History-sensitive error recovery.pdf

IEEE TRANSACTIONS ON SOFTWARE ENGINEEERING, VOL. XX, NO. Y, MONTH 1999 April 6, 1997 AT 20 : 12 1 History-Sensitive Error Recovery Tim A. Wagner, Susan L. Graham Abstract—We present a novel approach to incremental re- covery from lexical and syntactic errors in an interactive soft- ware development environment. Unlike existing techniques, we utilize the history of changes to the program to discover the natural correlation between user modifications and er- rors detected during incremental lexical and syntactic analy- sis. Our technique is non-correcting—the analysis refuses to in- corporate invalid modifications, while still permitting correct changes to be applied. Errors are presented to the user simply by highlighting the invalid changes. The approach is automated—no user action is required to detect or recover from errors. Multiple textual and structural edits, arbitrary timing of incremental analysis, multiple er- rors per analysis, and nested errors are supported. History- based error recovery is language independent and is compat- ible with the best known methods for incremental lexing and parsing, adding neither time nor space overhead to those al- gorithms. Effective integration with the environment’s his- tory services ensures that other tools can efficiently discover regions of the program (un)affected by errors, and that any transformations of the program required to isolate or present errors are themselves efficiently reversible operations. Keywords—Error recovery, software development environ- ments, incremental parsing, incremental lexing, development log, program presentation I. INTRODUCTIONSYNTACTIC error recovery in batch systems is essen-tially a solved problem, involving a heuristic com- putation based on the configuration of the parser when the error is detected [1]. The best methods known rely on the ability to delay actions or reproduce part of the parse on demand, so that a variety of repairs may be tried at locations other than the detection