displays no degradations, only improvements.
  6. You approve the merge request and authorize its deployment to staging.
  7. Once verified, their changes are deployed to production.

Example configuration

Caution: The job definition shown below is supported on GitLab 11.11 and later versions. It also requires the GitLab Runner 11.5 or later. For earlier versions, use the previous job definitions.

This example shows how to run Code Quality on your code by using GitLab CI/CD and Docker.

First, you need GitLab Runner configured:

Once you set up the Runner, include the Code Quality template in your CI configuration:

include:
  - template: Code-Quality.gitlab-ci.yml

The above example will create a code_quality job in your CI/CD pipeline which will scan your source code for code quality issues. The report will be saved as a Code Quality report artifact that you can later download and analyze.

It’s also possible to override the URL to the Code Quality image by setting the CODE_QUALITY_IMAGE variable. This is particularly useful if you want to lock in a specific version of Code Quality, or use a fork of it:

include:
  - template: Code-Quality.gitlab-ci.yml

code_quality:
  variables:
    CODE_QUALITY_IMAGE: "registry.example.com/codequality-fork:latest"

By default, report artifacts are not downloadable. If you need them downloadable on the job details page, you can add gl-code-quality-report.json to the artifact paths like so:

include:
  - template: Code-Quality.gitlab-ci.yml

code_quality:
  artifacts:
    paths: [gl-code-quality-report.json]

The included code_quality job is running in the test stage, so it needs to be included in your CI configuration, like so:

stages:
  - test
Tip: This information will be automatically extracted and shown right in the merge request widget.
Caution: On self-managed instances, if a malicious actor compromises the Code Quality job definition they will be able to execute privileged Docker commands on the Runner host. Having proper access control policies mitigates this attack vector by allowing access only to trusted actors.

Previous job definitions

Caution: Before GitLab 11.5, Code Quality job and artifact had to be named specifically to automatically extract report data and show it in the merge request widget. While these old job definitions are still maintained they have been deprecated and are no longer supported on GitLab 12.0 or higher. You’re advised to update your .gitlab-ci.yml configuration to reflect that change.

For GitLab 11.5 and later, the job should look like:

code_quality:
  image: docker:stable
  variables:
    DOCKER_DRIVER: overlay2
  allow_failure: true
  services:
    - docker:stable-dind
  script:
    - export SP_VERSION=$(echo "$CI_SERVER_VERSION" | sed 's/^\([0-9]*\)\.\([0-9]*\).*/\1-\2-stable/')
    - docker run
        --env SOURCE_CODE="$PWD"
        --volume "$PWD":/code
        --volume /var/run/docker.sock:/var/run/docker.sock
        "registry.gitlab.com/gitlab-org/ci-cd/codequality:$SP_VERSION" /code
  artifacts:
    reports:
      codequality: gl-code-quality-report.json

In GitLab 12.6, Code Quality switched to the new versioning scheme. It’s highly recommended to include the Code Quality template as shown in the example configuration, which uses the new versioning scheme. If not using the template, the SP_VERSION variable can be hardcoded to use the new image versions:

code_quality:
  image: docker:stable
  variables:
    DOCKER_DRIVER: overlay2
    SP_VERSION: 0.85.6
  allow_failure: true
  services:
    - docker:stable-dind
  script:
    - docker run
        --env SOURCE_CODE="$PWD"
        --volume "$PWD":/code
        --volume /var/run/docker.sock:/var/run/docker.sock
        "registry.gitlab.com/gitlab-org/ci-cd/codequality:$SP_VERSION" /code
  artifacts:
    reports:
      codequality: gl-code-quality-report.json

For GitLab 11.4 and earlier, the job should look like:

code_quality:
  image: docker:stable
  variables:
    DOCKER_DRIVER: overlay2
  allow_failure: true
  services:
    - docker:stable-dind
  script:
    - export SP_VERSION=$(echo "$CI_SERVER_VERSION" | sed 's/^\([0-9]*\)\.\([0-9]*\).*/\1-\2-stable/')
    - docker run
        --env SOURCE_CODE="$PWD"
        --volume "$PWD":/code
        --volume /var/run/docker.sock:/var/run/docker.sock
        "registry.gitlab.com/gitlab-org/ci-cd/codequality:$SP_VERSION" /code
  artifacts:
      paths: [gl-code-quality-report.json]

Alternatively the job name could be codeclimate or codequality and the artifact name could be codeclimate.json. These names have been deprecated with GitLab 11.0 and may be removed in the next major release, GitLab 12.0.

For GitLab 10.3 and earlier, the job should look like:

codequality:
  image: docker:latest
  variables:
    DOCKER_DRIVER: overlay
  services:
    - docker:dind
  script:
    - docker pull codeclimate/codeclimate:0.69.0
    - docker run --env CODECLIMATE_CODE="$PWD" --volume "$PWD":/code --volume /var/run/docker.sock:/var/run/docker.sock --volume /tmp/cc:/tmp/cc codeclimate/codeclimate:0.69.0 init
    - docker run --env CODECLIMATE_CODE="$PWD" --volume "$PWD":/code --volume /var/run/docker.sock:/var/run/docker.sock --volume /tmp/cc:/tmp/cc codeclimate/codeclimate:0.69.0 analyze -f json > codeclimate.json || true
  artifacts:
    paths: [codeclimate.json]

Configuring jobs using variables

The Code Quality job supports environment variables that users can set to configure job execution at runtime.

For a list of available environment variables, see Environment variables.

Implementing a custom tool

It’s possible to have a custom tool provide Code Quality reports in GitLab. To do this:

  1. Define a job in your .gitlab-ci.yml file that generates the Code Quality report artifact.
  2. Configure your tool to generate the Code Quality report artifact as a JSON file that implements a subset of the Code Climate spec.

The Code Quality report artifact JSON file must contain an array of objects with the following properties:

Name Description
description A description of the code quality violation.
fingerprint A unique fingerprint to identify the code quality violation. For example, an MD5 hash.
location.path The relative path to the file containing the code quality violation.
location.lines.begin The line on which the code quality violation occurred.

Example:

[
  {
    "description": "'unused' is assigned a value but never used.",
    "fingerprint": "7815696ecbf1c96e6894b779456d330e",
    "location": {
      "path": "lib/index.js",
      "lines": {
        "begin": 42
      }
    }
  }
]
Note: Although the Code Climate spec supports more properties, those are ignored by GitLab.

Code Quality reports

Once the Code Quality job has completed:

  • The full list of code quality violations generated by a pipeline is available in the Code Quality tab of the Pipeline Details page.
  • Potential changes to code quality are shown directly in the merge request. The Code Quality widget in the merge request compares the reports from the base and head of the branch, then lists any violations that will be resolved or created when the branch is merged.
  • The full JSON report is available as a downloadable artifact for the code_quality job.

Extending functionality

Using Analysis Plugins

Should there be a need to extend the default functionality provided by Code Quality, as stated in Code Quality, Analysis Plugins are available.

For example, to use the SonarJava analyzer, add a file named .codeclimate.yml containing the enablement code for the plugin to the root of your repository:

version: "2"
plugins:
  sonar-java:
    enabled: true

This adds SonarJava to the plugins: section of the default .codeclimate.yml included in your project.

Changes to the plugins: section do not affect the exclude_patterns section of the defeault .codeclimate.yml. See the Code Climate documentation for excluding files and folders for more details.

Here’s an example project that uses Code Quality with a .codeclimate.yml file.

Troubleshooting

Changing the default configuration has no effect

A common issue is that the terms Code Quality (GitLab specific) and Code Climate (Engine used by GitLab) are very similar. You must add a .codeclimate.yml file to change the default configuration, not a .codequality.yml file. If you use the wrong filename, the default .codeclimate.yml is still used.

No Code Quality report is displayed in a Merge Request

This can be due to multiple reasons:

  • You just added the Code Quality job in your .gitlab-ci.yml. The report does not have anything to compare to yet, so no information can be displayed. Future merge requests will have something to compare to.
  • If no degradation or error is detected, nothing will be displayed.
  • The artifacts:expire_in CI/CD setting can cause the Code Quality artifact(s) to expire faster than desired.
  • Large codeclimate.json files (esp. >10 MB) are known to prevent the report from being displayed. As a work-around, try removing properties that are ignored by GitLab. You can:
    • Configure the Code Quality tool to not output those types.
    • Use sed, awk or similar commands in the .gitlab-ci.yml script to edit the codeclimate.json before the job completes.

Only a single Code Quality report is displayed, but more are defined

GitLab only uses the Code Quality artifact from the latest created job (with the largest job ID). If multiple jobs in a pipeline generate a code quality artifact, those of earlier jobs are ignored. To avoid confusion, configure only one job to generate a codeclimate.json.