[6.0.x] Merge pull request #7749 from bluetech/fix-get_source-crash

changelog/4984.bugfix.rst

@@ -0,0 +1,3 @@
+Fixed an internal error crash with ``IndexError: list index out of range`` when
+collecting a module which starts with a decorated function, the decorator
+raises, and assertion rewriting is enabled.

src/_pytest/assertion/rewrite.py

@@ -694,13 +694,18 @@ def run(self, mod: ast.Module) -> None:
                     return
                 expect_docstring = False
             elif (
-                not isinstance(item, ast.ImportFrom)
-                or item.level > 0
-                or item.module != "__future__"
+                isinstance(item, ast.ImportFrom)
+                and item.level == 0
+                and item.module == "__future__"
             ):
-                lineno = item.lineno
+                pass
+            else:
                 break
             pos += 1
+        # Special case: for a decorated function, set the lineno to that of the
+        # first decorator, not the `def`. Issue #4984.
+        if isinstance(item, ast.FunctionDef) and item.decorator_list:
+            lineno = item.decorator_list[0].lineno
         else:
             lineno = item.lineno
         imports = [

testing/test_collection.py

@@ -1427,3 +1427,17 @@ def test_modules_not_importable_as_side_effect(self, testdir):
                 "* 1 failed in *",
             ]
         )
+
+
+def test_does_not_crash_on_error_from_decorated_function(testdir: Testdir) -> None:
+    """Regression test for an issue around bad exception formatting due to
+    assertion rewriting mangling lineno's (#4984)."""
+    testdir.makepyfile(
+        """
+        @pytest.fixture
+        def a(): return 4
+        """
+    )
+    result = testdir.runpytest()
+    # Not INTERNAL_ERROR
+    assert result.ret == ExitCode.INTERRUPTED