support pytest.set_trace in collection

_pytest/pdb.py

@@ -19,11 +19,13 @@ def pytest_configure(config):
 class pytestPDB:
     """ Pseudo PDB that defers to the real pdb. """
     item = None
+    collector = None
 
     def set_trace(self):
         """ invoke PDB set_trace debugging, dropping any IO capturing. """
         frame = sys._getframe().f_back
-        item = getattr(self, 'item', None)
+        item = self.item or self.collector
+
         if item is not None:
             capman = item.config.pluginmanager.getplugin("capturemanager")
             out, err = capman.suspendcapture()
@@ -38,6 +40,14 @@ def pdbitem(item):
     pytestPDB.item = item
 pytest_runtest_setup = pytest_runtest_call = pytest_runtest_teardown = pdbitem
 
+@pytest.mark.tryfirst
+def pytest_make_collect_report(__multicall__, collector):
+    try:
+        pytestPDB.collector = collector
+        return __multicall__.execute()
+    finally:
+        pytestPDB.collector = None
+
 def pytest_runtest_makereport():
     pytestPDB.item = None
     

testing/test_pdb.py

@@ -144,6 +144,19 @@ class TestPDB:
         child.sendeof()
         child.wait()
 
+    def test_pdb_used_in_generate_tests(self, testdir):
+        p1 = testdir.makepyfile("""
+            import pytest
+            def pytest_generate_tests(metafunc):
+                pytest.set_trace()
+                x = 5
+            def test_foo(a):
+                pass
+        """)
+        child = testdir.spawn_pytest(str(p1))
+        child.expect("x = 5")
+        child.sendeof()
+        child.wait()
     def test_pdb_collection_failure_is_shown(self, testdir):
         p1 = testdir.makepyfile("""xxx """)
         result = testdir.runpytest("--pdb", p1)