Jinja2-Linter

AVD Ecosystem - Jinja2 Linter

The goal of this project is to build a Jinja2 linter that will provide the following capabilities:

• Validate syntax according to AVD style guide
• Develop extension that works with VSCode and potentianly others IDEs i.e PyCharm
  • if supporting multiple IDEs adds to much complexity, support for VSCode will take priority
• Capability to run as a GitHub Action and used to enforce style in our CI pipeline

Syntax and code style issues detected by Jinja2 Linter are:

1. S0 Jinja2 syntax should be correct
2. S1 A single space shall be added between Jinja2 curly brackets and a variable's name
3. S2 When variables are used in combination with a filter, | shall be enclosed by space
4. S3 Nested jinja code block shall follow next rules:
   • All J2 statements must be enclosed by 1 space
   • All J2 statements must be indented by 4 more spaces within jinja delimiter
   • To close a control, end tag must have same indentation level
   • Indentation are 4 spaces and NOT tabulation
5. S7 Jinja statements should be on separate lines
6. S8 Jinja statements should not have {%- or {%+ or -%} as delimeters
7. VAR-1 All variables shall use lower case
8. VAR-2 If variable is multi-words, underscore _ shall be used as a separator

Getting Started

Install with pip

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

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

Git approach

To get started with j2lint code, clone the Jinja2 Linter project on your system:

git clone https://github.com/aristanetworks/j2lint.git

Prerequisites

1. Python version 3.6+

Creating the environment

1. Create a virtual environment and activate it

python3 -m venv myenv
source myenv/bin/activate

1. Install pip, jinja2 and jinja2-linter

sudo apt-get install python3-pip
pip3 install jinja2
cd jinja2-linter
python setup.py install

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 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 of these values: syntax-error, single-space-decorator, filter-enclosed-by-spaces, jinja-statement-single-space, jinja-statements-indentation, no-tabs, single-statement-per-line, jinja-delimeter, 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>

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=S8}

# OR
{# j2lint: disable=jinja-delimeter #}

4. Disabling multiple rules

{# j2lint: disable=jinja-delimeter 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.
3. Run the jinja2 linter using --rules-dir option

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

Acknowledgement

This project is based on salt-lint and jinjalint