Fix S907 FP: Don't use `goto case`

[DaleStan]

Description

(False positive, I guess? This template fits better than the new rule template.) The existing S907 goto label rule also triggers on goto case/goto default.

I have a switch statement with (currently) 26 string cases, akin to the one below. For the sake of finding the labels and reducing merge conflicts when new cases are added, the case labels are in alphabetical order. This requires either code duplication or goto case statements. It would be nice to be able to configure goto case/goto default separately from goto label.

Reproducer

switch (insectType) {
    case "ant":
        goto case "termite";
    case "bee":
        goto case "wasp";
    case "termite":
        // handle ants and termites
        break;
    case "wasp":
        // handle bees and wasps
        break;
}

In my case, none of the case blocks with goto case contain any other code, but it might also be good to have a third setting for cases terminated with goto case, e.g.

    case "bee":
        // handle bee stuff that doesn't apply to wasps
        goto case "wasp";
    // ...
    case "wasp":
        // handle bees and wasps
        // (everything that applies to wasps also applies to bees)
        break;

Product and Version

SonarQube 8.27.0.14275 and Visual Studio 17.14.16

[jilles-sg]

I agree that it makes little sense that case fallthrough is allowed in e.g. C and JavaScript (best add a comment) but not in C# because the spelling for it contains the four letters goto. This would, however, only apply to jumping to the immediately following case. Jumping to other cases would be the exact issue that S907 is intended to catch.

In this particular case, I would personally give up the alphabetical order and use case "ant": case "termite": (on two lines) or case "ant" or "termite":.

[DaleStan]

I still believe S907 is too general. goto label can jump to arbitrary locations in the current method, while goto case and goto default can only jump to valid case labels in the current switch statement. I can't jump to a dummy case null label when switching on an enum value, nor can I jump to a label in an enclosing switch statement.