Add validation when parsing enum fields.

Invalid values from the wire are silently ignored.
Unlike full/lite, the invalid values are not stored into the
unknown fields, because there's no way to get them out from
Nano's unknown fields without a matching Extension.

Edited README and slightly moved it towards a standalone
section for Nano, independent of the Micro section.

Change-Id: I2c1eb07f4d6d8f3aea242b8ddd95b9c966f3f177

7 files changed, 299 insertions, 52 deletions

diff --git a/java/README.txt b/java/README.txt
index 0646c23..13865f6 100644
--- a/java/README.txt
+++ b/java/README.txt
@@ -409,33 +409,33 @@ still generated as integer constants in the message class.
 Nano version
 ============================
 
-Nano is even smaller than micro, especially in the number of generated
-functions. It is like micro:
-
-- No support for descriptors and reflection;
-- Enum constants are integers with no protection against invalid
-  values set to enum fields.
-
-Except:
-
-- Setter/getter/hazzer/clearer functions are opt-in.
+Nano is a special code generator and runtime library designed specially
+for Android, and is very resource-friendly in both the amount of code
+and the runtime overhead. An overview of Nano features:
+
+- No descriptors or message builders.
+- All messages are mutable; fields are public Java fields.
+- For optional fields only, encapsulation behind setter/getter/hazzer/
+  clearer functions is opt-in, which provide proper 'has' state support.
 - If not opted in, has state is not available. Serialization outputs
-  all fields not equal to their default. (See important implications
-  below.)
+  all fields not equal to their defaults (see important implications
+  below).
+- Required fields are always serialized.
+- Enum constants are integers; protection against invalid values only
+  when parsing from the wire.
 - Enum constants can be generated into container interfaces bearing
   the enum's name (so the referencing code is in Java style).
-- CodedInputStreamMicro is renamed to CodedInputByteBufferNano and can
-  only take byte[] (not InputStream).
-- Similar rename from CodedOutputStreamMicro to
-  CodedOutputByteBufferNano.
-- Repeated fields are in arrays, not ArrayList or Vector.
+- CodedInputByteBufferNano can only take byte[] (not InputStream).
+- Similarly CodedOutputByteBufferNano can only write to byte[].
+- Repeated fields are in arrays, not ArrayList or Vector. Null array
+  elements are allowed and silently ignored.
 - Full support of serializing/deserializing repeated packed fields.
+- Support of extensions.
 - Unset messages/groups are null, not an immutable empty default
   instance.
-- Required fields are always serialized.
 - toByteArray(...) and mergeFrom(...) are now static functions of
   MessageNano.
-- "bytes" are of java type byte[].
+- The 'bytes' type translates to the Java type byte[].
 
 IMPORTANT: If you have fields with defaults and opt out of accessors
 
diff --git a/java/pom.xml b/java/pom.xml
index d7ea4d1..ba281ff 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -176,6 +176,16 @@
                   <arg value="../src/google/protobuf/unittest_enum_class_nano.proto" />
                   <arg value="../src/google/protobuf/unittest_enum_class_multiple_nano.proto" />
                   <arg value="../src/google/protobuf/unittest_repeated_packables_nano.proto" />
+                  <arg value="../src/google/protobuf/unittest_enum_validity_nano.proto" />
+                </exec>
+                <exec executable="../src/protoc">
+                  <arg value="--javanano_out=
+                                  optional_field_style=accessors,
+                                  java_outer_classname=google/protobuf/unittest_enum_validity_nano.proto|EnumValidityAccessors
+                                :target/generated-test-sources" />
+                  <arg value="--proto_path=../src" />
+                  <arg value="--proto_path=src/test/java" />
+                  <arg value="../src/google/protobuf/unittest_enum_validity_nano.proto" />
                 </exec>
                 <exec executable="../src/protoc">
                   <arg value="--javanano_out=optional_field_style=reftypes,generate_equals=true:target/generated-test-sources" />
diff --git a/java/src/test/java/com/google/protobuf/NanoTest.java b/java/src/test/java/com/google/protobuf/NanoTest.java
index 687bc16..2a56fa8 100644
--- a/java/src/test/java/com/google/protobuf/NanoTest.java
+++ b/java/src/test/java/com/google/protobuf/NanoTest.java
@@ -33,6 +33,8 @@ package com.google.protobuf;
 import com.google.protobuf.nano.CodedInputByteBufferNano;
 import com.google.protobuf.nano.EnumClassNanoMultiple;
 import com.google.protobuf.nano.EnumClassNanos;
+import com.google.protobuf.nano.EnumValidity;
+import com.google.protobuf.nano.EnumValidityAccessors;
 import com.google.protobuf.nano.Extensions;
 import com.google.protobuf.nano.Extensions.AnotherMessage;
 import com.google.protobuf.nano.Extensions.MessageWithGroup;
@@ -2093,6 +2095,126 @@ public class NanoTest extends TestCase {
   }
 
   /**
+   * Tests that invalid enum values from the wire are not accepted.
+   */
+  public void testNanoEnumValidity() throws Exception {
+    final int invalid = 120;
+    final int alsoInvalid = 121;
+
+    EnumValidity.M m = new EnumValidity.M();
+    // Sanity check & baseline of the assertions for the first case below.
+    assertEquals(EnumValidity.E.default_, m.optionalE);
+    assertEquals(EnumValidity.E.BAZ, m.defaultE);
+
+    m.optionalE = invalid;
+    m.defaultE = invalid;
+    // E contains all valid values
+    m.repeatedE = new int[] {EnumValidity.E.FOO, EnumValidity.E.BAR};
+    m.packedE = new int[] {EnumValidity.E.FOO, EnumValidity.E.BAZ};
+    // E2 contains some invalid values
+    m.repeatedE2 = new int[] {invalid, EnumValidity.E.BAR, alsoInvalid};
+    m.packedE2 = new int[] {EnumValidity.E.FOO, invalid, alsoInvalid};
+    // E3 contains all invalid values
+    m.repeatedE3 = new int[] {invalid, invalid};
+    m.packedE3 = new int[] {alsoInvalid, alsoInvalid};
+    byte[] serialized = MessageNano.toByteArray(m);
+    // Sanity check that we do have all data in the byte array.
+    assertEquals(31, serialized.length);
+
+    // Test 1: tests that invalid values aren't included in the deserialized message.
+    EnumValidity.M deserialized = MessageNano.mergeFrom(new EnumValidity.M(), serialized);
+    assertEquals(EnumValidity.E.default_, deserialized.optionalE);
+    assertEquals(EnumValidity.E.BAZ, deserialized.defaultE);
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.FOO, EnumValidity.E.BAR}, deserialized.repeatedE));
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.FOO, EnumValidity.E.BAZ}, deserialized.packedE));
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.BAR}, deserialized.repeatedE2));
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.FOO}, deserialized.packedE2));
+    assertEquals(0, deserialized.repeatedE3.length);
+    assertEquals(0, deserialized.packedE3.length);
+
+    // Test 2: tests that invalid values do not override previous values in the field, including
+    // arrays, including pre-existing invalid values.
+    deserialized.optionalE = EnumValidity.E.BAR;
+    deserialized.defaultE = alsoInvalid;
+    deserialized.repeatedE = new int[] {EnumValidity.E.BAZ};
+    deserialized.packedE = new int[] {EnumValidity.E.BAZ, alsoInvalid};
+    deserialized.repeatedE2 = new int[] {invalid, alsoInvalid};
+    deserialized.packedE2 = null;
+    deserialized.repeatedE3 = null;
+    deserialized.packedE3 = new int[0];
+    MessageNano.mergeFrom(deserialized, serialized);
+    assertEquals(EnumValidity.E.BAR, deserialized.optionalE);
+    assertEquals(alsoInvalid, deserialized.defaultE);
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.BAZ, /* + */ EnumValidity.E.FOO, EnumValidity.E.BAR},
+        deserialized.repeatedE));
+    assertTrue(Arrays.equals(
+        new int[] {EnumValidity.E.BAZ, alsoInvalid, /* + */ EnumValidity.E.FOO, EnumValidity.E.BAZ},
+        deserialized.packedE));
+    assertTrue(Arrays.equals(
+        new int[] {invalid, alsoInvalid, /* + */ EnumValidity.E.BAR},
+        deserialized.repeatedE2));
+    assertTrue(Arrays.equals(
+        new int[] {/* <null> + */ EnumValidity.E.FOO},
+        deserialized.packedE2));
+    assertNull(deserialized.repeatedE3); // null + all invalid == null
+    assertEquals(0, deserialized.packedE3.length); // empty + all invalid == empty
+
+    // Test 3: reading by alternative forms
+    EnumValidity.Alt alt = MessageNano.mergeFrom(new EnumValidity.Alt(), serialized);
+    assertEquals(EnumValidity.E.BAR, // last valid value in m.repeatedE2
+        alt.repeatedE2AsOptional);
+    assertTrue(Arrays.equals(new int[] {EnumValidity.E.FOO}, alt.packedE2AsNonPacked));
+    assertEquals(0, alt.nonPackedE3AsPacked.length);
+  }
+
+  /**
+   * Tests the same as {@link #testNanoEnumValidity()} with accessor style. Repeated fields are
+   * not re-tested here because they are not affected by the accessor style.
+   */
+  public void testNanoEnumValidityAccessors() throws Exception {
+    final int invalid = 120;
+    final int alsoInvalid = 121;
+
+    EnumValidityAccessors.M m = new EnumValidityAccessors.M();
+    // Sanity check & baseline of the assertions for the first case below.
+    assertEquals(EnumValidityAccessors.default_, m.getOptionalE());
+    assertEquals(EnumValidityAccessors.BAZ, m.getDefaultE());
+
+    m.setOptionalE(invalid);
+    m.setDefaultE(invalid);
+    // Set repeatedE2 for Alt.repeatedE2AsOptional
+    m.repeatedE2 = new int[] {invalid, EnumValidityAccessors.BAR, alsoInvalid};
+    byte[] serialized = MessageNano.toByteArray(m);
+    // Sanity check that we do have all data in the byte array.
+    assertEquals(10, serialized.length);
+
+    // Test 1: tests that invalid values aren't included in the deserialized message.
+    EnumValidityAccessors.M deserialized =
+        MessageNano.mergeFrom(new EnumValidityAccessors.M(), serialized);
+    assertEquals(EnumValidityAccessors.default_, deserialized.getOptionalE());
+    assertEquals(EnumValidityAccessors.BAZ, deserialized.getDefaultE());
+
+    // Test 2: tests that invalid values do not override previous values in the field, including
+    // pre-existing invalid values.
+    deserialized.setOptionalE(EnumValidityAccessors.BAR);
+    deserialized.setDefaultE(alsoInvalid);
+    MessageNano.mergeFrom(deserialized, serialized);
+    assertEquals(EnumValidityAccessors.BAR, deserialized.getOptionalE());
+    assertEquals(alsoInvalid, deserialized.getDefaultE());
+
+    // Test 3: reading by alternative forms
+    EnumValidityAccessors.Alt alt =
+        MessageNano.mergeFrom(new EnumValidityAccessors.Alt(), serialized);
+    assertEquals(EnumValidityAccessors.BAR, // last valid value in m.repeatedE2
+        alt.getRepeatedE2AsOptional());
+  }
+
+  /**
    * Tests that code generation correctly wraps a single message into its outer
    * class. The class {@code SingleMessageNano} is imported from the outer
    * class {@code UnittestSingleNano}, whose name is implicit. Any error would
diff --git a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
index eb73232..6a18834 100644
--- a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
@@ -71,9 +71,35 @@ void SetEnumVariables(const Params& params,
   (*variables)["tag"] = SimpleItoa(internal::WireFormat::MakeTag(descriptor));
   (*variables)["tag_size"] = SimpleItoa(
       internal::WireFormat::TagSize(descriptor->number(), descriptor->type()));
+  (*variables)["non_packed_tag"] = SimpleItoa(
+      internal::WireFormatLite::MakeTag(descriptor->number(),
+          internal::WireFormat::WireTypeForFieldType(descriptor->type())));
   (*variables)["message_name"] = descriptor->containing_type()->name();
 }
 
+void LoadEnumValues(const Params& params,
+    const EnumDescriptor* enum_descriptor, vector<string>* canonical_values) {
+  string enum_class_name = ClassName(params, enum_descriptor);
+  for (int i = 0; i < enum_descriptor->value_count(); i++) {
+    const EnumValueDescriptor* value = enum_descriptor->value(i);
+    const EnumValueDescriptor* canonical_value =
+        enum_descriptor->FindValueByNumber(value->number());
+    if (value == canonical_value) {
+      canonical_values->push_back(
+          enum_class_name + "." + RenameJavaKeywords(value->name()));
+    }
+  }
+}
+
+void PrintCaseLabels(
+    io::Printer* printer, const vector<string>& canonical_values) {
+  for (int i = 0; i < canonical_values.size(); i++) {
+    printer->Print(
+      "  case $value$:\n",
+      "value", canonical_values[i]);
+  }
+}
+
 }  // namespace
 
 // ===================================================================
@@ -82,6 +108,7 @@ EnumFieldGenerator::
 EnumFieldGenerator(const FieldDescriptor* descriptor, const Params& params)
   : FieldGenerator(params), descriptor_(descriptor) {
   SetEnumVariables(params, descriptor, &variables_);
+  LoadEnumValues(params, descriptor->enum_type(), &canonical_values_);
 }
 
 EnumFieldGenerator::~EnumFieldGenerator() {}
@@ -111,12 +138,21 @@ GenerateClearCode(io::Printer* printer) const {
 void EnumFieldGenerator::
 GenerateMergingCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "this.$name$ = input.readInt32();\n");
-
+    "int value = input.readInt32();\n"
+    "switch (value) {\n");
+  PrintCaseLabels(printer, canonical_values_);
+  printer->Print(variables_,
+    "    this.$name$ = value;\n");
   if (params_.generate_has()) {
     printer->Print(variables_,
-      "has$capitalized_name$ = true;\n");
+      "    has$capitalized_name$ = true;\n");
   }
+  printer->Print(
+    "    break;\n"
+    "}\n");
+  // No default case: in case of invalid value from the wire, preserve old
+  // field value. Also we are not storing the invalid value into the unknown
+  // fields, because there is no way to get the value out.
 }
 
 void EnumFieldGenerator::
@@ -209,6 +245,7 @@ AccessorEnumFieldGenerator(const FieldDescriptor* descriptor,
     const Params& params, int has_bit_index)
   : FieldGenerator(params), descriptor_(descriptor) {
   SetEnumVariables(params, descriptor, &variables_);
+  LoadEnumValues(params, descriptor->enum_type(), &canonical_values_);
   SetBitOperationVariables("has", has_bit_index, &variables_);
 }
 
@@ -245,8 +282,17 @@ GenerateClearCode(io::Printer* printer) const {
 void AccessorEnumFieldGenerator::
 GenerateMergingCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "$name$_ = input.readInt32();\n"
-    "$set_has$;\n");
+    "int value = input.readInt32();\n"
+    "switch (value) {\n");
+  PrintCaseLabels(printer, canonical_values_);
+  printer->Print(variables_,
+    "    $name$_ = value;\n"
+    "    $set_has$;\n"
+    "    break;\n"
+    "}\n");
+  // No default case: in case of invalid value from the wire, preserve old
+  // field value. Also we are not storing the invalid value into the unknown
+  // fields, because there is no way to get the value out.
 }
 
 void AccessorEnumFieldGenerator::
@@ -287,6 +333,7 @@ RepeatedEnumFieldGenerator::
 RepeatedEnumFieldGenerator(const FieldDescriptor* descriptor, const Params& params)
   : FieldGenerator(params), descriptor_(descriptor) {
   SetEnumVariables(params, descriptor, &variables_);
+  LoadEnumValues(params, descriptor->enum_type(), &canonical_values_);
 }
 
 RepeatedEnumFieldGenerator::~RepeatedEnumFieldGenerator() {}
@@ -305,46 +352,82 @@ GenerateClearCode(io::Printer* printer) const {
 
 void RepeatedEnumFieldGenerator::
 GenerateMergingCode(io::Printer* printer) const {
-  // First, figure out the length of the array, then parse.
+  // First, figure out the maximum length of the array, then parse,
+  // and finally copy the valid values to the field.
   printer->Print(variables_,
-    "int arrayLength = com.google.protobuf.nano.WireFormatNano\n"
-    "    .getRepeatedFieldArrayLength(input, $tag$);\n"
-    "int i = this.$name$ == null ? 0 : this.$name$.length;\n"
-    "int[] newArray = new int[i + arrayLength];\n"
-    "if (i != 0) {\n"
-    "  java.lang.System.arraycopy(this.$name$, 0, newArray, 0, i);\n"
-    "}\n"
-    "for (; i < newArray.length - 1; i++) {\n"
-    "  newArray[i] = input.readInt32();\n"
-    "  input.readTag();\n"
+    "int length = com.google.protobuf.nano.WireFormatNano\n"
+    "    .getRepeatedFieldArrayLength(input, $non_packed_tag$);\n"
+    "int[] validValues = new int[length];\n"
+    "int validCount = 0;\n"
+    "for (int i = 0; i < length; i++) {\n"
+    "  if (i != 0) { // tag for first value already consumed.\n"
+    "    input.readTag();\n"
+    "  }\n"
+    "  int value = input.readInt32();\n"
+    "  switch (value) {\n");
+  printer->Indent();
+  PrintCaseLabels(printer, canonical_values_);
+  printer->Outdent();
+  printer->Print(variables_,
+    "      validValues[validCount++] = value;\n"
+    "      break;\n"
+    "  }\n"
     "}\n"
-    "// Last one without readTag.\n"
-    "newArray[i] = input.readInt32();\n"
-    "this.$name$ = newArray;\n");
+    "if (validCount != 0) {\n"
+    "  int i = this.$name$ == null ? 0 : this.$name$.length;\n"
+    "  if (i == 0 && validCount == validValues.length) {\n"
+    "    this.$name$ = validValues;\n"
+    "  } else {\n"
+    "    int[] newArray = new int[i + validCount];\n"
+    "    if (i != 0) {\n"
+    "      java.lang.System.arraycopy(this.$name$, 0, newArray, 0, i);\n"
+    "    }\n"
+    "    java.lang.System.arraycopy(validValues, 0, newArray, i, validCount);\n"
+    "    this.$name$ = newArray;\n"
+    "  }\n"
+    "}\n");
 }
 
 void RepeatedEnumFieldGenerator::
 GenerateMergingCodeFromPacked(io::Printer* printer) const {
   printer->Print(variables_,
-    "int length = input.readRawVarint32();\n"
-    "int limit = input.pushLimit(length);\n"
+    "int bytes = input.readRawVarint32();\n"
+    "int limit = input.pushLimit(bytes);\n"
     "// First pass to compute array length.\n"
     "int arrayLength = 0;\n"
     "int startPos = input.getPosition();\n"
     "while (input.getBytesUntilLimit() > 0) {\n"
-    "  input.readInt32();\n"
-    "  arrayLength++;\n"
-    "}\n"
-    "input.rewindToPosition(startPos);\n"
-    "int i = this.$name$ == null ? 0 : this.$name$.length;\n"
-    "int[] newArray = new int[i + arrayLength];\n"
-    "if (i != 0) {\n"
-    "  java.lang.System.arraycopy(this.$name$, 0, newArray, 0, i);\n"
+    "  switch (input.readInt32()) {\n");
+  printer->Indent();
+  PrintCaseLabels(printer, canonical_values_);
+  printer->Outdent();
+  printer->Print(variables_,
+    "      arrayLength++;\n"
+    "      break;\n"
+    "  }\n"
     "}\n"
-    "for (; i < newArray.length; i++) {\n"
-    "  newArray[i] = input.readInt32();\n"
+    "if (arrayLength != 0) {\n"
+    "  input.rewindToPosition(startPos);\n"
+    "  int i = this.$name$ == null ? 0 : this.$name$.length;\n"
+    "  int[] newArray = new int[i + arrayLength];\n"
+    "  if (i != 0) {\n"
+    "    java.lang.System.arraycopy(this.$name$, 0, newArray, 0, i);\n"
+    "  }\n"
+    "  while (input.getBytesUntilLimit() > 0) {\n"
+    "    int value = input.readInt32();\n"
+    "    switch (value) {\n");
+  printer->Indent();
+  printer->Indent();
+  PrintCaseLabels(printer, canonical_values_);
+  printer->Outdent();
+  printer->Outdent();
+  printer->Print(variables_,
+    "        newArray[i++] = value;\n"
+    "        break;\n"
+    "    }\n"
+    "  }\n"
+    "  this.$name$ = newArray;\n"
     "}\n"
-    "this.$name$ = newArray;\n"
     "input.popLimit(limit);\n");
 }
 
diff --git a/src/google/protobuf/compiler/javanano/javanano_enum_field.h b/src/google/protobuf/compiler/javanano/javanano_enum_field.h
index c477af2..55bf635 100644
--- a/src/google/protobuf/compiler/javanano/javanano_enum_field.h
+++ b/src/google/protobuf/compiler/javanano/javanano_enum_field.h
@@ -37,6 +37,7 @@
 
 #include <map>
 #include <string>
+#include <vector>
 #include <google/protobuf/compiler/javanano/javanano_field.h>
 
 namespace google {
@@ -62,6 +63,7 @@ class EnumFieldGenerator : public FieldGenerator {
  private:
   const FieldDescriptor* descriptor_;
   map<string, string> variables_;
+  vector<string> canonical_values_;
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(EnumFieldGenerator);
 };
@@ -84,6 +86,7 @@ class AccessorEnumFieldGenerator : public FieldGenerator {
  private:
   const FieldDescriptor* descriptor_;
   map<string, string> variables_;
+  vector<string> canonical_values_;
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(AccessorEnumFieldGenerator);
 };
@@ -109,6 +112,7 @@ class RepeatedEnumFieldGenerator : public FieldGenerator {
 
   const FieldDescriptor* descriptor_;
   map<string, string> variables_;
+  vector<string> canonical_values_;
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RepeatedEnumFieldGenerator);
 };
diff --git a/src/google/protobuf/compiler/javanano/javanano_helpers.cc b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
index b3bedcb..ede4c6f 100644
--- a/src/google/protobuf/compiler/javanano/javanano_helpers.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
@@ -412,7 +412,7 @@ string DefaultValue(const Params& params, const FieldDescriptor* field) {
 
     case FieldDescriptor::CPPTYPE_ENUM:
       return ClassName(params, field->enum_type()) + "." +
-             field->default_value_enum()->name();
+             RenameJavaKeywords(field->default_value_enum()->name());
 
     case FieldDescriptor::CPPTYPE_MESSAGE:
       return "null";
diff --git a/src/google/protobuf/unittest_enum_validity_nano.proto b/src/google/protobuf/unittest_enum_validity_nano.proto
new file mode 100644
index 0000000..f7f5742
--- /dev/null
+++ b/src/google/protobuf/unittest_enum_validity_nano.proto
@@ -0,0 +1,28 @@
+package protobuf_unittest;
+
+option java_package = "com.google.protobuf.nano";
+option java_outer_classname = "EnumValidity";
+
+enum E {
+  default = 1; // test java keyword renaming
+  FOO = 2;
+  BAR = 3;
+  BAZ = 4;
+}
+
+message M {
+  optional E optional_e = 1;
+  optional E default_e = 2 [ default = BAZ ];
+  repeated E repeated_e = 3;
+  repeated E packed_e = 4 [ packed = true ];
+  repeated E repeated_e2 = 5;
+  repeated E packed_e2 = 6 [ packed = true ];
+  repeated E repeated_e3 = 7;
+  repeated E packed_e3 = 8 [ packed = true ];
+}
+
+message Alt {
+  optional E repeated_e2_as_optional = 5;
+  repeated E packed_e2_as_non_packed = 6;
+  repeated E non_packed_e3_as_packed = 7 [ packed = true ];
+}