Cookbook: In Situ Code Completion using Edit Recipes Learned from Examples

Existing code completion engines leverage only pre-defined templates or match a set of user-defined APIs to complete the rest of changes. We propose a new code completion technique, called COOKBOOK, where developers can define custom edit recipes a reusable template of complex edit operations by specifying change examples. It generates an abstract edit recipe that describes the most specific generalization of the demonstrated example program transformations. Given a library of edit recipes, it matches a developer's edit stream to recommend a suitable recipe that is capable of filling out the rest of change customized to the target. We evaluate COOKBOOK using 68 systematic changed methods drawn from the version history of Eclipse SWT. COOKBOOK is able to narrow down to the most suitable recipe in 75% of the cases. It takes 120 milliseconds to find the correct suitable recipe on average, and the edits produced by the selected recipe are on average 82% similar to developers' hand edit. This shows CooKBooK's potential to speed up manual editing and to minimize developers' errors. Our demo video is available at https : //www. youtube. com/watch?y=y4BNc8FT4RU.