feat: support null-conditional operator (#147)

Author: arjendev

src/data_factory_testing_framework/_expression_runtime/data_factory_expression/expression_transformer.py

@@ -40,7 +40,7 @@ def __init__(self) -> None:
 
         expression_grammar = f"""
             expression_start: "@" expression_evaluation
-            expression_evaluation: (expression_logical_bool | expression_branch | expression_call) ((("." EXPRESSION_PARAMETER_NAME) | EXPRESSION_ARRAY_INDEX)+)? EXPRESSION_WS*
+            expression_evaluation: (expression_logical_bool | expression_branch | expression_call) ((EXPRESSION_NULL_CONDITIONAL_OPERATOR? (expression_field_reference | EXPRESSION_ARRAY_INDEX))+)? EXPRESSION_WS*
             ?expression_call: expression_function_call
                               // used to translate to expression_pipeline_reference
                               | expression_datafactory_parameters_reference
@@ -55,9 +55,8 @@ def __init__(self) -> None:
             expression_datafactory_parameters_reference: EXPRESSION_DATAFACTORY_REFERENCE "()"
             expression_datafactory_activity_reference: "activity" "(" EXPRESSION_ACTIVITY_NAME ")"
             expression_item_reference: "item" "()"
-            expression_pipeline_reference: "pipeline" "()" "." EXPRESSION_PIPELINE_PROPERTY
-
-
+            expression_pipeline_reference: "pipeline" "()" EXPRESSION_NULL_CONDITIONAL_OPERATOR? "." EXPRESSION_PIPELINE_PROPERTY
+            expression_field_reference: "." EXPRESSION_PARAMETER_NAME
 
             // branch rules
             expression_logical_bool: EXPRESSION_LOGICAL_BOOL "(" expression_parameter "," expression_parameter ")"
@@ -83,6 +82,7 @@ def __init__(self) -> None:
             EXPRESSION_STRING: SINGLE_QUOTED_STRING
             EXPRESSION_SYSTEM_VARIABLE_NAME: /[a-zA-Z0-9_]+/
             EXPRESSION_VARIABLE_NAME: "'" /[^']*/ "'"
+            EXPRESSION_NULL_CONDITIONAL_OPERATOR: "?"
             EXPRESSION_WS: WS
         """  # noqa: E501
 

tests/unit/functions/test_data_factory_testing_framework_expression_evaluator.py

@@ -368,6 +368,65 @@ def test_evaluate_function_names_are_case_insensitive() -> None:
     assert evaluated_value == "ab"
 
 
+def test_evaluate_function_with_null_conditional_operator() -> None:
+    # Arrange
+    expression = "@pipeline().parameters.parameter.field1?.field2"
+    expression_runtime = ExpressionRuntime()
+    state = PipelineRunState(
+        parameters=[
+            RunParameter(
+                RunParameterType.Pipeline,
+                "parameter",
+                {
+                    "field1": {"field2": "value1"},
+                },
+            ),
+        ]
+    )
+
+    # Act
+    evaluated_value = expression_runtime.evaluate(expression, state)
+
+    # Assert
+    assert evaluated_value == "value1"
+
+
+def test_evaluate_function_with_null_conditional_operator_and_null_value() -> None:
+    # Arrange
+    expression = "@pipeline().parameters.parameter?.field1?.field2"
+    expression_runtime = ExpressionRuntime()
+    state = PipelineRunState(
+        parameters=[
+            RunParameter(
+                RunParameterType.Pipeline,
+                "parameter",
+                {
+                    "field1": None,
+                },
+            ),
+        ]
+    )
+
+    # Act
+    evaluated_value = expression_runtime.evaluate(expression, state)
+
+    # Assert
+    assert evaluated_value is None
+
+
+def test_evaluate_function_with_null_conditional_operator_and_system_variable() -> None:
+    # Arrange
+    expression = "@pipeline()?.TriggeredByPipelineRunId"
+    expression_runtime = ExpressionRuntime()
+    state = PipelineRunState()
+
+    # Act
+    evaluated_value = expression_runtime.evaluate(expression, state)
+
+    # Assert
+    assert evaluated_value is None
+
+
 def test_evaluate_parameter_with_complex_object_and_array_index() -> None:
     # Arrange
     expression = "@pipeline().parameters.parameter[0].field1.field2"