House Style Code Comments

House Style: Code Comments

Every comment must earn its place. Code is the single source of truth for what it does, so a comment restating it is redundant on the day it lands and a lie the first time the code changes without it.

The only comments worth keeping explain why.

Default to removal

Keep a comment only when you can name the specific wrong action a reader would take without it — a change they would make that silently breaks something. "It adds useful context" is not an answer.

Always remove

• Restates or paraphrases what the code does — // increment counter, // return the result, // loop through items
• Names the operation being performed — // fetch user data above a fetchUserData() call
• Describes control flow the code structure already expresses — // check if null, // handle error case
• Translates code into English without adding anything the code does not convey
• Exists because the function or block "should have a comment"
• Argues with an approach that is not in the code — // rather than X, // the obvious way would be Y, but. These pass the why-not-what test but answer a question the reader never asked, and they age badly as the alternative loses relevance. The line is whether a concrete failure mode is named: "the obvious map here deadlocks under concurrent writes" is worth keeping; "rather than a map" on its own is not.
• Narrates the change that introduced it — // as discussed, // new approach, // per the plan. Temporally coupled to a moment the reader was not present for and cannot recover.
• Describes what the code used to do — // previously returned null, // no longer uses the cache. Comments describe what is; historical narration contradicts the code the instant it is read.

There are no exceptions for "what" comments. If code is too opaque to follow without one, fix the code — better names, extracted functions, clearer structure — rather than papering over it.

Bug-fix archaeology — the sequence of attempts behind the current code — belongs in the commit message, which is where someone will go looking for it.

Worth keeping

• Why a non-obvious approach was necessary, when the obvious one has a concrete failure mode worth naming
• Why a workaround exists, linking the issue when possible
• Why a particular value, threshold, or constraint was chosen
• A load-bearing subtlety whose removal would silently break something
• Domain or business context the code cannot express

Also flag

• Comments likely to churn when the code structure changes
• References to temporary states or transitional implementations
• TODOs and FIXMEs that have already been addressed