Debug Protocol: breakpoint hit counts

[jacdavis]

In order to use the vscode protocol in vs and xamerin, we would need the ability to support breakpoint hit counts. This is similar to a breakpoint condition, but allows the debug engine to control the number of times a bp would be hit. We currently support four types of hit counts:
public enum enum_BP_PASSCOUNT_STYLE {
BP_PASSCOUNT_NONE = 0x0000,
BP_PASSCOUNT_EQUAL = 0x0001,
BP_PASSCOUNT_EQUAL_OR_GREATER = 0x0002,
BP_PASSCOUNT_MOD = 0x0003
};

These are:

1. No hit count (default)
2. hit count equal to a value
3. hit count greater than or equal to a value
4. hit count is a multiple of a hit count.

The VS interface for this provides the user's value (number of interest) and a type:
https://msdn.microsoft.com/en-us/library/bb146656.aspx

[weinand]

I propose to add a string typed "hitCount" attribute to the breakpoints requests.
The frontend would provide UI for editing this attribute and the backend would have to interpret the string appropriately. E.g. the 3 VS options from above could be encoded as '= n', '>= n', and '% n'.
node-debug would only accept a positive integer.

[roblourens]

I think it would be easier to work with if the 'type' was broken out into an enum or string, like in the VS protocol.

[weinand]

@roblourens how should we support this in the UI then? Breaking out 'type' would require additional protocol to enumerate the UI strings for the 'type' options.
I've tried to keep this section of the protocol minimal because I expect most adapters to only implement the hit count type 'equal'.