feat: add field annotations merging functionality (#83)

src/main/java/com/google/cloud/discotoproto3converter/proto3/ProtoMerger.java

@@ -19,12 +19,14 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 // This class does not intend to do a fully-functional merge of two proto models, instead it focuses
 // on merging currently known potential discrepancies between old and new proto files:
-// - Missing field in a new proto file
-// - Missing values in enums
-// - Mismatching service method google.api.method_signature option values
+// - missing field in a new proto file;
+// - missing values in enums;
+// - mismatching service method google.api.method_signature option values (old overwrite new);
+// - mismatching field annotations (old overwrite new).
 //
 // Additional merging functionality is expected to be added to this class as needed.
 public class ProtoMerger {
@@ -79,32 +81,50 @@ private void mergeMessages(Map<String, Message> newMessages, Map<String, Message
       mergeFields(newMessage, oldMessage, newMessages);
 
       // Merge enums
-      Map<String, Message> newEnumsMap = new HashMap<>();
-      for (Message nestedEnum : newMessage.getEnums()) {
-        newEnumsMap.put(nestedEnum.getName(), nestedEnum);
-      }
-      for (Message oldEnum : oldMessage.getEnums()) {
-        Message newEnum = newEnumsMap.get(oldEnum.getName());
-        mergeFields(newEnum, oldEnum, newMessages);
-      }
+      mergeEnums(newMessages, oldMessage, newMessage);
+    }
+  }
+
+  private void mergeEnums(
+      Map<String, Message> newMessages, Message oldMessage, Message newMessage) {
+    Map<String, Message> newEnumsMap = new HashMap<>();
+    for (Message nestedEnum : newMessage.getEnums()) {
+      newEnumsMap.put(nestedEnum.getName(), nestedEnum);
+    }
+    for (Message oldEnum : oldMessage.getEnums()) {
+      Message newEnum = newEnumsMap.get(oldEnum.getName());
+      mergeFields(newEnum, oldEnum, newMessages);
     }
   }
 
   private void mergeFields(
       Message newMessage, Message oldMessage, Map<String, Message> newMessages) {
     // Merge fields
+    Map<String, Field> newFieldsMap =
+        newMessage.getFields().stream().collect(Collectors.toMap(ProtoElement::getName, f -> f));
+
     for (Field oldField : oldMessage.getFields()) {
       // compareTo() will be used by contains() to search for the field, not equals().
       if (!newMessage.getFields().contains(oldField)) {
-        newMessage.getFields().add(copyField(oldField, newMessages));
+        // Copy removed field
+        newMessage.getFields().add(copyField(null, oldField, newMessages));
+      } else {
+        Field newField = newFieldsMap.get(oldField.getName());
+        // Copy missing options if a new field has less options than old field.
+        // This is a very primitive merge logic. Add a proper merge logic if ever needed.
+        if (oldField.getOptions().size() > newField.getOptions().size()
+            || oldField.isOptional() != newField.isOptional()) {
+          newMessage.getFields().remove(oldField);
+          newMessage.getFields().add(copyField(newField, oldField, newMessages));
+        }
       }
     }
   }
 
   // We need to replace references for message types from oldMessages to newMessages.
   // Despite message types having the same names, they are two independently created
   // sets of objects.
-  private Field copyField(Field oldField, Map<String, Message> newMessages) {
+  private Field copyField(Field newField, Field oldField, Map<String, Message> newMessages) {
     Message valueType = Message.PRIMITIVES.get(oldField.getValueType().getName());
     if (valueType == null) {
       valueType = newMessages.get(oldField.getValueType().getName());
@@ -123,7 +143,7 @@ private Field copyField(Field oldField, Map<String, Message> newMessages) {
             oldField.isRepeated(),
             oldField.isOptional(),
             keyType,
-            oldField.getDescription(),
+            newField != null ? newField.getDescription() : oldField.getDescription(),
             oldField.isFirstInOrder());
 
     // Do not do deep copy for options because they are all generic immutable objects (strings or

src/main/java/com/google/cloud/discotoproto3converter/proto3/ProtoParser.java

@@ -204,7 +204,7 @@ private Field parseField(String fieldString, SortedMap<String, Message> nestedEn
     }
     Message keyType = Message.PRIMITIVES.get(m.group("keyType"));
     boolean repeated = m.group("repeated") != null || keyType != null;
-    boolean optional = m.group("optional") != null;
+    boolean optional = repeated || m.group("optional") != null;
 
     Field parsedField =
         new Field(m.group("name"), valueType, repeated, optional, keyType, null, false);

src/test/resources/google/cloud/compute/v1small/compute.merge.proto.baseline

@@ -327,7 +327,7 @@ message DeleteAddressRequest {
   // For example, consider a situation where you make an initial request and the request times out. If you make the request again with the same request ID, the server can check if original operation with the same request ID was received, and if so, will ignore the second request. This prevents clients from accidentally creating duplicate commitments.
   //
   // The request ID must be a valid UUID with the exception that zero UUID is not supported (00000000-0000-0000-0000-000000000000).
-  optional string request_id = 37109963;
+  string request_id = 37109963 [(google.api.field_behavior) = REQUIRED];
 
 }
 

src/test/resources/google/cloud/compute/v1small/compute.proto

@@ -327,8 +327,7 @@ message DeleteAddressRequest {
   // For example, consider a situation where you make an initial request and the request times out. If you make the request again with the same request ID, the server can check if original operation with the same request ID was received, and if so, will ignore the second request. This prevents clients from accidentally creating duplicate commitments.
   //
   // The request ID must be a valid UUID with the exception that zero UUID is not supported (00000000-0000-0000-0000-000000000000).
-  optional string request_id = 37109963;
-
+  string request_id = 37109963 [(google.api.field_behavior) = REQUIRED];
 }
 
 // [Output Only] If errors are generated during processing of the operation, this field will be populated.