Add JSR 305 nullability annotations.

pom.xml

@@ -156,7 +156,11 @@
         <artifactId>moshi</artifactId>
         <version>${moshi.version}</version>
       </dependency>
-
+      <dependency>
+        <groupId>com.google.code.findbugs</groupId>
+        <artifactId>jsr305</artifactId>
+        <version>3.0.2</version>
+      </dependency>
       <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>

retrofit-adapters/guava/pom.xml

@@ -23,6 +23,11 @@
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-adapters/guava/src/main/java/retrofit2/adapter/guava/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.adapter.guava;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-adapters/java8/pom.xml

@@ -23,6 +23,11 @@
       <artifactId>retrofit</artifactId>
       <version>${project.version}</version>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-adapters/java8/src/main/java/retrofit2/adapter/java8/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.adapter.java8;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-adapters/rxjava/pom.xml

@@ -23,6 +23,11 @@
       <groupId>io.reactivex</groupId>
       <artifactId>rxjava</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/Result.java

@@ -16,24 +16,27 @@
 package retrofit2.adapter.rxjava;
 
 import java.io.IOException;
+import javax.annotation.Nullable;
 import retrofit2.Response;
 
 /** The result of executing an HTTP request. */
 public final class Result<T> {
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static <T> Result<T> error(Throwable error) {
     if (error == null) throw new NullPointerException("error == null");
     return new Result<>(null, error);
   }
 
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static <T> Result<T> response(Response<T> response) {
     if (response == null) throw new NullPointerException("response == null");
     return new Result<>(response, null);
   }
 
-  private final Response<T> response;
-  private final Throwable error;
+  private final @Nullable Response<T> response;
+  private final @Nullable Throwable error;
 
-  private Result(Response<T> response, Throwable error) {
+  private Result(@Nullable Response<T> response, @Nullable Throwable error) {
     this.response = response;
     this.error = error;
   }
@@ -42,7 +45,7 @@ private Result(Response<T> response, Throwable error) {
    * The response received from executing an HTTP request. Only present when {@link #isError()} is
    * false, null otherwise.
    */
-  public Response<T> response() {
+  public @Nullable Response<T> response() {
     return response;
   }
 
@@ -54,7 +57,7 @@ public Response<T> response() {
    * remote server. Any other exception type indicates an unexpected failure and should be
    * considered fatal (configuration error, programming error, etc.).
    */
-  public Throwable error() {
+  public @Nullable Throwable error() {
     return error;
   }
 

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/RxJavaCallAdapter.java

@@ -16,6 +16,7 @@
 package retrofit2.adapter.rxjava;
 
 import java.lang.reflect.Type;
+import javax.annotation.Nullable;
 import retrofit2.Call;
 import retrofit2.CallAdapter;
 import retrofit2.Response;
@@ -25,15 +26,15 @@
 
 final class RxJavaCallAdapter<R> implements CallAdapter<R, Object> {
   private final Type responseType;
-  private final Scheduler scheduler;
+  private final @Nullable Scheduler scheduler;
   private final boolean isAsync;
   private final boolean isResult;
   private final boolean isBody;
   private final boolean isSingle;
   private final boolean isCompletable;
 
-  RxJavaCallAdapter(Type responseType, Scheduler scheduler, boolean isAsync, boolean isResult,
-      boolean isBody, boolean isSingle, boolean isCompletable) {
+  RxJavaCallAdapter(Type responseType, @Nullable Scheduler scheduler, boolean isAsync,
+      boolean isResult, boolean isBody, boolean isSingle, boolean isCompletable) {
     this.responseType = responseType;
     this.scheduler = scheduler;
     this.isAsync = isAsync;

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/RxJavaCallAdapterFactory.java

@@ -19,6 +19,7 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
+import javax.annotation.Nullable;
 import retrofit2.CallAdapter;
 import retrofit2.HttpException;
 import retrofit2.Response;
@@ -77,15 +78,16 @@ public static RxJavaCallAdapterFactory createAsync() {
    * Returns an instance which creates synchronous observables that
    * {@linkplain Observable#subscribeOn(Scheduler) subscribe on} {@code scheduler} by default.
    */
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static RxJavaCallAdapterFactory createWithScheduler(Scheduler scheduler) {
     if (scheduler == null) throw new NullPointerException("scheduler == null");
     return new RxJavaCallAdapterFactory(scheduler, false);
   }
 
-  private final Scheduler scheduler;
+  private final @Nullable Scheduler scheduler;
   private final boolean isAsync;
 
-  private RxJavaCallAdapterFactory(Scheduler scheduler, boolean isAsync) {
+  private RxJavaCallAdapterFactory(@Nullable Scheduler scheduler, boolean isAsync) {
     this.scheduler = scheduler;
     this.isAsync = isAsync;
   }

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.adapter.rxjava;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-adapters/rxjava2/pom.xml

@@ -23,6 +23,11 @@
       <groupId>io.reactivex.rxjava2</groupId>
       <artifactId>rxjava</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-adapters/rxjava2/src/main/java/retrofit2/adapter/rxjava2/Result.java

@@ -16,24 +16,27 @@
 package retrofit2.adapter.rxjava2;
 
 import java.io.IOException;
+import javax.annotation.Nullable;
 import retrofit2.Response;
 
 /** The result of executing an HTTP request. */
 public final class Result<T> {
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static <T> Result<T> error(Throwable error) {
     if (error == null) throw new NullPointerException("error == null");
     return new Result<>(null, error);
   }
 
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static <T> Result<T> response(Response<T> response) {
     if (response == null) throw new NullPointerException("response == null");
     return new Result<>(response, null);
   }
 
-  private final Response<T> response;
-  private final Throwable error;
+  private final @Nullable Response<T> response;
+  private final @Nullable Throwable error;
 
-  private Result(Response<T> response, Throwable error) {
+  private Result(@Nullable Response<T> response, @Nullable Throwable error) {
     this.response = response;
     this.error = error;
   }
@@ -42,7 +45,7 @@ private Result(Response<T> response, Throwable error) {
    * The response received from executing an HTTP request. Only present when {@link #isError()} is
    * false, null otherwise.
    */
-  public Response<T> response() {
+  public @Nullable Response<T> response() {
     return response;
   }
 
@@ -54,7 +57,7 @@ public Response<T> response() {
    * remote server. Any other exception type indicates an unexpected failure and should be
    * considered fatal (configuration error, programming error, etc.).
    */
-  public Throwable error() {
+  public @Nullable Throwable error() {
     return error;
   }
 

retrofit-adapters/rxjava2/src/main/java/retrofit2/adapter/rxjava2/RxJava2CallAdapter.java

@@ -19,13 +19,14 @@
 import io.reactivex.Observable;
 import io.reactivex.Scheduler;
 import java.lang.reflect.Type;
+import javax.annotation.Nullable;
 import retrofit2.Call;
 import retrofit2.CallAdapter;
 import retrofit2.Response;
 
 final class RxJava2CallAdapter<R> implements CallAdapter<R, Object> {
   private final Type responseType;
-  private final Scheduler scheduler;
+  private final @Nullable Scheduler scheduler;
   private final boolean isAsync;
   private final boolean isResult;
   private final boolean isBody;
@@ -34,8 +35,8 @@ final class RxJava2CallAdapter<R> implements CallAdapter<R, Object> {
   private final boolean isMaybe;
   private final boolean isCompletable;
 
-  RxJava2CallAdapter(Type responseType, Scheduler scheduler, boolean isAsync, boolean isResult,
-      boolean isBody, boolean isFlowable, boolean isSingle, boolean isMaybe,
+  RxJava2CallAdapter(Type responseType, @Nullable Scheduler scheduler, boolean isAsync,
+      boolean isResult, boolean isBody, boolean isFlowable, boolean isSingle, boolean isMaybe,
       boolean isCompletable) {
     this.responseType = responseType;
     this.scheduler = scheduler;

retrofit-adapters/rxjava2/src/main/java/retrofit2/adapter/rxjava2/RxJava2CallAdapterFactory.java

@@ -25,6 +25,7 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
+import javax.annotation.Nullable;
 import retrofit2.CallAdapter;
 import retrofit2.HttpException;
 import retrofit2.Response;
@@ -75,15 +76,16 @@ public static RxJava2CallAdapterFactory createAsync() {
    * Returns an instance which creates synchronous observables that
    * {@linkplain Observable#subscribeOn(Scheduler) subscribe on} {@code scheduler} by default.
    */
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static RxJava2CallAdapterFactory createWithScheduler(Scheduler scheduler) {
     if (scheduler == null) throw new NullPointerException("scheduler == null");
     return new RxJava2CallAdapterFactory(scheduler, false);
   }
 
-  private final Scheduler scheduler;
+  private final @Nullable Scheduler scheduler;
   private final boolean isAsync;
 
-  private RxJava2CallAdapterFactory(Scheduler scheduler, boolean isAsync) {
+  private RxJava2CallAdapterFactory(@Nullable Scheduler scheduler, boolean isAsync) {
     this.scheduler = scheduler;
     this.isAsync = isAsync;
   }

retrofit-adapters/rxjava2/src/main/java/retrofit2/adapter/rxjava2/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.adapter.rxjava2;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-converters/gson/pom.xml

@@ -23,6 +23,11 @@
       <groupId>com.google.code.gson</groupId>
       <artifactId>gson</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-converters/gson/src/main/java/retrofit2/converter/gson/GsonConverterFactory.java

@@ -46,14 +46,15 @@ public static GsonConverterFactory create() {
    * Create an instance using {@code gson} for conversion. Encoding to JSON and
    * decoding from JSON (when no charset is specified by a header) will use UTF-8.
    */
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static GsonConverterFactory create(Gson gson) {
+    if (gson == null) throw new NullPointerException("gson == null");
     return new GsonConverterFactory(gson);
   }
 
   private final Gson gson;
 
   private GsonConverterFactory(Gson gson) {
-    if (gson == null) throw new NullPointerException("gson == null");
     this.gson = gson;
   }
 

retrofit-converters/gson/src/main/java/retrofit2/converter/gson/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.converter.gson;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-converters/jackson/pom.xml

@@ -23,6 +23,11 @@
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-converters/jackson/src/main/java/retrofit2/converter/jackson/JacksonConverterFactory.java

@@ -41,14 +41,15 @@ public static JacksonConverterFactory create() {
   }
 
   /** Create an instance using {@code mapper} for conversion. */
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static JacksonConverterFactory create(ObjectMapper mapper) {
+    if (mapper == null) throw new NullPointerException("mapper == null");
     return new JacksonConverterFactory(mapper);
   }
 
   private final ObjectMapper mapper;
 
   private JacksonConverterFactory(ObjectMapper mapper) {
-    if (mapper == null) throw new NullPointerException("mapper == null");
     this.mapper = mapper;
   }
 

retrofit-converters/jackson/src/main/java/retrofit2/converter/jackson/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.converter.jackson;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-converters/moshi/pom.xml

@@ -23,6 +23,11 @@
       <groupId>com.squareup.moshi</groupId>
       <artifactId>moshi</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>

retrofit-converters/moshi/src/main/java/retrofit2/converter/moshi/MoshiConverterFactory.java

@@ -49,6 +49,7 @@ public static MoshiConverterFactory create() {
   }
 
   /** Create an instance using {@code moshi} for conversion. */
+  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
   public static MoshiConverterFactory create(Moshi moshi) {
     if (moshi == null) throw new NullPointerException("moshi == null");
     return new MoshiConverterFactory(moshi, false, false, false);

retrofit-converters/moshi/src/main/java/retrofit2/converter/moshi/package-info.java

@@ -0,0 +1,4 @@
+@ParametersAreNonnullByDefault
+package retrofit2.converter.moshi;
+
+import javax.annotation.ParametersAreNonnullByDefault;

retrofit-converters/protobuf/pom.xml

@@ -23,6 +23,11 @@
       <groupId>com.google.protobuf</groupId>
       <artifactId>protobuf-java</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
 
     <dependency>
       <groupId>junit</groupId>