Add nullness annotations to Preconditions.checkNotNull.

This commit also adds annotations to TextFormat that were required after the
change in checkNotNull.

4 files changed, 32 insertions, 9 deletions

diff --git a/api/src/main/java/io/opencensus/trace/propagation/TextFormat.java b/api/src/main/java/io/opencensus/trace/propagation/TextFormat.java
index eaa7bf00..66d018ce 100644
--- a/api/src/main/java/io/opencensus/trace/propagation/TextFormat.java
+++ b/api/src/main/java/io/opencensus/trace/propagation/TextFormat.java
@@ -24,6 +24,10 @@ import java.util.Collections;
 import java.util.List;
 import javax.annotation.Nullable;
 
+/*>>>
+import org.checkerframework.checker.nullness.qual.NonNull;
+*/
+
 /**
  * Injects and extracts {@link SpanContext trace identifiers} as text into carriers that travel
  * in-band across process boundaries. Identifiers are often encoded as messaging or RPC request
@@ -103,7 +107,8 @@ public abstract class TextFormat {
    * @param setter invoked for each propagation key to add or remove.
    * @since 0.11
    */
-  public abstract <C> void inject(SpanContext spanContext, C carrier, Setter<C> setter);
+  public abstract <C /*>>> extends @NonNull Object*/> void inject(
+      SpanContext spanContext, C carrier, Setter<C> setter);
 
   /**
    * Class that allows a {@code TextFormat} to set propagated fields into a carrier.
@@ -138,8 +143,8 @@ public abstract class TextFormat {
    * @throws SpanContextParseException if the input is invalid
    * @since 0.11
    */
-  public abstract <C> SpanContext extract(C carrier, Getter<C> getter)
-      throws SpanContextParseException;
+  public abstract <C /*>>> extends @NonNull Object*/> SpanContext extract(
+      C carrier, Getter<C> getter) throws SpanContextParseException;
 
   /**
    * Class that allows a {@code TextFormat} to read propagated fields from a carrier.
@@ -183,14 +188,15 @@ public abstract class TextFormat {
     }
 
     @Override
-    public <C> void inject(SpanContext spanContext, C carrier, Setter<C> setter) {
+    public <C /*>>> extends @NonNull Object*/> void inject(
+        SpanContext spanContext, C carrier, Setter<C> setter) {
       checkNotNull(spanContext, "spanContext");
       checkNotNull(carrier, "carrier");
       checkNotNull(setter, "setter");
     }
 
     @Override
-    public <C> SpanContext extract(C carrier, Getter<C> getter) {
+    public <C /*>>> extends @NonNull Object*/> SpanContext extract(C carrier, Getter<C> getter) {
       checkNotNull(carrier, "carrier");
       checkNotNull(getter, "getter");
       return SpanContext.INVALID;
diff --git a/checker-framework/stubs/guava.astub b/checker-framework/stubs/guava.astub
index ff7a795d..42ed251e 100644
--- a/checker-framework/stubs/guava.astub
+++ b/checker-framework/stubs/guava.astub
@@ -1,4 +1,5 @@
 import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 package com.google.common.base;
@@ -7,3 +8,7 @@ class Strings {
   @EnsuresNonNullIf(result = false, expression = "#1")
   static boolean isNullOrEmpty(@Nullable String str);
 }
+
+class Preconditions {
+  static <T extends @NonNull Object> T checkNotNull(T reference, @Nullable Object errorMessage);
+}
diff --git a/contrib/http_util/src/main/java/io/opencensus/contrib/http/util/CloudTraceFormat.java b/contrib/http_util/src/main/java/io/opencensus/contrib/http/util/CloudTraceFormat.java
index a6acc985..70811ee7 100644
--- a/contrib/http_util/src/main/java/io/opencensus/contrib/http/util/CloudTraceFormat.java
+++ b/contrib/http_util/src/main/java/io/opencensus/contrib/http/util/CloudTraceFormat.java
@@ -31,6 +31,10 @@ import java.nio.ByteBuffer;
 import java.util.Collections;
 import java.util.List;
 
+/*>>>
+import org.checkerframework.checker.nullness.qual.NonNull;
+*/
+
 /**
  * Implementation of the "X-Cloud-Trace-Context" format, defined by the Google Cloud Trace.
  *
@@ -80,7 +84,8 @@ final class CloudTraceFormat extends TextFormat {
   }
 
   @Override
-  public <C> void inject(SpanContext spanContext, C carrier, Setter<C> setter) {
+  public <C /*>>> extends @NonNull Object*/> void inject(
+      SpanContext spanContext, C carrier, Setter<C> setter) {
     checkNotNull(spanContext, "spanContext");
     checkNotNull(setter, "setter");
     checkNotNull(carrier, "carrier");
@@ -96,7 +101,8 @@ final class CloudTraceFormat extends TextFormat {
   }
 
   @Override
-  public <C> SpanContext extract(C carrier, Getter<C> getter) throws SpanContextParseException {
+  public <C /*>>> extends @NonNull Object*/> SpanContext extract(C carrier, Getter<C> getter)
+      throws SpanContextParseException {
     checkNotNull(carrier, "carrier");
     checkNotNull(getter, "getter");
     try {
diff --git a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
index 3a9f2420..67c66ea9 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
@@ -29,6 +29,10 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
+/*>>>
+import org.checkerframework.checker.nullness.qual.NonNull;
+*/
+
 /**
  * Implementation of the B3 propagation protocol. See <a
  * href=https://github.com/openzipkin/b3-propagation>b3-propagation</a>.
@@ -58,7 +62,8 @@ final class B3Format extends TextFormat {
   }
 
   @Override
-  public <C> void inject(SpanContext spanContext, C carrier, Setter<C> setter) {
+  public <C /*>>> extends @NonNull Object*/> void inject(
+      SpanContext spanContext, C carrier, Setter<C> setter) {
     checkNotNull(spanContext, "spanContext");
     checkNotNull(setter, "setter");
     checkNotNull(carrier, "carrier");
@@ -70,7 +75,8 @@ final class B3Format extends TextFormat {
   }
 
   @Override
-  public <C> SpanContext extract(C carrier, Getter<C> getter) throws SpanContextParseException {
+  public <C /*>>> extends @NonNull Object*/> SpanContext extract(C carrier, Getter<C> getter)
+      throws SpanContextParseException {
     checkNotNull(carrier, "carrier");
     checkNotNull(getter, "getter");
     try {