Static Code Analysis Tools for Next.js
Tags: webdev, nextjs, javascript, typescript
Published: 2024-03-11 00:59:59

Writing high-quality code is not always easy, especially when we are in a team, have to deal with complex logic, multiple dependencies, and different coding styles. That's why it is important to use static analysis tools to help detect and fix errors, bugs, vulnerabilities, code smells, and other issues in our code before they cause problems.

### What is Static Analysis?
Static analysis is the process of analyzing the source code of a program without executing it. It can help to find potential problems in our code, such as syntax errors, type mismatches, unused variables, security risks, performance bottlenecks, and more. Static analysis tools can also help us enforce coding standards and measure code quality.

### SonarCloud/SonarQube
SonarCloud/SonarQube are cloud-based/self-hosted platforms, that provide comprehensive and continuous code quality analysis and measurement. It's a tool that scans your entire codabase, looking for bugs, code smells, duplications, and even security vulnerabilities. We can integrate Sonar with version control system, such as GitHub, GitLab, or Bitbucket. We can also automate it into our CI/CD pipeline. 

To use SonarCloud or SonarQube for Next.js project, we need to follow these general steps:

1. Create an account on SonarCloud or install SonarQube on your server.
2. Create a project on SonarCloud or SonarQube and generate a token for authentication.
3. Install the SonarScanner tool on your local machine or your CI/CD server.
4. Create a `sonar-project.properties` file in the root directory of your project, and configure the following parameters:

```
# The unique identifier of your project
sonar.projectKey=your-project-key

# The name of your project
sonar.projectName=your-project-name

# The sonar host url (sonarcload/sonarqube)
sonar.host.url=

# The version of your project
sonar.projectVersion=1.0

# The source code encoding
sonar.sourceEncoding=UTF-8

# The directories where your source code is located
sonar.sources=pages,components,lib

# The directories where your test code is located
sonar.tests=test

# The directories where your coverage reports are located
sonar.javascript.lcov.reportPaths=coverage/lcov.info

```
5. Run the SonarScanner command in your terminal or your CI/CD script, and pass the token as an argument:

```
sonar-scanner -Dsonar.login=your-token
```
Wait for the analysis to complete, and then check the results on SonarCloud/SonarQube (you can simply click the given url on your terminal when the analysis is completed)
![Scan Result on SonarQube](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/5mf4si88y9nvza3lpez8.png)

### Linters and ESLint
Linters are like code style police officers. They make sure our code follows a set of rules, which can improve readability and maintainability. Linters can also enforce coding standards and best practices, such as indentation, naming, spacing, and formatting.

ESLint is a popular and widely used tool for linting JavaScript and TypeScript code. It can help us find and fix syntax errors, style issues, code smells, and more. It can also help us enforce coding standards, such as the Airbnb JavaScript Style Guide or the Google JavaScript Style Guide. ESLint is highly customizable and extensible, and supports many plugins and rules for different frameworks and libraries, such as React, Next.js, Jest, and more.

When creating a Next.js project using `create-next-app`, there will be prompts that asking to use EsLint or not.
![create-next-app prompts](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/n4ru83qsdd8qrfr3huvv.png)
When we answer the prompt 'Yes', we can already use the linter to analyze our code. To use the linter, simply run

```
npm run lint
```

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4rlolqysg71ot6j3drbt.png)

---
SonarCloud/SonarQube and ESLint can work together to create a great  quality of code for out Next.js app. SonarCloud/SonarQube takes a broad view, looking for overall code health and security, while ESLint focuses on specific coding style and catching common errors.

By using both these tools, we can ensure our Next.js app is not only functional but also clean, well-maintained, and secure.