Jinja2-Linter

AVD Ecosystem - Jinja2 Linter

Project Goals

Build a Jinja2 linter that will provide the following capabilities:

• Validate syntax according to AVD style guide.
• Capability to run as part of a CI pipeline to enforce j2lint rules.
• Develop an extension that works with VSCode and potentially other IDEs i.e PyCharm.

Syntax and code style issues

Getting Started

Requirements

Minimum Python version: 3.10

Install with pip

To get started, you can use Python pip to install j2lint:

Install the latest stable version:

pip3 install j2lint

Install the latest development version:

pip3 install git+https://github.com/aristanetworks/j2lint.git

Install For Development

Create a virtual environment, then install the project in editable mode with the dependency groups you need:

python3 -m venv .venv
source .venv/bin/activate
python -m pip install --upgrade pip
python -m pip install -e . --group dev --group test --group lint --group type

If you only need a subset of the contributor tooling, install only the relevant groups.

Common Contributor Commands

pytest
tox -e lint
tox -e type
pre-commit run --all-files

Running the linter

j2lint <path-to-directory-of-templates>

Running the linter on a specific file

j2lint <path-to-directory-of-templates>/template.j2

Listing linting rules

j2lint --list

Running the linter with verbose linter error output

j2lint <path-to-directory-of-templates> --verbose

Running the linter with custom file extensions

j2lint <path-to-directory-of-templates> --extensions j2,html,yml

Running the linter with logs enabled. Logs saved in jinja2-linter.log in the current directory

j2lint <path-to-directory-of-templates> --log

To enable debug logs, use both options:

j2lint <path-to-directory-of-templates> --log --debug

Running the linter with JSON format for linter error output

j2lint <path-to-directory-of-templates> --json

Ignoring rules

1. The --ignore option can have one or more rule IDs or short descriptions: S0, S1, S2, S3, S4, S5, S6, S7, V1, V2, jinja-syntax-error, single-space-decorator, operator-enclosed-by-spaces, jinja-statements-single-space, jinja-statements-indentation, jinja-statements-no-tabs, single-statement-per-line, jinja-statements-delimiter, jinja-variable-lower-case, jinja-variable-format.

2. If multiple rules are to be ignored, use the --ignore option along with rule descriptions separated by space.

   j2lint <path-to-directory-of-templates> --ignore <rule_description1> <rule_desc>
   

Note When using the -i/--ignore or -w/--warn options, the arguments MUST either:

• Be entered at the end of the CLI as in the example above

• Be entered as the last options before the <path-to-directory-of-templates> with -- separator. e.g.

  j2lint --ignore <rule_description1> <rule_desc> -- <path-to-directory-of-templates>
  

3. If one or more linting rules are to be ignored only for a specific jinja template file, add a Jinja comment at the top of the file. The rule can be disabled using the short description of the rule or the id of the rule.

   {# j2lint: disable=S6 #}
   
   # OR
   {# j2lint: disable=jinja-statements-delimiter #}
   

4. Disabling multiple rules

   {# j2lint: disable=jinja-statements-delimiter j2lint: disable=S1 #}
   

Adding custom rules

1. Create a new rules directory under j2lint folder.

2. Add custom rule classes which are similar to classes in j2lint/rules directory: The file name of rules should be in snake_case and the class name should be the PascalCase version of the file name. For example:

   • File name: jinja_operator_has_spaces_rule.py
   • Class name: JinjaOperatorHasSpacesRule

3. Run the jinja2 linter using the -r or --rules_dir option

   j2lint <path-to-directory-of-templates> -r <custom-rules-directory>
   

Note This runs the custom linting rules in addition to the default linting rules.

Running jinja2 linter help command

j2lint --help

Running jinja2 linter on STDIN template. This option can be used with VS Code

j2lint --stdin

Using j2lint as a pre-commit-hook

1. Add j2lint pre-commit hook inside your repository in .pre-commit-config.yaml.

   - repo: https://github.com/aristanetworks/j2lint.git
       rev: <release_tag/sha>
       hooks:
       - id: j2lint
   

2. Run pre-commit -> pre-commit run --all-files

Note When using -i/--ignore or -w/--warn argument in pre-commit, use the following syntax

- repo: https://github.com/aristanetworks/j2lint.git
    rev: <release_tag/sha>
    hooks:
    - id: j2lint
    # Using -- to separate the end of ignore from the positional arguments
    # passed to j2lint
      args: [--ignore, S3, jinja-statements-single-space, --]

Acknowledgments

This project is based on salt-lint and jinjalint