[Engineering Paper] Built-in Clone Detection in Meta Languages

Developers often practice re-use by copying and pasting code. Copied and pasted code is also known as clones. Clones may be found in all programming languages. Automated clone detection may help to detect clones in order to support software maintenance and language design. Syntax-based clone detectors find similar syntax subtrees and, hence, are guaranteed to yield only syntactic clones. They are also known to have high precision and good recall. Developing a syntax-based clone detector for each language from scratch may be an expensive task. In this paper, we explore the idea to integrate syntax-based clone detection into workbenches for language engineering. Such workbenches allow developers to create their own domain-specific language or to create parsers for existing languages. With the integration of clone detection into these workbenches, a clone detector comes as a free byproduct of the grammar specification. The effort is spent only once for the workbench and not multiple times for every language built with the workbench. We report our lessons learned in applying this idea for three language workbenches: the popular parser generator ANTLR and two language workbenches for domain-specific languages, namely, MPS, developed by JetBrains, and Xtext, which is based on the Eclipse Modeling Framework.