# Linting in CI

Trunk Code Quality can be run in CI to prevent new issues form being introduced by PRs and on a nightly/scheduled cadence to report on existing issues.

### Configuring base branch

Trunk operates in **hold-the-line** mode by default. This means Trunk will run linters only on the **files that have changed** according to Git, by comparing it to the appropriate upstream branch.

If you're not using `main` or `master` as the base branch, make sure it's specified in `.trunk/trunk.yaml`.

```yaml
version: 0.1
cli:
  version: 1.22.2
repo:
  # specify the base branch for hold-the-line
  trunk_branch: develop
```

### Linting on pull requests

```yaml
name: Trunk Code Quality
on:
  push:
    branches: main
  pull_request:
    branches: main
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      # ... other setup steps
      - name: Trunk Code Quality
        uses: trunk-io/trunk-action@v1
        with:
          post-annotations: true 
      # ... other CI steps
```

This step will automatically run Trunk Code Quality to reveal problems found when comparing the branch to `main` or another base branch you configured.

If you want to run the `trunk check` command directly in your workflow, or you're not using GitHub, you can run the following commands:

<pre><code><strong>curl -fsSLO --retry 3 https://trunk.io/releases/trunk \
</strong>chmod +x trunk \
./trunk check --ci
</code></pre>

Trunk Code Quality can be run in CI to prevent new issues form being introduced by PRs and on a nightly/scheduled cadence to report on existing issues.

### Configuring base branch

Trunk operates in **hold-the-line** mode by default. This means Trunk will run linters only on the **files that have changed** according to Git, by comparing it to the appropriate upstream branch.

If you're not using `main` or `master` as the base branch, make sure it's specified in `.trunk/trunk.yaml`.

```yaml
version: 0.
cli:
  version: 1.22.2
repo:
  # specify the base branch for hold-the-line
  trunk_branch: develop
```

#### Manual configuration and Non-GitHub CI

If you want to run the `trunk check` command directly in your workflow, or you're not using GitHub, you can run the following commands:

```
curl -fsSLO --retry 3 https://trunk.io/releases/trunk \
chmod +x trunk \
./trunk check --ci
```

#### Skipping Trunk Code Quality on pull requests

You can include `/trunk skip-check` in the body of a PR description (i.e. the first comment on a given PR) to mark Trunk Code Quality as "skipped". Trunk Code Quality will still run on your PR and report issues, but this will allow the PR to pass a GitHub-required status check on `Trunk Check`.

This can be helpful if Code Quality is flagging known issues in a given PR that you don't want to ignore, which can come in handy if you're doing a large refactor.

### Caching and persistence

* Trunk caches the version of `trunk` itself, linters, formatters, and lint results in `~/.cache/trunk`
* If your build machines are persistent, make sure this directory is not wiped out between CI jobs for best performance. If Trunk has to re-download every linter for every job because this directory is wiped out, it will be very slow.
* If your build machines are ephemeral, there are a few options for caching:
  * CI systems have support for caching between CI jobs on ephemeral runners:
    * [GitHub Actions](https://github.com/actions/cache)
    * [CircleCI](https://circleci.com/docs/caching/)
    * [Travis CI](https://docs.travis-ci.com/user/caching/)
  * You can include a seeded trunk cache in a regularly updated image used for CI by running `trunk check download`, which will download all requirements to `~/.cache/trunk`

### Hourly and nightly builds

If you'd like to set Code Quality to run on an hourly/nightly CI, you can run

<pre class="language-yaml"><code class="lang-yaml"><strong>name: Trunk Code Quality
</strong>on:
  schedule:
    # Run at 4 PM UTC daily (cron uses UTC time)
    - cron: '0 16 * * *'

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      # ... other setup steps
      - name: Trunk Code Quality
        uses: trunk-io/trunk-action@v1
        with:
          check-mode: all
      # ... other CI steps
</code></pre>

You can do the same without Trunk's GitHub Action using the following command:

```bash
curl -fsSLO --retry 3 https://trunk.io/releases/trunk \
chmod +x trunk \
./trunk check --all --ci-progress --monitor=false
```

`--ci-progress` will print out the tool's progress every 30 seconds, whereas `--no-progress` will suppress any progress reporting.

You can also explicitly set the upstream branch if needed via `--upstream`, but we do detect your main branch by default.