Debug protocol: `setVariable` identifies variables by display name

From @vadimcn on August 5, 2016 19:43

• VSCode Version: 1.4
• OS Version: All

The new setVariable request identifies variables by display name.
This is fragile because the name may have been generated by the adapter (e.g. [N] for array indices).
There may also be more than one variable with the same name in the stack frame in languages that allow variable shadowing. For example, in C++ one can write

int a = 10; 
{ 
    int a = 20;
    ... // There are now two `a`'s here! 

The debugger can see both, even though in C++ there's no way to access the outer one.

To make this work robustly, I would suggest adding an optional "handle" field into Variable, which gets round-tripped back to the adapter in setVariable.

Copied from original issue: Microsoft/vscode#10219

Start by reviewing the Variable definition and the setVariable request described in the issue. Define how an optional handle is carried through the protocol and returned to the adapter, then verify that generated display names and shadowed variables can be distinguished.