StringSwitchJavacFilter fails to recognize switch that has just a few cases

[Godin]

StringSwitchJavacFilter fails to recognize switch that has just a few cases

	private static void example(Object s) {
		switch (String.valueOf(s)) {
		case "a":
			nop("case a");
			break;
		case "b":
			nop("case b");
			break;
		}
	}

In this case javac generates lookupswitch, while filter expects tableswitch -

jacoco/org.jacoco.core/src/org/jacoco/core/internal/analysis/filter/StringSwitchJavacFilter.java

Line 94 in 90af085

nextIs(Opcodes.TABLESWITCH);

lookupswitch was noticed by @forax during my talk at Devoxx France and seems to be due to following algorithm that estimates space and time costs between lookupswitch and tableswitch - https://github.com/dmlloyd/openjdk/blob/84ba2b90d46ee4b06664d32594ef0cd2038373a6/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java#L1170

[Godin]

@marchof could you please review?

Also maybe you can advice how to recording this in changelog - wording? bug fix or new feature?

[marchof]

@Godin Ups, sorry, I overlooked your question. For me is a bug fix, because we claimed that we can filter switch in string for javac. But probably no one ever noticed this corner case. Anyway, if we want to fix the latest commit here is my proposal:

Also filter part of bytecode generated for switch statements on java.lang.String values when only a few cases are present.

[Godin]

@marchof Changelog is also useful for us 😉 Fixed in f2c79fe