[swift-dev] Using git-clang-format in the Swift compiler code base.

[Jordan Rose]

> On Jan 26, 2017, at 12:55, Andrew Trick via swift-dev <swift-dev at swift.org> wrote:
> 
>> 
>> On Jan 26, 2017, at 11:38 AM, Graydon Hoare <ghoare at apple.com> wrote:
>> 
>> 
>>> On Jan 26, 2017, at 2:07 AM, Andrew Trick via swift-dev <swift-dev at swift.org> wrote:
>>> 
>>> Before I pull in a large PR that "accidentally" reformats a bunch of code, I want to get feedback on how Swift compiler devs plan to use `clang-format`. (BTW, here's the PR https://github.com/apple/swift/pull/6922).
>>> 
>>> During the code review, I ran `git clang-format` as part of being a good citizen. There's only one problem with the tool. It rewraps long boolean expressions, hiding those unsightly operators at the end of lines (after all who wants to see those?).
>>> 
>>>      if (some_expression->with_calls() ||
>>>          another_expression->with(nested_calls()) &&
>>>          an_even_longer_expression->making_your_eyes->glaze_over())
>>> 
>>> I don't get involved in style wars, but this is not a style change, it's an objective code quality degradation. It's a demonstrably bug-prone thing to do. It's hurt me too many times in the past, and I'm not happy using a formatting tool that injects future bugs and harms code comprehension.
>> 
>> It's funny you'd mention this! I often format code that way, not out of any great love of it, but from muscle-memory of living under an old coding guideline somewhere in the distant past claiming that the ugliness of trailing unfinished-binops draws the eye to them and makes the user pay attention. Doug Crockford recommends this style; but of course Don Knuth agrees with you. I don't feel strongly about them as such, but I feel ... anti-strongly, I guess? Like changing that one thing isn't worth a cross-codebase rewrite / merge collision.
> 
> I’m not sure who’s recommending what. The above style obscures operators. Does anyone disagree with that? A lot of code has been written in that way; I think because developers value aesthetics over clarity, or just don’t think about it. I care because when something doesn’t stand out, my brain fills in the gaps with whatever it expects. For me, that leads to a bunch of silly logic errors.
> 
> I need to see it this way:
> 
>      if (some_expression->with_calls()
>          || another_expression->with(nested_calls())
>          && an_even_longer_expression->making_your_eyes->glaze_over())
> 
> The need for parens now stands out. Sorry this isn’t a good example. Nested expressions would make it much more compelling.
> 
> That’s the coding convention we use for Swift code (at least in the stdlib). The compiler C++ code is just a hodge-podge.
> If anyone actually thinks trailing operators are a good idea for our code base, I won’t argue, but I’ve never heard that argument.
> 
> BTW- I’m not interested at all in doing a mass reformatting or forcing a convention on people. I just don’t want to apply clang-format to every line of code I touch without knowing what settings to use.

I've never had a problem with the trailing operators, and find them mildly more aesthetically pleasing (when not in an if, it makes it clearer what I plan to do with the next line), but I see how they put it in your face in an if. I can change my style.

Jordan

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