Fix error prone warns (#2320)

* Adds `@SuppressWarnings("NarrowingCompoundAssignment")`

* Adds `@SuppressWarnings("TypeParameterUnusedInFormals")`

* Adds `@SuppressWarnings("JavaUtilDate")`

* Adds a limit to `String.split()`

* Add `error_prone_annotations` to the `pom.xml`

* Adds `@InlineMe(...)` to deprecated methods

* Adds `@SuppressWarnings("ImmutableEnumChecker")`

* Adds `@SuppressWarnings("ModifiedButNotUsed")`

* Adds `@SuppressWarnings("MixedMutabilityReturnType")`

* Removes an unused import

* Adds `requires` to `module-info.java`

* Adds ErrorProne `link` into `pom.xml`

* Remove unused imports

Removed from:
- ParseBenchmark

* Adds `@SuppressWarnings("EqualsGetClass")`

* Excludes from `proto` just the generated code.

Replaces `.*proto.*` with `.*/generated-test-sources/protobuf/.*` in such way will be excluded just the generated code and not the whole `proto` directory

* Removes an unused variable

Removes the `descriptor` variable because is unused.

* Fixes the `BadImport` warn into `ProtosWithAnnotationsTest`

* Fixes the `BadImport` warns into `ProtosWithAnnotationsTest`

* Enables ErrorProne in `gson/src/test.*`

Removes the `gson/src/test.*` path from the `-XepExcludedPaths` parameter of the ErrorProne plugin

* Fixes `UnusedVariable` warns

This commit fix all `UnusedVariable` warns given by ErrorProne in the `gson/src/test.*` path.

Some field is annotated with `@Keep` that means is used by reflection.
In some other case the record is annotated with `@SuppressWarnings("unused")`

* Fixes `JavaUtilDate` warns

This commit fix all `JavaUtilDate` warns given by ErrorProne in the `gson/src/test.*` path.

Classes/Methods are annotated with `@SuppressWarnings("JavaUtilDate")` because it's not possible use differente Date API.

* Fixes `EqualsGetClass` warns

This commit fix all `EqualsGetClass` warns given by ErrorProne in the `gson/src/test.*` path.

I have rewrite the `equals()` methods to use `instanceof`

* Replaces pattern matching for instanceof with casts

* Fixes `JdkObsolete` warns

This commit fix all `JdkObsolete` warns given by ErrorProne in the `gson/src/test.*` path.

In some cases I have replaced the obsolete JDK classes with the newest alternatives.  In other cases, I have added the `@SuppressWarnings("JdkObsolete")`

* Fixes `ClassCanBeStatic` warns

This commit fix all `ClassCanBeStatic` warns given by ErrorProne in the `gson/src/test.*` path.

I have added the `static` keyword, or I have added `@SuppressWarnings("ClassCanBeStatic")`

* Fixes `UndefinedEquals` warns

This commit fix all `UndefinedEquals` warns given by ErrorProne in the `gson/src/test.*` path.

I have added `@SuppressWarnings("UndefinedEquals")` or fixed the asserts

Note: In this commit I have also renamed a test from `testRawCollectionDeserializationNotAlllowed` to `testRawCollectionDeserializationNotAllowed`

* Fixes `GetClassOnEnum` warns

This commit fix all `GetClassOnEnum` warns given by ErrorProne in the `gson/src/test.*` path.

I have replaced the `.getClass()` with `.getDeclaringClass()`

* Fixes `ImmutableEnumChecker` warns

This commit fix all `ImmutableEnumChecker` warns given by ErrorProne in the `gson/src/test.*` path.

I have added the `final` keyword, or I have added the `@SuppressWarnings("ImmutableEnumChecker")` annotation

* Fixes `StaticAssignmentOfThrowable` warns

This commit fix all `StaticAssignmentOfThrowable` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `AssertionFailureIgnored` warns

This commit fix all `AssertionFailureIgnored` warns given by ErrorProne in the `gson/src/test.*` path.

I have added the `@SuppressWarnings("AssertionFailureIgnored")` annotation

* Fixes `ModifiedButNotUsed` warns

This commit fix all `ModifiedButNotUsed` warns given by ErrorProne in the `gson/src/test.*` path.

I have added the `@SuppressWarnings("ModifiedButNotUsed")` annotation

* Fixes `MissingSummary` warns

This commit fix all `MissingSummary` warns given by ErrorProne in the `gson/src/test.*` path.

I have remove the Javadoc `@author`

* Fixes `FloatingPointLiteralPrecision` warns

This commit fix all `FloatingPointLiteralPrecision` warns given by ErrorProne in the `gson/src/test.*` path.

I have added the `@SuppressWarnings("FloatingPointLiteralPrecision")` annotation

* Fixes `StringSplitter` warns

This commit fix all `StringSplitter` warns given by ErrorProne in the `gson/src/test.*` path.

I have replaced the `String.split(...)` with `Splitter`

* Fixes `EmptyCatch` warns

This commit fix all `EmptyCatch` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `UnicodeEscape` warns

This commit fix all `UnicodeEscape` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `EmptyBlockTag` warns

This commit fix all `EmptyBlockTag` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `LongFloatConversion` warns

This commit fix all `LongFloatConversion` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `LongDoubleConversion` warns

This commit fix all `LongDoubleConversion` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `TruthAssertExpected` warns

This commit fix all `TruthAssertExpected` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `UnusedMethod` warns

This commit fix all `UnusedMethod` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `UnusedTypeParameter` warns

This commit fix all `UnusedTypeParameter` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `CatchFail` warns

This commit fix all `CatchFail` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `MathAbsoluteNegative` warns

This commit fix all `MathAbsoluteNegative` warns given by ErrorProne in the `gson/src/test.*` path.

* Fixes `LoopOverCharArray` warns

This commit fix all `LoopOverCharArray` warns given by ErrorProne in the `gson/src/test.*` path.

`toCharArray` allocates a new array, using `charAt` is more efficient

* Fixes `HidingField` warns

This commit fix all `HidingField` warns given by ErrorProne in the `gson/src/test.*` path.

* Implements code review feedback

* Implements code review feedback

This commit implements some other code review feedback

* Enable ErrorProne in `extra`

Thi commit removes the `.*extras/src/test.*` path from the `-XepExcludedPaths` parameter of ErrorProne.

* Fix the `JavaUtilDate` warns

This commit fix all `JavaUtilDate` warns given by ErrorProne in the `extras/src/test.*` path.

* Implements code review feedback

* Removes redundant new-line

* Implements code review feedback

* Adds `JDK11` to run test with `--release 11`

* Revert "Adds `JDK11` to run test with `--release 11`"

This reverts commit a7cca38.

extras/src/test/java/com/google/gson/typeadapters/UtcDateTypeAdapterTest.java

@@ -29,6 +29,7 @@
 import java.util.TimeZone;
 import org.junit.Test;
 
+@SuppressWarnings("JavaUtilDate")
 public final class UtcDateTypeAdapterTest {
   private final Gson gson = new GsonBuilder()
     .registerTypeAdapter(Date.class, new UtcDateTypeAdapter())

gson/pom.xml

@@ -55,6 +55,12 @@
       <version>31.1-jre</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>com.google.errorprone</groupId>
+      <artifactId>error_prone_annotations</artifactId>
+      <version>2.18.0</version>
+      <optional>true</optional>
+    </dependency>
   </dependencies>
 
   <build>

gson/src/main/java/com/google/gson/Gson.java

@@ -1011,7 +1011,7 @@ public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException
    * @see #fromJson(String, Class)
    * @see #fromJson(String, TypeToken)
    */
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings({"unchecked", "TypeParameterUnusedInFormals"})
   public <T> T fromJson(String json, Type typeOfT) throws JsonSyntaxException {
     return (T) fromJson(json, TypeToken.get(typeOfT));
   }
@@ -1104,7 +1104,7 @@ public <T> T fromJson(Reader json, Class<T> classOfT) throws JsonSyntaxException
    * @see #fromJson(Reader, Class)
    * @see #fromJson(Reader, TypeToken)
    */
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings({"unchecked", "TypeParameterUnusedInFormals"})
   public <T> T fromJson(Reader json, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     return (T) fromJson(json, TypeToken.get(typeOfT));
   }
@@ -1183,7 +1183,7 @@ private static void assertFullConsumption(Object obj, JsonReader reader) {
    * @see #fromJson(Reader, Type)
    * @see #fromJson(JsonReader, TypeToken)
    */
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings({"unchecked", "TypeParameterUnusedInFormals"})
   public <T> T fromJson(JsonReader reader, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     return (T) fromJson(reader, TypeToken.get(typeOfT));
   }
@@ -1297,7 +1297,7 @@ public <T> T fromJson(JsonElement json, Class<T> classOfT) throws JsonSyntaxExce
    * @see #fromJson(JsonElement, Class)
    * @see #fromJson(JsonElement, TypeToken)
    */
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings({"unchecked", "TypeParameterUnusedInFormals"})
   public <T> T fromJson(JsonElement json, Type typeOfT) throws JsonSyntaxException {
     return (T) fromJson(json, TypeToken.get(typeOfT));
   }

gson/src/main/java/com/google/gson/JsonDeserializationContext.java

@@ -40,5 +40,6 @@ public interface JsonDeserializationContext {
    * @return An object of type typeOfT.
    * @throws JsonParseException if the parse tree does not contain expected data.
    */
+  @SuppressWarnings("TypeParameterUnusedInFormals")
   public <T> T deserialize(JsonElement json, Type typeOfT) throws JsonParseException;
 }

gson/src/main/java/com/google/gson/JsonParser.java

@@ -15,6 +15,7 @@
  */
 package com.google.gson;
 
+import com.google.errorprone.annotations.InlineMe;
 import com.google.gson.internal.Streams;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
@@ -111,18 +112,21 @@ public static JsonElement parseReader(JsonReader reader)
 
   /** @deprecated Use {@link JsonParser#parseString} */
   @Deprecated
+  @InlineMe(replacement = "JsonParser.parseString(json)", imports = "com.google.gson.JsonParser")
   public JsonElement parse(String json) throws JsonSyntaxException {
     return parseString(json);
   }
 
   /** @deprecated Use {@link JsonParser#parseReader(Reader)} */
   @Deprecated
+  @InlineMe(replacement = "JsonParser.parseReader(json)", imports = "com.google.gson.JsonParser")
   public JsonElement parse(Reader json) throws JsonIOException, JsonSyntaxException {
     return parseReader(json);
   }
 
   /** @deprecated Use {@link JsonParser#parseReader(JsonReader)} */
   @Deprecated
+  @InlineMe(replacement = "JsonParser.parseReader(json)", imports = "com.google.gson.JsonParser")
   public JsonElement parse(JsonReader json) throws JsonIOException, JsonSyntaxException {
     return parseReader(json);
   }

gson/src/main/java/com/google/gson/internal/JavaVersion.java

@@ -45,7 +45,7 @@ static int getMajorJavaVersion(String javaVersion) {
   // Parses both legacy 1.8 style and newer 9.0.4 style 
   private static int parseDotted(String javaVersion) {
     try {
-      String[] parts = javaVersion.split("[._]");
+      String[] parts = javaVersion.split("[._]", 3);
       int firstVer = Integer.parseInt(parts[0]);
       if (firstVer == 1 && parts.length > 1) {
         return Integer.parseInt(parts[1]);

gson/src/main/java/com/google/gson/internal/bind/ReflectiveTypeAdapterFactory.java

@@ -81,6 +81,7 @@ private boolean includeField(Field f, boolean serialize) {
   }
 
   /** first element holds the default name */
+  @SuppressWarnings("MixedMutabilityReturnType")
   private List<String> getFieldNames(Field f) {
     SerializedName annotation = f.getAnnotation(SerializedName.class);
     if (annotation == null) {

gson/src/main/java/com/google/gson/internal/bind/TreeTypeAdapter.java

@@ -174,8 +174,9 @@ private final class GsonContextImpl implements JsonSerializationContext, JsonDes
     @Override public JsonElement serialize(Object src, Type typeOfSrc) {
       return gson.toJsonTree(src, typeOfSrc);
     }
-    @SuppressWarnings("unchecked")
-    @Override public <R> R deserialize(JsonElement json, Type typeOfT) throws JsonParseException {
+    @Override
+    @SuppressWarnings({"unchecked", "TypeParameterUnusedInFormals"})
+    public <R> R deserialize(JsonElement json, Type typeOfT) throws JsonParseException {
       return gson.fromJson(json, typeOfT);
     }
   }

gson/src/main/java/com/google/gson/internal/sql/SqlDateTypeAdapter.java

@@ -36,6 +36,7 @@
  * this class state. DateFormat isn't thread safe either, so this class has
  * to synchronize its read and write methods.
  */
+@SuppressWarnings("JavaUtilDate")
 final class SqlDateTypeAdapter extends TypeAdapter<java.sql.Date> {
   static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
     @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal

gson/src/main/java/com/google/gson/internal/sql/SqlTimeTypeAdapter.java

@@ -37,6 +37,7 @@
  * this class state. DateFormat isn't thread safe either, so this class has
  * to synchronize its read and write methods.
  */
+@SuppressWarnings("JavaUtilDate")
 final class SqlTimeTypeAdapter extends TypeAdapter<Time> {
   static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
     @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal

gson/src/main/java/com/google/gson/internal/sql/SqlTimestampTypeAdapter.java

@@ -27,6 +27,7 @@
 import java.sql.Timestamp;
 import java.util.Date;
 
+@SuppressWarnings("JavaUtilDate")
 class SqlTimestampTypeAdapter extends TypeAdapter<Timestamp> {
   static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
     @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal

gson/src/main/java/com/google/gson/internal/sql/SqlTypesSupport.java

@@ -33,6 +33,7 @@
  * it is {@code false} all other constants will be {@code null} and
  * there will be no support for {@code java.sql} types.
  */
+@SuppressWarnings("JavaUtilDate")
 public final class SqlTypesSupport {
   /**
    * {@code true} if {@code java.sql} types are supported,

gson/src/main/java/com/google/gson/stream/JsonReader.java

@@ -1603,7 +1603,7 @@ private char readEscapeCharacter() throws IOException {
         throw syntaxError("Unterminated escape sequence");
       }
       // Equivalent to Integer.parseInt(stringPool.get(buffer, pos, 4), 16);
-      char result = 0;
+      int result = 0;
       for (int i = pos, end = i + 4; i < end; i++) {
         char c = buffer[i];
         result <<= 4;
@@ -1618,7 +1618,7 @@ private char readEscapeCharacter() throws IOException {
         }
       }
       pos += 4;
-      return result;
+      return (char) result;
 
     case 't':
       return '\t';

gson/src/main/java/module-info.java

@@ -24,6 +24,9 @@
   exports com.google.gson.reflect;
   exports com.google.gson.stream;
 
+  // Dependency on Error Prone Annotations
+  requires static com.google.errorprone.annotations;
+
   // Optional dependency on java.sql
   requires static java.sql;
 

gson/src/test/java/com/google/gson/CommentsTest.java

@@ -23,6 +23,8 @@
 import org.junit.Test;
 
 /**
+ * Tests that by default Gson accepts several forms of comments.
+ *
  * @author Jesse Wilson
  */
 public final class CommentsTest {

gson/src/test/java/com/google/gson/InnerClassExclusionStrategyTest.java

@@ -56,6 +56,7 @@ public void testIncludeStaticNestedClassField() throws Exception {
     assertThat(excluder.excludeField(f, true)).isFalse();
   }
 
+  @SuppressWarnings("ClassCanBeStatic")
   class InnerClass {
   }
 

gson/src/test/java/com/google/gson/JsonArrayTest.java

@@ -26,6 +26,8 @@
 import org.junit.Test;
 
 /**
+ * Tests handling of JSON arrays.
+ *
  * @author Jesse Wilson
  */
 public final class JsonArrayTest {

gson/src/test/java/com/google/gson/JsonNullTest.java

@@ -22,6 +22,8 @@
 import org.junit.Test;
 
 /**
+ * Tests handling of JSON nulls.
+ *
  * @author Jesse Wilson
  */
 public final class JsonNullTest {

gson/src/test/java/com/google/gson/ObjectTypeAdapterTest.java

@@ -111,7 +111,7 @@ public void testDeserializeDeeplyNestedObjects() throws IOException {
     assertThat(actualTimes).isEqualTo(times);
   }
 
-  @SuppressWarnings("unused")
+  @SuppressWarnings({"unused", "ClassCanBeStatic"})
   private class RuntimeType {
     Object a = 5;
     Object b = Arrays.asList(1, 2, null);

gson/src/test/java/com/google/gson/OverrideCoreTypeAdaptersTest.java

@@ -25,6 +25,8 @@
 import org.junit.Test;
 
 /**
+ * Tests handling of Core Type Adapters
+ *
  * @author Jesse Wilson
  */
 public class OverrideCoreTypeAdaptersTest {

gson/src/test/java/com/google/gson/ParameterizedTypeFixtures.java

@@ -16,6 +16,7 @@
 
 package com.google.gson;
 
+import com.google.common.base.Objects;
 import com.google.gson.internal.$Gson$Types;
 
 import com.google.gson.internal.Primitives;
@@ -35,7 +36,7 @@
  */
 public class ParameterizedTypeFixtures {
 
-  public static class MyParameterizedType<T> {
+  public static final class MyParameterizedType<T> {
     public final T value;
     public MyParameterizedType(T value) {
       this.value = value;
@@ -80,27 +81,16 @@ public int hashCode() {
       return value == null ? 0 : value.hashCode();
     }
 
-    @SuppressWarnings("unchecked")
     @Override
     public boolean equals(Object obj) {
       if (this == obj) {
         return true;
       }
-      if (obj == null) {
-        return false;
-      }
-      if (getClass() != obj.getClass()) {
-        return false;
-      }
-      MyParameterizedType<T> other = (MyParameterizedType<T>) obj;
-      if (value == null) {
-        if (other.value != null) {
-          return false;
-        }
-      } else if (!value.equals(other.value)) {
+      if (!(obj instanceof MyParameterizedType<?>)) {
         return false;
       }
-      return true;
+      MyParameterizedType<?> that = (MyParameterizedType<?>) obj;
+      return Objects.equal(getValue(), that.getValue());
     }
   }
 
@@ -112,8 +102,6 @@ public static class MyParameterizedTypeInstanceCreator<T>
      * This means that the fields of the same objects will be overwritten by Gson.
      * This is usually fine in tests since there we deserialize just once, but quite
      * dangerous in practice.
-     *
-     * @param instanceOfT
      */
     public MyParameterizedTypeInstanceCreator(T instanceOfT) {
       this.instanceOfT = instanceOfT;

gson/src/test/java/com/google/gson/VersionExclusionStrategyTest.java

@@ -18,6 +18,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
+import com.google.errorprone.annotations.Keep;
 import com.google.gson.annotations.Since;
 import com.google.gson.annotations.Until;
 import com.google.gson.internal.Excluder;
@@ -75,13 +76,15 @@ public void testOlderVersion() throws Exception {
   private static class MockClassSince {
 
     @Since(VERSION)
+    @Keep
     public final int someField = 0;
   }
 
   @Until(VERSION)
   private static class MockClassUntil {
 
     @Until(VERSION)
+    @Keep
     public final int someField = 0;
   }
 
@@ -91,6 +94,7 @@ private static class MockClassBoth {
 
     @Since(VERSION)
     @Until(VERSION + 2)
+    @Keep
     public final int someField = 0;
   }
 }

gson/src/test/java/com/google/gson/common/TestTypes.java

@@ -16,6 +16,7 @@
 
 package com.google.gson.common;
 
+import com.google.common.base.Objects;
 import com.google.gson.JsonDeserializationContext;
 import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
@@ -146,26 +147,18 @@ public int hashCode() {
     }
 
     @Override
-    public boolean equals(Object obj) {
-      if (this == obj)
+    public boolean equals(Object o) {
+      if (this == o) {
         return true;
-      if (obj == null)
-        return false;
-      if (getClass() != obj.getClass())
-        return false;
-      BagOfPrimitives other = (BagOfPrimitives) obj;
-      if (booleanValue != other.booleanValue)
-        return false;
-      if (intValue != other.intValue)
-        return false;
-      if (longValue != other.longValue)
-        return false;
-      if (stringValue == null) {
-        if (other.stringValue != null)
-          return false;
-      } else if (!stringValue.equals(other.stringValue))
+      }
+      if (!(o instanceof BagOfPrimitives)) {
         return false;
-      return true;
+      }
+      BagOfPrimitives that = (BagOfPrimitives) o;
+      return longValue == that.longValue
+          && getIntValue() == that.getIntValue()
+          && booleanValue == that.booleanValue
+          && Objects.equal(stringValue, that.stringValue);
     }
 
     @Override
@@ -233,7 +226,7 @@ public static class ClassWithNoFields {
     // Nothing here..
     @Override
     public boolean equals(Object other) {
-      return other.getClass() == ClassWithNoFields.class;
+      return other instanceof ClassWithNoFields;
     }
   }