Adjust stacklevel of implprefix warning

changelog/166.trivial.rst

@@ -0,0 +1 @@
+Add ``stacklevel=2`` to implprefix warning so that the reported location of warning is the caller of PluginManager.

pluggy/manager.py

@@ -53,6 +53,7 @@ def __init__(self, project_name, implprefix=None):
                 "Support for the `implprefix` arg is now deprecated and will "
                 "be removed in an upcoming release. Please use HookimplMarker.",
                 DeprecationWarning,
+                stacklevel=2,
             )
         self._implprefix = implprefix
         self._inner_hookexec = lambda hook, methods, kwargs: hook.multicall(

testing/test_pluginmanager.py

@@ -579,6 +579,12 @@ def he_method1(self):
         undo()
 
 
+def test_implprefix_warning(recwarn):
+    PluginManager(hookspec.project_name, "hello_")
+    w = recwarn.pop(DeprecationWarning)
+    assert "test_pluginmanager.py" in w.filename
+
+
 @pytest.mark.parametrize("include_hookspec", [True, False])
 def test_prefix_hookimpl(include_hookspec):
     with pytest.deprecated_call():