1 files changed, 109 insertions, 0 deletions
diff --git a/testing/web-platform/tests/tools/pytest/_pytest/pdb.py b/testing/web-platform/tests/tools/pytest/_pytest/pdb.py
new file mode 100644
index 000000000..84c920d17
--- /dev/null
+++ b/testing/web-platform/tests/tools/pytest/_pytest/pdb.py
@@ -0,0 +1,109 @@
+""" interactive debugging with PDB, the Python Debugger. """
+from __future__ import absolute_import
+import pdb
+import sys
+
+import pytest
+
+
+def pytest_addoption(parser):
+    group = parser.getgroup("general")
+    group._addoption('--pdb',
+               action="store_true", dest="usepdb", default=False,
+               help="start the interactive Python debugger on errors.")
+
+def pytest_namespace():
+    return {'set_trace': pytestPDB().set_trace}
+
+def pytest_configure(config):
+    if config.getvalue("usepdb"):
+        config.pluginmanager.register(PdbInvoke(), 'pdbinvoke')
+
+    old = (pdb.set_trace, pytestPDB._pluginmanager)
+    def fin():
+        pdb.set_trace, pytestPDB._pluginmanager = old
+        pytestPDB._config = None
+    pdb.set_trace = pytest.set_trace
+    pytestPDB._pluginmanager = config.pluginmanager
+    pytestPDB._config = config
+    config._cleanup.append(fin)
+
+class pytestPDB:
+    """ Pseudo PDB that defers to the real pdb. """
+    _pluginmanager = None
+    _config = None
+
+    def set_trace(self):
+        """ invoke PDB set_trace debugging, dropping any IO capturing. """
+        import _pytest.config
+        frame = sys._getframe().f_back
+        if self._pluginmanager is not None:
+            capman = self._pluginmanager.getplugin("capturemanager")
+            if capman:
+                capman.suspendcapture(in_=True)
+            tw = _pytest.config.create_terminal_writer(self._config)
+            tw.line()
+            tw.sep(">", "PDB set_trace (IO-capturing turned off)")
+            self._pluginmanager.hook.pytest_enter_pdb(config=self._config)
+        pdb.Pdb().set_trace(frame)
+
+
+class PdbInvoke:
+    def pytest_exception_interact(self, node, call, report):
+        capman = node.config.pluginmanager.getplugin("capturemanager")
+        if capman:
+            out, err = capman.suspendcapture(in_=True)
+            sys.stdout.write(out)
+            sys.stdout.write(err)
+        _enter_pdb(node, call.excinfo, report)
+
+    def pytest_internalerror(self, excrepr, excinfo):
+        for line in str(excrepr).split("\n"):
+            sys.stderr.write("INTERNALERROR> %s\n" %line)
+            sys.stderr.flush()
+        tb = _postmortem_traceback(excinfo)
+        post_mortem(tb)
+
+
+def _enter_pdb(node, excinfo, rep):
+    # XXX we re-use the TerminalReporter's terminalwriter
+    # because this seems to avoid some encoding related troubles
+    # for not completely clear reasons.
+    tw = node.config.pluginmanager.getplugin("terminalreporter")._tw
+    tw.line()
+    tw.sep(">", "traceback")
+    rep.toterminal(tw)
+    tw.sep(">", "entering PDB")
+    tb = _postmortem_traceback(excinfo)
+    post_mortem(tb)
+    rep._pdbshown = True
+    return rep
+
+
+def _postmortem_traceback(excinfo):
+    # A doctest.UnexpectedException is not useful for post_mortem.
+    # Use the underlying exception instead:
+    from doctest import UnexpectedException
+    if isinstance(excinfo.value, UnexpectedException):
+        return excinfo.value.exc_info[2]
+    else:
+        return excinfo._excinfo[2]
+
+
+def _find_last_non_hidden_frame(stack):
+    i = max(0, len(stack) - 1)
+    while i and stack[i][0].f_locals.get("__tracebackhide__", False):
+        i -= 1
+    return i
+
+
+def post_mortem(t):
+    class Pdb(pdb.Pdb):
+        def get_stack(self, f, t):
+            stack, i = pdb.Pdb.get_stack(self, f, t)
+            if f is None:
+                i = _find_last_non_hidden_frame(stack)
+            return stack, i
+    p = Pdb()
+    p.reset()
+    p.interaction(None, t)