# codereview: phrase code review comments as questions

it's well established by now that code reviews are incredibly useful. but how should i phrase the comments?

i found pretty good guidelines on commit messages and code comments but i haven't found any good guidelines on code review comment phrasing. for my own reference, let me recap what i found on those first two topics.

# commit messages

git recommends imperative mood for the first line of the commit message, the commit title. "fix bug" rather than "fixed bug" or "fixes bug". it explains what the commit should do when applied to the codebase.

i'm not sure if there is a strong reason for this custom but it's quite common, unambiguous in this context, and is the shortest english form. i quite like it.

# code comments

for code comments the 3rd person form is the best (indicative mood). take this snippet:

  // fill the slice with zeros.
  func frobnicate(v []int);

what does that tell you? it can either tell what the function does:

  // (frobnicate) fills the slice with zeros.
  func frobnicate(v []int);

or it can be a request towards the user:

  // (you should) fill the slice with zeros (before calling frobnicate).
  func frobnicate(v []int);

with the imperative it's unclear whether the comment is a function description or an instruction towards the function's user.

this problem is significantly reduced in go, since godoc requires that the function doc comment starts with the function's name. this ensures that only the 3rd person form can be used.

# review comments

but what about code reviews?

if the reviewer has to ask for a clarification then that's easy: they ask. but what if the reviewer has requests? take the following code snippet:

  // fill the slice with zeros.
  func frobnicate(v []int) {
    for i := 0; i < len(v); i++ {
      v[i] = 1
    }
  }

there are 3 problems:

• strong stylistic: the function comment doesn't follow go's recommendation.
• weak stylistic: a range loop could be used here.
• bug: the function fills the loop with one rather than 0.

the reviewer thinks this is how it should look like:

  // frobnicate fills the slice with zeros.
  func frobnicate(v []int) {
    for i := range v {
      v[i] = 0
    }
  }

but how should the reviewer ask for the necessary changes?

# survey

i surveyed a couple folks that if they were the author, what comments would they like and what comments would annoy them. now keep in mind that we are all professionals and we always communicate in a respectful manner. but even respectful communication has small nuances to it.

note that our code is company owned, there's no "this is my code" mentality among my peers. in this particular case i asked about the "setting to one" bug. nor i do i like comments like "why did you assign one?" or "couldn't you assign zero here?" because that's commenting about the person, not the code. they were mentioned in the survey but people didn't really like them (nor were they the worst alternatives).

(i admit i used a different, much longer code snippet in my original survey but i'll try my best to paraphrase the comments so that they apply to this scenario. i've sent out the survey on a whim without thinking it through. oh well.)

• most annoying comment: "i'd prefer assigning 0 here."

here the reviewer is trying to phrase a request in an overly soft way. but this comment is annoying because it states a preference: why should the author care about the reviewer's preferences? the author might not even sure how to respond to such a comment.

a similar analysis could apply to comments starting with "we should", "you could", "can we" etc.

• second most annoying comment: "assign 0 here!"

in the survey i differentiated "assign 0 here." and "please assign 0 here." people found the one with the exclamation mark the most annoying. i guess the problem is that it makes you feel like a subordinate to the reviewer because all you can do here is to follow the other person's commands to the word or start arguing with them.

the word "please" also annoys a lot of people (including me). for me the command form already creates this subordinate feeling and then you top it off with "please" which makes the whole sound patronising. (i'm exaggerating here, i actually have pretty thick skin when it comes to any online messaging.)

• second most preferred message: "function comment talks about 0?"

this phrases the comment as a question. this is pretty neat: it clearly points out a problem without radiating any antagonistic intent.

answering after fixing the bug is easy: "oops, fixed, thanks!" such a positive response flows very naturally.

the answer is quite positive even if the author's code is correct: "nah, that should be one. the function comment is wrong, let me fix that instead."

questions are cool.

• most preferred message: "i think this value mismatches the function comment."

this message is a clear indication of the problem but it doesn't have that commanding mannerism around it. the "think" makes it clear that the reviewer considers themselves a fallible person, they are here to catch problems rather than telling the author how to do their job.

# my suggestion

the preferred comments are more of descriptive nature. they point out problems rather than simply tell the author what to do. the author might even have better solutions for resolving the reviewer's concerns since they probably have more context about the particular code snippet due to the fact they are working on it right now.

giving a request is also possible. phrasing it as a question opens a discussion which is a more pleasant form of exchange than commands sprinkled with fake pleasantries (e.g. please).

two together leads to this 2 part form:

• [description of the problem or concern.] [a suggestion in the form of a question.]

often one part makes the other part obvious. in that case the other part (either of them) can be left out.

# examples

here are some examples how my comment style changed after the above thoughts.

  // fill the slice with zeros.
  func frobnicate(v []int) {

• old: "frobnicate fills ..."
• new: go recommends that "the first sentence should be a one-sentence summary that starts with the name being declared." (https://go.dev/doc/effective_go#commentary). "frobnicate fills the slice ..."?

though in this particular case i often might omit the first part if i know that the author is well familiar with the style guide and this is just an omission. in that case i'd say only "frobnicate fills" but with the question mark.

  for i := 0; i < len(v); i++ {
    v[i] = 1
  }

• old: consider a range loop here.
• new: nit: `for i := range v {`?

  // fill the slice with zeros.
  func frobnicate(v []int) {
    for i := 0; i < len(v); i++ {
      v[i] = 1
    }
  }

• old: assign zero.
• new: comment says filling with 0. assign zero?

here the "assign zero?" part could perhaps be left out (more precisely: left implied).

  err := doX()
  if err != nil {
    return err
  }

• old: `if err := doX(); err != nil {`
• new: err is unused later on. `if err := doX(); err != nil {`?

  enabled: false

• old: add comment why you disable this.
• new: i think on its own it might be unclear why this is disabled. add a comment?

  for _, v := range a {
    if err := doX(v); err != nil {
      log.Error(err)
    }
    doY(v)
  }

• old: shouldn't the error handled e.g. by `return err`?
• new: doY() runs even if doX() errors out. missing `return err`?

  for _, v := range a {
    go func() { a(b(v) + c(v)) }
  }

• old: this doesn't do what you want. make a copy of v before using in the func.
• new: i think this makes all goroutines reuse the same variable (https://github.com/golang/go/wiki/CommonMistakes#using-goroutines-on-loop-iterator-variables). pass v as a parameter to the func?

  func (o *obj) f() {
    o.mu.Lock()
    o.count++
  }

• old: don't forget unlock too!
• new: missing unlock?

i'd use "what do you think about" for the cases where i'm less certain about:

  if err := g(); err != nil {
    return err
  }

• old: i'd add a log message too because an error here is unexpected.
• new: i think an error here is quite unexpected. what do you think about adding a log message too here?

  if err := g(); err != nil {
    return err
  }

• old: i'd prefer annotating the error.
• new: the returned error might be pretty generic and unhelpful. what do you think about annotating it before returning?

# other considerations

these types of comments work best for authors whose judgment i already trust. for junior members i might lean to have a more instructive style rather than the questioning style. the rationale would be that they might really just want someone to tell them what to do until they get the hang of all the things.

i generally approve early on and trust that the author addresses my comments. i try to avoid nitpicking about naming, commenting style, even at design choices as long as everything looks reasonable enough. i'd rather err more on "let's make mistakes and learn" than obsessing too much about perfectionism. the author will feel less ownership and control of the code if they have to rewrite all their code to the reviewer's preferences. it sours the relationship with the code review, makes it something that people will dread rather than look forward to. note that with this i'm making gross simplifications and omitting a lot of nuance here; i just want to raise this aspect of the reviews: it's sometimes ok to submit lesser quality code to make sure people make progress and are not trapped in a bad place.

in any case now i just need to get into the habit of using this new style of communication.

published on 2021-12-25

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