[apex] Prevent classes from shadowing System Namespace

[noerremark]

We brainstormed about this rule in #2322. Believe it or not, I had the issue the other day, in a real environment. Salesforce Developers Blog has a 2012 post about it, so it's an official "feature", but pretty bad design.

Proposed Rule Name: ClassShadowsSystemNamespace

Proposed Category: Code Style

Description:

Code Sample:

public class Database {
    public static String query() {
        return 'wherefore art thou namespace?';
    }
}

Since Database is also in System this is a violation.

[noerremark]

@rsoesemann / @daveespo - I'll see if I can provide a PR for this.

[rsoesemann]

@noerremark please think about your implementation options. This could be a super lean XPath rule just checking a few classes against the class name. The footprint of a real Java rule is only of use when you make it work with previously unknown System classes.

[noerremark]

@rsoesemann - I agree, XPath is the best option here.

[noerremark]

@rsoesemann - I started looking into this, and there is a LOT of classes. I know XPath is the easy route, but what about doing a Java-rule that uses reflections to generate a list of bad names to test against? @adangel - I see you have been doing the stuff on jorle, would it be possible?

[rsoesemann]

@noerremark I absolutely agree that a Java rule is smart if AND ONLY if it really not only enumerates such classes but actually finds them out magically. Meaning if Salesforce adds a NEW system class this rule should auto-detect it.
If it is just a Java rule enumerating all classes I think XPath is better.

Can we reference a separate file in XPath?!