Overview of PMD
PMD (Programmer’s Mate Detector) is an extensible, multilanguage static code analyzer designed to identify common programming flaws and enforce coding standards across various programming languages.
What PMD Does
PMD analyzes source code to detect issues such as unused variables, empty catch blocks, unnecessary object creation, and other coding problems that can affect the quality and maintainability of software. It is particularly useful when integrated into the build process, serving as a quality gate to ensure adherence to coding standards.
Key Features and Functionality
- Language Support: PMD supports a wide range of programming languages, including Java, JavaScript, Salesforce.com Apex and Visualforce, Kotlin, Swift, Modelica, PLSQL, Apache Velocity, JSP, WSDL, Maven POM, HTML, XML, XSL, and several others. It currently supports over 16 languages.
- Built-in Rules: PMD comes with over 400 built-in rules that can be applied to different languages. These rules are documented and can be customized to fit specific coding standards.
- Custom Rules: Users can extend PMD by writing their own rules, either in Java or using XPath queries. This allows for the creation of rules tailored to specific coding practices or project requirements.
- Copy-Paste Detector (CPD): PMD includes CPD, a tool that detects duplicated code in various languages, helping to maintain code quality and reduce redundancy.
- Integration Options: PMD can be run in multiple ways, including as a Maven goal, an Ant task, a Gradle task, or directly from the command line. This flexibility makes it easy to incorporate into existing build processes.
- Reporting and Alerts: PMD can generate SARIF reports and create code scanning alerts on platforms like GitHub. It also supports adding annotations to pull requests based on the detected violations.
Extensibility and Customization
- Abstract Syntax Tree (AST): PMD parses source files into an AST, which represents the syntactic structure of the code. This allows rules to be applied in a structured and efficient manner.
- Rule Writing: Users can write custom rules using Java or XPath queries, enabling the detection of specific patterns or coding practices that are relevant to their projects.
Use Cases
PMD is most beneficial when integrated into the development workflow, particularly during the build process. It helps in enforcing coding standards, identifying potential issues early, and maintaining high code quality across the project lifecycle. It can also be used as a code scanner to create alerts and annotations in development platforms like GitHub.