Added a method to remove the extensions

core/src/main/java/io/cloudevents/core/builder/CloudEventBuilder.java

@@ -146,11 +146,27 @@ public interface CloudEventBuilder extends CloudEventWriter<CloudEvent> {
     /**
      * Add to the builder all the extension key/values of the provided extension
      *
-     * @param extension materialized extension to set in the event
+     * @param extension materialized extension to set in the builder
      * @return self
      */
     CloudEventBuilder withExtension(@Nonnull Extension extension);
 
+    /**
+     * Remove from the the builder the provided extension key, if any
+     *
+     * @param key key of the extension attribute
+     * @return self
+     */
+    CloudEventBuilder withoutExtension(@Nonnull String key);
+
+    /**
+     * Remove from the the builder the provided extension, if any
+     *
+     * @param extension materialized extension to remove from the builder
+     * @return self
+     */
+    CloudEventBuilder withoutExtension(@Nonnull Extension extension);
+
     /**
      * Build the event
      *

core/src/main/java/io/cloudevents/core/impl/BaseCloudEventBuilder.java

@@ -91,6 +91,18 @@ public SELF withExtension(@Nonnull String key, boolean value) {
         return self;
     }
 
+    @Override
+    public SELF withoutExtension(@Nonnull String key) {
+        this.extensions.remove(key);
+        return self;
+    }
+
+    @Override
+    public SELF withoutExtension(@Nonnull Extension extension) {
+        extension.getKeys().forEach(this::withoutExtension);
+        return self;
+    }
+
     public SELF withExtension(@Nonnull Extension extension) {
         for (String key : extension.getKeys()) {
             Object value = extension.getValue(key);

core/src/test/java/io/cloudevents/core/impl/BaseCloudEventBuilderTest.java

@@ -0,0 +1,48 @@
+package io.cloudevents.core.impl;
+
+import io.cloudevents.CloudEvent;
+import io.cloudevents.core.builder.CloudEventBuilder;
+import io.cloudevents.core.extensions.DistributedTracingExtension;
+import io.cloudevents.core.test.Data;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BaseCloudEventBuilderTest {
+
+    @Test
+    public void copyAndRemoveExtension() {
+        assertThat(Data.V1_WITH_JSON_DATA_WITH_EXT.getExtensionNames())
+            .contains("astring");
+
+        CloudEvent event = CloudEventBuilder.v1(Data.V1_WITH_JSON_DATA_WITH_EXT)
+            .withoutExtension("astring")
+            .build();
+
+        assertThat(event.getExtensionNames())
+            .doesNotContain("astring");
+    }
+
+    @Test
+    public void copyAndRemoveMaterializedExtension() {
+        DistributedTracingExtension ext = new DistributedTracingExtension();
+        ext.setTraceparent("aaa"); // Set only traceparent
+
+        CloudEvent given = CloudEventBuilder.v1(Data.V1_WITH_JSON_DATA_WITH_EXT)
+            .withExtension(ext)
+            .build();
+        assertThat(given.getExtensionNames())
+            .contains("traceparent")
+            .doesNotContain("tracestate");
+
+        CloudEvent have = CloudEventBuilder.v1(given)
+            .withoutExtension(ext)
+            .build();
+
+        assertThat(have.getExtensionNames())
+            .doesNotContain("traceparent", "tracestate");
+        assertThat(Data.V1_WITH_JSON_DATA_WITH_EXT)
+            .isEqualTo(have);
+    }
+
+}