The idea has always been floating around, and a number of feature requests had been made to support something like it.
Not to mention all the Stack Overflow questions asking how to iterate the members of a module, with answers explaining how to use the VBIDE API to achieve some level of “reflection”.
The VBIDE API works: it gives you the members of a module rather easily. But if you need anything more granular, like iterating the local variables in a given member, you’ll have to write code to manually parse that member’s code, and if you’re trying to programmatically access all references to a global variable, you’re in for lots of “fun”.
Truth is, the VBIDE API is bare-bones, and if you want to do anything remotely sophisticated with it, you basically need to write your own parser.
Rubberduck 2.0 will expose [some of] its guts to VBA clients, through COM reflection – using the ParserState API, you’ll be able to write code like this:
..and leverage the richness of Rubberduck’s own API to iterate not only module members, but any declaration Rubberduck is aware of – that includes everything from modules and their members, down to variables, constants, events, Declare statements, and even line labels. You can also iterate the references of any declaration, so in theory you could implement your own code inspections with VBA and, in conjunction with the VBIDE API, you could even implement your own refactorings…
This API can easily grow TONS of features, so the initial 2.0 release will only include a minimalist, basic functionality.
One can easily imagine that this API will eventually enable surgically parsing a given specific class module, and then iterating its public properties to create form controls for each one, e.g. a Boolean property maps to a checkbox, a String property maps to a textbox, etc. – takes dynamic UI generation to a whole new level.
What will you do with that power?