Addressing PR comments

core/src/main/java/feign/Capability.java

@@ -21,14 +21,35 @@
 import feign.codec.Decoder;
 import feign.codec.Encoder;
 
+/**
+ * Capabilities expose core feign artifacts to implementations so parts of core can be customized
+ * around the time the client being built.
+ *
+ * For instance, capabilities take the {@link Client}, make changes to it and feed the modified
+ * version back to feign.
+ *
+ * @see Metrics5Capability
+ */
 public interface Capability {
 
-  static <E> E enrich(E target, List<Capability> capabilities) {
+
+  static <E> E enrich(E componentToEnrich, List<Capability> capabilities) {
     return capabilities.stream()
+        // invoke each individual capability and feed the result to the next one.
+        // This is equivalent to:
+        // Capability cap1 = ...;
+        // Capability cap2 = ...;
+        // Capability cap2 = ...;
+        // Contract contract = ...;
+        // Contract contract1 = cap1.enrich(contract);
+        // Contract contract2 = cap2.enrich(contract1);
+        // Contract contract3 = cap3.enrich(contract2);
+        // or in a more compact version
+        // Contract enrichedContract = cap3.enrich(cap2.enrich(cap1.enrich(contract)));
         .reduce(
-            target,
-            (c, capability) -> invoke(c, capability),
-            (a, b) -> b);
+            componentToEnrich,
+            (component, capability) -> invoke(component, capability),
+            (component, enrichedComponent) -> enrichedComponent);
   }
 
   static <E> E invoke(E target, Capability capability) {

metrics5/pom.xml

@@ -44,11 +44,6 @@
       <artifactId>metrics-core</artifactId>
       <version>5.0.0</version>
     </dependency>
-    <dependency>
-      <groupId>com.google.guava</groupId>
-      <artifactId>guava</artifactId>
-      <version>28.0-jre</version>
-    </dependency>
     <dependency>
       <groupId>org.hamcrest</groupId>
       <artifactId>java-hamcrest</artifactId>

metrics5/src/main/java/feign/metrics5/CountingInputStream.java

@@ -0,0 +1,105 @@
+/**
+ * Copyright 2012-2020 The Feign Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+/*
+ * Copyright (C) 2007 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package feign.metrics5;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import feign.Util;
+
+/**
+ * Copy from guava CountingInputStream
+ *
+ * An {@link InputStream} that counts the number of bytes read.
+ *
+ * @author Chris Nokleberg
+ * @since 1.0
+ */
+public final class CountingInputStream extends FilterInputStream {
+
+  private long count;
+  private long mark = -1;
+
+  /**
+   * Wraps another input stream, counting the number of bytes read.
+   *
+   * @param in the input stream to be wrapped
+   */
+  public CountingInputStream(InputStream in) {
+    super(Util.checkNotNull(in, "InputStream must not be null"));
+  }
+
+  /** Returns the number of bytes read. */
+  public long getCount() {
+    return count;
+  }
+
+  @Override
+  public int read() throws IOException {
+    final int result = in.read();
+    if (result != -1) {
+      count++;
+    }
+    return result;
+  }
+
+  @Override
+  public int read(byte[] b, int off, int len) throws IOException {
+    final int result = in.read(b, off, len);
+    if (result != -1) {
+      count += result;
+    }
+    return result;
+  }
+
+  @Override
+  public long skip(long n) throws IOException {
+    final long result = in.skip(n);
+    count += result;
+    return result;
+  }
+
+  @Override
+  public synchronized void mark(int readlimit) {
+    in.mark(readlimit);
+    mark = count;
+    // it's okay to mark even if mark isn't supported, as reset won't work
+  }
+
+  @Override
+  public synchronized void reset() throws IOException {
+    if (!in.markSupported()) {
+      throw new IOException("Mark not supported");
+    }
+    if (mark == -1) {
+      throw new IOException("Mark not set");
+    }
+
+    in.reset();
+    count = mark;
+  }
+}

metrics5/src/main/java/feign/metrics5/FeignMetricName.java

@@ -22,26 +22,26 @@
 import io.dropwizard.metrics5.MetricName;
 import io.dropwizard.metrics5.MetricRegistry;
 
-final class FeignMetricName {
+public final class FeignMetricName {
 
   private final Class<?> meteredComponent;
 
 
-  FeignMetricName(Class<?> meteredComponent) {
+  public FeignMetricName(Class<?> meteredComponent) {
     this.meteredComponent = meteredComponent;
   }
 
 
-  MetricName metricName(MethodMetadata methodMetadata, Target<?> target, String suffix) {
+  public MetricName metricName(MethodMetadata methodMetadata, Target<?> target, String suffix) {
     return metricName(methodMetadata, target)
         .resolve(suffix);
   }
 
-  MetricName metricName(MethodMetadata methodMetadata, Target<?> target) {
+  public MetricName metricName(MethodMetadata methodMetadata, Target<?> target) {
     return metricName(methodMetadata.targetType(), methodMetadata.method(), target.url());
   }
 
-  MetricName metricName(Class<?> targetType, Method method, String url) {
+  public MetricName metricName(Class<?> targetType, Method method, String url) {
     return MetricRegistry.name(meteredComponent)
         .tagged("client", targetType.getName())
         .tagged("method", method.getName())

metrics5/src/main/java/feign/metrics5/MeteredBody.java

@@ -14,7 +14,6 @@
 package feign.metrics5;
 
 import static feign.Util.UTF_8;
-import com.google.common.io.CountingInputStream;
 import java.io.*;
 import java.nio.charset.Charset;
 import java.util.function.Supplier;
@@ -23,12 +22,12 @@
 /**
  * {@link Body} implementation that keeps track of how many bytes are read.
  */
-final class MeteredBody implements Body {
+public final class MeteredBody implements Body {
 
   private final Body delegate;
   private Supplier<Long> count;
 
-  MeteredBody(Body body) {
+  public MeteredBody(Body body) {
     this.delegate = body;
     count = () -> 0L;
   }

metrics5/src/main/java/feign/metrics5/MeteredClient.java

@@ -23,7 +23,7 @@
 /**
  * Warp feign {@link Client} with metrics.
  */
-final class MeteredClient implements Client {
+public class MeteredClient implements Client {
 
   private final Client client;
   private final MetricRegistry metricRegistry;

metrics5/src/main/java/feign/metrics5/MeteredDecoder.java

@@ -16,19 +16,18 @@
 
 import java.io.IOException;
 import java.lang.reflect.Type;
-import java.util.concurrent.TimeUnit;
 import feign.FeignException;
 import feign.RequestTemplate;
 import feign.Response;
 import feign.codec.DecodeException;
 import feign.codec.Decoder;
-import io.dropwizard.metrics5.*;
+import io.dropwizard.metrics5.MetricRegistry;
 import io.dropwizard.metrics5.Timer.Context;
 
 /**
  * Warp feign {@link Decoder} with metrics.
  */
-final class MeteredDecoder implements Decoder {
+public class MeteredDecoder implements Decoder {
 
   private final Decoder decoder;
   private final MetricRegistry metricRegistry;

metrics5/src/main/java/feign/metrics5/MeteredEncoder.java

@@ -24,7 +24,7 @@
 /**
  * Warp feign {@link Encoder} with metrics.
  */
-final class MeteredEncoder implements Encoder {
+public class MeteredEncoder implements Encoder {
 
   private final Encoder encoder;
   private final MetricRegistry metricRegistry;

metrics5/src/main/java/feign/metrics5/MeteredInvocationHandleFactory.java

@@ -28,7 +28,7 @@
 /**
  * Warp feign {@link InvocationHandler} with metrics.
  */
-final class MeteredInvocationHandleFactory implements InvocationHandlerFactory {
+public class MeteredInvocationHandleFactory implements InvocationHandlerFactory {
 
   private static final Logger LOG = LoggerFactory.getLogger(MeteredInvocationHandleFactory.class);
 
@@ -47,7 +47,7 @@ final class MeteredInvocationHandleFactory implements InvocationHandlerFactory {
 
   private final MetricSuppliers metricSuppliers;
 
-  MeteredInvocationHandleFactory(InvocationHandlerFactory invocationHandler,
+  public MeteredInvocationHandleFactory(InvocationHandlerFactory invocationHandler,
       MetricRegistry metricRegistry, MetricSuppliers metricSuppliers) {
     this.invocationHandler = invocationHandler;
     this.metricRegistry = metricRegistry;