fix: ODCS to .proto, problem with array of objects (#1012)

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* Update datacontract/export/protobuf_exporter.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update datacontract/export/protobuf_exporter.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix

* fix

* fix

* fix: correct nested message indentation and add changelog for protobuf exporter

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: ruff import block formatting

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Jochen Christ <jochen.christ@entropy-data.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Jakob Schödl <jakob.schoedl@entropy-data.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 5 people

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+- Fix Protobuf export for arrays of objects and improve message/enum naming to UpperCamelCase (#1012 @Schokuroff)
+
 ## [0.11.8] - 2026-04-10
 
 ### Added

datacontract/export/protobuf_exporter.py

@@ -1,20 +1,21 @@
-import sys
 from typing import List, Optional
 
 from open_data_contract_standard.model import OpenDataContractStandard, SchemaProperty
 
 from datacontract.export.exporter import Exporter
 
+OBJECT_TYPES: set = {"object", "record", "struct"}
+
 
 class ProtoBufExporter(Exporter):
     def export(self, data_contract, schema_name, server, sql_server_type, export_args) -> dict:
-        # Returns a dict containing the protobuf representation.
+        """Exports data contract to Protobuf format."""
         proto = to_protobuf(data_contract)
         return proto
 
 
 def _get_config_value(prop: SchemaProperty, key: str) -> Optional[str]:
-    """Get a custom property value."""
+    """Get a custom property value from customProperties."""
     if prop.customProperties is None:
         return None
     for cp in prop.customProperties:
@@ -57,10 +58,10 @@ def to_protobuf(data_contract: OpenDataContractStandard) -> str:
 
     # Build header with syntax and package declarations.
     header = 'syntax = "proto3";\n\n'
-    package = "example"  # Default package
+    package = "example"  # Default package, can be customized
     header += f"package {package};\n\n"
 
-    # Append enum definitions.
+    # Append enum definitions before messages.
     for enum_name, enum_values in enum_definitions.items():
         header += f"// Enum for {enum_name}\n"
         header += f"enum {enum_name} {{\n"
@@ -72,6 +73,7 @@ def to_protobuf(data_contract: OpenDataContractStandard) -> str:
         else:
             header += f"  // Warning: Enum values for {enum_name} are not a dictionary\n"
         header += "}\n\n"
+
     return header + messages
 
 
@@ -86,11 +88,12 @@ def _is_enum_field(prop: SchemaProperty) -> bool:
 def _get_enum_name(prop: SchemaProperty) -> str:
     """
     Returns the enum name either from the field's "enum_name" or derived from the field name.
+    Uses UpperCamelCase formatting.
     """
     enum_name = _get_config_value(prop, "enum_name")
     if enum_name:
-        return enum_name
-    return _to_protobuf_message_name(prop.name)
+        return _snake_to_upper_camel(enum_name)
+    return _snake_to_upper_camel(prop.name)
 
 
 def _get_enum_values(prop: SchemaProperty) -> dict:
@@ -103,69 +106,126 @@ def _get_enum_values(prop: SchemaProperty) -> dict:
     return {}
 
 
-def _to_protobuf_message_name(name: str) -> str:
+def _snake_to_upper_camel(name: str) -> str:
     """
-    Returns a valid Protobuf message/enum name by capitalizing the first letter.
+    Convert snake_case to UpperCamelCase.
+    Preserves existing capitalization in parts.
+
+    Examples:
+      "fsa_room" -> "FsaRoom"
+      "FsaRegister" -> "FsaRegister" (already in UpperCamelCase)
+      "simple_obj" -> "SimpleObj"
     """
-    return name[0].upper() + name[1:] if name else name
+    if not name:
+        return name
 
+    # If already UpperCamelCase (first letter uppercase, no underscores after first word)
+    if name and name[0].isupper() and "_" not in name:
+        return name
 
-def to_protobuf_message(
-    model_name: str, properties: List[SchemaProperty], description: str, indent_level: int = 0
-) -> str:
+    parts = name.split("_")
+    # Capitalize each part while preserving internal capitalization
+    return "".join(part[0].upper() + part[1:] if part else "" for part in parts)
+
+
+def _get_type_name(prop: SchemaProperty) -> str:
     """
-    Generates a Protobuf message definition from the model's fields.
-    Handles nested messages for complex types.
+    Get appropriate message/enum type name in UpperCamelCase.
+    Used for message declarations and field type references.
     """
-    result = ""
-    if description:
-        result += f"{indent(indent_level)}// {description}\n"
+    # For enums
+    if _is_enum_field(prop):
+        return _get_enum_name(prop)
 
-    result += f"message {_to_protobuf_message_name(model_name)} {{\n"
-    number = 1
-    for prop in properties:
-        # For nested objects, generate a nested message.
-        field_type = prop.logicalType or ""
-        if field_type.lower() in ["object", "record", "struct"]:
-            nested_desc = prop.description or ""
-            nested_props = prop.properties or []
-            nested_message = to_protobuf_message(prop.name, nested_props, nested_desc, indent_level + 1)
-            result += nested_message + "\n"
+    # For regular objects
+    if prop.logicalType and prop.logicalType.lower() in OBJECT_TYPES:
+        return _snake_to_upper_camel(prop.name)
 
-        field_desc = prop.description or ""
-        result += to_protobuf_field(prop, field_desc, number, indent_level + 1) + "\n"
-        number += 1
+    # For objects inside arrays
+    if (
+        prop.logicalType
+        and prop.logicalType.lower() == "array"
+        and prop.items
+        and prop.items.logicalType
+        and prop.items.logicalType.lower() in OBJECT_TYPES
+    ):
+        # If explicit name is provided in items.name
+        if hasattr(prop.items, "name") and prop.items.name:
+            # Normalize items.name the same way as message declarations
+            return _snake_to_upper_camel(prop.items.name)
 
-    result += f"{indent(indent_level)}}}\n"
-    return result
+        # Otherwise generate from field name
+        return _snake_to_upper_camel(prop.name)
+
+    return _snake_to_upper_camel(prop.name)
 
 
-def to_protobuf_field(prop: SchemaProperty, description: str, number: int, indent_level: int = 0) -> str:
+def _should_create_nested_message(prop: SchemaProperty) -> bool:
     """
-    Generates a field definition within a Protobuf message.
+    Check if we need to create a nested message for this property.
+    Returns True for objects and arrays of objects.
     """
-    result = ""
-    if description:
-        result += f"{indent(indent_level)}// {description}\n"
-    result += f"{indent(indent_level)}{_convert_type(prop)} {prop.name} = {number};"
-    return result
+    if not prop.logicalType:
+        return False
 
+    lower_type = prop.logicalType.lower()
 
-def indent(indent_level: int) -> str:
-    return "  " * indent_level
+    # Regular object
+    if lower_type in OBJECT_TYPES:
+        return True
+
+    # Array of objects
+    if lower_type == "array" and prop.items:
+        items_lower_type = prop.items.logicalType.lower() if prop.items.logicalType else ""
+        return items_lower_type in OBJECT_TYPES
+
+    return False
 
 
-def _convert_type(prop: SchemaProperty) -> str:
+def _get_nested_properties(prop: SchemaProperty) -> Optional[List[SchemaProperty]]:
     """
-    Converts a field's type (from the data contract) to a Protobuf type.
-    Prioritizes enum conversion if a non-empty "values" property exists.
+    Get properties for nested message.
+    Returns None if no nested properties.
     """
-    # For debugging purposes
-    print("Converting field:", prop.name, file=sys.stderr)
-    # If the field should be treated as an enum, return its enum name.
-    if _is_enum_field(prop):
-        return _get_enum_name(prop)
+    if prop.logicalType and prop.logicalType.lower() in OBJECT_TYPES:
+        return prop.properties or []
+
+    if (
+        prop.logicalType
+        and prop.logicalType.lower() == "array"
+        and prop.items
+        and prop.items.logicalType
+        and prop.items.logicalType.lower() in OBJECT_TYPES
+    ):
+        return prop.items.properties or []
+
+    return None
+
 
+def _get_nested_description(prop: SchemaProperty) -> str:
+    """
+    Get description for nested message.
+    """
+    if prop.logicalType and prop.logicalType.lower() in OBJECT_TYPES:
+        return prop.description or ""
+
+    if (
+        prop.logicalType
+        and prop.logicalType.lower() == "array"
+        and prop.items
+        and prop.items.logicalType
+        and prop.items.logicalType.lower() in OBJECT_TYPES
+    ):
+        return prop.items.description or ""
+
+    return ""
+
+
+def _get_primitive_type(prop: SchemaProperty) -> str:
+    """
+    Get Protobuf type for primitive fields.
+    Handles recursive type resolution for arrays of primitives.
+    """
     field_type = prop.logicalType or ""
     lower_type = field_type.lower()
 
@@ -185,19 +245,112 @@ def _convert_type(prop: SchemaProperty) -> str:
         return "bool"
     if lower_type in ["bytes"]:
         return "bytes"
-    if lower_type in ["object", "record", "struct"]:
-        return _to_protobuf_message_name(prop.name)
+
+    # Recursive handling for arrays of primitives
+    if lower_type == "array" and prop.items:
+        return _get_primitive_type(prop.items)
+
+    return "string"  # Fallback for unrecognized types
+
+
+def _get_field_type(prop: SchemaProperty) -> str:
+    """
+    Get Protobuf type for field (string, int32, repeated TypeName, etc).
+    Combines repeated keyword with type name for arrays.
+    """
+    field_type = prop.logicalType or ""
+    lower_type = field_type.lower()
+
+    # Handle arrays
     if lower_type == "array":
-        # Handle array types. Check for an "items" property.
         if prop.items:
             items_type = prop.items.logicalType or ""
-            if items_type.lower() in ["object", "record", "struct"]:
-                # Singularize the field name (a simple approach).
-                singular = prop.name[:-1] if prop.name.endswith("s") else prop.name
-                return "repeated " + _to_protobuf_message_name(singular)
+            items_lower_type = items_type.lower()
+
+            # If array contains objects
+            if items_lower_type in OBJECT_TYPES:
+                type_name = _get_type_name(prop)  # e.g., FsaRoom
+                return f"repeated {type_name}"
             else:
-                return "repeated " + _convert_type(prop.items)
+                # For primitive types
+                primitive_type = _get_primitive_type(prop.items)
+                return f"repeated {primitive_type}"
         else:
-            return "repeated string"
-    # Fallback for unrecognized types.
-    return "string"
+            return "repeated string"  # Default array type
+
+    # Handle regular objects
+    if lower_type in OBJECT_TYPES:
+        type_name = _get_type_name(prop)  # e.g., SimpleObj
+        return type_name
+
+    # Handle enums
+    if _is_enum_field(prop):
+        return _get_enum_name(prop)
+
+    # Handle primitive types
+    return _get_primitive_type(prop)
+
+
+def to_protobuf_message(
+    model_name: str, properties: List[SchemaProperty], description: str, indent_level: int = 0
+) -> str:
+    """
+    Generates a Protobuf message definition from the model's fields.
+    Handles nested messages for complex types recursively.
+    """
+    result = ""
+    if description:
+        result += f"{indent(indent_level)}// {description}\n"
+
+    # Message name always in UpperCamelCase
+    message_name = _snake_to_upper_camel(model_name)
+    result += f"{indent(indent_level)}message {message_name} {{\n"
+
+    # Phase 1: Create all nested messages
+    for prop in properties:
+        if _should_create_nested_message(prop):
+            type_name = _get_type_name(prop)  # UpperCamelCase
+            nested_props = _get_nested_properties(prop)
+            nested_desc = _get_nested_description(prop)
+
+            if nested_props is not None:
+                nested_message = to_protobuf_message(type_name, nested_props, nested_desc, indent_level + 1)
+                result += nested_message + "\n"
+
+    # Phase 2: Create all fields
+    number = 1
+    for prop in properties:
+        field_name = prop.name  # snake_case (preserve as in YAML)
+        field_decl = _get_field_declaration(prop)
+        field_desc = prop.description or ""
+
+        result += f"{indent(indent_level + 1)}"
+        if field_desc:
+            result += f"// {field_desc}\n{indent(indent_level + 1)}"
+
+        result += f"{field_decl} {field_name} = {number};\n"
+        number += 1
+
+    result += f"{indent(indent_level)}}}\n"
+    return result
+
+
+def indent(indent_level: int) -> str:
+    """Generate indentation string for Protobuf formatting."""
+    return "  " * indent_level
+
+
+def _get_field_declaration(prop: SchemaProperty) -> str:
+    """
+    Returns field declaration with optional keyword if needed.
+    """
+    field_type = _get_field_type(prop)  # includes "repeated" if needed
+
+    logical_type = (prop.logicalType or "").lower()
+    is_array = logical_type == "array"
+    is_message_type = logical_type in OBJECT_TYPES
+
+    # Add 'optional' only for non-required, non-array, non-message fields (scalars/enums)
+    if hasattr(prop, "required") and prop.required is False and not is_array and not is_message_type:
+        return f"optional {field_type}"
+    return field_type