Suppress some Checker Framework warnings and add TODOs (issue #359).

Fixing these warnings will require significant refactoring.

4 files changed, 17 insertions, 4 deletions

diff --git a/api/src/main/java/io/opencensus/internal/NullnessUtils.java b/api/src/main/java/io/opencensus/internal/NullnessUtils.java
index ca3419cd..0301b798 100644
--- a/api/src/main/java/io/opencensus/internal/NullnessUtils.java
+++ b/api/src/main/java/io/opencensus/internal/NullnessUtils.java
@@ -17,15 +17,25 @@
 package io.opencensus.internal;
 
 import io.opencensus.common.Function;
+import javax.annotation.Nullable;
 
 /*>>>
 import org.checkerframework.checker.nullness.qual.KeyForBottom;
 */
 
-/** Utility methods for working around Checker Framework issues. */
+/**
+ * Utility methods for suppressing nullness warnings and working around Checker Framework issues.
+ */
 public final class NullnessUtils {
   private NullnessUtils() {}
 
+  /** Suppress warnings about a nullable value. */
+  // TODO(sebright): Try to remove all uses of this method.
+  @SuppressWarnings("nullness")
+  public static <T> T castNonNull(@Nullable T arg) {
+    return arg;
+  }
+
   /**
    * Work around https://github.com/typetools/checker-framework/issues/1712 by removing {@code ?
    * super} from a {@code Function}'s argument type.
diff --git a/api/src/main/java/io/opencensus/stats/Stats.java b/api/src/main/java/io/opencensus/stats/Stats.java
index d02780f8..0830313a 100644
--- a/api/src/main/java/io/opencensus/stats/Stats.java
+++ b/api/src/main/java/io/opencensus/stats/Stats.java
@@ -17,6 +17,7 @@
 package io.opencensus.stats;
 
 import com.google.common.annotations.VisibleForTesting;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.internal.Provider;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -26,7 +27,7 @@ public final class Stats {
   private static final Logger logger = Logger.getLogger(Stats.class.getName());
 
   private static final StatsComponent statsComponent =
-      loadStatsComponent(StatsComponent.class.getClassLoader());
+      loadStatsComponent(NullnessUtils.castNonNull(StatsComponent.class.getClassLoader()));
 
   /** Returns the default {@link StatsRecorder}. */
   public static StatsRecorder getStatsRecorder() {
diff --git a/api/src/main/java/io/opencensus/tags/Tags.java b/api/src/main/java/io/opencensus/tags/Tags.java
index 593312ae..f480714d 100644
--- a/api/src/main/java/io/opencensus/tags/Tags.java
+++ b/api/src/main/java/io/opencensus/tags/Tags.java
@@ -17,6 +17,7 @@
 package io.opencensus.tags;
 
 import com.google.common.annotations.VisibleForTesting;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.internal.Provider;
 import io.opencensus.tags.propagation.TagPropagationComponent;
 import java.util.logging.Level;
@@ -27,7 +28,7 @@ public final class Tags {
   private static final Logger logger = Logger.getLogger(Tags.class.getName());
 
   private static final TagsComponent tagsComponent =
-      loadTagsComponent(TagsComponent.class.getClassLoader());
+      loadTagsComponent(NullnessUtils.castNonNull(TagsComponent.class.getClassLoader()));
 
   private Tags() {}
 
diff --git a/api/src/main/java/io/opencensus/trace/Tracing.java b/api/src/main/java/io/opencensus/trace/Tracing.java
index c68f66ad..8e575265 100644
--- a/api/src/main/java/io/opencensus/trace/Tracing.java
+++ b/api/src/main/java/io/opencensus/trace/Tracing.java
@@ -18,6 +18,7 @@ package io.opencensus.trace;
 
 import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.common.Clock;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.internal.Provider;
 import io.opencensus.trace.config.TraceConfig;
 import io.opencensus.trace.export.ExportComponent;
@@ -29,7 +30,7 @@ import java.util.logging.Logger;
 public final class Tracing {
   private static final Logger logger = Logger.getLogger(Tracing.class.getName());
   private static final TraceComponent traceComponent =
-      loadTraceComponent(TraceComponent.class.getClassLoader());
+      loadTraceComponent(NullnessUtils.castNonNull(TraceComponent.class.getClassLoader()));
 
   /**
    * Returns the global {@link Tracer}.