Linters: A Full Guide for 2020

This post was originally published here on Caylent.com.

Maintaining coding standards has its benefits. While the process is often tedious—especially when the team is not used to following the required standards—the final code is easier to organize and maintain. Clean and organized code also presents a huge advantage when you need to trace bugs; you can pinpoint the section of the code that causes errors almost immediately.

Another big advantage of maintaining a coding standard across your projects is easier onboarding of new team members. Handing over tasks and maintaining continuity are challenges that you don’t need to worry about. You also have the ability to outsource better and divide projects into smaller, more manageable chunks for more efficient sprints.

While there are a lot of benefits to be enjoyed, the task of tidying up lines of codes is still not something that many developers enjoy. Fortunately, there are tools that help automate the process in a clever way. Those tools are called linters.

What Is a Linter?

A linter, in simple terms, is a tool that analyzes your code for certain things such as programming errors, bugs, stylistic and formatting errors, and even suspicious entries. Rather than running code through a compiler and being stopped by errors and bugs, for instance, you can run the same code through a linter and get early notifications.

Of course, checking for errors and bugs is not the only thing linters can do. Linters can also force the code to adhere to certain code formatting standards and coding standards in general. You can, for instance, make sure that notes are formatted in a certain way, and that sections of code in the same file are separated properly.

In fact, linters can go further than that. You can enforce a coding style entirely. If you want to incorporate PMD when coding in Java, for instance, you can enforce the coding style using a linter. You can also check variable types, remote unused variables, and make your codes more efficient. Every bit counts, and using a linter simplifies the process of slimming down your codes.

The most important thing to note about linters is that they work prior to the code being compiled. Yes, some linters work with compiled codes, but it is best to run these checks and cleanups before the codes are compiled to avoid unnecessary errors. Some linters will even go as far as making sure that there are no memory leaks.

Linter vs. Formatter

When it comes to styling code and tidying up source files, developers usually turn to code formatters. There are a lot of formatters to choose from too. Beautifier works with JavaScript and does not require special inputs. Prettier can be used with Visual Studio and a wide variety of other coding tools. You can also format multiple languages using tools like Awesome Code Formatters.

Formatters, however, are not linters. For starters, they only format code based on predetermined formats rather than a set of rules. This means they don’t always offer the flexibility that linters can offer; this usually means you may still end up with formatting errors when the process is completed, mainly because you have lines that are misidentified.

Linters take a smarter approach. It analyzes code and identifies violations before fixing the code in place. Flags are raised when there are violations that cannot be fixed immediately, but the linter will also identify the fixes you implement and will not raise a similar flag in the future. Your fixes are added to the rules that code must follow to pass the test.

Linters can also catch coding errors in one go, while formatters focus more on styling. Many developers now run a formatter after a linter to make sure that their code is tidy—or vice versa in some cases—but this approach is not always necessary if the linter you use works well with the programming language you choose.

On the other hand, formatters support complex styling patterns and can be more detailed when reviewing coding styles. The end results are usually tidier visually, although you may still have to make a few adjustments to avoid runtime errors. Choosing between the two—or using both of them—is a matter of deciding which functions you need the most.

Linters

As mentioned before, there are multiple linters to choose from, usually based on the programming languages you use. Linters can also focus on specific areas of programming and code standardization, such as security, coding conventions, and bug tracking. Similar to choosing between linter and formatter, which linter you use depends on the objective you want to achieve.

Pylint, for instance, works with Python and offers an extensive suite of code checking features including detailed reports. There is also Rome; a linter, compiler, bundler, and more for JavaScript, TypeScript, JSON, HTML, Markdown, and CSS. There is even a linter for those who code in Swift (Tailor) and Rust (Dotenv Linter). Check out this comprehensive list of ‘Top 215 Linter Open Source Projects’ for more information.

Universal linters are gaining traction and Super-Linter heads the leaderboard. You can run Super-Linter as GitHub Action and immediately enforce coding standards across your branches. The linter also supports multiple programming languages, including Golang, PHP, Ruby, and domain-specific languages like Terraform and Dockerfile.

An added note about Super-Linter: you can add the Super-Linter status badge to your repository. It is amazing how this linter can be integrated as GitHub Action with a simple linter.yaml file and automation. It even supports environment variables. Different functions can be triggered at different times using the correct ENV variables.

The one disadvantage to keep in mind when using Super-Linter is its lack of support for dependencies. Super-Linter cannot automatically update dependencies and may trigger an error when additional codebases are downloaded as dependencies from private repos. Enough permissions need to be added manually for Super-Linter to work.

That brings us to our initial question. Which linter should you use? The answer depends on your team of developers and how you run your projects. What you cannot afford to do is miss out on the benefits offered by linters.

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