How to Set Up the xmllint Pre-Commit Hook

This guide explains how to set up a pre-commit hook to automatically format .xml, .html, and .htm files using the xmllint tool. Pre-commit hooks ensure files are formatted correctly before being committed to version control, maintaining consistency across your repository. NOTE: The script has been modified to work with only GitBash in 2.0.2 IF you need the script to work with other versions, you might need to try 2.0.0/2.0.1 (bash - depending on where it is),or sh (version 1.0.1).

What is xmllint?

xmllint is a command-line tool for validating and formatting XML files. It ensures files are formatted correctly according to standard XML conventions. In this guide, we'll integrate xmllint into a pre-commit hook to automatically format .xml, .html, and .htm files.

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Pre-Commit Hook Overview

1. format-xmllint:

   • Formats .xml, .html, and .htm files using xmllint --format.
   • Overwrites the files if they are not properly formatted.

2. check-xmllint:

   • Checks if the files are formatted according to xmllint --format.
   • Note: We recommend using format-xmllint, as check-xmllint only verifies formatting without fixing it.

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Step 1: Install Pre-Commit

Before setting up the hook, you'll need to install the pre-commit tool. Here's how to install it on different environments:

Installing Pre-Commit

On macOS:

1. Open your terminal.

2. Install pre-commit using Homebrew:

   brew install pre-commit

3. Verify the installation:

   pre-commit --version

On Linux:

1. Open your terminal.

2. Install pre-commit using pip (Python package manager):

   pip install pre-commit

3. Verify the installation:

   pre-commit --version

4. On some distributions, you may need to install additional dependencies:

   sudo apt install python3-pip

On Windows:

1. If you don't have Python installed, download and install Python, which comes with pip.

2. Open PowerShell or Command Prompt.

3. Install pre-commit using pip:

   pip install pre-commit

4. Verify the installation:

   pre-commit --version

Using Docker:

If you prefer Docker, you can run pre-commit in a Docker container:

docker run --rm -v $(pwd):/repo pre-commit run --all-files

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Step 2: Install xmllint

Ensure that xmllint is installed on your system. Here’s how to install it on different operating systems:

On macOS (via Homebrew):

brew install libxml2

On Linux:

sudo apt install libxml2-utils

On Windows:

You can use Windows Subsystem for Linux (WSL) or a package manager like Cygwin to install xmllint. In WSL, run:

sudo apt install libxml2-utils

Verify that xmllint is available by running:

xmllint --version

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Step 3: Create or Update the .pre-commit-config.yaml

In the root directory of your repository, create or update a .pre-commit-config.yaml file with the following configuration:

repos:
  - repo: https://github.com/Patrick-Bonini/xml-format-githook
    rev: v1.0.1
    hooks:
      - id: format-xmllint

Explanation:

• repo: The repository URL hosting the pre-commit hook.
• rev: The version of the hook to use (v1.0.1 in this example).
• id: The identifier for the hook (format-xmllint).
• files: The regex pattern that specifies which file types the hook should target (.xml, .html, and .htm).

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Step 4: Install the Pre-Commit Hook

After configuring the .pre-commit-config.yaml file, install the pre-commit hook by running:

pre-commit install

This will ensure that every time you make a commit, the hook will check and format any .xml, .html, and .htm files before committing them.

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Step 5: Running the Hook

You can manually trigger the pre-commit hook to check and format all files in your repository by running:

pre-commit run --all-files

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What Happens During a Commit?

• When you attempt to commit files, the hook will automatically run and check the formatting of any .xml, .html, or .htm files.
• If the files are not properly formatted, format-xmllint will reformat them, and you’ll need to stage the corrected files and commit again.
• This process ensures that your repository maintains consistent and correct formatting.

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Troubleshooting

• xmllint not found: Ensure that xmllint is installed and accessible via your command line.

• Hook not running on .html or .htm files: Double-check that your .pre-commit-config.yaml file is correctly targeting the file extensions.

• Permission errors: Make sure the check-xmllint script is executable by running:

  chmod +x check-xmllint

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Conclusion

By setting up the xmllint pre-commit hook, you ensure that your .xml, .html, and .htm files are always formatted correctly before they are committed. This automated process helps maintain code quality, consistency, and readability across your project.

For further assistance or questions, feel free to reach out to your development team or consult the pre-commit documentation.