Creating a Custom Rule for Credo in Elixir

The post outlines the process of creating a custom rule for Credo, a static code analysis tool for Elixir, aimed at enforcing the use of pattern matching with structs instead of using maps with atom keys, which enhances code readability and type safety. It begins by explaining the rationale behind the rule and how it can help maintainability in codebases. The guide details the installation of Credo if not already present, generating a new rule, and testing the rule's effectiveness. The implementation involves traversing the Abstract Syntax Tree (AST) of the code to detect functions that pattern match on maps with atom keys and flagging them. With careful attention to edge cases and thorough testing, it establishes a robust method of enforcing this coding style. The complete code is available in a GitHub repository linked at the end of the post.