Automating bug report assignment

Bug reports are widely employed to facilitate software tasks in software maintenance. Since bug reports are contributed by people, the authorship characteristics of contributors may heavily impact the performance of resolving software tasks. Poorly written bug reports may delay developers when fixing bugs. However, no in-depth investigation has been conducted over the authorship characteristics. In this study, we first leverage byte-level $N$-grams to model the authorship characteristics and employ Normalized Simplified Profile Intersection (NSPI) to identify the similarity of the authorship characteristics. Then, we investigate a series of properties related to contributors authorship characteristics, including the evolvement over time and the variation among distinct products in open source projects. Moreover, we show how to leverage the authorship characteristics to facilitate a well-known task in software maintenance, namely Bug Report Summarization (BRS). Experiments on open source projects validate that incorporating the authorship characteristics can effectively improve a state-of-the-art method in BRS. Our findings suggest that contributors should retain stable authorship characteristics and the authorship characteristics can assist in resolving software tasks.

With the increasing number of bug reports coming into the open bug repository, it is impossible to triage bug reports manually by software managers. This paper proposes a novel approach called En-LDA (Entropy optimized Latent Dirichlet Allocation (LDA)) for automatic bug report assignment. Specifically, we propose entropy to optimize the number of topics of the LDA model and further use the entropy optimized LDA to capture the expertise and interest of developers in bug resolution. A developer’s interest in a topic is modeled by the number of the developer’s comments on bug reports of the topic divided by the number of all the developer’s comments. A developer’s expertise in a topic is modeled by the number of the developer’s comments on bug reports of the topic divided by the number of all developers’ comments on the topic. Given a new bug report, En-LDA recommends a ranked list of developers who are potentially adequate to resolve the new bug. Experiments on Eclipse JDT and Mozilla Firefox projects show that En-LDA can achieve high recall up to 84% and 58%, and precision up to 28% and 41%, respectively, which indicates promising aspects of the proposed approach.

In this paper, we present a new approach to localize a bug in the software source file hierarchy. The proposed approach uses log files of the revision control system and bug reports information in open bug repository of open source projects to train a Support Vector Machine (SVM) classifier. Our approach employs textual information in summary and description of bugs reported to the bug repository, in order to form machine learning features. The class labels are revision paths of fixed issues, as recorded in the log file of the revision control system. Given an unseen bug instance, the trained classifier can predict which part of the software source file hierarchy (revision path) is more likely to be related to this issue. Experimental results on more than 2000 bug reports of ‘UI’component of the Eclipse JDT project from the initiation date of the project until November 24, 2009 (about 8 years) using this approach, show weighted precision and recall values of about 98% on average.

For large open source projects (e.g., Eclipse, Mozilla), developers usually utilize bug reports to facilitate software maintenance tasks such as fixer assignment. However, there are a large portion of short reports in bug repositories. We find that 78.1% of bug reports only include less than 100 words in Eclipse and require bug fixers to spend more time on resolving them due to limited informative contents. To address this problem, in this paper, we propose a novel approach to enrich bug reports. Concretely, we design a sentence ranking algorithm based on a new textual similarity metric to select the proper contents for bug report enrichment. For the enriched bug reports, we conduct a user study to assess whether the additional sentences can provide further help to fixer assignment. Moreover, we assess whether the enriched versions can improve the performance of automated fixer recommendation. In particular, we perform three popular automated fixer recommendation approaches on the enriched bug reports of Eclipse, Mozilla, and GNU Compiler Collection (GCC). The experimental results show that enriched bug reports improve the average F-measure scores of the automated fixer recommendation approaches by up to 10% for DREX, 13.37% for DRETOM, and 8% for DevRec when top-10 bug fixers are recommended.

Bug handling is an essential part of the software development process. Ideally, in a bug‐tracking system, bugs are reported, fixed, verified, and closed. In some cases, bugs have to be reopened mostly due to an incorrect fix. However, instead of reopening the existing bug report, users may submit a new report for a previously reported bug, which results in duplicate bug reports. Users might report duplicate bugs if they miss the previous bug report or if the previous bug is unresolved (i.e., in progress) and therefore cannot be reopened. These duplicate bug reports may cost extra maintenance efforts in triaging and bug fixing. There have been several studies on characterizing reopened bugs and duplicate bug reports; however, to the best of our knowledge, there has been no prior work on understanding the dynamics of their interaction, which ismissed reopenbugs. Our study is based on analyzing the difference between duplicate and nonduplicate bugs and further categorizing the duplicate bugs. In this regard, we categorize duplicate bugs according to the original bug's resolution status at the duplicate's creation time as Master‐Unresolved bugs and Master‐Resolved (Missed Reopen) bugs to distinguish their properties. We compare these two types of bugs in terms of their relationship to their master bug, bug surface time, bug fix time, bug's severity, and the number of users involved. We perform case studies using the Eclipse and Mozilla projects' bug repositories that include more than 165,500 and 394,000 bug reports, respectively. Additionally, we investigate the perceived importance, impact, and causes of duplicate bugs, as well as the difference between nonduplicate and duplicate bugs and its categories for practitioners in the software industry by conducting a survey.

“We do not appreciate being experimented on”: Developer and researcher views on the ethics of experiments on open-source projects

With the use of increasingly complex software, software bugs are inevitable. Software developers rely on bug reports to identify and fix these issues. In this process, developers inspect suspected buggy source code files, relying heavily on a bug report. This process is often time-consuming and increases the cost of software maintenance. To resolve this problem, we propose a novel bug localization method using topic-based similar commit information. First, the method determines similar topics for a given bug report. Then, it extracts similar bug reports and similar commit information for these topics. To extract similar bug reports on a topic, a similarity measure is calculated for a given bug report. In the process, for a given bug report and source code, features shared by similar source codes are classified and extracted; combining these features improves the method’s performance. The extracted features are presented to the convolutional neural network’s long short-term memory algorithm for model training. Finally, when a bug report is submitted to the model, a suspected buggy source code file is detected and recommended. To evaluate the performance of our method, a baseline performance comparison was conducted using code from open-source projects. Our method exhibits good performance.

Owing to the ever-expanding scale of software, solving the problem of bug triage efficiently and reasonably has become one of the most important issues in software project maintenance. However, there are two challenges in bug triage: low quality of bug reports and engagement of developers. Most of the existing bug triage solutions are based on the text information and have no consideration of developer engagement, which leads to the loss of bug triage accuracy. To overcome these two challenges, we propose a high-dimensional hybrid data reduction method that combines feature selection with instance selection to build a small-scale and high-quality dataset of bug reports by removing redundant or noninformative bug reports and words. In addition, we also study the recent engagement of developers, which can effectively distinguish similar bug reports and provide a more suitable list of the recommended developers. Finally, we experiment with four bug repositories: GCC, OpenOffice, Mozilla, and NetBeans. We experimentally verify that our method can effectively improve the efficiency of bug triage.

Bug repository systems have become an integral component of software development activities. Ideally, each bug report should help developers to find and fix a software fault. However, there is a subset of reported bugs that is not (easily) reproducible, on which developers spend considerable amounts of time and effort. We present an empirical analysis of non-reproducible bug reports to characterize their rate, nature, and root causes. We mine one industrial and five open-source bug repositories, resulting in 32K non-reproducible bug reports. We (1) compare properties of non-reproducible reports with their counterparts such as active time and number of authors, (2) investigate their life-cycle patterns, and (3) examine 120 Fixed non-reproducible reports. In addition, we qualitatively classify a set of randomly selected non-reproducible bug reports (1,643) into six common categories. Our results show that, on average, non-reproducible bug reports pertain to 17% of all bug reports, remain active three months longer than their counterparts, can be mainly (45%) classified as "Interbug Dependencies'', and 66% of Fixed non-reproducible reports were indeed reproduced and fixed.

The accurate severity classification of a bug report is an important aspect of bug fixing. The bug reports are submitted into the bug tracking system with high speed, and owing to this, bug repository size has been increasing at an enormous rate. This increased bug repository size introduces biases in the bug triage process. Therefore, it is necessary to classify the severity of a bug report to balance the bug triaging process. Previously, many machine learning models were proposed for automation of bug severity classification. The accuracy of these models is not up to the mark because they do not extract the important feature patterns for learning the classifier. This paper proposes a novel deep learning model for multiclass severity classification called Bug Severity classification to address these challenges by using a Convolutional Neural Network and Random forest with Boosting (BCR). This model directly learns the latent and highly representative features. Initially, the natural language techniques preprocess the bug report text, and then n-gram is used to extract the features. Further, the Convolutional Neural Network extracts the important feature patterns of respective severity classes. Lastly, the random forest with boosting classifies the multiple bug severity classes. The average accuracy of the proposed model is 96.34% on multiclass severity of five open source projects. The average F-measures of the proposed BCR and the existing approach were 96.43% and 84.24%, respectively, on binary class severity classification. The results prove that the proposed BCR approach enhances the performance of bug severity classification over the state-of-the-art techniques.

With a great number of software applications that have been developed, software maintenance has become an important and challenging task, particularly due to the increasing scale of software projects. Even if developers can create and update bug reports in bug repositories to support software maintenance, a large software project receives a large number of bug reports each day. For reducing the workload of developers, many researchers and software engineers have begun recommending appropriate developers to fix bugs. This process is called bug triage and is a hot research topic for software maintenance. In this paper, we propose a hybrid bug triage algorithm, combining a probability model and an experience model to rank all candidate developers for fixing a new bug. For this study, we adopted the smoothed Unigram Model (UM) instead of the traditional Vector Space Model (VSM) to search similar bug reports. In the probability model, we used a social network to analyze the probability of fixing a new bug for a candidate developer. We first proposed to add a new feature (the number of re-opened bugs) in order to get the fixing probability. In the experience model, we considered the number of fixed bugs and fixing cost for each candidate developer as the estimate factor. In addition, we introduced a new concept, activity factor, to better model developers' experience. We performed the experiments on two large-scale, open source projects. The results show that our method can effectively recommend the best developer for fixing bugs.

Traditional bug management systems, like Bugzilla, are widely used in open source and commercial projects. Stack Exchange uses its online question and answer (Q&A) platform to collect and manage bugs, which brings several new unique features that are not offered in traditional bug management systems. Users can edit bug reports, use different communication channels, and vote on bug reports, answers, and their associated comments. Understanding how these features manage bug reports can provide insights to the designers of traditional bug management systems, like whether a feature should be introduced? and how would users leverage such a feature? We performed a large-scale analysis of 19,151 bug reports of the bug management system of Stack Exchange and studied the in-place editing, the answering and commenting, and the voting features. We find that: 1) The three features are used actively. 2) 57 percent of the edits improved the quality of bug reports. 3) Commenting provides a channel for discussing bug-related information, while answering offers a channel for explaining the causes of a bug and bug-fix information. 4) Downvotes are made due to the disagreement of the reported “bug” being a real bug and the low quality of bug reports. Based on our findings, we provide suggestions for traditional bug management systems.

With the increasing number of software bugs, bug fixing plays an important role in software development and maintenance. To improve the efficiency of bug resolution, developers utilize bug reports to resolve given bugs. Especially, bug triagers usually depend on bugs' descriptions to suggest priority levels for reported bugs. However, manual priority assignment is a time-consuming and cumbersome task. To resolve this problem, recent studies have proposed many approaches to automatically predict the priority levels for the reported bugs. Unfortunately, these approaches still face two challenges that include words' nonconsecutive semantics in bug reports and the imbalanced data. In this article, we propose a novel approach that graph convolutional networks (GCN) based on weighted loss function to perform the priority prediction for bug reports. For the first challenge, we build a heterogeneous text graph for bug reports and apply GCN to extract words' semantics in bug reports. For the second challenge, we construct a weighted loss function in the training phase. We conduct the priority prediction on four open-source projects, including Mozilla, Eclipse, Netbeans, and GNU compiler collection. Experimental results show that our method outperforms two baseline approaches in terms of the F-measure by weighted average of 13.22%.

A large open source project consists of a wide range of bug reports. In open source project, bug reports are available and these reports can be modified by anyone. Bugs are software defects whose prediction is highly difficult. To detect the bugs, machine learning classifier has been proposed. It segregates the bug reports and developers and it learns the type of report suitable for each developer. Bug triage is the process of assigning the bug for the appropriate developer. The techniques include preprocessing, machine learning classifier, instance selection and feature selection. The aim of this paper is to attain a data set reduction in bug triage by including the representative values along with the statistical values of the bug data set. Our work considers the dataset from the open source project Eclipse. We focus on reducing the data scale and thereby improving the accuracy. This can be achieved by building a representative model for prediction of reduction orders by including the summary, metadata. Our proposed work attains an accuracy result of 96.5% that is better when compared with existing work.

We propose an approach called Bug report assignment with topic modeling and heterogeneous network analysis (BAHA) to automatically assign bug reports to developers. Existing studies adopt social network analysis to characterize the collaboration of developers. The networks used in these studies are all homogenous. In real practice of bug resolution, different developers collaborate on different bug reports that makes the homogenous network unable to capture this information. We use heterogeneous network to describe the relations between reporters, bug reports and developers to characterize developers' collaboration. Experiments on Eclipse JDT project show that BAHA outperforms the state of art methods on automatic bug report assignment.