Use UnaryOperator<X> instead of Function<X, X> where it simplifies things

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/builder/internal/DefaultHttpClientInstrumenterBuilder.java

@@ -38,6 +38,7 @@
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
 import javax.annotation.Nullable;
 
 /**
@@ -54,16 +55,16 @@ public final class DefaultHttpClientInstrumenterBuilder<REQUEST, RESPONSE> {
 
   private final List<AttributesExtractor<? super REQUEST, ? super RESPONSE>> additionalExtractors =
       new ArrayList<>();
-  private Function<SpanStatusExtractor<REQUEST, RESPONSE>, SpanStatusExtractor<REQUEST, RESPONSE>>
-      statusExtractorTransformer = Function.identity();
+  private UnaryOperator<SpanStatusExtractor<REQUEST, RESPONSE>> statusExtractorTransformer =
+      UnaryOperator.identity();
   private final HttpClientAttributesExtractorBuilder<REQUEST, RESPONSE>
       httpAttributesExtractorBuilder;
   private final HttpClientAttributesGetter<REQUEST, RESPONSE> attributesGetter;
   private final HttpSpanNameExtractorBuilder<REQUEST> httpSpanNameExtractorBuilder;
 
   @Nullable private final TextMapSetter<REQUEST> headerSetter;
-  private Function<SpanNameExtractor<REQUEST>, ? extends SpanNameExtractor<REQUEST>>
-      spanNameExtractorTransformer = Function.identity();
+  private UnaryOperator<SpanNameExtractor<REQUEST>> spanNameExtractorTransformer =
+      UnaryOperator.identity();
   private boolean emitExperimentalHttpClientTelemetry = false;
   private Consumer<InstrumenterBuilder<REQUEST, RESPONSE>> builderCustomizer = b -> {};
 
@@ -113,8 +114,7 @@ public DefaultHttpClientInstrumenterBuilder<REQUEST, RESPONSE> addAttributesExtr
 
   @CanIgnoreReturnValue
   public DefaultHttpClientInstrumenterBuilder<REQUEST, RESPONSE> setStatusExtractor(
-      Function<SpanStatusExtractor<REQUEST, RESPONSE>, SpanStatusExtractor<REQUEST, RESPONSE>>
-          statusExtractor) {
+      UnaryOperator<SpanStatusExtractor<REQUEST, RESPONSE>> statusExtractor) {
     this.statusExtractorTransformer = statusExtractor;
     return this;
   }
@@ -192,9 +192,8 @@ public DefaultHttpClientInstrumenterBuilder<REQUEST, RESPONSE> setRedactQueryPar
   /** Sets custom {@link SpanNameExtractor} via transform function. */
   @CanIgnoreReturnValue
   public DefaultHttpClientInstrumenterBuilder<REQUEST, RESPONSE> setSpanNameExtractor(
-      Function<SpanNameExtractor<REQUEST>, SpanNameExtractor<REQUEST>>
-          spanNameExtractorTransformer) {
-    this.spanNameExtractorTransformer = spanNameExtractorTransformer;
+      UnaryOperator<SpanNameExtractor<REQUEST>> spanNameExtractor) {
+    this.spanNameExtractorTransformer = spanNameExtractor;
     return this;
   }
 

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/builder/internal/DefaultHttpServerInstrumenterBuilder.java

@@ -31,8 +31,8 @@
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Consumer;
-import java.util.function.Function;
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
 import javax.annotation.Nullable;
 
 /**
@@ -46,15 +46,15 @@ public final class DefaultHttpServerInstrumenterBuilder<REQUEST, RESPONSE> {
 
   private final List<AttributesExtractor<? super REQUEST, ? super RESPONSE>> additionalExtractors =
       new ArrayList<>();
-  private Function<SpanStatusExtractor<REQUEST, RESPONSE>, SpanStatusExtractor<REQUEST, RESPONSE>>
-      statusExtractorTransformer = Function.identity();
+  private UnaryOperator<SpanStatusExtractor<REQUEST, RESPONSE>> statusExtractorTransformer =
+      UnaryOperator.identity();
   private final HttpServerAttributesExtractorBuilder<REQUEST, RESPONSE>
       httpAttributesExtractorBuilder;
   private final HttpSpanNameExtractorBuilder<REQUEST> httpSpanNameExtractorBuilder;
 
   @Nullable private final TextMapGetter<REQUEST> headerGetter;
-  private Function<SpanNameExtractor<REQUEST>, SpanNameExtractor<REQUEST>>
-      spanNameExtractorTransformer = Function.identity();
+  private UnaryOperator<SpanNameExtractor<REQUEST>> spanNameExtractorTransformer =
+      UnaryOperator.identity();
   private final HttpServerRouteBuilder<REQUEST> httpServerRouteBuilder;
   private final HttpServerAttributesGetter<REQUEST, RESPONSE> attributesGetter;
   private boolean emitExperimentalHttpServerTelemetry = false;
@@ -107,8 +107,7 @@ public DefaultHttpServerInstrumenterBuilder<REQUEST, RESPONSE> addAttributesExtr
 
   @CanIgnoreReturnValue
   public DefaultHttpServerInstrumenterBuilder<REQUEST, RESPONSE> setStatusExtractor(
-      Function<SpanStatusExtractor<REQUEST, RESPONSE>, SpanStatusExtractor<REQUEST, RESPONSE>>
-          statusExtractor) {
+      UnaryOperator<SpanStatusExtractor<REQUEST, RESPONSE>> statusExtractor) {
     this.statusExtractorTransformer = statusExtractor;
     return this;
   }
@@ -175,9 +174,8 @@ public DefaultHttpServerInstrumenterBuilder<REQUEST, RESPONSE> setKnownMethods(
   /** Sets custom {@link SpanNameExtractor} via transform function. */
   @CanIgnoreReturnValue
   public DefaultHttpServerInstrumenterBuilder<REQUEST, RESPONSE> setSpanNameExtractor(
-      Function<SpanNameExtractor<REQUEST>, SpanNameExtractor<REQUEST>>
-          spanNameExtractorTransformer) {
-    this.spanNameExtractorTransformer = spanNameExtractorTransformer;
+      UnaryOperator<SpanNameExtractor<REQUEST>> spanNameExtractor) {
+    this.spanNameExtractorTransformer = spanNameExtractor;
     return this;
   }
 

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/instrumenter/InstrumenterCustomizer.java

@@ -12,6 +12,7 @@
 import io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics;
 import io.opentelemetry.instrumentation.api.instrumenter.SpanNameExtractor;
 import java.util.function.Function;
+import java.util.function.UnaryOperator;
 
 /**
  * Provides customizations for instrumentation, including operation metrics, attributes extraction,
@@ -75,7 +76,23 @@ InstrumenterCustomizer addAttributesExtractors(
    *
    * @param spanNameExtractorTransformer function that transforms the original span name extractor
    * @return this InstrumenterCustomizer for method chaining
+   * @deprecated Use {@link #setSpanNameExtractor(UnaryOperator)} instead.
+   */
+  @Deprecated
+  @SuppressWarnings("FunctionalInterfaceClash")
+  default InstrumenterCustomizer setSpanNameExtractor(
+      Function<SpanNameExtractor<?>, SpanNameExtractor<?>> spanNameExtractorTransformer) {
+    return setSpanNameExtractor(
+        (UnaryOperator<SpanNameExtractor<?>>) spanNameExtractorTransformer::apply);
+  }
+
+  /**
+   * Sets a transformer function that will modify the {@link SpanNameExtractor}. This allows
+   * customizing how span names are generated for the instrumented operations.
+   *
+   * @param spanNameExtractor function that transforms the original span name extractor
+   * @return this InstrumenterCustomizer for method chaining
    */
   InstrumenterCustomizer setSpanNameExtractor(
-      Function<SpanNameExtractor<?>, SpanNameExtractor<?>> spanNameExtractorTransformer);
+      UnaryOperator<SpanNameExtractor<?>> spanNameExtractor);
 }

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/instrumenter/internal/InstrumenterCustomizerImpl.java

@@ -11,7 +11,7 @@
 import io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics;
 import io.opentelemetry.instrumentation.api.instrumenter.SpanNameExtractor;
 import io.opentelemetry.instrumentation.api.internal.InternalInstrumenterCustomizer;
-import java.util.function.Function;
+import java.util.function.UnaryOperator;
 
 /**
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
@@ -56,9 +56,10 @@ public InstrumenterCustomizer addContextCustomizer(ContextCustomizer<?> customiz
   }
 
   @Override
+  @SuppressWarnings("FunctionalInterfaceClash") // interface has deprecated overload
   public InstrumenterCustomizer setSpanNameExtractor(
-      Function<SpanNameExtractor<?>, SpanNameExtractor<?>> spanNameExtractorTransformer) {
-    customizer.setSpanNameExtractor(spanNameExtractorTransformer);
+      UnaryOperator<SpanNameExtractor<?>> spanNameExtractor) {
+    customizer.setSpanNameExtractor(spanNameExtractor);
     return this;
   }
 }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/InstrumenterBuilder.java

@@ -33,7 +33,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
-import java.util.function.Function;
+import java.util.function.UnaryOperator;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -427,8 +427,7 @@ public void addContextCustomizer(ContextCustomizer<REQUEST> customizer) {
 
             @Override
             public void setSpanNameExtractor(
-                Function<SpanNameExtractor<? super REQUEST>, SpanNameExtractor<? super REQUEST>>
-                    spanNameExtractorTransformer) {
+                UnaryOperator<SpanNameExtractor<? super REQUEST>> spanNameExtractorTransformer) {
               builder.spanNameExtractor =
                   spanNameExtractorTransformer.apply(builder.spanNameExtractor);
             }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/internal/InternalInstrumenterCustomizer.java

@@ -9,7 +9,7 @@
 import io.opentelemetry.instrumentation.api.instrumenter.ContextCustomizer;
 import io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics;
 import io.opentelemetry.instrumentation.api.instrumenter.SpanNameExtractor;
-import java.util.function.Function;
+import java.util.function.UnaryOperator;
 
 /**
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
@@ -29,6 +29,5 @@ void addAttributesExtractors(
   void addContextCustomizer(ContextCustomizer<REQUEST> customizer);
 
   void setSpanNameExtractor(
-      Function<SpanNameExtractor<? super REQUEST>, SpanNameExtractor<? super REQUEST>>
-          spanNameExtractorTransformer);
+      UnaryOperator<SpanNameExtractor<? super REQUEST>> spanNameExtractorTransformer);
 }

instrumentation/apache-dubbo-2.7/library-autoconfigure/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/DubboTelemetryBuilder.java

@@ -23,6 +23,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Function;
+import java.util.function.UnaryOperator;
 import javax.annotation.Nullable;
 import org.apache.dubbo.rpc.Result;
 
@@ -38,12 +39,10 @@ public final class DubboTelemetryBuilder {
   @Nullable private String peerService;
   private final List<AttributesExtractor<DubboRequest, Result>> attributesExtractors =
       new ArrayList<>();
-  private Function<
-          SpanNameExtractor<DubboRequest>, ? extends SpanNameExtractor<? super DubboRequest>>
-      clientSpanNameExtractorTransformer = Function.identity();
-  private Function<
-          SpanNameExtractor<DubboRequest>, ? extends SpanNameExtractor<? super DubboRequest>>
-      serverSpanNameExtractorTransformer = Function.identity();
+  private UnaryOperator<SpanNameExtractor<DubboRequest>> clientSpanNameExtractorTransformer =
+      UnaryOperator.identity();
+  private UnaryOperator<SpanNameExtractor<DubboRequest>> serverSpanNameExtractorTransformer =
+      UnaryOperator.identity();
 
   DubboTelemetryBuilder(OpenTelemetry openTelemetry) {
     this.openTelemetry = openTelemetry;
@@ -65,20 +64,50 @@ public DubboTelemetryBuilder addAttributesExtractor(
     return this;
   }
 
-  /** Sets custom client {@link SpanNameExtractor} via transform function. */
+  /**
+   * Sets custom client {@link SpanNameExtractor} via transform function.
+   *
+   * @deprecated Use {@link #setClientSpanNameExtractor(UnaryOperator)} instead.
+   */
+  @Deprecated
   @CanIgnoreReturnValue
+  @SuppressWarnings("unchecked") // safe cast from Function to UnaryOperator
   public DubboTelemetryBuilder setClientSpanNameExtractor(
       Function<SpanNameExtractor<DubboRequest>, ? extends SpanNameExtractor<? super DubboRequest>>
           clientSpanNameExtractor) {
+    return setClientSpanNameExtractor(
+        (UnaryOperator<SpanNameExtractor<DubboRequest>>)
+            input -> (SpanNameExtractor<DubboRequest>) clientSpanNameExtractor.apply(input));
+  }
+
+  /** Sets custom client {@link SpanNameExtractor} via transform function. */
+  @CanIgnoreReturnValue
+  public DubboTelemetryBuilder setClientSpanNameExtractor(
+      UnaryOperator<SpanNameExtractor<DubboRequest>> clientSpanNameExtractor) {
     this.clientSpanNameExtractorTransformer = clientSpanNameExtractor;
     return this;
   }
 
-  /** Sets custom server {@link SpanNameExtractor} via transform function. */
+  /**
+   * Sets custom server {@link SpanNameExtractor} via transform function.
+   *
+   * @deprecated Use {@link #setServerSpanNameExtractor(UnaryOperator)} instead.
+   */
+  @Deprecated
   @CanIgnoreReturnValue
+  @SuppressWarnings("unchecked") // safe cast from Function to UnaryOperator
   public DubboTelemetryBuilder setServerSpanNameExtractor(
       Function<SpanNameExtractor<DubboRequest>, ? extends SpanNameExtractor<? super DubboRequest>>
           serverSpanNameExtractor) {
+    return setServerSpanNameExtractor(
+        (UnaryOperator<SpanNameExtractor<DubboRequest>>)
+            input -> (SpanNameExtractor<DubboRequest>) serverSpanNameExtractor.apply(input));
+  }
+
+  /** Sets custom server {@link SpanNameExtractor} via transform function. */
+  @CanIgnoreReturnValue
+  public DubboTelemetryBuilder setServerSpanNameExtractor(
+      UnaryOperator<SpanNameExtractor<DubboRequest>> serverSpanNameExtractor) {
     this.serverSpanNameExtractorTransformer = serverSpanNameExtractor;
     return this;
   }
@@ -90,9 +119,9 @@ public DubboTelemetry build() {
     DubboRpcAttributesGetter rpcAttributesGetter = DubboRpcAttributesGetter.INSTANCE;
     SpanNameExtractor<DubboRequest> spanNameExtractor =
         RpcSpanNameExtractor.create(rpcAttributesGetter);
-    SpanNameExtractor<? super DubboRequest> clientSpanNameExtractor =
+    SpanNameExtractor<DubboRequest> clientSpanNameExtractor =
         clientSpanNameExtractorTransformer.apply(spanNameExtractor);
-    SpanNameExtractor<? super DubboRequest> serverSpanNameExtractor =
+    SpanNameExtractor<DubboRequest> serverSpanNameExtractor =
         serverSpanNameExtractorTransformer.apply(spanNameExtractor);
     DubboClientNetworkAttributesGetter netClientAttributesGetter =
         new DubboClientNetworkAttributesGetter();

instrumentation/apache-httpclient/apache-httpclient-4.3/library/src/main/java/io/opentelemetry/instrumentation/apachehttpclient/v4_3/ApacheHttpClientTelemetryBuilder.java

@@ -14,6 +14,7 @@
 import io.opentelemetry.instrumentation.api.semconv.http.HttpClientAttributesExtractorBuilder;
 import java.util.Collection;
 import java.util.function.Function;
+import java.util.function.UnaryOperator;
 import org.apache.http.HttpResponse;
 
 /** A builder for {@link ApacheHttpClientTelemetry}. */
@@ -89,13 +90,27 @@ public ApacheHttpClientTelemetryBuilder setKnownMethods(Collection<String> known
     return this;
   }
 
-  /** Sets custom {@link SpanNameExtractor} via transform function. */
+  /**
+   * Sets custom {@link SpanNameExtractor} via transform function.
+   *
+   * @deprecated Use {@link #setSpanNameExtractor(UnaryOperator)} instead.
+   */
+  @Deprecated
   @CanIgnoreReturnValue
   public ApacheHttpClientTelemetryBuilder setSpanNameExtractor(
       Function<
               SpanNameExtractor<ApacheHttpClientRequest>,
               SpanNameExtractor<ApacheHttpClientRequest>>
           spanNameExtractorTransformer) {
+    return setSpanNameExtractor(
+        (UnaryOperator<SpanNameExtractor<ApacheHttpClientRequest>>)
+            spanNameExtractorTransformer::apply);
+  }
+
+  /** Sets custom {@link SpanNameExtractor} via transform function. */
+  @CanIgnoreReturnValue
+  public ApacheHttpClientTelemetryBuilder setSpanNameExtractor(
+      UnaryOperator<SpanNameExtractor<ApacheHttpClientRequest>> spanNameExtractorTransformer) {
     builder.setSpanNameExtractor(spanNameExtractorTransformer);
     return this;
   }

instrumentation/apache-httpclient/apache-httpclient-5.2/library/src/main/java/io/opentelemetry/instrumentation/apachehttpclient/v5_2/ApacheHttpClientTelemetryBuilder.java

@@ -14,6 +14,7 @@
 import io.opentelemetry.instrumentation.api.semconv.http.HttpClientAttributesExtractorBuilder;
 import java.util.Collection;
 import java.util.function.Function;
+import java.util.function.UnaryOperator;
 import org.apache.hc.core5.http.HttpResponse;
 
 /** A builder for {@link ApacheHttpClientTelemetry}. */
@@ -89,13 +90,27 @@ public ApacheHttpClientTelemetryBuilder setKnownMethods(Collection<String> known
     return this;
   }
 
-  /** Sets custom {@link SpanNameExtractor} via transform function. */
+  /**
+   * Sets custom {@link SpanNameExtractor} via transform function.
+   *
+   * @deprecated Use {@link #setSpanNameExtractor(UnaryOperator)} instead.
+   */
+  @Deprecated
   @CanIgnoreReturnValue
   public ApacheHttpClientTelemetryBuilder setSpanNameExtractor(
       Function<
               SpanNameExtractor<ApacheHttpClientRequest>,
               SpanNameExtractor<ApacheHttpClientRequest>>
           spanNameExtractorTransformer) {
+    return setSpanNameExtractor(
+        (UnaryOperator<SpanNameExtractor<ApacheHttpClientRequest>>)
+            spanNameExtractorTransformer::apply);
+  }
+
+  /** Sets custom {@link SpanNameExtractor} via transform function. */
+  @CanIgnoreReturnValue
+  public ApacheHttpClientTelemetryBuilder setSpanNameExtractor(
+      UnaryOperator<SpanNameExtractor<ApacheHttpClientRequest>> spanNameExtractorTransformer) {
     builder.setSpanNameExtractor(spanNameExtractorTransformer);
     return this;
   }