Collections-17's buggy version is wrong

[zeyugao]

Original issue: https://issues.apache.org/jira/browse/COLLECTIONS-239

The current reverted patch is https://github.com/rjust/defects4j/blob/master/framework/projects/Collections/patches/17.src.patch and it is originate from this commit.

However, according to the surrounding commit messages, the COLLECTIONS-239 is fixed by multiple commit, including apache/commons-collections@459f14b and apache/commons-collections@b7327a4

The current patch (17.src.patch) only represents the effect to keep backwards compatibility, instead of revealing the original buggy code.

[zeyugao]

btw, I don't think the code can fairly be labeled as "buggy" at all. It simply attempts to implement a new feature. You can see the changes in the following diff: apache/commons-collections@b7327a4.

[rjust]

Related to partial and multi-commit bugs (#619).

[rjust]

Similar to issue #619, we would welcome contributions that add metadata for the bugs in the dataset.

What constitutes a bug vs. a feature is a tricky question, though. For example, is a missing functionality stated in a specification, together with a triggering test that exposes the missing functionality, a bug or a feature? Does the answer depend on whether the specification has evolved or whether the functionality was missing all along? Rather than trying to narrow down the definitions for bug vs. feature, I think it might be helpful to characterize the type of change required to fix a failing test. These characteristics can then be correlated with different definitions of bug vs. feature as well as efficacy results for tools etc.