Fixing DJLint Per-file-ignores In VSCode: The Stdin Problem

Are you a developer who loves keeping your code clean and consistent? If you're working with HTML templates, especially in a Django or Jinja2 environment, chances are you've heard of or even already use DJLint. It's a fantastic linter that helps catch common errors and enforces style guidelines in your HTML, Django, or Jinja2 templates. When integrated with your favorite editor, like VSCode, it makes your development workflow incredibly smooth. However, you might have hit a snag with a really useful feature: per-file-ignores. Many users find that while per-file-ignores works perfectly from the command line, it seems to mysteriously fail when linting files through the djlint-vscode extension. This often leads to frustrating and confusing results, making you wonder why your carefully crafted pyproject.toml configuration isn't being honored. The good news is, you're not alone, and there's a clear explanation for this behavior, primarily stemming from how the VSCode extension handles file input using stdin mode. Let's dive deep into understanding this djlint challenge and explore the best ways to tackle it, ensuring your VSCode setup provides consistent and accurate linting feedback, exactly as you expect. We’ll uncover the root cause, discuss potential solutions, and provide practical workarounds so you can get back to building amazing things without linting headaches. Understanding this stdin problem is key to unlocking granular control over your linting exceptions.

Understanding per-file-ignores and How It Should Work

When it comes to maintaining a clean and consistent codebase, linters like DJLint are indispensable. They act as vigilant code guardians, pointing out potential issues, enforcing stylistic choices, and ultimately making your templates more readable and maintainable. But what happens when you have specific files or sections within your project that intentionally deviate from your standard linting rules? This is where per-file-ignores comes into play. The per-file-ignores configuration option in your pyproject.toml or .djlintrc file is designed to give you granular control over your linting exceptions. Instead of disabling a rule globally (which might hide issues in other parts of your project), per-file-ignores allows you to specify certain files or patterns of files where particular djlint rules should be ignored. This is incredibly powerful for managing legacy code, third-party libraries that you don't control, or specific design choices that might conflict with a rule but are necessary for a particular template.

Imagine you have a templates/cotton/header.html file that uses an id attribute in a way that djlint flags as non-standard, perhaps DL0003 (ID attribute in non-id element) or DL0004 (duplicate ID). While you generally want to enforce strict ID usage across your project, for this specific header file, changing the id might break an external dependency or a critical JavaScript function. Without per-file-ignores, your options would be limited: you could disable DL0003 globally, but then you'd miss legitimate ID issues elsewhere; or you could manually suppress the id on that line, which can clutter your template code. per-file-ignores offers a much cleaner solution. You could simply add an entry to your pyproject.toml like this:

[tool.djlint]
ignore = [
    "DL0001",
    # ... other global ignores
]
per-file-ignores = [
    "templates/cotton/.*\.html::DL0003,DL0004",
    "*/admin/base.html::DL0002",
]

This configuration tells DJLint: "Hey, when you're linting any HTML file within the templates/cotton/ directory, specifically ignore rules DL0003 and DL0004. And for any base.html file found under an admin directory, ignore rule DL0002." The power here is evident – you maintain global standards while accommodating specific, justified exceptions. This level of control is paramount for larger projects with diverse template structures or for teams collaborating on a codebase where different sections might have unique requirements. When you run djlint directly from your command line, for instance, djlint templates/cotton/header.html, it processes the file, recognizes its path, and correctly applies the per-file-ignores patterns, leading to the desired linting output. This expected behavior forms the foundation of how per-file-ignores is intended to enhance your linting experience, providing both flexibility and precision in managing your template code quality. Without this feature working reliably, developers often find themselves making unnecessary compromises on global linting rules or dealing with persistent, ignorable warnings that clutter their workflow and diminish the value of the linter itself. It’s a crucial aspect of a finely tuned development environment.

The Core Issue: stdin Mode and Missing Filenames in VSCode

Now that we understand how vital per-file-ignores is for a flexible linting setup, let's get to the heart of why it often seems to fall short when you're using DJLint through its VSCode extension. The core problem lies in a fundamental difference in how the djlint-vscode extension passes file content to the djlint executable, compared to running djlint directly from your terminal. When you use the djlint command-line tool, you typically provide it with a file path, for example, djlint my_template.html. In this scenario, djlint knows the exact path of the file it's processing, allowing it to correctly match per-file-ignores patterns defined in your pyproject.toml like `