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What Is a Linter? – Everything You Need to Know to Get Up to Speed

When it comes to code quality, software teams that take pride in the quality of their code often employ a linter to help prevent undesired quality deviations. However, many teams are still learning about these tools. If you have folks on your team wondering just what a linter is and need an explanation of the details, this quick guide will hopefully equip you with everything necessary to get your team up to speed.

What is a linter?

In a nutshell, lint, or a linter, is used to analyze the static source code of your software project to look for problems and flag them. 

Software teams usually use linters to quickly identify any problems in the code in an automated way with checks and validation. After the linter analyzes the code, the team can then check the details of the flagged items to see if the problems exist, where they exist, as well as get other context so that the team can make any improvements needed to help address any issues.

While linters were initially developed with the objective of finding areas of optimization for the compiler of a software project, linters are now used well beyond just the aim of optimizing the compiling process. Linters don’t even need to be restricted to compiled languages. They can even be applied to interpreted languages that don’t have a compiler to detect errors in the same way as compiled languages do. 

You may be wondering where the term linter came from, and why it sounds like a tool for cleaning clothes. The term linter comes from the tool named “lint” developed by Stephen C. Johnson at Bell Labs in 1978, which was designed to analyze source code in C. Since then, other similar tools have emerged in the field of linters.

Why linting can be a big help

While linting may sound simple in concept, the advantages of effectively applying a linter are significant and worth spending the time to consider adding to your software project. 

First, linters can help reduce the number of errors in production by automatically scanning the code to find and detect errors so that the software team can fix them more quickly than if the issues went undetected.

Another major benefit of linters is that they help make code more readable, maintainable, and consistent, which is often a goal that everyone agrees is desirable, but humans often inevitably deviate from it. Linters help keep code tidy and easier to understand and use throughout the project for anyone who needs to look at the project code in the future. 

As a result of keeping code consistent, this usually also means that the team spends less time discussing code style and aesthetics during code reviews or other similar discussions, because linters can simply enforce the standard. By using a linter, teams can largely remove some of the subjectivity in measuring code quality and provide an objective and measurable way to evaluate code quality instead. 

The process of upholding code quality standards can also help educate more developers on its importance and help foster a code quality culture that can be especially helpful to less formally experienced team members.

On a more functional level, linters can also help check the software project code for potential security vulnerabilities, which can help make the software project more secure – by getting security issues detected and addressed faster. Linters can also do the same in terms of performance by looking for areas of code that may result in detectable performance issues (that can be anticipated ahead of time).

Checks covered by linters

There are a lot of different types of checks that linters can perform, but there is a handful that we can cover here to give you an idea of some common cases. 

First, as we mentioned earlier, security and performance checks are only becoming increasingly important in the modern software world, where hacks and data breaches are turning into headlines on a regular basis. 

As you’ve likely already gathered, linters also perform code smells to check for potential problems automatically, so that they can be flagged for you to look further into to see if there are actual issues requiring an action to address. For example, you can use linters to check for highly complex code or for unusually long functions to see if the code really needs that level of complexity or function length. 

Adherence to code standards is another important check performed by linters to help make the software project code more usable for both the current team and any new team members joining the team in the future. Most software teams know how painful it is to review a section of code that they’ve never seen before or haven’t seen in a while, and team members usually really appreciate it when that code is easier to read and understand as they’re trying to get up to speed. 

Finally, syntax errors are a basic but invaluable check that linters can be used for, catching all kinds of simple problems with interpreted languages like JavaScript. Usually, linters are used to flag these syntax errors and require that they are fixed before pushing code into the mainline of the software project.

Examples of linters

There are a lot of linters out there, and ultimately teams should choose the right tool for their software project based on the needs of their team and the specifics of their project. 

Different linters are often used for various purposes and code languages as well. 

For example, common linters for code formatting and coding conventions include Prettier for JavaScript, Rubocop for Ruby, and StyleCop for C#. 

Python projects often use Bandit for security, and LGTM is used across projects of many language types.

For static analysis overall, other examples include StandardJS for JavaScript and PHPMD for PHP projects.

In terms of popularity, two of the most popular linters for JavaScript are ESLint and JSHint, which typically are very easy to install and configure.

Linting within the big picture

While linters provide an extremely valuable service for software teams, and should be used whenever possible, it’s important to remember that they’re just one tool in what needs to be a wide range of software quality tools employed by software teams. Linters should be seen as more of a starting place or baseline tool when it comes to ensuring the quality of your software.

In the context of your software project overall, be sure to use linters as a vital tool for checking your code and ensure that you’re using it alongside automated testing, code reviews, refactoring, and other tools and processes that will help your team maintain quality. 

Whether you’re trying to establish and clean up processes to manage the basics, or looking for cutting-edge solutions to help your project scale efficiently – tools provided by specialized teams like ours at testRigor can help take the burden off of the shoulders of your team members and allow you to focus on other important work. If you need any help with your software testing and quality practices, please be sure to reach out to our team to get the help you need rather than trying to work through it alone.