1497779 - clang-format is over-eager to break after '(' - Configure clang-format for Mozilla style of argument lists in function calls

Status: RESOLVED WONTFIX

(Developer Infrastructure :: Lint and Formatting, defect)

Description

[Karl Tomlinson (:karlt)]

Since clang-format has become available, I've started seeing function call
argument styles that look like AlignAfterOpenBracket: AlwaysBreak.
This is not Mozilla style (unless perhaps when there is no other option due to very long function names).  Although not explicitly specified, the format I almost always saw previously was AlignAfterOpenBracket: Align.

See the GetFlavorData() arguments, for example, at line 315 of
https://phabricator.services.mozilla.com/D8074?id=22428#change-GEIhCAaWkyvA

Expected:

            rv = dataProvider->GetFlavorData(this, aFlavor,
                                             getter_AddRefs(dataBytes), &len);

Actual:
            rv = dataProvider->GetFlavorData(
              this, aFlavor, getter_AddRefs(dataBytes), &len);


The actual is very different from line 398.
Actual and tolerable:

​        mFormatConv->Convert(aFlavor,
                             aData,
                             aDataLen,
                             data.GetFlavor().get(),
                             getter_AddRefs(ConvertedData),
                             &ConvertedLen);

Expected:

        mFormatConv->Convert(aFlavor, aData, aDataLen, data.GetFlavor().get(),
​                             getter_AddRefs(ConvertedData), &ConvertedLen);

The expected formats above are what I get with BasedOnStyle: Mozilla at http://cf.monofraps.net/, so I don't know what is causing the actual formats.

Comment 1

[Andi [:andi]]

I wouldn't consider this to be a bug, but more of the desired behavior. clang-format tries to fit all parameters onto a single line and if it fails than it brakes. 
The implementation was done here: https://reviews.llvm.org/D14104

Comment 2

[Karl Tomlinson (:karlt)]

The implementation just adds another option.

Can you point me at the discussion that led to changing Mozilla's style, please?

Comment 3

[Sylvestre Ledru [:Sylvestre]]

afaik, we didn't have a discussion on this and we didn't change this behavior with the Mozilla coding style in clang-format.
So, I guess we are using the default option in clang-format :)

Comment 4

[Karl Tomlinson (:karlt)]

My assumption was that bug 1188202 would use clang-format to "reformat everything to Mozilla style", in which case this bug would track one feature required in setting up clang-format to do that.  https://bugzilla.mozilla.org/show_bug.cgi?id=1188202#c0 at least seems to support that interpretation.

Are you implying that there has been a change in direction for bug 1188202 to instead reformat everything to clang-format's default style for BasedOnStyle: Mozilla, even though that is not Mozilla style?

Comment 5

[Sylvestre Ledru [:Sylvestre]]

Yeah, I have been experimenting, I will share more information with the finding when ready!

Comment 6

[Karl Tomlinson (:karlt)]

Thanks for taking a look.  I assume we agree it is helpful to keep this open while still under investigation.

Comment 7

[Emilio Cobos Álvarez (:emilio)]

I think other parts of the codebase use single-line-per-argument, so yeah, this bug probably requires some discussion to figure out what is Mozilla style... :)

Comment 8

[Karl Tomlinson (:karlt)]

This will be wontfix based on the "update" in https://phabricator.services.mozilla.com/D12221?id=36525