Configure Linters

Trunk Code Quality's linter integrations are fully configurable. This means that you can easily tune existing linters or leverage our caching and hold-the-line solution with your own custom linters.

Here's an overview of the ways you can configure linters.

Config Hierarchy

Linters can be configured at different places:

1. The source plugin repo usually https://github.com/trunk-io/plugins.

2. The repo-wide Trunk config file overrides the definitions in the plugin repos, .trunk/trunk.yaml

3. Local, per-user configuration in .trunk/user.yaml which is used for local overrides of .trunk/trunk.yaml and doesn't

4. Per linter configuration in linter config files such as eslint.config.js or .prettierrc.

Plugin system

Trunk defines linter configuration in a plugin system. By default, it'll point to the Trunk plugin repo on GitHub. You can check if other custom plugin sources are specified in your trunk.yaml file for Shared Configs.

version: 0.1
cli:
  version: 1.22.2
# Trunk provides extensibility via plugins. (https://docs.trunk.io/plugins)
plugins:
  sources:
    - id: trunk
      ref: v1.6.1
      uri: https://github.com/trunk-io/plugins

Linter Definitions

Each linter implemented in the Plugin Repo has its own linter definition. Let's take clang-tidy as an example, which ships with the following default configuration:

definitions:
  ...
  - name: clang-tidy
    files: [c/c++-source]
    type: llvm
    commands:
      - output: llvm
        run: clang-tidy --export-fixes=- ${target}
        success_codes: [0]
    download: clang-tidy
    direct_configs: [.clang-tidy]
    disable_upstream: true
    include_scanner_type: compile_command
    environment:
      - name: PATH
        list: ["${linter}/bin"]
  ...

Linter Definition Reference

You can find the default definitions for linters in the Plugin Repo and find reference for these fields in the Definitions page.

Overriding Default Linter Definitions

You may find while using Trunk that you want to modify one of these defaults: perhaps you want clang-tidy to not run on the upstream, or maybe you want the node runtime to include another environment variable. In these cases, you can specify the field in your trunk.yaml to override the default value.

If you wanted to flip the value of disable_upstream to false, you could, in your own trunk.yaml, specify:

definitions:
  ...
  - name: clang-tidy
    disable_upstream: false
  ...

Overriding definitions in your trunk.yaml file doesn't require you to specify the entire definition again. You only need to specify what's being overridden.

Some linters have multiple commands, such as trivy, which can run in different ways. Similarly, some linters are configured to run differently on different platforms or at different versions. When overriding a command definition, overrides are applied on the tuple [name, version, platforms].

For example, if you wanted to disable batching when running ktlint on Windows, you could consider its default configuration:

definitions:
  ...
  - name: ktlint
    ...
    commands:
      - name: format
        platforms: [windows]
        run: java -jar ${linter}/ktlint.exe -F "${target}"
        output: rewrite
        cache_results: true
        formatter: true
        in_place: true
        batch: true
        success_codes: [0, 1]
      - name: format
        run: ktlint -F "${target}"
        output: rewrite
        cache_results: true
        formatter: true
        in_place: true
        batch: true
        success_codes: [0, 1]
  ...

And override it as such:

definitions:
  ...
  - name: ktlint
    ...
    commands:
      - name: format
        platforms: [windows]
        batch: false
  ...

When executing linters, Trunk will execute the first matching command based on its compatible platforms and linter version. Note when overriding that new commands that don't match an existing tuple are prepended to the resulting commands list.

Alternatively, consider the default node runtime:

runtimes:
  definitions:
    - type: node
      download: node
      runtime_environment:
        - name: HOME
          value: ${home}
        - name: PATH
          list: ["${runtime}/bin"]
      linter_environment:
        - name: PATH
          list: ["${linter}/node_modules/.bin"]
      version: 16.14.2
      version_commands:
        - run: "node --version"
          parse_regex: ${semver}

If you wanted to add ${home}/my/special/node/path to PATH, you could specify the following:

runtimes:
  - type: node
    runtime_environment:
      - name: HOME
        value: ${home}
      - name: PATH
        list: ["${home}/my/special/node/path", "${runtime}/bin"]

Blocking Thresholds

All issue severities low-high are considered blocking by default. In cases where you might want to slowly try out a new linter, we provide a mechanism to set specific thresholds for each linter.

lint:
  threshold:
    - linters: [clang-tidy]
      level: high

Every entry in threshold defines a set of linters and the severity threshold that is considered blocking. In this example, we're saying that only high lint issues should be considered blocking for clang-tidy.

Key	Value
linters	List of linters (e.g. [black, eslint]) or the special [ALL] tag
level	Default low. Threshold at which issues are considered blocking. One of: note, low, medium, high, or none (this last option will result in issues never blocking)

Trigger rules

Some linters do not operate on individual files. Instead you must lint your entire repo at once. The way this is handled in trunk is to set up a trigger rule. Most linters will not require the use of a trigger rule.

Trigger rules work on 3 principles:

1. Input(s) that trigger the linters. These can be files, directories, or extended globs.

2. Linter(s) to run when a triggered file is modified.

3. Targets(s) to pass to the linters (can be files or directories).

An example for ansible-lint:

lint:
  enabled:
    - ansible-lint@5.3.2

  triggers:
    - linters:
        - ansible-lint
      paths:
        - ansible # A directory
      targets:
        - ansible # A directory

Triggered linters will also be run when executing trunk check with --all so long as a file exists that matches one of the listed paths.

You may use . as a target to run on the entire repo instead of an isolated directory.

File Size

By default, Trunk only lints files up to 4 MiB in size. To override this globally, specify a default_max_file_size in lint:

lint:
  default_max_file_size: 1048576 # Bytes

To override this for a specific linter, specify a max_file_size in its definition:

lint:
  definitions:
    - name: prettier
      max_file_size: 2097152 # Bytes

Timeout

Each linter has a default timeout of 10 minutes. If its execution takes longer than this amount of time, Trunk Code Quality will terminate the process and return an error to the user.

To override the timeout for a specific linter, specify a run_timeout in its definition:

lint:
    definitions:
    - name: clang-tidy
      run_timeout: 5m

The run_timeout value can be specified in seconds (s), minutes (m), or hours (h).

Local Linter Overrides

Trunk can also be managed by the .trunk/user.yaml file in your repository. This file is optional, but it allows individual developers to customize how they want trunk to run on their machines.

Simply configure .trunk/user.yaml as you would for .trunk/trunk.yaml. Be mindful that .trunk/user.yaml takes precedence over .trunk/trunk.yaml, so substantial modifications could violate hermeticity.

Per Linter Definitions

Trunk allows you to keep using your existing linter configs, and new linters recommended by Trunk will have their configs added in the .trunk/configs folder. These config files will be symlinked in during any trunk check run.

If you're using an IDE Extension like clangd with an LSP that relies on those configs being in the root, you will need to create an additional symlink from the hidden config to the workspace root.

Moving Linters

You can move existing linter config files into the .trunk/config folder. You can check which files are automatically symlinked by looking for the direct_configs of each plugin's definition. If there are config files not listed, you can add them by overriding the definition like this:

lint:
  definitions:
    - name: some_linter_name
      direct_configs:
        - .custom_config.file