Java Logger with Supplier<String>: @UnknownKeyFor String instead of @KeyForBottom String

[bmarwell]

Hi again,

• Java 8 (tested multiple JDKs)
• Checker 2.10.0

I got the following code snippet:

  private static final java.util.logging.Logger LOGGER = Logger.getLogger("Query");
  // … enter method
  String query = String.format("%s", myList.stream().collect(joining(", ")));
  LOGGER.log(Level.FINEST, () -> String.format("Query [%s].", query));

This results in:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project my-project: Compilation failure: Compilation failure: 
[ERROR] Query.java:[4,27] error: [return.type.incompatible] incompatible types in return.
[ERROR]   type of expression: @UnknownKeyFor String
[ERROR]   method return type: @KeyForBottom String

Those are both Map-related annotations, and I have no idea what Map-related annotations are doing in my logging statement.
Haven’t found this combination in the issues or docs either.

Thanks in advance :)

[mernst]

Here is a complete reproduction for the problem: run

javacheck -g KeyForTest.java -processor nullness

on the following file.

import java.util.logging.Level;
import java.util.logging.Logger;

public class KeyForTest {

  Logger LOGGER = Logger.getLogger("Query");

  void test() {
    LOGGER.log(Level.FINEST, () -> String.format("%s", "hello, world"));
  }
}

As noted, the output is

KeyForTest.java:12: error: [return.type.incompatible] incompatible types in return.
    LOGGER.log(Level.FINEST, () -> String.format("%s", "hello, world"));
                                                ^
  type of expression: @UnknownKeyFor String
  method return type: @KeyForBottom String
1 error

[roded]

We're seeing the same issue on JUL logger methods. At the moment we've suppressed the keyFor check via a javac argument. Please look into this, it is somewhat preventing us from adopting NullnessChecker more widely.

P.S. We've enabled only the NullnessChecker, is keyFor entailed in Nullness checking?

[bmarwell]

Workaround: create another stub for the logger methods.

[smillst]

This error is no longer issued.