[args] Custom order for categories

[dcharkes]

In dart-archive/args#202, support for categories was added.

These categories are ordered alphabetically.

However, users might want to order them in a different order of importance. (For example https://dart-review.googlesource.com/c/sdk/+/441581/15/pkg/dartdev/test/commands/help_test.dart#82)

cc @jakemac53 @natebosch

[dcharkes]

cc @mit-mit We need this feature upstream to sort the categories in Dart.

@jakemac53 @natebosch Any concerns about me making a PR for this? Should this be solved in a different way then adding a categorySorting parameter somewhere?

[natebosch]

We removed some alpha sorting for allowedHelp in #845

I'm a little curious to see whether anything actually breaks if we remove the alpha sorting here too, and rely on the on the order that commands are added. It's a little uglier than that other case though, because the calling code doesn't actually define the Map whose order is becoming meaningful. It also adds an extra layer of indirection to understand the category order, but I would not be surprised if many uses are already added in a meaningful category grouped order.

@dcharkes - If we use the addCommand order to define both the category and command ordering in the usage would that work for your use case? If so we could investigate whether it's possible to land it for everyone, or if we need it to e opt-in somehow.

[dcharkes]

It's a little uglier than that other case though, because the calling code doesn't actually define the Map whose order is becoming meaningful.

Agreed, it does feel indirect. Especially because category is a getter on the commands instead of a parameter to addCommand. However, a setCategoryOrder method would also be indirect due to that being on the command runner and the categories being a getter on the commands. So, we'll get an indirection no matter what unfortunately.

If we use the addCommand order to define both the category and command ordering in the usage would that work for your use case?

Yes it would. We would order https://github.com/dart-lang/sdk/blob/5fcf3cf91d0b00b25f7dcd8c8e0e976f434d3947/pkg/dartdev/lib/dartdev.dart#L101-L145 accordingly.

[dcharkes]

If so we could investigate whether it's possible to land it for everyone, or if we need it to e opt-in somehow.

What are the next steps here @natebosch?