Add configurable null-checking methods to AnnotateNullableParameters

[stefanodallapalma]

Problem

The AnnotateNullableParameters recipe currently uses a hardcoded list of known null-checking methods (e.g., Objects.isNull(), StringUtils.isEmpty()). While this covers common utility libraries, many teams have custom utility methods for null checking that the recipe doesn't recognize.

Example scenario:

public PersonBuilder setInfo(String name, String lastName) {
    if (MyUtils.hasText(name)) {        // ❌ Custom method not recognized
        this.name = name;
    }
    if (Objects.isNull(lastName)) {     // ✅ Built-in method recognized  
        this.lastName = lastName;
    }
    return this;
}

Currently, only lastName would get the @Nullable annotation despite both parameters being null-checked.

Solution

Added an optional additionalNullCheckingMethods parameter that accepts a list of custom null-checking method patterns in OpenRewrite's MethodMatcher format.

Key features:

• ✨ Backward compatible - All existing functionality preserved
• 🔧 Configurable - Teams can specify their custom null-checking utilities
• 📝 Flexible patterns - Supports OpenRewrite's method matching syntax

Usage

Programmatic:

List<String> customMethods = List.of(
    "org.my.util.Text hasText(java.lang.String)",
    "org.my.util.Text isEmptyOrNull(java.lang.String)"
);
var recipe = new AnnotateNullableParameters(null, customMethods);

YAML configuration:

- org.openrewrite.staticanalysis.AnnotateNullableParameters:
    additionalNullCheckingMethods:
      - "org.my.util.Text hasText(..))"
      - "org.my.util.Text isEmptyOrNull(..)"

Result:

// Both parameters now get annotated
public PersonBuilder setInfo(@Nullable String name, @Nullable String lastName) {
    if (Text.hasText(name)) {           // ✅ Now recognized
        this.name = name;
    }
    if (!Text.isEmptyOrNull(lastName)) { // ✅ Now recognized (negated)
        this.lastName = lastName;
    }
    return this;
}

Implementation Details

• Method patterns are combined with the default list at runtime
• Supports both specific parameter types and wildcard patterns (..)
• Works with negated conditions (!customMethod(param))

Testing

• ✅ Validates both positive and negated null checks
• ✅ Backward compatibility verified - all existing tests pass
• ❌ Invalid patterns not covered

Motivation

This enhancement enables teams with custom utility libraries to benefit from automated nullable annotation without needing to modify their existing code patterns. It's particularly valuable for:

• Legacy codebases with established utility patterns
• Organizations with domain-specific null-checking methods

---

@timtebeek

Relates to: #578

[github-actions]

Some suggestions could not be made:

• src/main/java/org/openrewrite/staticanalysis/AnnotateNullableParameters.java
  • lines 68-72
  • lines 200-201

[timtebeek]

Thanks for your continued involvement here! I've added a light bit of touch up to avoid unnecessary array allocations per visitor instance, and to use proper markdown in the docs. 🙏🏻

[github-actions]

Some suggestions could not be made:

• src/main/java/org/openrewrite/staticanalysis/AnnotateNullableParameters.java
  • lines 66-70