How do developers use dynamic features? The case of Ruby

Abstract Programming languages provide features that allow developers—at run time—to evaluate strings as expressions, to define and invoke methods, etc. Nevertheless, the overuse of dynamic features may negatively impact performance, decrease the accuracy of static code analysis techniques, and hinder compiler optimizations. This paper, therefore, investigates how developers use dynamic features based on 28 open-source Ruby projects. The main findings are fourfold: (i) dynamic features correspond on average to 2.58% of the language features in a Ruby project, and almost half of them are send when we disregard features that are ascribed to common programming practices; (ii) we identified that 1417 out of 2849 dynamic statements (49.7%) could be easily converted to static code; (iii) we identified, classified, and also illustrated the ten most common scenarios where developers opt for dynamic statements instead of static ones, e.g., we found that developers rely mostly on dynamic features to access private members (20.35%), which reveals flaws in the architectural design; and (iv) we identified five motivations why developers use dynamic features: unusual coding style, overpassing privacy restrictions, defining new structures, contextualizing block executions, and generalizing code tasks.