feat: Allow variables to be defined outside a Component (#4316)

* feat: Allow variables to be defined outside a Component

Fixes #4315

Modify `prepare_global_scope` function in `src/backend/base/langflow/utils/validate.py` to evaluate classes, functions, and variables defined outside the Component's class.

* **Function Changes:**
  - Add evaluation of external classes using `ast.ClassDef`.
  - Add evaluation of external functions using `ast.FunctionDef`.
  - Add evaluation of external variables using `ast.Assign`.

* **Unit Tests:**
  - Add tests in `src/backend/tests/unit/test_validate_code.py` to verify the evaluation of external classes, functions, and variables.
  - Include tests for multiple external classes and external variables and functions.

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/langflow-ai/langflow/issues/4315?shareId=XXXX-XXXX-XXXX-XXXX).

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

.devcontainer/devcontainer.json

@@ -34,6 +34,9 @@
         "GitHub.vscode-pull-request-github"
       ]
     }
+  },
+  "tasks": {
+    "test": "make unit_tests"
   }
 
   // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.

src/backend/base/langflow/utils/validate.py

@@ -227,6 +227,16 @@ def prepare_global_scope(code, module):
             except ModuleNotFoundError as e:
                 msg = f"Module {node.module} not found. Please install it and try again"
                 raise ModuleNotFoundError(msg) from e
+        elif isinstance(node, ast.ClassDef):
+            # Compile and execute the class definition to properly create the class
+            class_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(class_code, exec_globals)
+        elif isinstance(node, ast.FunctionDef):
+            function_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(function_code, exec_globals)
+        elif isinstance(node, ast.Assign):
+            assign_code = compile(ast.Module(body=[node], type_ignores=[]), "<string>", "exec")
+            exec(assign_code, exec_globals)
     return exec_globals
 
 

src/backend/tests/unit/test_validate_code.py

@@ -2,7 +2,13 @@ from pathlib import Path
 from unittest import mock
 
 import pytest
-from langflow.utils.validate import create_function, execute_function, extract_function_name, validate_code
+from langflow.utils.validate import (
+    create_class,
+    create_function,
+    execute_function,
+    extract_function_name,
+    validate_code,
+)
 from requests.exceptions import MissingSchema
 
 
@@ -100,3 +106,67 @@ def my_function(x):
     """
     with mock.patch("requests.get", side_effect=MissingSchema), pytest.raises(MissingSchema):
         execute_function(code, "my_function", "invalid_url")
+
+
+def test_create_class():
+    code = """
+from langflow.custom import CustomComponent
+
+class ExternalClass:
+    def __init__(self, value):
+        self.value = value
+
+class MyComponent(CustomComponent):
+    def build(self):
+        return ExternalClass("test")
+"""
+    class_name = "MyComponent"
+    created_class = create_class(code, class_name)
+    instance = created_class()
+    result = instance.build()
+    assert result.value == "test"
+
+
+def test_create_class_with_multiple_external_classes():
+    code = """
+from langflow.custom import CustomComponent
+
+class ExternalClass1:
+    def __init__(self, value):
+        self.value = value
+
+class ExternalClass2:
+    def __init__(self, value):
+        self.value = value
+
+class MyComponent(CustomComponent):
+    def build(self):
+        return ExternalClass1("test1"), ExternalClass2("test2")
+"""
+    class_name = "MyComponent"
+    created_class = create_class(code, class_name)
+    instance = created_class()
+    result1, result2 = instance.build()
+    assert result1.value == "test1"
+    assert result2.value == "test2"
+
+
+def test_create_class_with_external_variables_and_functions():
+    code = """
+from langflow.custom import CustomComponent
+
+external_variable = "external_value"
+
+def external_function():
+    return "external_function_value"
+
+class MyComponent(CustomComponent):
+    def build(self):
+        return external_variable, external_function()
+"""
+    class_name = "MyComponent"
+    created_class = create_class(code, class_name)
+    instance = created_class()
+    result_variable, result_function = instance.build()
+    assert result_variable == "external_value"
+    assert result_function == "external_function_value"