Analyzing an analyzer - A dive into how RuboCop works
summary
RuboCop parses Ruby into an AST using the parser gem, walks that tree with RuboCop AST traversal so cops can implement focused on_ handlers, and performs fixes through a tree rewriter* that uses node.location.expression ranges to replace source. It runs iteratively (reprocessing after edits, risking loops), supports custom cops for migrations and deprecations, and ships a working autocorrector that solved many CI pain points. Project is ten years old and ≈270 million downloads.
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