Deprecate Stats.setState, and throw an exception when it is called after getState. (#792)

* Throw IllegalStateException if setState is called after getState

* Deprecate Stats.setState

* Remove a test that has potential race condition.

* Remove Deprecated from impl

2 files changed, 18 insertions, 1 deletions

diff --git a/api/src/test/java/io/opencensus/stats/NoopStatsTest.java b/api/src/test/java/io/opencensus/stats/NoopStatsTest.java
index 9a52b7db..b3f81715 100644
--- a/api/src/test/java/io/opencensus/stats/NoopStatsTest.java
+++ b/api/src/test/java/io/opencensus/stats/NoopStatsTest.java
@@ -67,6 +67,7 @@ public final class NoopStatsTest {
   }
 
   @Test
+  @SuppressWarnings("deprecation")
   public void noopStatsComponent_SetState_IgnoresInput() {
     StatsComponent noopStatsComponent = NoopStats.newNoopStatsComponent();
     noopStatsComponent.setState(StatsCollectionState.ENABLED);
@@ -74,12 +75,24 @@ public final class NoopStatsTest {
   }
 
   @Test
+  @SuppressWarnings("deprecation")
   public void noopStatsComponent_SetState_DisallowsNull() {
     StatsComponent noopStatsComponent = NoopStats.newNoopStatsComponent();
     thrown.expect(NullPointerException.class);
     noopStatsComponent.setState(null);
   }
 
+  @Test
+  @SuppressWarnings("deprecation")
+  public void noopStatsComponent_DisallowsSetStateAfterGetState() {
+    StatsComponent noopStatsComponent = NoopStats.newNoopStatsComponent();
+    noopStatsComponent.setState(StatsCollectionState.DISABLED);
+    noopStatsComponent.getState();
+    thrown.expect(IllegalStateException.class);
+    thrown.expectMessage("State was already read, cannot set state.");
+    noopStatsComponent.setState(StatsCollectionState.ENABLED);
+  }
+
   // The NoopStatsRecorder should do nothing, so this test just checks that record doesn't throw an
   // exception.
   @Test
diff --git a/api/src/test/java/io/opencensus/stats/StatsTest.java b/api/src/test/java/io/opencensus/stats/StatsTest.java
index cc60d6c0..4219173a 100644
--- a/api/src/test/java/io/opencensus/stats/StatsTest.java
+++ b/api/src/test/java/io/opencensus/stats/StatsTest.java
@@ -69,13 +69,17 @@ public final class StatsTest {
   }
 
   @Test
+  @SuppressWarnings("deprecation")
   public void setState_IgnoresInput() {
     Stats.setState(StatsCollectionState.ENABLED);
     assertThat(Stats.getState()).isEqualTo(StatsCollectionState.DISABLED);
   }
 
-  @Test(expected = NullPointerException.class)
+  @Test
+  @SuppressWarnings("deprecation")
   public void setState_DisallowsNull() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("state");
     Stats.setState(null);
   }
 }