Add reftypes field generator option.

This option generates fields as reference types, and serializes
based on nullness.

Change-Id: Ic32e0eebff59d14016cc9a19e15a9bb08ae0bba5
Signed-off-by: Brian Duff <bduff@google.com>

9 files changed, 287 insertions, 29 deletions

diff --git a/java/README.txt b/java/README.txt
index e2e698e..adc1972 100644
--- a/java/README.txt
+++ b/java/README.txt
@@ -487,34 +487,67 @@ java_nano_generate_has={true,false} (default: false)
   many cases reading the default works and determining whether the
   field was received over the wire is irrelevant.
 
-optional_field_style={default,accessors} (default: default)
-  Defines the style of the generated code for _optional_ fields only.
+optional_field_style={default,accessors,reftypes} (default: default)
+  Defines the style of the generated code for fields.
+
+  * default *
+
   In the default style, optional fields translate into public mutable
   Java fields, and the serialization process is as discussed in the
-  "IMPORTANT" section above. When set to 'accessors', each optional
-  field is encapsulated behind 4 accessors, namely get<fieldname>(),
-  set<fieldname>(), has<fieldname>() and clear<fieldname>() methods,
-  with the standard semantics. The hazzer's return value determines
-  whether a field is serialized, so this style is useful when you need
-  to serialize a field with the default value, or check if a field has
-  been explicitly set to its default value from the wire.
-
-  Required fields are still translated to one public mutable Java
-  field each, and repeated fields are still translated to arrays. No
-  accessors are generated for them.
-
-  optional_field_style=accessors cannot be used together with
-  java_nano_generate_has=true. If you need the 'has' flag for any
-  required field (you have no reason to), you can only use
-  java_nano_generate_has=true.
+  "IMPORTANT" section above. 
 
-  IMPORTANT: When using the 'accessor' style, ProGuard should always
+  * accessors *
+
+  When set to 'accessors', each optional field is encapsulated behind
+  4 accessors, namely get<fieldname>(), set<fieldname>(), has<fieldname>()
+  and clear<fieldname>() methods, with the standard semantics. The hazzer's
+  return value determines whether a field is serialized, so this style is
+  useful when you need to serialize a field with the default value, or check
+  if a field has been explicitly set to its default value from the wire.
+
+  In the 'accessors' style, required fields are still translated to one
+  public mutable Java field each, and repeated fields are still translated
+  to arrays. No accessors are generated for them.
+
+  IMPORTANT: When using the 'accessors' style, ProGuard should always
   be enabled with optimization (don't use -dontoptimize) and allowing
   access modification (use -allowaccessmodification). This removes the
   unused accessors and maybe inline the rest at the call sites,
   reducing the final code size.
   TODO(maxtroy): find ProGuard config that would work the best.
 
+  * reftypes *
+
+  When set to 'reftypes', each proto field is generated as a public Java
+  field. For primitive types, these fields use the Java reference types
+  such as java.lang.Integer instead of primitive types such as int.
+
+  In the 'reftypes' style, fields are initialized to null (or empty
+  arrays for repeated fields), and their default values are not available.
+  They are serialized over the wire based on equality to null.
+
+  The 'reftypes' mode has some additional cost due to autoboxing and usage
+  of reference types. In practice, many boxed types are cached, and so don't
+  result in object creation. However, references do take slightly more memory
+  than primitives.
+
+  The 'reftypes' mode is useful when you want to be able to serialize fields
+  with default values, or check if a field has been explicitly set to the
+  default over the wire without paying the extra method cost of the
+  'accessors' mode.
+
+  Note that if you attempt to write null to a required field in the reftypes
+  mode, serialization of the proto will cause a NullPointerException. This is
+  an intentional indicator that you must set required fields.
+
+
+  NOTE
+  optional_field_style=accessors or reftypes cannot be used together with
+  java_nano_generate_has=true. If you need the 'has' flag for any
+  required field (you have no reason to), you can only use
+  java_nano_generate_has=true.
+
+
 To use nano protobufs:
 
 - Link with the generated jar file
diff --git a/java/pom.xml b/java/pom.xml
index a34c164..1f43670 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -171,6 +171,12 @@
                   <arg value="../src/google/protobuf/unittest_enum_class_nano.proto" />
                   <arg value="../src/google/protobuf/unittest_enum_class_multiple_nano.proto" />
                 </exec>
+                <exec executable="../src/protoc">
+                  <arg value="--javanano_out=optional_field_style=reftypes:target/generated-test-sources" />
+                  <arg value="--proto_path=../src" />
+                  <arg value="--proto_path=src/test/java" />
+                  <arg value="../src/google/protobuf/unittest_reference_types_nano.proto" />
+                </exec>
               </tasks>
               <testSourceRoot>target/generated-test-sources</testSourceRoot>
               <!--testSourceRoot>target/generated-test-sources/opt-space</testSourceRoot-->
diff --git a/java/src/test/java/com/google/protobuf/NanoTest.java b/java/src/test/java/com/google/protobuf/NanoTest.java
index ca0bcda..4f2ac3f 100644
--- a/java/src/test/java/com/google/protobuf/NanoTest.java
+++ b/java/src/test/java/com/google/protobuf/NanoTest.java
@@ -48,6 +48,7 @@ import com.google.protobuf.nano.NanoAccessorsOuterClass.TestNanoAccessors;
 import com.google.protobuf.nano.NanoHasOuterClass.TestAllTypesNanoHas;
 import com.google.protobuf.nano.NanoOuterClass;
 import com.google.protobuf.nano.NanoOuterClass.TestAllTypesNano;
+import com.google.protobuf.nano.NanoReferenceTypes;
 import com.google.protobuf.nano.UnittestImportNano;
 import com.google.protobuf.nano.UnittestMultipleNano;
 import com.google.protobuf.nano.UnittestRecursiveNano.RecursiveMessageNano;
@@ -2624,6 +2625,67 @@ public class NanoTest extends TestCase {
     assertEquals(123, msg.synchronized_);
   }
 
+  public void testReferenceTypesForPrimitives() throws Exception {
+    NanoReferenceTypes.TestAllTypesNano message = new NanoReferenceTypes.TestAllTypesNano();
+
+    // Base check - when nothing is set, we serialize nothing.
+    assertHasWireData(message, false);
+
+    message.defaultBool = true;
+    assertHasWireData(message, true);
+
+    message.defaultBool = false;
+    assertHasWireData(message, true);
+
+    message.defaultBool = null;
+    assertHasWireData(message, false);
+
+    message.defaultInt32 = 5;
+    assertHasWireData(message, true);
+
+    message.defaultInt32 = null;
+    assertHasWireData(message, false);
+
+    message.defaultInt64 = 123456L;
+    assertHasWireData(message, true);
+
+    message.defaultInt64 = null;
+    assertHasWireData(message, false);
+
+    message.defaultFloat = 1f;
+    assertHasWireData(message, true);
+
+    message.defaultFloat = null;
+    assertHasWireData(message, false);
+
+    message.defaultDouble = 2.1;
+    assertHasWireData(message, true);
+
+    message.defaultDouble = null;
+    assertHasWireData(message, false);
+
+    message.defaultString = "hello";
+    assertHasWireData(message, true);
+
+    message.defaultString = null;
+    assertHasWireData(message, false);
+
+    message.defaultBytes = new byte[] { 1, 2, 3 };
+    assertHasWireData(message, true);
+
+    message.defaultBytes = null;
+    assertHasWireData(message, false);
+  }
+
+  private void assertHasWireData(MessageNano message, boolean expected) {
+    int wireLength = MessageNano.toByteArray(message).length;
+    if (expected) {
+      assertFalse(wireLength == 0);
+    } else {
+      assertEquals(0, wireLength);
+    }
+  }
+
   private <T> List<T> list(T first, T... remaining) {
     List<T> list = new ArrayList<T>();
     list.add(first);
diff --git a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
index b30b9fb..acb8dc2 100644
--- a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
@@ -58,8 +58,16 @@ void SetEnumVariables(const Params& params,
   (*variables)["capitalized_name"] =
     RenameJavaKeywords(UnderscoresToCapitalizedCamelCase(descriptor));
   (*variables)["number"] = SimpleItoa(descriptor->number());
-  (*variables)["type"] = "int";
-  (*variables)["default"] = DefaultValue(params, descriptor);
+  if (params.use_reference_types_for_primitives()
+      && !descriptor->is_repeated()) {
+    (*variables)["type"] = "java.lang.Integer";
+    (*variables)["default"] = "null";
+  } else {
+    (*variables)["type"] = "int";
+    (*variables)["default"] = DefaultValue(params, descriptor);
+  }
+  (*variables)["repeated_default"] =
+      "com.google.protobuf.nano.WireFormatNano.EMPTY_INT_ARRAY";
   (*variables)["tag"] = SimpleItoa(internal::WireFormat::MakeTag(descriptor));
   (*variables)["tag_size"] = SimpleItoa(
       internal::WireFormat::TagSize(descriptor->number(), descriptor->type()));
@@ -81,7 +89,7 @@ EnumFieldGenerator::~EnumFieldGenerator() {}
 void EnumFieldGenerator::
 GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
-    "public int $name$ = $default$;\n");
+    "public $type$ $name$ = $default$;\n");
 
   if (params_.generate_has()) {
     printer->Print(variables_,
@@ -233,7 +241,7 @@ RepeatedEnumFieldGenerator::~RepeatedEnumFieldGenerator() {}
 void RepeatedEnumFieldGenerator::
 GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
-    "public int[] $name$ = com.google.protobuf.nano.WireFormatNano.EMPTY_INT_ARRAY;\n");
+    "public $type$[] $name$ = $repeated_default$;\n");
   if (descriptor_->options().packed()) {
     printer->Print(variables_,
       "private int $name$MemoizedSerializedSize;\n");
@@ -243,7 +251,7 @@ GenerateMembers(io::Printer* printer) const {
 void RepeatedEnumFieldGenerator::
 GenerateClearCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "$name$ = com.google.protobuf.nano.WireFormatNano.EMPTY_INT_ARRAY;\n");
+    "$name$ = $repeated_default$;\n");
 }
 
 void RepeatedEnumFieldGenerator::
diff --git a/src/google/protobuf/compiler/javanano/javanano_generator.cc b/src/google/protobuf/compiler/javanano/javanano_generator.cc
index 8ba3f50..48c3a21 100644
--- a/src/google/protobuf/compiler/javanano/javanano_generator.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_generator.cc
@@ -124,15 +124,21 @@ bool JavaNanoGenerator::Generate(const FileDescriptor* file,
       params.set_java_enum_style(options[i].second == "java");
     } else if (options[i].first == "optional_field_style") {
       params.set_optional_field_accessors(options[i].second == "accessors");
+      params.set_use_reference_types_for_primitives(options[i].second == "reftypes");
     } else {
       *error = "Ignore unknown javanano generator option: " + options[i].first;
     }
   }
 
   // Check illegal parameter combinations
-  if (params.generate_has() && params.optional_field_accessors()) {
+  // Note: the enum-like optional_field_style generator param ensures
+  // that we can never have illegal combinations of field styles
+  // (e.g. reftypes and accessors can't be on at the same time).
+  if (params.generate_has()
+      && (params.optional_field_accessors()
+          || params.use_reference_types_for_primitives())) {
     error->assign("java_nano_generate_has=true cannot be used in conjunction"
-        " with optional_field_style=accessors");
+        " with optional_field_style=accessors or optional_field_style=reftypes");
     return false;
   }
 
diff --git a/src/google/protobuf/compiler/javanano/javanano_helpers.cc b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
index c424165..ed6dbd7 100644
--- a/src/google/protobuf/compiler/javanano/javanano_helpers.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
@@ -357,6 +357,10 @@ string DefaultValue(const Params& params, const FieldDescriptor* field) {
     return EmptyArrayName(params, field);
   }
 
+  if (params.use_reference_types_for_primitives()) {
+    return "null";
+  }
+
   // Switch on cpp_type since we need to know which default_value_* method
   // of FieldDescriptor to call.
   switch (field->cpp_type()) {
diff --git a/src/google/protobuf/compiler/javanano/javanano_params.h b/src/google/protobuf/compiler/javanano/javanano_params.h
index 5be5ff9..6e5379c 100644
--- a/src/google/protobuf/compiler/javanano/javanano_params.h
+++ b/src/google/protobuf/compiler/javanano/javanano_params.h
@@ -60,6 +60,7 @@ class Params {
   bool generate_has_;
   bool java_enum_style_;
   bool optional_field_accessors_;
+  bool use_reference_types_for_primitives_;
 
  public:
   Params(const string & base_name) :
@@ -69,7 +70,8 @@ class Params {
     store_unknown_fields_(false),
     generate_has_(false),
     java_enum_style_(false),
-    optional_field_accessors_(false) {
+    optional_field_accessors_(false),
+    use_reference_types_for_primitives_(false) {
   }
 
   const string& base_name() const {
@@ -177,6 +179,13 @@ class Params {
   bool optional_field_accessors() const {
     return optional_field_accessors_;
   }
+
+  void set_use_reference_types_for_primitives(bool value) {
+    use_reference_types_for_primitives_ = value;
+  }
+  bool use_reference_types_for_primitives() const {
+    return use_reference_types_for_primitives_;
+  }
 };
 
 }  // namespace javanano
diff --git a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
index 69664d3..ec93cef 100644
--- a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
@@ -245,7 +245,12 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor, const Params param
   (*variables)["capitalized_name"] =
     RenameJavaKeywords(UnderscoresToCapitalizedCamelCase(descriptor));
   (*variables)["number"] = SimpleItoa(descriptor->number());
-  (*variables)["type"] = PrimitiveTypeName(GetJavaType(descriptor));
+  if (params.use_reference_types_for_primitives()
+      && !descriptor->is_repeated()) {
+    (*variables)["type"] = BoxedPrimitiveTypeName(GetJavaType(descriptor));
+  } else {
+    (*variables)["type"] = PrimitiveTypeName(GetJavaType(descriptor));
+  }
   (*variables)["default"] = DefaultValue(params, descriptor);
   (*variables)["default_constant"] = FieldDefaultConstantName(descriptor);
   // For C++-string types (string and bytes), we might need to have
@@ -254,7 +259,8 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor, const Params param
   // once into a "private static final" field and re-use that from
   // then on.
   if (descriptor->cpp_type() == FieldDescriptor::CPPTYPE_STRING &&
-      !descriptor->default_value_string().empty()) {
+      !descriptor->default_value_string().empty() &&
+      !params.use_reference_types_for_primitives()) {
     string default_value;
     if (descriptor->type() == FieldDescriptor::TYPE_BYTES) {
       default_value = strings::Substitute(
@@ -315,6 +321,7 @@ GenerateMembers(io::Printer* printer) const {
     printer->Print(variables_,
       "private static final $type$ $default_constant$ = $default_constant_value$;\n");
   }
+
   printer->Print(variables_,
     "public $type$ $name$ = $default_copy_if_needed$;\n");
 
@@ -348,6 +355,13 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void PrimitiveFieldGenerator::
 GenerateSerializationConditional(io::Printer* printer) const {
+  if (params_.use_reference_types_for_primitives()) {
+    // For reference type mode, serialize based on equality
+    // to null.
+    printer->Print(variables_,
+      "if (this.$name$ != null) {\n");
+    return;
+  }
   if (params_.generate_has()) {
     printer->Print(variables_,
       "if (has$capitalized_name$ || ");
diff --git a/src/google/protobuf/unittest_reference_types_nano.proto b/src/google/protobuf/unittest_reference_types_nano.proto
new file mode 100644
index 0000000..2b24615
--- /dev/null
+++ b/src/google/protobuf/unittest_reference_types_nano.proto
@@ -0,0 +1,116 @@
+package protobuf_unittest;
+
+option java_package = "com.google.protobuf.nano";
+option java_outer_classname = "NanoReferenceTypes";
+
+message TestAllTypesNano {
+
+  enum NestedEnum {
+    FOO = 1;
+    BAR = 2;
+    BAZ = 3;
+  }
+
+  message NestedMessage {
+    optional int32 foo = 1;
+  }
+
+  // Singular
+  optional    int32 optional_int32    =  1;
+  optional    int64 optional_int64    =  2;
+  optional   uint32 optional_uint32   =  3;
+  optional   uint64 optional_uint64   =  4;
+  optional   sint32 optional_sint32   =  5;
+  optional   sint64 optional_sint64   =  6;
+  optional  fixed32 optional_fixed32  =  7;
+  optional  fixed64 optional_fixed64  =  8;
+  optional sfixed32 optional_sfixed32 =  9;
+  optional sfixed64 optional_sfixed64 = 10;
+  optional    float optional_float    = 11;
+  optional   double optional_double   = 12;
+  optional     bool optional_bool     = 13;
+  optional   string optional_string   = 14;
+  optional    bytes optional_bytes    = 15;
+
+  optional group OptionalGroup = 16 {
+    optional int32 a = 17;
+  }
+
+  optional NestedMessage      optional_nested_message  = 18;
+
+  optional NestedEnum      optional_nested_enum     = 21;
+
+  optional string optional_string_piece = 24 [ctype=STRING_PIECE];
+  optional string optional_cord = 25 [ctype=CORD];
+
+  // Repeated
+  repeated    int32 repeated_int32    = 31;
+  repeated    int64 repeated_int64    = 32;
+  repeated   uint32 repeated_uint32   = 33;
+  repeated   uint64 repeated_uint64   = 34;
+  repeated   sint32 repeated_sint32   = 35;
+  repeated   sint64 repeated_sint64   = 36;
+  repeated  fixed32 repeated_fixed32  = 37;
+  repeated  fixed64 repeated_fixed64  = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated    float repeated_float    = 41;
+  repeated   double repeated_double   = 42;
+  repeated     bool repeated_bool     = 43;
+  repeated   string repeated_string   = 44;
+  repeated    bytes repeated_bytes    = 45;
+
+  repeated group RepeatedGroup = 46 {
+    optional int32 a = 47;
+  }
+
+  repeated NestedMessage      repeated_nested_message  = 48;
+
+  repeated NestedEnum      repeated_nested_enum  = 51;
+
+  repeated string repeated_string_piece = 54 [ctype=STRING_PIECE];
+  repeated string repeated_cord = 55 [ctype=CORD];
+
+  // Repeated packed
+  repeated    int32 repeated_packed_int32    = 87 [packed=true];
+  repeated sfixed64 repeated_packed_sfixed64 = 88 [packed=true];
+
+  repeated NestedEnum repeated_packed_nested_enum  = 89 [packed=true];
+
+  // Singular with defaults
+  optional    int32 default_int32    = 61 [default =  41    ];
+  optional    int64 default_int64    = 62 [default =  42    ];
+  optional   uint32 default_uint32   = 63 [default =  43    ];
+  optional   uint64 default_uint64   = 64 [default =  44    ];
+  optional   sint32 default_sint32   = 65 [default = -45    ];
+  optional   sint64 default_sint64   = 66 [default =  46    ];
+  optional  fixed32 default_fixed32  = 67 [default =  47    ];
+  optional  fixed64 default_fixed64  = 68 [default =  48    ];
+  optional sfixed32 default_sfixed32 = 69 [default =  49    ];
+  optional sfixed64 default_sfixed64 = 70 [default = -50    ];
+  optional    float default_float    = 71 [default =  51.5  ];
+  optional   double default_double   = 72 [default =  52e3  ];
+  optional     bool default_bool     = 73 [default = true   ];
+  optional   string default_string   = 74 [default = "hello"];
+  optional    bytes default_bytes    = 75 [default = "world"];
+
+
+  optional  float default_float_inf      = 97  [default =  inf];
+  optional  float default_float_neg_inf  = 98  [default = -inf];
+  optional  float default_float_nan      = 99  [default =  nan];
+  optional double default_double_inf     = 100 [default =  inf];
+  optional double default_double_neg_inf = 101 [default = -inf];
+  optional double default_double_nan     = 102 [default =  nan];
+
+}
+
+message ForeignMessageNano {
+  optional int32 c = 1;
+}
+
+enum ForeignEnumNano {
+  FOREIGN_NANO_FOO = 4;
+  FOREIGN_NANO_BAR = 5;
+  FOREIGN_NANO_BAZ = 6;
+}
+