Error-prone: Check slf4j log messages are constant

[markelliot]

slf4j expects format strings to prevent unnecessary string concatenation; as a result, these format strings should be constant.

Positive example:

void f(String param) {
    ...
    // BUG: Diagnostic contains: non-constant expression
    log.warn("some message param=" + param);
}

Negative example:

void f(String param) {
    ...
    log.warn("some message param {}", param);
}

with extension to the full set of slf4j Logger methods.

I'd be happy to contribute this if appropriate/will set up as a plugin otherwise.

[uschi2000]

another negative example:

void f(String param) {
    ...
    log.warn("some message param {}" + "  for f method", param);
}

[basil]

Another thing that could be checked is that the number of parameters matches the number of {} expressions in the format string.

[mattnelson]

If you are willing to use findbugs, all those rules already exist.

https://github.com/KengoTODA/findbugs-slf4j

[uschi2000]

Correct. We're actually trying to move away from Findbugs.

On Fri, Mar 17, 2017, 19:12 Matt Nelson [e-mail] wrote:

If are willing to use findbugs, all those rules already exist.

https://github.com/KengoTODA/findbugs-slf4j

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[markelliot]

We've implemented this as a plugin, but happy to contribute it:
https://github.com/palantir/gradle-baseline/blob/develop/baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/Slf4jConstantLogMessage.java

[KengoTODA]

Hello, I also developed a Errorprone plugin for SLF4J users, you may check it:
https://github.com/KengoTODA/errorprone-slf4j