Improvements for `- expected, + actual` legends

Fails are reported like this right now:

  - expected
  + actual

  - ObjectContaining { a: 0 }
  + { a: 0, b: 0 }

For a lot of people, the - expected, + actual legend will not be helpful if it is printed every time. There are already color hints and the - and + signs. And people also get used to reading the reports rather quickly

Ideas for improvements:

Add an option to control the legend (as we may implement different ways to show it)

1. legend === 'standard'
2. legend === 'compact'

  - expected  - ObjectContaining { a: 0 }
  + actual    + { a: 0, b: 0 }

Check the length of the stringified values, print them as a single line with the legend if there are small enough

1. legend === 'once' compact + in watch mode, only show the legend on the first error, then later avoid it.
2. legend === 'none' Don’t show it
3. legend === 'auto' NO_COLOR or CI is present ? ‘compact’ : ‘none’

We don’t need to have all the options, maybe just ‘compact’ and ‘auto’ are good to start with and users may not ask for anything else. And I think we should use ‘auto’ as the default

[patak-dev]

I like that @tony-go, it is what I had in mind for compact (if the length isn’t needed, better) One detail, I would prefer:

  expected   ObjectContaining { a: 0 }
  actual     { a: 0, b: 0 }

1. remove the :, as it could be confused with object notation, just add a few extra spaces and I think is enough to separate the legend from the value (like a table)
2. align the values, important when they are similar, and also helps with the table look
3. Maybe expected and actual could be colored with a darken tone, so the user can focus on the values instead of the legends, and we again better separate the two

Maybe we could start with this, and we don’t need options then as you said. What do you think?

[tony-go]

I could give a try on this one ☝🏼 😃