Merge pull request #153 from DataDog/tyler/fix-tags

Null tags are intended for “deletion”

Author: tylerbenson

dd-trace/src/main/java/com/datadoghq/trace/DDSpanContext.java

@@ -181,6 +181,7 @@ public DDTracer getTracer() {
    */
   public synchronized void setTag(final String tag, final Object value) {
     if (value == null) {
+      tags.remove(tag);
       return;
     }
 

dd-trace/src/test/groovy/com/datadoghq/trace/DDSpanContextTest.groovy

@@ -4,22 +4,26 @@ import spock.lang.Specification
 
 class DDSpanContextTest extends Specification {
 
-  def "null values for tags are ignored"() {
+  def "null values for tags delete existing tags"() {
     setup:
     def context = SpanFactory.newSpanOf(0).context
+    context.setTag("some.tag", "asdf")
     context.setTag(name, null)
     context.setErrorFlag(true)
-    def thread = Thread.currentThread()
 
     expect:
-    context.getTags() == [(DDTags.THREAD_NAME): thread.name, (DDTags.THREAD_ID): thread.id]
+    context.getTags() == tags
     context.serviceName == "fakeService"
     context.resourceName == "fakeResource"
     context.spanType == "fakeType"
-    context.toString() == "Span [ t_id=1, s_id=1, p_id=0] trace=fakeService/fakeOperation/fakeResource *errored* tags={thread.id=$thread.id, thread.name=$thread.name}"
+    context.toString() == "Span [ t_id=1, s_id=1, p_id=0] trace=fakeService/fakeOperation/fakeResource *errored* tags={${extra}thread.id=${Thread.currentThread().id}, thread.name=${Thread.currentThread().name}}"
 
     where:
-    name << [DDTags.SERVICE_NAME, DDTags.RESOURCE_NAME, DDTags.SPAN_TYPE, "some.tag"]
+    name                 | extra             | tags
+    DDTags.SERVICE_NAME  | "some.tag=asdf, " | ["some.tag": "asdf", (DDTags.THREAD_NAME): Thread.currentThread().name, (DDTags.THREAD_ID): Thread.currentThread().id]
+    DDTags.RESOURCE_NAME | "some.tag=asdf, " | ["some.tag": "asdf", (DDTags.THREAD_NAME): Thread.currentThread().name, (DDTags.THREAD_ID): Thread.currentThread().id]
+    DDTags.SPAN_TYPE     | "some.tag=asdf, " | ["some.tag": "asdf", (DDTags.THREAD_NAME): Thread.currentThread().name, (DDTags.THREAD_ID): Thread.currentThread().id]
+    "some.tag"           | ""                | [(DDTags.THREAD_NAME): Thread.currentThread().name, (DDTags.THREAD_ID): Thread.currentThread().id]
   }
 
   def "special tags set certain values"() {