feat: Add default value support for function tools

fix: Add more test cases inside `test_build_function_declaration.py` for passing Enums as arguments

Author: SOORAJTS2001

src/google/adk/tools/_function_parameter_parse_util.py

@@ -76,7 +76,7 @@ def _raise_if_schema_unsupported(
 ):
   if variant == GoogleLLMVariant.GEMINI_API:
     _raise_for_any_of_if_mldev(schema)
-    _update_for_default_if_mldev(schema)
+    # _update_for_default_if_mldev(schema) # No need of this since GEMINI now supports default value
 
 
 def _is_default_value_compatible(
@@ -150,9 +150,10 @@ def _parse_schema_from_parameter(
       schema.type = types.Type.STRING
       schema.enum = [e.value for e in param.annotation]
       if param.default is not inspect.Parameter.empty:
-          if not _is_default_value_compatible(param.default, param.annotation):
+          default_value = param.default.value if isinstance(param.default, Enum) else param.default
+          if default_value not in schema.enum:
               raise ValueError(default_value_error_msg)
-          schema.default = param.default
+          schema.default = default_value
       _raise_if_schema_unsupported(variant, schema)
       return schema
   if (

tests/unittests/tools/test_build_function_declaration.py

@@ -23,6 +23,7 @@
 # from crewai_tools import FileReadTool
 from pydantic import BaseModel
 from enum import Enum
+import pytest
 
 def test_string_input():
   def simple_function(input_str: str) -> str:
@@ -225,7 +226,7 @@ class InputEnum(Enum):
     AGENT = "agent"
     TOOL = "tool"
 
-  def simple_function(input:InputEnum):
+  def simple_function(input:InputEnum=InputEnum.AGENT):
     return input.value
 
   function_decl = _automatic_function_calling_util.build_function_declaration(
@@ -235,8 +236,16 @@ def simple_function(input:InputEnum):
   assert function_decl.name == 'simple_function'
   assert function_decl.parameters.type == 'OBJECT'
   assert function_decl.parameters.properties['input'].type == 'STRING'
+  assert function_decl.parameters.properties['input'].default == 'agent'
   assert function_decl.parameters.properties['input'].enum == ['agent', 'tool']
 
+  def simple_function_with_wrong_enum(input:InputEnum="WRONG_ENUM"):
+    return input.value
+
+  with pytest.raises(ValueError):
+    _automatic_function_calling_util.build_function_declaration(
+      func=simple_function_with_wrong_enum
+    )
 
 def test_basemodel_list():
   class ChildInput(BaseModel):