When working with a document, users often perform context-specific
repetitive edits – changes to the document that are similar but specific
to the contexts at their locations. Programming by demonstration/examples
(PBD/PBE) systems automate these tasks by learning programs to perform the
repetitive edits from demonstration or examples. However, PBD/PBE systems are
not widely adopted, mainly because they require modal UIs – users must enter a
special mode to give the demonstration/examples. This paper presents
Blue-Pencil, a modeless system for synthesizing edit suggestions on the
fly. Blue-Pencil observes users as they make changes to the document, silently
identifies repetitive changes, and automatically suggests transformations that
can apply at other locations. Blue-Pencil is parameterized – it allows
the "plug-and-play" of different PBE engines to support different document types and
different kinds of transformations. We demonstrate this parameterization by
instantiating Blue-Pencil to several domains – C# and SQL code, markdown documents,
and spreadsheets – using various existing PBE engines. Our evaluation on
37 code editing sessions shows that Blue-Pencil synthesized edit
suggestions with a precision of 0.89 and a recall of 1.0, and took
199 ms to return suggestions on average. Finally, we report on several improvements based on feedback gleaned
from a field study with professional programmers to investigate the use of Blue-Pencil during
long code editing sessions. Blue-Pencil has been integrated with Visual Studio IntelliCode to power the IntelliCode refactorings feature.