bugfix: false positive in AnnotateNullableParameters when parameter …

[stefanodallapalma]

Fix false positive in AnnotateNullableParameters when parameter is dereferenced before null check

Problem

The AnnotateNullableParameters recipe was incorrectly annotating parameters as @Nullable when they were dereferenced before being passed to additional null-checking methods.

For example, in this code:

public void setInfo(Map<String, String> infoMap) {
    if (!Text.isEmptyOrNull(infoMap.get("name"))) {
        this.name = infoMap.get("name");
    }
}

The recipe would incorrectly annotate infoMap as @Nullable because it detected Text.isEmptyOrNull() being called. However, infoMap itself is being dereferenced (via .get()), which means it cannot be null at that point. The null check is for the return value of get(), not for infoMap itself.

Solution

Modified the handleMethodInvocation method to only consider a parameter as null-checked when it's passed directly as an identifier to the null-checking method, not when it's dereferenced first.

Before: Used a visitor to traverse all identifiers within the method arguments, capturing any that matched parameter names.

After: Only checks if the first argument is a direct J.Identifier matching a parameter name.

Changes

• AnnotateNullableParameters.java: Simplified handleMethodInvocation to prevent false positives from dereferenced parameters
• AnnotateNullableParametersTest.java: Added regression test unchangedWhenParameterDereferencedBeforeNullCheckingMethod to verify the fix

Requested Reviewer

@timtebeek

[timtebeek]

Thanks again @stefanodallapalma ! Good to see a clear example and improvement.