Allow for ref-type arrays containing null elements.

Strip the null elements out before serializing the array.
This is helpful in the cases where the user wants to construct
an array of an inexact size for serialization. For example:
User constructs array of size 5 because they anticipate adding
more than 1 element before serialization. Only 3 get added, so
the array looks like [Obj, Obj, Obj, null, null]. This would
curently crash without this CL.

All repeated fields of ref-type elements can contain null
elements: repeated strings, repeated bytes, and repeated
messages/groups.

Change-Id: I117391c868c9a436536d70d6151780e9cc7e8227

Conflicts:
	src/google/protobuf/compiler/javanano/javanano_message_field.cc

java/src/test/java/com/google/protobuf/NanoTest.java

@@ -2724,8 +2724,6 @@ public class NanoTest extends TestCase {
     // Complete equality for messages with accessors:
     TestNanoAccessors f = createMessageWithAccessorsForHashCodeEqualsTest();
     TestNanoAccessors fEquivalent = createMessageWithAccessorsForHashCodeEqualsTest();
-    System.out.println("equals: " + f.equals(fEquivalent));
-    System.out.println("hashCode: " + f.hashCode() + " vs " + fEquivalent.hashCode());
 
     // If using accessors, explicitly setting a field to its default value
     // should make the message different.
@@ -2965,6 +2963,37 @@ public class NanoTest extends TestCase {
     assertEquals(TestAllTypesNano.BAR, message.repeatedPackedNestedEnum[1]);
   }
 
+  public void testNullRepeatedFieldElements() throws Exception {
+    // Check that serialization with null array elements doesn't NPE.
+    String string1 = "1";
+    String string2 = "2";
+    byte[] bytes1 = {3, 4};
+    byte[] bytes2 = {5, 6};
+    TestAllTypesNano.NestedMessage msg1 = new TestAllTypesNano.NestedMessage();
+    msg1.bb = 7;
+    TestAllTypesNano.NestedMessage msg2 = new TestAllTypesNano.NestedMessage();
+    msg2.bb = 8;
+
+    TestAllTypesNano message = new TestAllTypesNano();
+    message.repeatedString = new String[] {null, string1, string2};
+    message.repeatedBytes = new byte[][] {bytes1, null, bytes2};
+    message.repeatedNestedMessage = new TestAllTypesNano.NestedMessage[] {msg1, msg2, null};
+    message.repeatedGroup = new TestAllTypesNano.RepeatedGroup[] {null, null, null};
+
+    byte[] serialized = MessageNano.toByteArray(message); // should not NPE
+    TestAllTypesNano deserialized = MessageNano.mergeFrom(new TestAllTypesNano(), serialized);
+    assertEquals(2, deserialized.repeatedString.length);
+    assertEquals(string1, deserialized.repeatedString[0]);
+    assertEquals(string2, deserialized.repeatedString[1]);
+    assertEquals(2, deserialized.repeatedBytes.length);
+    assertTrue(Arrays.equals(bytes1, deserialized.repeatedBytes[0]));
+    assertTrue(Arrays.equals(bytes2, deserialized.repeatedBytes[1]));
+    assertEquals(2, deserialized.repeatedNestedMessage.length);
+    assertEquals(msg1.bb, deserialized.repeatedNestedMessage[0].bb);
+    assertEquals(msg2.bb, deserialized.repeatedNestedMessage[1].bb);
+    assertEquals(0, deserialized.repeatedGroup.length);
+  }
+
   public void testRepeatedMerge() throws Exception {
     // Check that merging repeated fields cause the arrays to expand with
     // new data.

src/google/protobuf/compiler/javanano/javanano_message_field.cc

@@ -304,9 +304,12 @@ GenerateMergingCode(io::Printer* printer) const {
 void RepeatedMessageFieldGenerator::
 GenerateSerializationCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "if (this.$name$ != null) {\n"
-    "  for ($type$ element : this.$name$) {\n"
-    "    output.write$group_or_message$($number$, element);\n"
+    "if (this.$name$ != null && this.$name$.length > 0) {\n"
+    "  for (int i = 0; i < this.$name$.length; i++) {\n"
+    "    $type$ element = this.$name$[i];\n"
+    "    if (element != null) {\n"
+    "      output.write$group_or_message$($number$, element);\n"
+    "    }\n"
     "  }\n"
     "}\n");
 }
@@ -314,10 +317,13 @@ GenerateSerializationCode(io::Printer* printer) const {
 void RepeatedMessageFieldGenerator::
 GenerateSerializedSizeCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "if (this.$name$ != null) {\n"
-    "  for ($type$ element : this.$name$) {\n"
-    "    size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
-    "      .compute$group_or_message$Size($number$, element);\n"
+    "if (this.$name$ != null && this.$name$.length > 0) {\n"
+    "  for (int i = 0; i < this.$name$.length; i++) {\n"
+    "    $type$ element = this.$name$[i];\n"
+    "    if (element != null) {\n"
+    "      size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
+    "        .compute$group_or_message$Size($number$, element);\n"
+    "    }\n"
     "  }\n"
     "}\n");
 }

src/google/protobuf/compiler/javanano/javanano_primitive_field.cc

@@ -685,7 +685,7 @@ GenerateClearCode(io::Printer* printer) const {
 void RepeatedPrimitiveFieldGenerator::
 GenerateMergingCode(io::Printer* printer) const {
   // First, figure out the length of the array, then parse.
-  if (descriptor_->options().packed()) {
+  if (descriptor_->is_packable() && descriptor_->options().packed()) {
     printer->Print(variables_,
       "int length = input.readRawVarint32();\n"
       "int limit = input.pushLimit(length);\n"
@@ -736,14 +736,28 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void RepeatedPrimitiveFieldGenerator::
 GenerateRepeatedDataSizeCode(io::Printer* printer) const {
-  // Creates a variable dataSize and puts the serialized size in
-  // there.
-  if (FixedSize(descriptor_->type()) == -1) {
+  // Creates a variable dataSize and puts the serialized size in there.
+  // If the element type is a Java reference type, also generates
+  // dataCount which stores the number of non-null elements in the field.
+  if (IsReferenceType(GetJavaType(descriptor_))) {
+    printer->Print(variables_,
+      "int dataCount = 0;\n"
+      "int dataSize = 0;\n"
+      "for (int i = 0; i < this.$name$.length; i++) {\n"
+      "  $type$ element = this.$name$[i];\n"
+      "  if (element != null) {\n"
+      "    dataCount++;\n"
+      "    dataSize += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
+      "        .compute$capitalized_type$SizeNoTag(element);\n"
+      "  }\n"
+      "}\n");
+  } else if (FixedSize(descriptor_->type()) == -1) {
     printer->Print(variables_,
       "int dataSize = 0;\n"
-      "for ($type$ element : this.$name$) {\n"
+      "for (int i = 0; i < this.$name$.length; i++) {\n"
+      "  $type$ element = this.$name$[i];\n"
       "  dataSize += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
-      "    .compute$capitalized_type$SizeNoTag(element);\n"
+      "      .compute$capitalized_type$SizeNoTag(element);\n"
       "}\n");
   } else {
     printer->Print(variables_,
@@ -757,18 +771,26 @@ GenerateSerializationCode(io::Printer* printer) const {
     "if (this.$name$ != null && this.$name$.length > 0) {\n");
   printer->Indent();
 
-  if (descriptor_->options().packed()) {
+  if (descriptor_->is_packable() && descriptor_->options().packed()) {
     GenerateRepeatedDataSizeCode(printer);
     printer->Print(variables_,
       "output.writeRawVarint32($tag$);\n"
       "output.writeRawVarint32(dataSize);\n"
-      "for ($type$ element : this.$name$) {\n"
-      "  output.write$capitalized_type$NoTag(element);\n"
+      "for (int i = 0; i < this.$name$.length; i++) {\n"
+      "  output.write$capitalized_type$NoTag(this.$name$[i]);\n"
+      "}\n");
+  } else if (IsReferenceType(GetJavaType(descriptor_))) {
+    printer->Print(variables_,
+      "for (int i = 0; i < this.$name$.length; i++) {\n"
+      "  $type$ element = this.$name$[i];\n"
+      "  if (element != null) {\n"
+      "    output.write$capitalized_type$($number$, element);\n"
+      "  }\n"
       "}\n");
   } else {
     printer->Print(variables_,
-      "for ($type$ element : this.$name$) {\n"
-      "  output.write$capitalized_type$($number$, element);\n"
+      "for (int i = 0; i < this.$name$.length; i++) {\n"
+      "  output.write$capitalized_type$($number$, this.$name$[i]);\n"
       "}\n");
   }
 
@@ -786,14 +808,17 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
 
   printer->Print(
     "size += dataSize;\n");
-  if (descriptor_->options().packed()) {
+  if (descriptor_->is_packable() && descriptor_->options().packed()) {
     printer->Print(variables_,
       "size += $tag_size$;\n"
       "size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
       "  .computeRawVarint32Size(dataSize);\n");
+  } else if (IsReferenceType(GetJavaType(descriptor_))) {
+    printer->Print(variables_,
+      "size += $tag_size$ * dataCount;\n");
   } else {
     printer->Print(variables_,
-        "size += $tag_size$ * this.$name$.length;\n");
+      "size += $tag_size$ * this.$name$.length;\n");
   }
 
   printer->Outdent();