fixes interpolation issues when inputs are type dict,list specificall… (#1992)

* fixes interpolation issues when inputs are type dict,list specifically when defined on expected_output

* improvements with type hints, doc fixes and rm print statements

* more tests

* test passing

---------

Co-authored-by: Brandon Hancock <brandon@brandonhancock.io>

src/crewai/task.py

@@ -431,7 +431,9 @@ class Task(BaseModel):
             content = (
                 json_output
                 if json_output
-                else pydantic_output.model_dump_json() if pydantic_output else result
+                else pydantic_output.model_dump_json()
+                if pydantic_output
+                else result
             )
             self._save_file(content)
 
@@ -452,7 +454,7 @@ class Task(BaseModel):
         return "\n".join(tasks_slices)
 
     def interpolate_inputs_and_add_conversation_history(
-        self, inputs: Dict[str, Union[str, int, float]]
+        self, inputs: Dict[str, Union[str, int, float, Dict[str, Any], List[Any]]]
     ) -> None:
         """Interpolate inputs into the task description, expected output, and output file path.
            Add conversation history if present.
@@ -524,7 +526,9 @@ class Task(BaseModel):
             )
 
     def interpolate_only(
-        self, input_string: Optional[str], inputs: Dict[str, Union[str, int, float]]
+        self,
+        input_string: Optional[str],
+        inputs: Dict[str, Union[str, int, float, Dict[str, Any], List[Any]]],
     ) -> str:
         """Interpolate placeholders (e.g., {key}) in a string while leaving JSON untouched.
 
@@ -532,17 +536,39 @@ class Task(BaseModel):
             input_string: The string containing template variables to interpolate.
                          Can be None or empty, in which case an empty string is returned.
             inputs: Dictionary mapping template variables to their values.
-                   Supported value types are strings, integers, and floats.
+                   Supported value types are strings, integers, floats, and dicts/lists
-                   If input_string is empty or has no placeholders, inputs can be empty.
+                   containing only these types and other nested dicts/lists.
 
         Returns:
             The interpolated string with all template variables replaced with their values.
             Empty string if input_string is None or empty.
 
         Raises:
-            ValueError: If a required template variable is missing from inputs.
+            ValueError: If a value contains unsupported types
-            KeyError: If a template variable is not found in the inputs dictionary.
         """
+
+        # Validation function for recursive type checking
+        def validate_type(value: Any) -> None:
+            if value is None:
+                return
+            if isinstance(value, (str, int, float, bool)):
+                return
+            if isinstance(value, (dict, list)):
+                for item in value.values() if isinstance(value, dict) else value:
+                    validate_type(item)
+                return
+            raise ValueError(
+                f"Unsupported type {type(value).__name__} in inputs. "
+                "Only str, int, float, bool, dict, and list are allowed."
+            )
+
+        # Validate all input values
+        for key, value in inputs.items():
+            try:
+                validate_type(value)
+            except ValueError as e:
+                raise ValueError(f"Invalid value for key '{key}': {str(e)}") from e
+
         if input_string is None or not input_string:
             return ""
         if "{" not in input_string and "}" not in input_string:
@@ -551,15 +577,7 @@ class Task(BaseModel):
             raise ValueError(
                 "Inputs dictionary cannot be empty when interpolating variables"
             )
-
         try:
-            # Validate input types
-            for key, value in inputs.items():
-                if not isinstance(value, (str, int, float)):
-                    raise ValueError(
-                        f"Value for key '{key}' must be a string, integer, or float, got {type(value).__name__}"
-                    )
-
             escaped_string = input_string.replace("{", "{{").replace("}", "}}")
 
             for key in inputs.keys():

tests/task_test.py

@@ -779,6 +779,43 @@ def test_interpolate_only():
     assert result == no_placeholders
 
 
+def test_interpolate_only_with_dict_inside_expected_output():
+    """Test the interpolate_only method for various scenarios including JSON structure preservation."""
+    task = Task(
+        description="Unused in this test",
+        expected_output="Unused in this test: {questions}",
+    )
+
+    json_string = '{"questions": {"main_question": "What is the user\'s name?", "secondary_question": "What is the user\'s age?"}}'
+    result = task.interpolate_only(
+        input_string=json_string,
+        inputs={
+            "questions": {
+                "main_question": "What is the user's name?",
+                "secondary_question": "What is the user's age?",
+            }
+        },
+    )
+    assert '"main_question": "What is the user\'s name?"' in result
+    assert '"secondary_question": "What is the user\'s age?"' in result
+    assert result == json_string
+
+    normal_string = "Hello {name}, welcome to {place}!"
+    result = task.interpolate_only(
+        input_string=normal_string, inputs={"name": "John", "place": "CrewAI"}
+    )
+    assert result == "Hello John, welcome to CrewAI!"
+
+    result = task.interpolate_only(input_string="", inputs={"unused": "value"})
+    assert result == ""
+
+    no_placeholders = "Hello, this is a test"
+    result = task.interpolate_only(
+        input_string=no_placeholders, inputs={"unused": "value"}
+    )
+    assert result == no_placeholders
+
+
 def test_task_output_str_with_pydantic():
     from crewai.tasks.output_format import OutputFormat
 
@@ -966,3 +1003,283 @@ def test_task_execution_times():
     assert task.start_time is not None
     assert task.end_time is not None
     assert task.execution_duration == (task.end_time - task.start_time).total_seconds()
+
+
+def test_interpolate_with_list_of_strings():
+    task = Task(
+        description="Test list interpolation",
+        expected_output="List: {items}",
+    )
+
+    # Test simple list of strings
+    input_str = "Available items: {items}"
+    inputs = {"items": ["apple", "banana", "cherry"]}
+    result = task.interpolate_only(input_str, inputs)
+    assert result == f"Available items: {inputs['items']}"
+
+    # Test empty list
+    empty_list_input = {"items": []}
+    result = task.interpolate_only(input_str, empty_list_input)
+    assert result == "Available items: []"
+
+
+def test_interpolate_with_list_of_dicts():
+    task = Task(
+        description="Test list of dicts interpolation",
+        expected_output="People: {people}",
+    )
+
+    input_data = {
+        "people": [
+            {"name": "Alice", "age": 30, "skills": ["Python", "AI"]},
+            {"name": "Bob", "age": 25, "skills": ["Java", "Cloud"]},
+        ]
+    }
+    result = task.interpolate_only("{people}", input_data)
+
+    parsed_result = eval(result)
+    assert isinstance(parsed_result, list)
+    assert len(parsed_result) == 2
+    assert parsed_result[0]["name"] == "Alice"
+    assert parsed_result[0]["age"] == 30
+    assert parsed_result[0]["skills"] == ["Python", "AI"]
+    assert parsed_result[1]["name"] == "Bob"
+    assert parsed_result[1]["age"] == 25
+    assert parsed_result[1]["skills"] == ["Java", "Cloud"]
+
+
+def test_interpolate_with_nested_structures():
+    task = Task(
+        description="Test nested structures",
+        expected_output="Company: {company}",
+    )
+
+    input_data = {
+        "company": {
+            "name": "TechCorp",
+            "departments": [
+                {
+                    "name": "Engineering",
+                    "employees": 50,
+                    "tools": ["Git", "Docker", "Kubernetes"],
+                },
+                {"name": "Sales", "employees": 20, "regions": {"north": 5, "south": 3}},
+            ],
+        }
+    }
+    result = task.interpolate_only("{company}", input_data)
+    parsed = eval(result)
+
+    assert parsed["name"] == "TechCorp"
+    assert len(parsed["departments"]) == 2
+    assert parsed["departments"][0]["tools"] == ["Git", "Docker", "Kubernetes"]
+    assert parsed["departments"][1]["regions"]["north"] == 5
+
+
+def test_interpolate_with_special_characters():
+    task = Task(
+        description="Test special characters in dicts",
+        expected_output="Data: {special_data}",
+    )
+
+    input_data = {
+        "special_data": {
+            "quotes": """This has "double" and 'single' quotes""",
+            "unicode": "文字化けテスト",
+            "symbols": "!@#$%^&*()",
+            "empty": "",
+        }
+    }
+    result = task.interpolate_only("{special_data}", input_data)
+    parsed = eval(result)
+
+    assert parsed["quotes"] == """This has "double" and 'single' quotes"""
+    assert parsed["unicode"] == "文字化けテスト"
+    assert parsed["symbols"] == "!@#$%^&*()"
+    assert parsed["empty"] == ""
+
+
+def test_interpolate_mixed_types():
+    task = Task(
+        description="Test mixed type interpolation",
+        expected_output="Mixed: {data}",
+    )
+
+    input_data = {
+        "data": {
+            "name": "Test Dataset",
+            "samples": 1000,
+            "features": ["age", "income", "location"],
+            "metadata": {
+                "source": "public",
+                "validated": True,
+                "tags": ["demo", "test", "temp"],
+            },
+        }
+    }
+    result = task.interpolate_only("{data}", input_data)
+    parsed = eval(result)
+
+    assert parsed["name"] == "Test Dataset"
+    assert parsed["samples"] == 1000
+    assert parsed["metadata"]["tags"] == ["demo", "test", "temp"]
+
+
+def test_interpolate_complex_combination():
+    task = Task(
+        description="Test complex combination",
+        expected_output="Report: {report}",
+    )
+
+    input_data = {
+        "report": [
+            {
+                "month": "January",
+                "metrics": {"sales": 15000, "expenses": 8000, "profit": 7000},
+                "top_products": ["Product A", "Product B"],
+            },
+            {
+                "month": "February",
+                "metrics": {"sales": 18000, "expenses": 8500, "profit": 9500},
+                "top_products": ["Product C", "Product D"],
+            },
+        ]
+    }
+    result = task.interpolate_only("{report}", input_data)
+    parsed = eval(result)
+
+    assert len(parsed) == 2
+    assert parsed[0]["month"] == "January"
+    assert parsed[1]["metrics"]["profit"] == 9500
+    assert "Product D" in parsed[1]["top_products"]
+
+
+def test_interpolate_invalid_type_validation():
+    task = Task(
+        description="Test invalid type validation",
+        expected_output="Should never reach here",
+    )
+
+    # Test with invalid top-level type
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only("{data}", {"data": set()})  # type: ignore we are purposely testing this failure
+
+    assert "Unsupported type set" in str(excinfo.value)
+
+    # Test with invalid nested type
+    invalid_nested = {
+        "profile": {
+            "name": "John",
+            "age": 30,
+            "tags": {"a", "b", "c"},  # Set is invalid
+        }
+    }
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only("{data}", {"data": invalid_nested})
+    assert "Unsupported type set" in str(excinfo.value)
+
+
+def test_interpolate_custom_object_validation():
+    task = Task(
+        description="Test custom object rejection",
+        expected_output="Should never reach here",
+    )
+
+    class CustomObject:
+        def __init__(self, value):
+            self.value = value
+
+        def __str__(self):
+            return str(self.value)
+
+    # Test with custom object at top level
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only("{obj}", {"obj": CustomObject(5)})  # type: ignore we are purposely testing this failure
+    assert "Unsupported type CustomObject" in str(excinfo.value)
+
+    # Test with nested custom object in dictionary
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only(
+            "{data}", {"data": {"valid": 1, "invalid": CustomObject(5)}}
+        )
+    assert "Unsupported type CustomObject" in str(excinfo.value)
+
+    # Test with nested custom object in list
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only("{data}", {"data": [1, "valid", CustomObject(5)]})
+    assert "Unsupported type CustomObject" in str(excinfo.value)
+
+    # Test with deeply nested custom object
+    with pytest.raises(ValueError) as excinfo:
+        task.interpolate_only(
+            "{data}", {"data": {"level1": {"level2": [{"level3": CustomObject(5)}]}}}
+        )
+    assert "Unsupported type CustomObject" in str(excinfo.value)
+
+
+def test_interpolate_valid_complex_types():
+    task = Task(
+        description="Test valid complex types",
+        expected_output="Validation should pass",
+    )
+
+    # Valid complex structure
+    valid_data = {
+        "name": "Valid Dataset",
+        "stats": {
+            "count": 1000,
+            "distribution": [0.2, 0.3, 0.5],
+            "features": ["age", "income"],
+            "nested": {"deep": [1, 2, 3], "deeper": {"a": 1, "b": 2.5}},
+        },
+    }
+
+    # Should not raise any errors
+    result = task.interpolate_only("{data}", {"data": valid_data})
+    parsed = eval(result)
+    assert parsed["name"] == "Valid Dataset"
+    assert parsed["stats"]["nested"]["deeper"]["b"] == 2.5
+
+
+def test_interpolate_edge_cases():
+    task = Task(
+        description="Test edge cases",
+        expected_output="Edge case handling",
+    )
+
+    # Test empty dict and list
+    assert task.interpolate_only("{}", {"data": {}}) == "{}"
+    assert task.interpolate_only("[]", {"data": []}) == "[]"
+
+    # Test numeric types
+    assert task.interpolate_only("{num}", {"num": 42}) == "42"
+    assert task.interpolate_only("{num}", {"num": 3.14}) == "3.14"
+
+    # Test boolean values (valid JSON types)
+    assert task.interpolate_only("{flag}", {"flag": True}) == "True"
+    assert task.interpolate_only("{flag}", {"flag": False}) == "False"
+
+
+def test_interpolate_valid_types():
+    task = Task(
+        description="Test valid types including null and boolean",
+        expected_output="Should pass validation",
+    )
+
+    # Test with boolean and null values (valid JSON types)
+    valid_data = {
+        "name": "Test",
+        "active": True,
+        "deleted": False,
+        "optional": None,
+        "nested": {"flag": True, "empty": None},
+    }
+
+    result = task.interpolate_only("{data}", {"data": valid_data})
+    parsed = eval(result)
+
+    assert parsed["active"] is True
+    assert parsed["deleted"] is False
+    assert parsed["optional"] is None
+    assert parsed["nested"]["flag"] is True
+    assert parsed["nested"]["empty"] is None