Color template with literals

[djbe]

Partially inspired by #72 and an old discussion #55 (comment).

[AliSoftware]

I still think that a lot of people dealing with colors palettes provided by their designers (e.g. via a Sketch document or a sheet listing all colors of the app theme, etc) generally deal either with hex or with rgba(51, 150, 104, 255) and less commonly with % for rgb values 😉

[AliSoftware]

Add a note (same in the documentations for other literals-swiftN of course) about the special Color name (maybe outside the table as it can be a paragraph of its own), e.g.

Note: if you use --param enumName=Color then the color constants will be generated as an extension of the UIColor (iOS) / NSColor (macOS) type directly without creating a separate enum type for namespacing those color constants

But tbf I think it would be less surprising if the test was on testing UIColor or NSColor, not Color.

Like adapting the template to:

{% set enumName %}{{param.enumName|default:"ColorName"}}{% endset %}
#if os(OSX)
  import AppKit.NSColor
  typealias Color = NSColor
  {% if enumName != 'NSColor' %}enum {{enumName}} { }{% endif %}
#elseif os(iOS) || os(tvOS) || os(watchOS)
  import UIKit.UIColor
  typealias Color = UIColor
  {% if enumName != 'UIColor' %}enum {{enumName}} { }{% endif %}
#endif

// swiftlint:disable file_length identifier_name line_length type_body_length
extension {{enumName}} {
…
}

And then explaining that in the doc that the exception is with --param enumName=UIColor for those who wish to make those constants as an extension of UIColor directly. Would feel more natural as a special name imho?

[AliSoftware]

💡 Once #68 is merged it could be nice to apply a similar idea for colors on the xcassets templates, making the named colors being directly static let foo = UIColor(name:) instead of using an intermediate struct type for colors (I wonder if #colorLiteral supports named colors btw? If not, we can just use UIColor(name: ) for that case)

[djbe]

#colorLiteral doesn't support names afaik.

I'm not sure if it's a good idea to have asset template variations just for that case, especially because there are so many more possible set types in catalogs we don't support yet. It would be better to decide now what'd be most useful for the user.

The thing we have to keep in mind is that named colors are iOS 11+ (macOS 10.13+), so I'm not even sure how that'd work? Place a whole bunch of #if available throughout the file?

[AliSoftware]

Ah, right, having to @available above every static let foo = UIColor(name:…) generated constant would be a bit too much probably.

[AliSoftware]

s/it's/its/

[AliSoftware]

s/it's/its/

[AliSoftware]

Shouldn't we also test the --param enumName=UIColor case too, to check the enum isn't created there?