Debugger requirement: language-specific frame hiding

[mlvdv]

The debugger needs to decide which stack frames to display, for example in a backtrace, during normal debugging. What's needed is a language-specific recommendation on whether any given frame would be sensible (useful) to a guest language programmer.

The debugger might display such frames anyway, for example in a special mode for language implementors.

To discuss: should the recommendation that a particular frame be hidden also be treated as a suggestion that the call-site that created the frame also be hidden? I'm thinking of Ruby's implementation of certain (but not all) looping constructs as calls. I specifically hid those calls in an early debugger prototype.

@mickjordan reports that this would be useful for current work

[entlicher]

In the past there was a suggestion to add a FrameFormat interface, which could be passed in through FrameDescriptor and that could have something like String getTraceLine(). That could return null for hidden frames.
But an idea with an introduction of CapabilityProvider suggested in issue #157 could solve this in an evolvable way...

[mlvdv]

I like the CapabilityProvider idea.

I would avoid String getTraceLine() for two reasons:

• client should have the option to display hidden frames
• client should be able to create tool-specific formatting of provided information

Language capability for displaying information should be restricted only to primitive things, e.g. values, names.

[chumer]

Tracked elsewhere: GR-88