Continuous Code Reviews

Originally published on Mar 17, 2017 on the Pluralsight Tech Blog

Code reviews are generally accepted as good thing in software development. Some of the benefits include improving quality, sharing knowledge of a system, and promoting collective code ownership.

But how you perform a code review matters. Herding multiple people into a single room where code is projected on a screen can be a boring (and expensive) process. Tools for managing code reviews have improved things dramatically. We can now review code asynchronously. Static code analysis tools can weed out mundane issues or company style violations. We can track progress on reviews and even combine them with our workflow (like with pull requests).

But can we do better?

Jump on the Continuous Bandwagon

These days we hear a lot about doing things continuously. Continuous integration. Continuous deployments. Even continuous retrospectives. But why do them "continuously?" In some cases it's to minimize pain (like with CI). In other cases, it's to incorporate more good things into our routines.

So is it possible to do a continuous code review? Yes! You simply have someone reviewing your code while you work on it. Reviewing code is definitely work, and there is a name for when we have two developers working on the same code at the same time: pair programming.

"Hang on," I imagine you saying, "you've tricked me into reading an article about pairing when I thought I was reading about code reviews!"

It's true. Pair programming (and its sister, mob programming) are definitely topics that I highly advocate. But in this article, I want to focus on how pairing can be an improved form of code review.

So what benefits do you get from a "continuous code review?"

Short Feedback Cycles

One of the biggest problems with a typical code review is the delay between writing the code and getting feedback. By the time you learn what changes have been recommended, you've already moved on to something else. (A coder's time is valuable after all; you probably can't afford to sit around doing nothing while you wait for Lisa to get out of that meeting and do the review.) So then you have to stop the other thing you were doing and get back to the problem you thought you had already solved — you did get the code working before you submitted the code review, didn't you?

Context switching incurs a lot of overhead. And you may need to do it more than once if there are multiple reviewers or if your changes require a resubmission. And this churn doesn't only affect the author; it also affects the reviewers who are context switching from their other work.

In a continuous code review you don't have this problem. Your pair is right there giving you feedback as you go. From little things like variable naming to bigger things like noticing a bug or telling you about an existing class you should use. The code is updated in realtime.

Shared Understanding

When you are working with a pair, that other person is helping you with the task as you go. They understand the decisions being made while you code and can give better advice. And they know that code much better if they have to come back to it later. They can even finish up something when you are unavailable.

Contrast that to a usual code review wherein the reviewer has to first understand the goal of the change, and then read the code to determine whether it is correct. How many times is the code under review just given a cursory glance? How often does the reviewer actually execute that code? Does the reviewer understand this part of the codebase very well?

It takes a lot of effort for an after-the-fact reviewer to give the same quality of feedback as someone you are actively working with. And all too often, those code reviews are done in a hurry or with little care.

Avoid Painful Reviews

Sometimes reviews hurt. At their worst, the reviewers chastise or demean the author. I'm ashamed to say that I've written some reviews like this in my sordid past. And even when the reviewers are behaving themselves, it can still be daunting to receive feedback that suggests massive overhauls or a vast quantity of little changes.

But when the review is continuous it rarely hurts. People are less likely to say something mean when you're working together because it's "us" instead of "them." The process is inherently less adversarial. All those little changes are discussed and fixed immediately. Pitfalls are avoided and improvements can be addressed before wasting a lot of time.

Reduced Need for Tooling

When someone is always reviewing your code, you begin to develop a shared coding style. This reduces the need for your team to define guidelines. Or, if you've got a company-wide style guide, the reviewer can help remind you to follow it because doing so helps them read what you are writing.

This can reduce (or in some cases eliminate) your need for static code analysis tools. That means you don't need to sit down in a big meeting to discuss the configuration. And since your review is happening continually, there isn't a need for specific code review tools either!

Try It Out

If these benefits sound good to you, why not give continuous code reviews a try? There are also a number of other great benefits to pair or mob programming.

Of course, there are always some caveats. Some coworkers are just grumpy and disagreeable. Other people just have clashing personalities. You might not want to work with them all day every day.

It can often be easier to pair when you are co-located, but remote pairing is getting easier for distributed teams. If that doesn't work for your team, then maybe asynchronous tools like pull requests can be better.

Some people might say that pairing isn't a code review. It's hard to remain an objective reviewer when you're not driving the code, so you become more of co-authors. At that point, are you too close to the work that you cannot see your errors (the same reason that people need copy editors)?

These concerns are very real and can mean that continuous code reviews may not work for some teams. In my experience, the benefits of pairing far outweigh the drawbacks. It has become my preferred way to work and it's how most of our teams work here at Pluralsight.

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