fix(step): support attribute access in step title placeholders

allure-python-commons/src/allure_commons/_allure.py

@@ -1,3 +1,5 @@
+import inspect
+import string
 from functools import wraps
 from typing import Any, Callable, TypeVar, Union, overload
 
@@ -10,6 +12,25 @@
 _TFunc = TypeVar("_TFunc", bound=Callable[..., Any])
 
 
+class _StepTitleFormatter(string.Formatter):
+    """
+    Custom string formatter for step titles.
+
+    Defers represent() conversion until format_field, so attribute access
+    placeholders such as {data.name} can traverse to the attribute on the
+    original object before its repr-style representation is produced.
+
+    Existing behavior is preserved for plain positional and keyword
+    placeholders: leaf values are still wrapped via represent().
+    """
+
+    def format_field(self, value, format_spec):
+        return format(represent(value), format_spec)
+
+
+_step_title_formatter = _StepTitleFormatter()
+
+
 def safely(result):
     if result:
         return result[0]
@@ -198,8 +219,27 @@ def __call__(self, func: _TFunc) -> _TFunc:
         def impl(*a, **kw):
             __tracebackhide__ = True
             params = func_parameters(func, *a, **kw)
-            args = list(map(lambda x: represent(x), a))
-            with StepContext(self.title.format(*args, **params), params):
+            # Build a kwargs mapping with the original (non-stringified)
+            # values so the formatter can traverse attributes on objects
+            # passed as arguments, e.g. {data.name} on a dataclass.
+            # Includes defaults to match func_parameters() behaviour.
+            try:
+                arg_spec = inspect.getfullargspec(func)
+                raw_kwargs = {}
+                if arg_spec.defaults:
+                    defaults_map = dict(zip(
+                        arg_spec.args[-len(arg_spec.defaults):],
+                        arg_spec.defaults,
+                    ))
+                    raw_kwargs.update(defaults_map)
+                raw_kwargs.update(dict(zip(arg_spec.args, a)))
+                raw_kwargs.update(kw)
+                if arg_spec.args and arg_spec.args[0] in ("self", "cls"):
+                    raw_kwargs.pop(arg_spec.args[0], None)
+            except TypeError:
+                raw_kwargs = dict(kw)
+            title = _step_title_formatter.format(self.title, *a, **raw_kwargs)
+            with StepContext(title, params):
                 return func(*a, **kw)
 
         return impl  # type: ignore

tests/allure_pytest/acceptance/step/step_attribute_placeholder_test.py

@@ -0,0 +1,98 @@
+"""
+Regression tests for object attribute access in step title placeholders.
+
+See https://github.com/allure-framework/allure-python/issues/896.
+"""
+
+from hamcrest import assert_that
+from tests.allure_pytest.pytest_runner import AllurePytestRunner
+
+from allure_commons_test.report import has_test_case
+from allure_commons_test.result import has_step
+
+
+def test_step_with_dataclass_attribute_placeholder(allure_pytest_runner: AllurePytestRunner):
+    """
+    >>> import allure
+    >>> from dataclasses import dataclass
+
+    >>> @dataclass
+    ... class Item:
+    ...     name: str
+
+    >>> @allure.step("Process item: {item.name}")
+    ... def process(item):
+    ...     pass
+
+    >>> def test_dataclass_attribute_access():
+    ...     process(Item(name="Widget"))
+    """
+
+    allure_results = allure_pytest_runner.run_docstring()
+
+    assert_that(
+        allure_results,
+        has_test_case(
+            "test_dataclass_attribute_access",
+            has_step("Process item: 'Widget'"),
+        ),
+    )
+
+
+def test_step_with_object_attribute_placeholder(allure_pytest_runner: AllurePytestRunner):
+    """
+    >>> import allure
+
+    >>> class Order:
+    ...     def __init__(self, status):
+    ...         self.status = status
+
+    >>> @allure.step("Order is {order.status}")
+    ... def check(order):
+    ...     pass
+
+    >>> def test_object_attribute_access():
+    ...     check(Order("delivered"))
+    """
+
+    allure_results = allure_pytest_runner.run_docstring()
+
+    assert_that(
+        allure_results,
+        has_test_case(
+            "test_object_attribute_access",
+            has_step("Order is 'delivered'"),
+        ),
+    )
+
+
+def test_step_with_nested_attribute_placeholder(allure_pytest_runner: AllurePytestRunner):
+    """
+    >>> import allure
+    >>> from dataclasses import dataclass
+
+    >>> @dataclass
+    ... class Address:
+    ...     city: str
+
+    >>> @dataclass
+    ... class User:
+    ...     address: Address
+
+    >>> @allure.step("User from {user.address.city}")
+    ... def greet(user):
+    ...     pass
+
+    >>> def test_nested_attribute_access():
+    ...     greet(User(address=Address(city="Brighton")))
+    """
+
+    allure_results = allure_pytest_runner.run_docstring()
+
+    assert_that(
+        allure_results,
+        has_test_case(
+            "test_nested_attribute_access",
+            has_step("User from 'Brighton'"),
+        ),
+    )