Sunday, November 11, 2012
Being for the Benefit of Future Developer
A successful software project is likely to pass between many developers in its lifetime. You are one link in your project's chain of custody and every line of code you commit to your project is an artifact you're leaving to be discovered by Future Developer. Just as you've inherited the decisions of the developers that came before you, other developers will inherit the decisions you're making today. Onto them we bequeath our misunderstandings, our shortcuts, our applications of half-understood patterns and technologies, our inconsistencies, our inattention to detail, our procrastinations, our quick-and-dirty changes, our hidden skeletons, our dirty laundry. More rarely, they will be the beneficiaries of our discipline, deliberation, and preparation.
As a developer on your project you are in the best possible position to empathize with and anticipate the needs of Future Developer. Every good decision we make for our project will have ripple effects on his or her productivity. Why is this important? As Bob Martin asks in Clean Code, “Have you ever been significantly impeded by bad code? So then – why did you write it?” The same strategies to improve the conditions for future generations of teams working on your project will serve your team well in the present. When you come back to some obscure corner of the codebase that you cobbled together six months ago, you're likely to have only a little more context than Future Developer will when he or she sees it or the first time. The clues and polish you've left for other developers will benefit your future self. Projects that are poorly maintained are draining to contribute to and lead to team attrition. Investing in the quality and future maintainability of the software you're creating is an investment in a happy, productive workplace for the present and future.
I'm going to pick a few practices in no particular order that we can use to set Future Developer up for success.
1. Refactor toward Consistency
As projects age and requirements become more complex, we tend to introduce new patterns and designs to manage this complexity. It's hard to tell if a pattern or approach is pulling its weight immediately. Most of the time the feedback that proves or disproves its value comes when another developer has to make a change to that area of the codebase. Sometimes these patterns grow into conventions that we begin to reach for to solve problems.
There's immense benefit to that: conventions communicate intent. If we tend to solve problems in the same sorts of ways in a codebase, Future Developer can start to predict how pieces of the codebase work together reducing the amount of time necessary to diagnose problems and implement changes.
Often what we leave behind is a hodgepodge of patterns which never quite became conventions or have been ignored in the codebase as old cruft. This happens for a variety of reasons: the conventions introduced didn't work well enough to make it into other areas of the codebase or maybe new developers didn't know there was a convention or pattern for handling a given requirement.
Rails' opinions and conventions are powerful. They allow developers to join a
project and quickly be productive if they've had any exposure to projects that
have used the framework. Sometimes we muddy these conventions and dilute their
power. For example, in Rails systems we sometimes see controllers built in
many different styles. Some are composed using a project like
resource_controller, others follow the standard Rails
while others are junk drawers of random actions. Another common anti-pattern
is having configuration data sprinkled and initialized all throughout your
Don't have half a dozen different ways of configuring aspects of your system and make it clear how a controller should be built in your system. Once you've experimented for a while and have settled on an approach, take the time to go back to previous work and refactor into the new pattern. This doesn't mean that you should add arbitrary constraints. There's good reason, for example, to have some configuration stored with the project and some stored in the environment to aid in deployment, but there should be one common structure and access pattern for using configuration data.
Add conventions to your README or selected documentation repository. This will give Future Developer a head start on adding functionality to the system and to in understanding how its components are constructed.
2. Prune Dead Code
Another common characteristic of systems that have existed for some time is the collection of barnacles in the form of dead code. These components in your project may have at one time been providing business value but they've been deprecated and hidden from production for months. There's probably even a slew of full-stack acceptance tests validating those parts of the system are functioning and slowing down your test suite.
Sometimes we're reluctant to delete this code because we're not sure if the feature will be resurrected. Your product manager, when asked, might say “no, leave it, we may reuse that one day.” This is a false dilemma – carrying around a slowly rotting section of code for possible future reuse assumes that reusing those parts of the codebase involves just flicking a switch. If we're ignoring it because it's not actually live, it's not likely to be something we can just “turn on” without significant work. You're carrying that old code around like a boat anchor, wasting cycles maintaining it because there's a small chance you may possibly one day need part of it. Maybe. You don't know, but you spent a lot of time building it so rather than deleting it you allow the code to slowly rot in your repository.
What's even more costly is that the continued existence of this code is a possible trap for Future Developer. It detracts attention from the components of your system that are actually live and is a possible red herring when he or she is trying to understand or troubleshoot some aspect of the system. In a system down emergency, old, dead code is noise waiting to waste valuable time. Keeping the amount of code present in your code repository synchronized to the amount of code actually functioning in your live system will reduce overall maintenance costs and allow Future Developer to more quickly understand your entire system.
Delete code that isn't in use with abandon. It'll still be under source control if you need to refer to it later. Don't fall onto the wrong side of the fallacy that you might be able to “turn it back on again later.” If it had any value then why did you turn it off to begin with?
3. Leave a Coherent Paper Trail
Aside from our project itself, some of the tools we use in support of writing
code have their own artifacts. For example, there are commonly accepted
about what constitutes good
git commit message hygiene and
yet projects continue to accumulate commit histories like this contrived
jp@oeuf:~/workspace/blog(master*)$ git log --oneline app/controllers/application_controller.rb 8ec7f99 fuck i dunno lol ffa919a shut up, atom parser a33e9fa fixing again cecc9dc one more time 968a28f fixing 3e3aeb2 ws 1fc597e pagination edea155 adding dumb feature
When Future Developer ends up inevitably using
git blame to get context
about a given feature, leave him or her the details they need to understand
the churn in the files in question. Use
rebase, and friends to massage your commits into a coherent set before
integrating your topic branch. Reword your commits after you're done – take a
moment to include anything that seems relevant and summarize. Proofread for
grammar and spelling; you're publishing something that somebody else will need
to read and understand. Do Future Developer a favor and ensure you're leaving behind
an intelligible paper trail that contains the right amount of detail.
jp@oeuf:~/workspace/blog(master*)$ git log app/controllers/application_controller.rb commit 8ec7f998fb74a80886ece47f0a51bd03b0460c7a Author: John Pignata <firstname.lastname@example.org> Date: Sat Nov 3 14:11:12 2012 -0400 Add Google Analytics helper commit 968a28f366e959081307e65253118a65301466f2 Author: John Pignata <email@example.com> Date: Sat Nov 3 13:49:50 2012 -0400 Correct ATOM feed validation issues Using the W3C Validator (http://validator.w3.org/appc/), a few trivial errors were reported: * <author> should have a <name> node within it and not text * Timestamps should be in ISO8601 format This change fixes these issues and improves the spec coverage for the XML document. commit 3e3aeb27ea99ecd612c436814c5a2b0dab69c2c3 Author: John Pignata <firstname.lastname@example.org> Date: Sat Nov 3 13:46:24 2012 -0400 Fixing whitespace We're no longer indenting methods after `private` or `protected` directives as a matter of style. This commit fixes whitespace in all remaining classes. commit 1fc597e788442e8cc774c6d11e7ac5e77b6c6e14 Author: John Pignata <email@example.com> Date: Sat Nov 3 12:34:50 2012 -0400 Implement Kaminari pagination Move from will_paginate to kaminari in all controllers. The motivation is to be able to paginate simple Array collections without the monkey patching that will_paginate uses. * Consolidate helpers * Clean up whitespace commit edea15560595bab044143149a7d6e528e8ae65d2 Author: John Pignata <firstname.lastname@example.org> Date: Sat Nov 3 12:27:16 2012 -0400 Add ATOM feed for RSS readers * Include Nokogiri in Gemfile for its builder * Add AtomFieldBuilder model * Add link to feed from index page
4. Polish Your Interfaces
Some Ruby developers eschew method visibility for the methods in their
objects. What's the point? Any method is really callable using
Why bother putting shackles around some methods? Just add that internal method
to the pile and if Future Developer wants to use it he or she can! We're all
If every object in your system is just a junk drawer of methods, it becomes very difficult for anyone (including you) to understand how each object was intended to be used and what messages it's intended to receive. The design of the public interface of an object should make it absolutely obvious how other objects in the system can interact with it. When each object's role and the interactions between the objects in your system are not obvious, it increases the amount of time it takes to understand not only each object but the system in toto.
Hide as much of a component's internals as possible to keep interface small and focused. Put extra energy into making sure your objects' public interfaces are obvious, well named, and consistent. This gives Future Developer clear signals about how you intend each object to be used and will highlight how each can be reused. Use explicit method visibility to communicate this intent and to enforce the surface area of the object's public interface.
5. Leave Comments, Not Too Many, Mostly RDoc
As developers our feelings about code comments can be best described as ambivalent. On one hand comments are extremely helpful in assisting a reader in understanding how a given piece of code works. On the other hand as nothing enforces their correctness, code comments are lies waiting to be told to the future. When asked developers will say they value documentation but often projects have very little beyond a mostly-out-of-date README and maybe a graveyard wiki somewhere. What's more, when working with open source libraries we'll often expect thorough RDoc documentation, an up-to-date README, and good example code and when not present we'll complain bitterly. Scumbag developer: doesn't maintain documentation, expects it from others.
As we pay more attention to things like the Single Responsibility Principle and use patterns to loosen the coupling between objects we start to see systems composed of many small objects wired together at runtime. While this makes systems more pliable and objects more reusable there's a trade-off: understanding an object's place within the larger system may be less obvious and as such take more effort. You can use all of the usual refactorings to eliminate pesky inline comments and make your object as readable as possible but it still might baffle Future Developer as to how the object fits into the system.
RDoc-style documentation can be found in many open source projects. When
you're using Google to figure out if
update_attribute fires callbacks or not
or what the signature for
select_tag is, you'll likely land on the extracted
RDoc for Ruby on Rails. Writing similar
documentation as part of your project will give Future Developer more context
when he or she is trying to understand the role of an object in the larger
context of your system. Adding a short, declarative sentence to the top of a
class and/or method indicating what it does could have substantial value for
future readers of the code. That said, without a strong shared culture of
keeping these comments up to date they could have negative value and
mislead a future reader of the code. The only thing worse than no documentation
is incorrect documentation.
6. Write Intention Revealing Tests
One way we provide documentation to a project is through the tests we leave
behind. These tests not only describe what the behavior of a given component
is but it enforces this documentation is correct as it's executable. Unlike a comment
we can't leave future lies in the test suite; it's either green or it isn't.
Tools like RSpec and
minitest/spec assist us in generating this
by-product documentation by encouraging prose within the defining block of the
example. Unfortunately we sometimes look past the English words we're typing in
our rush to get to the actual code in the red-green-refactor cycle. The
result of neglecting the English descriptions is that it's possible our tests
are not properly reflecting our objects' behavior as well as we think they might be.
Almost as painful as finding a project with no test suite is finding a project whose test suite doesn't help in understanding how the system works. Tests are code which also needs to be maintained and as such they need to very clearly assert why they exist to a future reader.
it "works" do data = File.open("fixtures/projects.txt").read index = ProjectIndex.new(data) index.should have(40).projects last_project = projects.last last_project.title.should eq("ORCA") last_project.customer.should eq("Romney-Ryan 2012") last_project.deploy_date.should eq(Date.parse("2012-11-06")) end
Well, what works? That one word description is meaningless and the example has multiple assertions which don't provide any context.
In building spec-style tests you should keep the English language descriptions you're writing front and center. One way to do this is to run RSpec with the documentation format:
jp@oeuf:~/workspace/project-manager(master)$ be rspec --format documentation spec ProjectIndex .new instantiates an index given the contents of a project CSV file #projects returns a collection of projects from the index Project #title returns the project title #customer returns the Customer record for the project #deploy_date calculates the deploy date from the latest project status
Instead of a field of green dots the documentation format outputs the nested descriptions, contexts, and example titles you've been typing. This allows you to skim through to see if your tests reveal actually how the object is intended to behave. Focusing on the output of the documentation formatter can help improve the communicative value of a test suite. Use the refactor step of red-green-refactor to actually make your tests a coherent explanation of why that object exists, how it behaves, and why this behavior exists.
Future Developer, Delighted
These are just a few of the ways we can optimize for change with the reasonable assumption that somebody else will be charged with making those changes. Think about the next sets of eyes that will be responsible for building and operating your current project when you're working on it. We've all felt pangs of guilt about the maintainability or quality of something we've shipped. Instead of feeling sympathy for all of the challenges you've left in the codebase, begin to tally all of the drinks Future Developer will owe you for all of the tidy work you've left behind.
Thanks to Dave Yeu from whom I've co-opted (read: stolen) the term “future developer.”