"copy value" from variables debugger window not working

[drungrin]

Fixes microsoft/vscode-java-debug#624

[msftclas]

All CLA requirements met.

[testforstephen]

Thanks for the contribution. The solution works well, except we need handle array/collection/map better.

[testforstephen]

For the Collection and Map type, we did special handling to show their logical structure, so their display style looks like array.

Currently when you hover on 0: HashMap$Node@64, and click Copy Value, the generated evaluateName is map.0. Evaluate engine will report Cannot evaluate because of compilation error(s): Syntax error on token ".0", delete this token..

There are two solutions in my mind.

1. The first solution is to generate the correct evaluate name. That means we need handle the evaluate name specially for the type java.util.Map, java.util.Collection, java.util.Map$Entry.

• If the container is java.util.Map, the evaluate name for the children is like map.entrySet().toArray()[0].
• If the container is java.util.Map$Entry, the evaluate name for the children is like map.entrySet().toArray(new java.util.Map.Entry[0])[0].getKey().

The cons is the problem will become complex when the hierarchy is deep.

2. The second solution is to disable Copy Value on the children of Map and Collection, only enable it on the Map and Collection itself, and return their toString value.
   For example, when hover on map, the copy operation should return {a=1}.

Similarly, when copy an array, we need return its toString() instead.

[drungrin]

For the first solution, when the hiearchy is deep, the evaluateName is already complex, in my opinion this isn't an issue.

I really dont like the second solution.

So, if you agree, I'll implement the solution 1.

[testforstephen]

In solution 1, it may be a little tricky for generating the correct evaluate expression for Collection type. For example, in order to copy the nth element's children, the evaluate expression is like collection.toArray()[n].x, this will report compilation error because of java type check.

[testforstephen]

@drungrin thanks for the initial PR, close it with another PR #338