djasper added a comment.
In https://reviews.llvm.org/D43290#1020537, @Typz wrote:
> >> Tweaking the penalty handling would still be needed in any case, since the
> >> problem happens also when Cpp11BracedListStyle is true (though the effect
> >> is more subtle)
> >
> > I don't understand this. Which style do you actually care about? With
> > Cpp11BracedListStyle=true or =false?
>
> I use the `Cpp11BracedListStyle=false` style.
> However, I think the current behavior is wrong also when
> `Cpp11BracedListStyle=true`. Here the behavior in this case:
>
> Before :
>
> const std::unordered_map<std::string, int> Something::MyHashTable =
> {{ "aaaaaaaaaaaaaaaaaaaaa", 0 },
> { "bbbbbbbbbbbbbbbbbbbbb", 1 },
> { "ccccccccccccccccccccc", 2 }};
>
>
> After :
>
> const std::unordered_set<std::string> Something::MyUnorderedSet = {
> { "aaaaaaaaaaaaaaaaaaaaa", 0 },
> { "bbbbbbbbbbbbbbbbbbbbb", 1 },
> { "ccccccccccccccccccccc", 2 }};
"Before" is the desired behavior. I don't know whether other people have
extensively analyzed how to format all the various C++11 braced lists, but we
have at Google and think this is good. It is formalized here:
https://google.github.io/styleguide/cppguide.html#Braced_Initializer_List_Format
We prefer breaking before "{" at the higher syntactic level or essentially
before the imaginary function call in place of the braced list.
>>> Generally, I think it is better to just rely on penalties, since it gives a
>>> way to compare and weight each solution. Then each style can decide what
>>> should break first: e.g. a style may also have a lower
>>> `PenaltyBreakAssignment`, thus wrapping after the equal sign would be
>>> expected...
>>
>> And with my reasoning, I think exactly the opposite. Penalties are nice, but
>> if the behavior is generally unwanted, than it's very hard to predict in
>> which situations it might still occur.
>
> Yet on the other hand enforcing too much can lead to cases where the
> optimizer fails to find a solution, and ends up simply not formatting the
> line: which is fine is the code is already formatted (but if there were the
> case we would not need the tool at all :-) )
> The beauty of penalties is that one can tweak the different penalties so
> that the behavior is "generally" what would be expected: definitely not
> predictable, but then there are always cases where the "regular" style does
> not work, and fallback solutions must be used... (for exemple, I would prefer
> never to never break after an assignment : yet sometimes it is needed...)
>
> I can change the patch to disallow breaking, but this would be a slightly
> more risky change, with possibly more side-effects; and i think that would
> not solve the issue when `Cpp11BracedListStyle=true`.
It is the better call here. I understand that people that set
Cpp11BracedListStyle to false want this behavior and I think it'll always be a
surprise when clang-format breaks before the "{". The chance of not coming up
with a formatting because of this is somewhat slim. It only adds an additional
two characters (we would also not break before the "="). It'd be really weird
to only have these exact two line length have a special behavior (slightly
shorter - everything fits on one line, slightly longer - a split between type
name and variable is necessary).
There is no issue for Cpp11BracedListStyle=true, the behavior is as desired.
Repository:
rC Clang
https://reviews.llvm.org/D43290
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