use pyfuncitem name for tmpdir in order to take generative test id into account

--HG--
branch : trunk

pytest/plugin/tmpdir.py

@@ -29,6 +29,6 @@ def pytest_funcarg__tmpdir(request):
     directory.  The returned object is a `py.path.local`_
     path object.
     """
-    name = request.function.__name__
+    name = request._pyfuncitem.name
     x = request.config.mktemp(name, numbered=True)
     return x.realpath()

testing/plugin/test_tmpdir.py

@@ -4,11 +4,16 @@ from pytest.plugin.tmpdir import pytest_funcarg__tmpdir
 from pytest.plugin.python import FuncargRequest
 
 def test_funcarg(testdir):
-    item = testdir.getitem("def test_func(tmpdir): pass")
+    item = testdir.getitem("""
+            def pytest_generate_tests(metafunc):
+                metafunc.addcall(id='a')
+                metafunc.addcall(id='b')
+            def test_func(tmpdir): pass
+            """, 'test_func[a]')
     p = pytest_funcarg__tmpdir(FuncargRequest(item))
     assert p.check()
     bn = p.basename.strip("0123456789")
-    assert bn.endswith("test_func")
+    assert bn.endswith("test_func[a]")
 
 def test_ensuretemp(recwarn):
     #py.test.deprecated_call(py.test.ensuretemp, 'hello')