A free continuous code review plug in for Eclipse

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1 A free continuous code review plug in for Eclipse Mario Bernhart, Christoph Mayerhofer, Thomas Grechenig Vienna University of Technology, Vienna/Austria

2 What are Code Reviews? A meeting at which software code is presented to project personnel, managers, users, customers, or other interested parties for comment or approval. (IEEE Standard Glossary, 1990) Why Code Reviews? Independend quality observation and assurance Authors lack of objectivity and expertise to find bugs Knowledge sharing Collective Code Ownership Goal Primarily focuses on finding defects early in the development phase 2

3 Accumulative effects of errors (Mizuno, 1983): 3

4 Costs to fix errors correlate with the error latency (Boehm, 2000): 4

5 Cost reduction and quality improvement at the same time: Many studies show the cost reduction by the use of code reviews Direct correlation between review effort and product quality (Takagi et.al., 1995) 5

6 Quality Improvement Collective Code Ownership Understanding the rationale behind existing code consumes a lot of time (42% of understanding time examining the source code, 20% using the debugger and 16% examining check in comments or scmdiffs; LaToza et.al., 2006) Management Support Process meassure against the it compiles let s ship it Knowledge about developers scope of work 6

7 Code is hard to read and understand Code generation, inheritance, dynamic binding, weaving, external libraries,... Delocalized team Resource Overhead Lack of time and resources If project runs out of time code reviews are first discarded Insufficient training to perform code reviews 7

8 Code modifications within a changeset are closely related and easy to understand by the reviewer Code reviews are scheduled and performed during development phase process adherence Only the diff has to be inspected for each review reduced overhead 8

9 Review Scope One Changeset of the SCM Continuous reviews Commit triggers the review Feed based assignments Assignments of authors/reviewers with filters IDE Integration Easy to use Eclipse Plugin low learning effort for developers and reviewers 9

10 CVS No changesets at all CVS commits every file within a unique transaction ReviewClipse has to find changesets based on author, timestamp, commit comment. SVN Revision Number CVS Version Number CVS Version Number not unique Git Local vs. Remote (Public) Repositories Users have to use the same workflow as Subversion SVN Revision Number Git Revision Number 10

Step 1: Implementation The developer implements his

to SCM The developer commits the code modifications to

Step 4: Performing the code review The source code

11 Step 1: Implementation The developer implements his programming task with the development environment. 1: if (magic_wand!= null) { 2: // hocus pocus, grab the focus 3: window.setfocus(true, 4: } 5:... Subversion Sourcecode management system Step 2: Commit to SCM The developer commits the code modifications to Subversion. A new changeset is created. Step 4: Performing the code review The source code changes are reviewed with a compare editor, which shows the previous and the current version. Defects are recorded in a review report. Step 3: Scheduling of the code review The review editor shows all related changesets (the current user is the author or the reviewer of the changeset). 11

12 Eclipse integrated easy to use UI Review scope = one changeset in the SVN No additional infrastructure File/SVN based storage Ideal for small teams, forge based and students Works with Subversive and Subclipse Assignments of reviewers/authors with filters Create Mylyn tasks out of (bad) reviews Freeware

13 Peer to Peer Reviews Master Reviewer 13

14 Team: Chris senior developer John test expert Ben Mike new to the team Scenario A: Chris (a senior developer) supervises Mike and reviews all changesets of the new team member Scenario B: John (the test expert) reviews all *Test*.java of all other team members

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18 More Adapters for CVS, Git, are currently developed Release of RC under an OSS Licence planned prior to 2010 Most requested feature: Inline Review Comments Additional planned features: Checklists, Review Reports (via BIRT), Notifications about new Reviews and Comments 18

4 Subversive or Subclipse SVN Client Subversion Repository >= 1.4.6 Optional: Mylyn Task List >= 3.

19 Update Site: site Eclipse >= 3.4 Subversive or Subclipse SVN Client Subversion Repository >= Optional: Mylyn Task List >= Contact: Freeware, downloads within 9 months

Mylyn Reviews Project Creation Review

Mylyn Reviews Project Creation Review Mario Bernhart and Kilian Matt 1 Introduction Code reviews have many benefits, most importantly to find bugs early in the development phase and to enforce coding standards