Add option to disable trailing commas on multi-line collections

[mlavergn]

Extends the configuration options to allow disabling the addtion of trailing commas on multi-line collections.

[mlavergn]

I gleaned the name multilineCollectionTrailingCommas from an older PR, but since this does affect single line dictionaries, I wonder if collectionTrailingCommas would be more appropriate.

[allevato]

I gleaned the name multilineCollectionTrailingCommas from an older PR, but since this does affect single line dictionaries, I wonder if collectionTrailingCommas would be more appropriate.

Yeah, "line" is the wrong word here, because the logic isn't based on whether the collection wraps across multiple lines, it's about whether it has multiple elements—single element arrays/dictionaries never have a trailing comma inserted, even if they wrap (because of Swift parser subtleties around how collection types are parsed in expression contexts). I think there are other places in swift-format where we use "line" when we really mean "statement" or "element", but fixing those up require ensuring compatibility with older configs.

How do you feel about multiElementCollectionTrailingCommas?

[mlavergn]

I gleaned the name multilineCollectionTrailingCommas from an older PR, but since this does affect single line dictionaries, I wonder if collectionTrailingCommas would be more appropriate.

Yeah, "line" is the wrong word here, because the logic isn't based on whether the collection wraps across multiple lines, it's about whether it has multiple elements—single element arrays/dictionaries never have a trailing comma inserted, even if they wrap (because of Swift parser subtleties around how collection types are parsed in expression contexts). I think there are other places in swift-format where we use "line" when we really mean "statement" or "element", but fixing those up require ensuring compatibility with older configs.

How do you feel about multiElementCollectionTrailingCommas?

It's a mouthful, but it certainly self-documents what the setting is for. I'll refactor it.

[mlavergn]

Refactored the setting name to multiElementCollectionTrailingCommas and use literal rather than initializer in the docs.

[mlavergn]

Added a DocC header to auto-gen proper documentation based on the styling of indentSwitchCaseLabels

[allevato]

This looks great. Thanks for your contribution!