Skeleton fluent-API for building type hierarchy predicates

Author: mcculls

class-match/src/main/java/datadog/instrument/classmatch/FieldMatcher.java

@@ -74,7 +74,7 @@ default FieldMatcher type(Class<?> type) {
    * @param typeMatcher the field type matcher
    * @return matcher of fields with a matching type
    */
-  default FieldMatcher type(Predicate<String> typeMatcher) {
+  default FieldMatcher type(TypeMatcher typeMatcher) {
     return and(f -> hasFieldType(f, typeMatcher));
   }
 

class-match/src/main/java/datadog/instrument/classmatch/InternalMatchers.java

@@ -55,7 +55,7 @@ static boolean hasParamDescriptor(MethodOutline method, int paramIndex, String p
   }
 
   /** Does the method's descriptor contain a matching parameter type at the given index? */
-  static boolean hasParamType(MethodOutline method, int paramIndex, Predicate<String> typeMatcher) {
+  static boolean hasParamType(MethodOutline method, int paramIndex, TypeMatcher typeMatcher) {
     // boundaries covers start of second parameter, to start of return descriptor
     int[] boundaries = method.descriptorBoundaries();
     if (paramIndex >= boundaries.length) { // ignore return descriptor boundary
@@ -70,7 +70,7 @@ static boolean hasParamType(MethodOutline method, int paramIndex, Predicate<Stri
   }
 
   /** Does the method's descriptor contain a matching return type? */
-  static boolean hasReturnType(MethodOutline method, Predicate<String> typeMatcher) {
+  static boolean hasReturnType(MethodOutline method, TypeMatcher typeMatcher) {
     // boundaries covers start of second parameter, to start of return descriptor
     int[] boundaries = method.descriptorBoundaries();
     // return type starts at 2 if no parameters, otherwise check last boundary
@@ -82,7 +82,7 @@ static boolean hasReturnType(MethodOutline method, Predicate<String> typeMatcher
   }
 
   /** Does the field's descriptor contain a matching type? */
-  static boolean hasFieldType(FieldOutline field, Predicate<String> typeMatcher) {
+  static boolean hasFieldType(FieldOutline field, TypeMatcher typeMatcher) {
     String descriptor = field.descriptor;
     // extract type from "L...;" descriptor string, ignore primitive/array types
     return descriptor.charAt(0) == 'L'
@@ -247,6 +247,40 @@ public boolean test(MethodOutline outline) {
     }
   }
 
+  /** Logical AND of two {@link TypeMatcher}s; nested conjunctions will be collapsed. */
+  static final class TypeConjunction extends MatcherUnion<TypeMatcher> implements TypeMatcher {
+    TypeConjunction(TypeMatcher lhs, TypeMatcher rhs) {
+      super(new TypeMatcher[] {lhs, rhs});
+    }
+
+    @Override
+    public boolean test(CharSequence typeString) {
+      for (TypeMatcher matcher : matchers) {
+        if (!matcher.test(typeString)) {
+          return false;
+        }
+      }
+      return true;
+    }
+  }
+
+  /** Logical OR of two {@link TypeMatcher}s; nested disjunctions will be collapsed. */
+  static final class TypeDisjunction extends MatcherUnion<TypeMatcher> implements TypeMatcher {
+    TypeDisjunction(TypeMatcher lhs, TypeMatcher rhs) {
+      super(new TypeMatcher[] {lhs, rhs});
+    }
+
+    @Override
+    public boolean test(CharSequence typeString) {
+      for (TypeMatcher matcher : matchers) {
+        if (matcher.test(typeString)) {
+          return true;
+        }
+      }
+      return false;
+    }
+  }
+
   /** Logical union of two matchers; nested unions of the same type will be collapsed. */
   abstract static class MatcherUnion<M> {
     protected final M[] matchers;

class-match/src/main/java/datadog/instrument/classmatch/MethodMatcher.java

@@ -172,7 +172,7 @@ default MethodMatcher parameter(int paramIndex, Class<?> paramType) {
    * @param typeMatcher the parameter type matcher
    * @return matcher of methods with a matching parameter type
    */
-  default MethodMatcher parameter(int paramIndex, Predicate<String> typeMatcher) {
+  default MethodMatcher parameter(int paramIndex, TypeMatcher typeMatcher) {
     return and(m -> hasParamType(m, paramIndex, typeMatcher));
   }
 
@@ -204,7 +204,7 @@ default MethodMatcher returning(Class<?> returnType) {
    * @param typeMatcher the return type matcher
    * @return matcher of methods with a matching return type
    */
-  default MethodMatcher returning(Predicate<String> typeMatcher) {
+  default MethodMatcher returning(TypeMatcher typeMatcher) {
     return and(m -> hasReturnType(m, typeMatcher));
   }
 

class-match/src/main/java/datadog/instrument/classmatch/TypeMatcher.java

@@ -0,0 +1,33 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache-2.0 License.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2025-Present Datadog, Inc.
+ */
+
+package datadog.instrument.classmatch;
+
+import java.util.function.Predicate;
+
+/** Fluent-API for building type hierarchy predicates. */
+public interface TypeMatcher extends Predicate<CharSequence> {
+
+  /**
+   * Conjunction of this matcher AND another.
+   *
+   * @param other the other matcher
+   * @return conjunction of both matchers
+   */
+  default TypeMatcher and(TypeMatcher other) {
+    return new InternalMatchers.TypeConjunction(this, other);
+  }
+
+  /**
+   * Disjunction of this matcher OR another.
+   *
+   * @param other the other matcher
+   * @return disjunction of both matchers
+   */
+  default TypeMatcher or(TypeMatcher other) {
+    return new InternalMatchers.TypeDisjunction(this, other);
+  }
+}